mad cow home or moly bio area or best links

3D mouse prion coordinates finally available?
New prion mRNA complexity found
New Zealand, Australia scramble to squelch rumors
Australia's scrapie program
GSS with V129 is very different from GSS with M129
Intron sequence alleles and CJD diagnosis
No prion plaque in M232R CJD
Oryx and kudu prion sequences
Caveolin-selected peptide ligands have spaced aromatics
Amino terminus of prion inessential
Copper ion orders octapeptide repeat region
Prion dimers and the species barrier
Octapeptide insertions/deletions explained by DNA slippage
Prion gene variation in primates: correction

Mouse prion: NMR coordinates released

8 May 1997. Webmaster comments on recent publications:

1. Prof. Dr. Rudi Glockshuber has kindly informed me that:

The coordinates of the mouse prion fragment PrP(121-231) will be posted online on October 1, 1997. (I'll post a interactive joystick model of this). His group has a paper currently in press with PNAS concerning the species barrier problem, positions of variable residues in the 3D structure, and possible sites of interactions between PrPc and PrPsc .. A second paper on the atomic details of the refined strucutre has been submitted to Nature Structural Biology.

Their earlier paper represented a very significant advance of our knowledge of many issues involving prion structure/function. (Nature 18 July 1996) http://mad-cow.org/~tom/3d_text.html There was talk that they had the structure of a larger piece, but apparently there is nothing at the manuscript stage.

The spatial coordinates for mouse prion, used in an oft-cited paper published in July 1996 Nature have been submitted to the protein structure database at Brookhaven. However, the data will apparently be under review for another 5 months by staff there:

Data under processing at PDB
Idcode:  1AG2          Tracking Number:  T11143
Entry Description:
    PRION PROTEIN DOMAIN PRP(121-231), DOMAIN 121-231
Authors: M. BILLETER,R. RIEK,G. WIDER,K. WUTHRICH,S. HORNEMANN,R. GLOCKSHUBER
Status for 1AG2: -incomplete->-processing->-depositor->**REVIEW**>**HLD
On hold until:  Sep 30 1997
All materials arrived as of:  Mar 31 1997
Accession Date:  Mar 31 1997
A second proprietary non-online source of the data can be found at BioMedNet:
Prion protein, residues 121-231 (mouse) NMR Macromolecular Structures Database 
Special offer Instructions  Subscription ID Macromolecular Structures Database and Reviews CD-ROM
subscribers edition. Current Biology Ltd are pleased to offer a free subscription to the electronic  version of Macromolecular Structures
Database and Current Opinion in  Structural Biology until the end of 1996 for their current CD-ROM subscribers  to Macromolecular Structures: Database and Reviews. 
Current work at the Rudi Glockshuber's ETH web site

2. Dr. Hideyo Inouye kindly sent me a preprint of his new :

JMolBio article. 268,#2 , May 2, 1997 p375-389. fulltext online and free: http://www.hbuk.co.uk/jmb/login.html. This is a very advanced paper with clever choice of experimental material (syrian hamster 90-145) that uses fiber diffraction to look directly at amyloid. Dr. Inouye has to be an expert on neuro-amyloid structures by anybody's standards. Most interesting to me was the proposal for turns in the middle of both the H1 and H2 domains.

X-ray Diffraction Analysis of Scrapie Prion: Intermediate and Folded
Structures in a Peptide Containing Two Putative [alpha]-Helices
Hideyo Inouye,Daniel A. Kirschner
It is instructive to compare Dr. Inouye's results with the Perutz's penetrating overview of amyloid-forming proteins, including prions, in the 27 Feb 97 Nature. pg 771 . It seems that the beta-sheets are quite consistently aligned normal to the fiber axis. The same issue contains an instructive article, pp787, on a lysozyme disorder, hereditary amyloidosis, where amyloid consists entirely of mutant allele product.

The word 'amyloid' was coined in 1853 by the German pathologist Rudolf Virchow to describe eosinophilic waxy tissue deposits. Unfortunately, amyloid means starch-like, whereas all known amyloids are protein.

3. Dr. Antoinette van der Kuyl has kindly sent me:

the oryx and greater kudu DNA sequences from an unavailable journal, Arch Virology 131: 193-199 1994. I have taken responsibility for getting these onto GenBank and also posting forced alignment on the current artiodactyl tree. Oryx had just one aa change from sheep, kudu was more like bovine (4 aa different). Recall that both antelope got TSE in English zoos.

4. James Warwicker, fax 44-1734-267917, has a couple of very clever papers out on prion quaternary structure in which he sought to identify the prion dimer interface through optimized molecular modelling. This paper is the sort that drives xray and NMR people crazy because he has probably gotten to a great result without setting foot in the lab -- they will have to cite it after a huge amount of confirmatory effort.

Warwicker concludes that it is our old friend, the invariant hydrophobic core domain 104-121, that forms the main interface across the Glockshuber-Wuthrich exposed apolar surface. I think he has it right because the least-energy fit just happened to coincide with the standard closed homodimer Z(2) symmetry model predicted decades ago by Jacques Monod. It all has to do with the evolution of complementary surfaces being best attained with a 180 degree rotation.

Biochem Biophys Res Commun 232 (2): 508-512 (1997)
Biochem-Biophys-Res-Commun. 1996 Sep 24; 226(3): 777-82
5. Dr. Edward Marcotte, recombinant prion expression postdoc at UCLA, told me today that there is a new book out about the molecular biology & geentics of prions by Reed Wickner that sounds very interesting:

Reed Wickner 
Prion Diseases of Mammals and Yeast: Molecular Mechanisms & Genetic Features
>from Medical Intelligence Unit, R.G.Landes Company, Chapman & Hall Publishing,
1997, ISBN:0-412-13731-3
6. Febs Letters 405 378-384 1997 by C. Smith, ,,,,,, J Collinge Conformational properties of the prion octa-repeat and hydrophobic sequences.

I was very sorry later that I spent 35¢ xeroxing this article. It is a result-less 7 page paper with 7 authors that makes me yearn for peer-review and better screening. Collinge could not possibly have had anything substantial to do with this paper.

The authors use circular dichoism to look at the repeat region and the hydrophobic core in various solvents (acetonitrile!?), including met/val 129 variations (no difference found, CD wrong tool for the job). They failed to include copper in the medium even though the paper was submitted in Feb 1997; the biological significance of the authors claim for a polyproline type II left-handed extended helix thus seems doubtful. A cookbook GCG chicken-human alignment is not publishable and the discussion of repeats in other proteins suggests no access to Medline. The lack of citations to earlier research on this particular topic is astonishing.

Biophysical Characterization of the Recombinant Mouse Prion Protein and its Carboxy-Terminal Domain, PrP(121-231)

Prion diseases are believed to be caused by a single protein, the prion protein, which may exist in two different conformations, the cellular form, and the infectious ''scrapie form''. We found that the carboxy-terminal domain of the mouse prion protein (residues 121-231) is an autonomous folding unit. In contrast with model predictions, its three-dimensional structure, which was solved in collaboration with the group of Prof. K. W¸thrich, contains a two-stranded beta-sheet and three alpha-helices. Mutations linked with inherited prion diseases in humans appear to destabilize the cellular prion protein and may facilitate its transition to the infectious form. We are currently introducing these mutations into PrP(121-231) of the mouse prion protein and analyzing their effects on the thermodynamic stability of the C-terminal domain. In addition, we are comparing the properties of the whole mouse prion prion (residues 23-231) with those of PrP(121-231).

A novel hamster prion protein mRNA contains an extra exon: increased expression in scrapie

Li G, Bolton DC
Brain Res 751 (2): 265-274 (Mar 1997)

Prion protein (PrP) is the only known constituent of the agents (called prions) that cause fatal neurodegenerative diseases in animals and humans. PrP derives from a host protein encoded by a single copy gene having three known exons in mice, cattle and sheep but only two exons in hamsters and humans. We have identified and sequenced the missing exon from the hamster PrP gene.

The new hamster PrP exon is 83% identical to mouse exon 2 and 76% identical to exon 2 from cattle and sheep. PrP mRNAs containing the new exon 2 (mRNA[1+2+3]) were expressed in the colliculi, frontal cortex and hippocampus of normal hamsters at approximately 30% to approximately 50% of the levels of the mRNA without exon 2 (mRNA[1+3]). Expression of PrP mRNA[1+2+3] was increased in the colliculi beginning 49 days after inoculation with scrapie prions and reached a level 2.5 times normal by day 77. Increased expression of PrP mRNA[1+2+3] in the colliculi correlated with expression of glial fibrillary acidic protein (GFAP) mRNA. Expression of GFAP and PrP mRNAs was not significantly increased in the hippocampus or the frontal cortex during the disease. Our study shows that exon 2 plays a role in regulating the cellular expression of hamster PrP and suggests that mRNA[1+2+3] may be preferentially expressed in hamster astrocytes.

Commentary/auxillary data -- webmaster: 8 May 1997. Li and Bolton re-sequenced the hamster prion gene, working back carefully to cDNA from various prion messenger RNAs found in differing proportions in assorted brain cell types. [There is a 7700 bp intron 2 still not fully sequenced.]

First, they cleared up a gene structure mystery as to why sheep, cattle, mice [and rat] have three prion exons whereas hamster and humans have just two: they don't. Hamsters (and probably humans too) in fact have the missing 99 bp second exon, it was missed by an earlier group. Homology of hamster exon 2 to the others is very high, especially 5', 84% to sheep etc.[but not to anything else in BLASTn except a 34bp stretch from C. elegans.]

Second, they established the existence of a new kind of prion isoform, this time in the mRNA. It seems that 1+2+3 mRNA is swamped by a factor of three by 1+3 mRNA, ie, the transcript is alternatively spliced in the upstream non-coding portion. It seems that astrocytes in particular preferentially express1+2+3 mRNA. Frontal cortex has more than hippocampus or the colliculi.

Note that these isoforms don't affect the amino acid sequence or covalent structure of the prion protein per se. They could affect efficiency or speed of translation, afford mRNA regulation opportunities, or direct site-specific translation, and so on. Other genes -- and their polymorphisms -- are necessarily brought into the picture to give rise to the observed differences in mRNAs. We might wonder too whether there are alleles in exon 2 and what their signficance might be in TSEs.

Third, there are some interesting quantitative results on prion mRNA during scrapie infection, relative to GFAP and synaptophysin: not an increase in rate, just more astrocytes making it at old rate.

Fourth, there is a cautionary message on assuming sequences in GenBank etc are correct. This came up in spades on the primate sequences, which were the subject of a major -- but still inadequate -- correction [from same group that mis-sequenced hamster], in J Mol Biol 265 (2): 257 (Jan 1997)

hamster exon 2 and some flanking intron 1 and intron 2.
        1 gaacgtgcca tgtttgcttt tgggaatcta tctgagctgt tcttatttcc gttttcaaat
       61 actgccccat ttttatgtgc ctgtatttat tagtggtttg gtaatttgta tattagatgg
      121 tatttcagta cttagattta ttcatcaatt ctaatttttc tttttcatgt tttgaaggac
      181 tcctgaatat attccaaaac tgaacaattt caactgagct gaagtactct gtttttctag
      241 aggtaccagt tcagtttagg agagtcacag cagatcgtaa gtgccctgtc aatcttggta
      301 gagggcttga aaatctccaa ctgtctgggg agatggggac cagaaaagac taagctccac
      361 acttgctcca gaggctccta gtaacgtggg acataagcct tgctgtgcac taatgtcctg
      421 taaagtcagc tttgtccagg ggacaaaggc cagagctttc tctaggactg tgccggttta
      481 gggaactgca ag


exon 2, pulled out:
gac tcctgaatat attccaaaac tgaacaattt caactgagct gaagtactct gtttttctag aggtaccagt tcagtttagg agagtcacag cagatc

Blast search against hamster exon 2:
gb|U78769|MAU78769    Mesocricetus auratus prion protein ...   495 1.0e-33   1
dbj|D50092|D50092S1   Rat DNA for prion protein, exon1,2       324 3.5e-19   1
emb|X79913|OAPRP2     O.aries PrP gene, exon 2 and flanki...   184 7.3e-08   1
gb|U67922|OAU67922    Ovis aries prion protein (PrP) gene...   184 1.6e-07   1
dbj|D10612|BOVPRP1    Bovine mRNA for prion protein.           175 4.4e-06   1
dbj|D26150|BOVPRPA    Bovine PrP gene for prion protein, ...   175 4.4e-06   1
dbj|AB001468|AB001468 Bovine mRNA for prion protein, comp...   175 4.5e-06   1
emb|Z19154|CEC40H1    Caenorhabditis elegans cosmid C40H1      116 0.93      1

 Score = 116 (32.1 bits), Expect = 2.7, P = 0.93
 Identities = 28/34 (82%), Positives = 28/34 (82%), Strand = Minus / Plus

Query:    61 AGAAAAACAGAGTACTTCAGCTCAGTTGAAATTG 28
             |||| || |||| |||||||||||  | ||||||
Sbjct:  9345 AGAATAAAAGAGAACTTCAGCTCAAATTAAATTG 9378

DNA slippage may explain unusual prion mutations

Quite a bit of familial CJD is due to insertions of variable length in the octapeptide region. Deletions also occur but aren't clearly associated with disease. There are no known point mutations in this region sufficient to cause CJD. Both insertions and deletions come in multiples of whole repeat units, here 5x8=40 aa insertion and 1x8=8 aa deletions. This region is a very unstable stretch of the human genome; whether this has some funtional significance is unknown. What's going on here? DNA slippage, sometimes multiple-event slippage. Repeats are tandem at amino acid level, but non-contiguous at DNA level because of degeneracy. Insertions result from DNA on the daughter strand slipping back to form complementary pairs with an earlier repeat, 3' exonuclease action, and extention. Deletions are similar but on the template strand. Wobble pairs aren't polymerase errors, but rather bases that have come to be errors only through slippage to an imperfect repeat. Predictions of the model are testable, using newly discovered cases of familial CJD:

Familial CJD with a five-repeat octapeptide insert mutation

Cochran,E.J...Goldfarb,L.G. and Brown,P.
Neurology 47 (3), 727-733 (1996)

S83341
PQGGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQPHG
GGWGQPHGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQ

   1 cctcagggcg gtggtggctg ggggcagcct catggtggtg gctgggggca gcctcatggt
  61 ggtggctggg ggcagcccca tggtggtggc tggggacagc ctcatggtgg tggctggggg
 121 cagcctcatg gtggtggctg ggggcagcct catggtggtg gctgggggca gcctcatggt
 181 ggtggctggg ggcagcccca tggtggtggc tggggacagc ctcatggtgg tggctggggt
 241 caa

Two different 24 bp prion gene deletions in an atypical Alzheimer's disease family

Am. J. Med. Genet. 60 (1), 12-18 (1995)
Perry,R.T., Go,R.C., Harrell,L.E. and Acton,R.T.
 
Single strand conformation polymorphism (SSCP) analysis was used to screen for mutations at the PrP locus in 82 AD
patients from 54 families (30 FAD), vs. 39 age-matched controls. A 24-bp deletion around codon 68 that codes for
one of five Gly-Pro rich octarepeats was identified in two affected sibs and one offspring of one late-onset FAD
family. Two other affected sibs, three unaffected sibs, and three offspring from this family, in addition to one
sporadic AD patient and three age-matched controls, were heterozygous for another octarepeat deletion located
around codon 82. Two of the four affected sibs had features of PD, including one who was autopsy-verified AD and PD.
Although these deletions were found infrequently in other AD patients and controls, they appear to be a rare
polymorphism that is segregating in this FAD family. It does not appear that mutations at the PRNP locus are
frequently associated with AD in this population. 

S80732 
QGSPGGNRYPPQGGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQGG

   1 cagggcagcc ctggaggcaa ccgctaccca cctcagggcg gtggtggctg ggggcagcct
  61 catggtggtg gctgggggca gcctcatggt ggtggctggg ggcagcccca tggtggtggc
 121 tggggtcaag gaggtg


S80743  insertion (codon 46, missing G)
QGSPGGNRYPPQGGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQGG

   1 cagggcagcc ctggaggcaa ccgctaccca cctcagggcg gtggtggctg ggggcagcct
  61 catggtggtg gctgggggca gccccatggt ggtggctggg gacagcctca tggtggtggc
 121 tggggtcaag gaggtg

The differences in the above two 24bp deletions are:

               70        80        90       100        
CATGGTGGTGGCTGGGGGCAGCCTCATGGTGGTGGCTGGGGGCAGCCCCATGG 
.......................C.................A.....T..... 

Prion Protein Gene Variation Among Primates -- CORRIGENDUM

J. Mol. Biol. (1997) 265, 257
H. M. Schatzl, M. Da Costa, L. Taylor, F E. Cohen and S. B. Prusiner
It has been pointed out to the authors that in J. Mol. Biol. (1995) 245, 362‚374, Figure 2 contained African green monkey (Cercopithecus) sequences that differed at amino acid 11 from those deposited in GenBank. This error occurred only in the article; the Cercopithecus sequences deposited at GenBank are correct and all of the trees generated for analysis and publication were based on these same correct sequences sent to GenBank. Another error was introduced at codon 211 in the preparation of Figure 2 of the article; the correct sequences were employed in the phylogenetic analysis and in the GenBank sequences. Finally a DNA sequence error in the Langur (Presbytis franciosi) identified by Professors Goudsmit and van der Kuyl has since been corrected in the submission to GenBank. Extensive re-evaluation reassures us that neither these manuscript errors, nor the now-corrected GenBank transposition of residues 107 and 108, affect in any substantial way the conclusions of the paper.

Evidence for an increased substitution rate of the hominoid protein gene during the period of brain expansion

PNAS (1996) cited in GenBank ... but this has not appeared as of April 13, 1997
 van der Kuyl,A.C., Dekker,J.T. and Goudsmit,J.
Department of Virology, Academic Medical Centre, Amsterdam, The Netherlands.
Figure 2: amino acid 211

203- YKMMERVVEQMCITQY -218 GenBank corrected
203- YKMMERVVRQMCITQY -218 Single residue error
---
Figure 2: Cercopithecus: African green monkey

1- MANLGCWMLVVFVAT -15 GenBank corrected
1- MANLGCWMLVLFVAT -15 Single residue error
-----
Presbytis francoisi: Langur  (Figure 2 is correct: aa 107 - T S- aa 108)
codon 107 -AGCAAC- codon 108  GenBank error
codon 107 -ACCAGC- codon 108  Submitted correction 
These changes do impact some of the analyses of our data. The three African green monkey lines in Table 1 should now refer to 32 (56) nucleotide changes and ten amino acid changes; the percentage rates remain correct. In Table 2, for primates, the total number of variations correlated to PrP C regions is now 34, variations in the N-terminal part should be 17/90 (19%) and in the N-/C-terminal peptides 4/44 (9%).

On page 364, in the second paragraph, the last sentence should start: with the exception of the African green monkey ....On page 365, in the first paragraph, the first sentence should begin: twenty-eight variant positions ...instead of twenty-seven variant positions ...; and the first sentence should end: ...25 of these were single amino acid substitutions instead of ...24 of these were single amino acid variations. The same paragraph, in the third sentence: . . . invariant among the primates ...should be changed to: . . . almost invariant among the primates .... On page 368, in the second paragraph, some of the percentage rates have to be changed according to the above-mentioned changes for Table 2. Finally on page 369, as noted by Goudsmit and van der Kuyl, in the first paragraph, fifth sentence: . . . codons 90 to 130 ...should be replaced by . . . codons 98 to130 .... The phylogenetic trees are somewhat sensitive to the alignments and to the choices of residues, gaps and repeats included in the analysis. Definitive conclusions about the very intriguing relationship between the gene trees and their failure to match the accepted species trees and the patterns of disease transmission await a careful body of work centered in phylogenetic analysis.

Scrapie: the risk of its introduction and effects on trade. Scrapie: recent trends.

Aust Vet J 73 (5): 161-164 (1996)  and Aust Vet J 74 (5): 383-387 (1996) 
MacDiarmid SC
MAF Regulatory Authority, Wellington, New Zealand. 
New Zealand and Australia are fortunate in that they are among the few sheep rearing countries free from scrapie, despite cases in imported sheep in the 1950s. The importance of sheep rearing in the Australasian economies, and the difficulties involved in importing sheep without risking the introduction of scrapie, has meant that there have been very few importations of new blood lines in the last 40 years, and those that have been imported have been through stringent programs designed to ensure freedom from scrapie.

While scrapie can be a cause of significant wastage in some sheep rearing situations, its major threat to Australasia is probably to the developing biopharmaceutical industries which, since the emergence of bovine spongiform encephalopathy, have benefitted from an international demand for products guaranteed to be derived from livestock free from the transmissible spongiform encephalopathies. This paper outlines one method which has been used to assess the risk of introducing scrapie as the result of importation of sheep and discusses the difficulty in ascertaining what constitutes an acceptable risk.

New Zealand, Australia scramble to squelch rumors

Times 1 July 96

Australian officials said that the country had diligent systems in place to prevent scrapie, and allegations that Australian sheep were infected were ludicrous.

The New Zealand Government said yesterday that it was seeking more detail on European scientific evidence that BSE could be passed to sheep through feed derived from infected cattle remains, but officials doubted whether the link was new. An Agriculture Ministry spokesman said: "We're not familiar with that research or the methodology used. It's always been known that scrapie and BSE are similar."

New Zealand has about 50 million sheep and exports more than 90 per cent of the lamb it processes each year, with Britain providing the largest market. It has an annual quota of 225,000 tonnes for lamb, mutton and goat exports to the EU.

NZ Veterinary Correspondent Tue, 2 July 1996

"In both scrapie epsiodes in New Zealand, one in the fifties and the other in 1974, the sheep never make it to the mainland. New Zealand has a quarantine island off the coast and when the scrapie was identified, all the sheep were eradicated before they ever set foot off the island. That's why we can say with confidence, New Zealand does not have scrapie.

In 1994, Australia had 24,732,000 cows, 132,609,000 sheep, 241,000 goats, 2,740,000 pigs, and 65,014,000 chickens, while New Zealand reported 8,550,000 cows, 50,124,000 sheep, 241,000 goats, 430,000 pigs, and 10,100,000 chickens.

Australia's Scrapie Free Status

Office of the Chief Veterinary Officer ... 25 July 1996

The sole outbreak of scrapie in Australia occurred in 1952 in a group of Suffolk sheep under quarantine following importation from the United Kingdom. Four of the group of 10 sheep were affected. The disease was eradicated by slaughter of affected and in-contact sheep and long term surveillance of the remaining animals on the property. Scrapie is a notifiable disease in Australia.

Following the incursion of scrapie in 1952, an active program of surveillance for scrapie was implemented. During the period up to 1981, over 2000 brains from throughout Australia from sheep showing neurological signs were examined for scrapie by Dr WJ Hartley at the University of Sydney (pers comm). Dr Hartley, who was familiar with scrapie pathology from work in New Zealand in the 1950s and late 1970s, found no evidence of scrapie in the brains examined.

The number of sheep brains examined by the various State and Territory authorities in recent years is shown in the table below.

State/TerritoryPeriod CoveredSheep brains
Tasmania 1992-199680
Western Australia1990-1995162
Victoria 1990-1995725
New South Wales1991-19951218
Queensland 1990-199666
South Australia1991-1995187
Total2438

The livestock industry in Australia is supported by field veterinary services provided by the State and Territory Governments. Most rural areas of Australia are also serviced by private veterinary services. These field veterinary services have access to official central or regional animal health laboratories. Pathological examinations for notifiable diseases are done, free of charge, at these laboratories. Private veterinarians also support a network of private veterinary laboratories. All cases of ovine central nervous system disorder would be subject to histopathological examination by veterinary pathologists who are fully aware of the continual vigilance required to monitor the possible introduction of ovine diseases exotic to Australia.

Australia also retains an infrastructure of stock inspectors among whose major activities have been the inspection of sheep at saleyards and on properties as part of sheep lice and footrot control campaigns, as well as for movement permits between States, and for animal welfare. These procedures have served well over many years for disease detections. Scrapie has never been detected.

Australian veterinary pathologists have a high level of expertise in the diagnosis of ovine central nervous system disorders as there are endemic degenerative ovine central nervous diseases for which scrapie is included in the differential diagnosis. These diseases include cerebral listeriosis, cerebrocortical necrosis, focal symmetrical encephalomalacia, Murrurundi disease, Yass ataxia, Coonabarabran disease and hepatic encepholopathy.

Australia has developed a detailed response strategy (AUSVETPLAN) for managing exotic animal disease incursions. When an exotic disease is suspected or occurs, various stages of response occur. Where, following the investigation phase, exotic disease remains a possibility, the response would involve a detailed field examination and, unless an alternative diagnosis is established, a laboratory investigation at the Australian Animal Health Laboratory to confirm or exclude the exotic animal disease suggested. Since 1993, such inquiries have led to six formal investigations for BSE and two for scrapie, all with confirmed negative results for these and other exotic diseases.

The importation of stockfeed of animal origin, other that stockfeed from New Zealand meeting strict heating parameters, is prohibited. Imports of live sheep and goats, and their genetic material, from countries which are not scrapie-free, are subject to a formal scrapie freedom assurance program on arrival. This program, which is designed to ensure detection of the scrapie agent if present, involves long term post-arrival quarantine, and the use of sentinels and biopsy techniques.

In 1995, there were 120.7 million sheep in Australia. The proportion of merinos in the Australian flock increased from 76% in 1984 to 90% in 1992. In 1992, the remaining 10% comprised crossbreds (7%) and other breeds (3%) ‚ mainly British breeds including small numbers of Cheviots and black-faced sheep such as Suffolks. Roughly two-thirds of Australia¼s merino ewes are within the 1‚4 year age category; about 25% are aged 4‚6 years and 12% are aged 6 years and over, representing 6% of the total merino sheep flock. Except for a very small number of sheep intensively reared, sheep production in Australia occurs completely at pasture. Feed supplements are given at periods of high nutritional demand and when there is a shortage of pasture. Supplements are mainly grains and hay, with cottonseed meal, canola meal and grain legumes being the major sources of bypass protein. Meat meal is not routinely fed to sheep. During 1995, 16.5 million adult sheep and 14.9 million lambs were slaughtered within Australia and 5.53 million were exported for slaughter overseas. The nature of the constant surveillance for neurological disorders of sheep and goats is evident in recent publications:

i) Hartley, WJ and Loomis, LN (1981) Aust Vet J 57: 399 Murrurundi disease: An encephalopathy of sheep.

ii) Harper, PAW, Duncan, DW, Plant, JW and Smeal, MG (1986) Aust Vet J 63: 18 Cerebellar abiotrophy and segmental axonopathy: two syndromes of progressive ataxia in Merino sheep.

iii) Lancaster, MJ, Gill, IJ and Hooper, PT (1987) Aust Vet J 64: 124 Progressive paresis in Angora goats.

iv) Thomas, KW, Turner, DL and Spicer EM (1987) Aust Vet J 64: 126 Thiamine, thiaminase and transketolase levels in goats with and without polioencephalomalacia.

v) Seaman, JT, Carter, GI, Carrigan, MJ and Cockram, FA (1990) Aust Vet J 67: 142 An outbreak of listerial myelitis in sheep.

vi) Harper, PAW and Morton, AG (1991) Aust Vet J 68: 152 Neuroaxonal dystrophy in Merino sheep.

vii) Harper, PAW, Plant, JW, Walker, KH and Timmins, KG (1991) Aust Vet J 68: 357 Progressive ataxia associated with degenerative thoracic myelopathy in Merino sheep.

viii) Bourke, CA, Carrigan, MJ and Dent, CHR (1993) Aust Vet J 70: 232 Chronic locomotor dysfunction, associated with a thalamic-cerebellar neuropathy, in Australian Merino sheep.

ix) Hartley, WJ et al (1994) Aust Vet J 71: 267 Cervicothoracic vertebral subluxation causing ataxia in sheep.

x) Bourke, CA (1995) Aust Vet J 72: 228 The clinical differentiation of nervous and muscular locomotor disorders of sheep in Australia.

GSS disease with the PRNP P102L mutation and valine at codon 129

Brain Res Mol Brain Res 44 (1): 147-150 (1997) 
Young K, Clark HB, Piccardo P, Dlouhy SR, Ghetti B
The most common mutation causing GSS disease is P102L in the prion protein. Previously, this mutation has only been found in coupling with methionine at residue 129. We describe a patient with GSS disease in whom the P102L mutation is in coupling with valine at residue 129. The clinical presentation in P102L-V129 differs greatly from that seen in P102-M129 patients.

Mutation in the prion protein gene at codon 232

Acta Neuropathol (Berl) 92: 441-6 (1996) 
Hoque MZ; Kitamoto T; Furukawa H; Muramoto T; Tateishi J 
We describe the clinical, neuropathological, immunohistochemical and transmission findings in three patients with CJD with a substitution from methionine to arginine at codon 232 (M232R) in the prion protein (PrP) gene. Immunohistochemical staining for PrP showed diffuse gray matter staining, including synaptic structures. However, no plaque-type PrP deposition was observed in the affected brain tissue sections. The brain homogenates from two patients were successfully transmitted to experimental animals. This mutation was not found in 100 healthy controls.

Sequence of prion protein from two species of antelope susceptible to TSE.

Arch Virol 131 (1-2): 193-199 (1993) 
Poidinger M, Kirkwood J, Almond W
The sequence of the coding regions of the PrP genes of the Arabian oryx and greater kudu have been determined and compared with the related sheep and bovine PrP gene sequences. The oryx gene sequence was found to be very closely related to that of the sheep, encoding just one amino acid difference. The greater kudu gene sequence was found to be more closely related to the bovine, encoding four amino acid differences. The possible influence that the gene sequences have on the transmission of spongiform encephalopathy to these antelope species is discussed.

Sequence variation in intron of prion protein gene, crucial for complete diagnostic strategies

Hum Mutat 7 (3): 280-281 (1996) 
Palmer MS, van Leeven RH, Mahal SP, Campbell TA, Humphreys CB, Collinge J

S82948 g at -21 is most common allele. Two coding triplets are included.
 1 tgataccatt gctatgcact cattcattat gcaggaaaca tttagtaatt tcaacataaa
61 tatgggactc tgacgttctc ctcttcattt tgcagagcag tcattatggc g

Species barriers in a model for specific prion protein dimerisation

Biochem Biophys Res Commun 232 (2): 508-512 (1997) 
Warwicker J
It has been proposed that the most highly conserved sequence segment within the prion protein (PrP) may be involved in dimer formation within both the normal (PrPC) and misfolded (PrPSe) forms. This hypothesis is now examined in the context of amino acids known to be involved in species barriers or in disease modifying polymorphisms, and the structure of a mouse PrP fragment. These locations can be plausibly explained on the basis of the specific dimer model, so that a potential role for a conserved dimerisation element in prion disease progression cannot be excluded.

[If the dimer interface has been identified, this might be a site of action for specific therapeutic agents. -- webmaster]

Peptide and Protein Ligands for the Caveolin-scaffolding Domain

JBC Volume 272, Number 10, Issue of March 7, 1997 pp. 6525-6533
Jacques Couet, Shengwen Li, Takashi Okamoto, Tsuneya Ikezu and Michael Lisanti 
Caveolin, a 21-24-kDa integral membrane protein, is a principal component of caveolae membranes. We have suggested that caveolin functions as a scaffolding protein to organize and concentrate certain caveolin-interacting proteins within caveolae membranes. In this regard, caveolin co-purifies with a variety of lipid-modified signaling molecules, including G-proteins, Src-like kinases, Ha-Ras, and eNOS.

It has been shown that a 20-amino acid membrane proximal region of the cytosolic amino-terminal domain of caveolin is sufficient to mediate these interactions. For example, this domain interacts with G-protein İsubunits and Src-like kinases and can functionally suppress their activity. This caveolin derived protein domain has been termed the caveolin-scaffolding domain. However, it remains unknown how the caveolin-scaffolding domain recognizes these molecules.

Here, we have used the caveolin-scaffolding domain as a receptor to select random peptide ligands from phage display libraries. These caveolin-selected peptide ligands are rich in aromatic amino acids and have a characteristic spacing in many cases. A known caveolin-interacting protein, Gi2, was used as a ligand to further investigate the nature of this interaction. Gi2 and other G-protein İsubunits contain a single region that generally resembles the sequences derived from phage display. We show that this short peptide sequence derived from Gi2 interacts directly with the caveolin-scaffolding domain and competitively inhibits the interaction of the caveolin-scaffolding domain with the appropriate region of Gi2. This interaction is strictly dependent on the presence of aromatic residues within the peptide ligand, as replacement of these residues with alanine or glycine prevents their interaction with the caveolin-scaffolding domain. In addition, we have used this interaction to define which residues within the caveolin-scaffolding domain are critical for recognizing these peptide and protein ligands. Also, we find that the scaffolding domains of caveolins 1İand 3İboth recognize the same peptide ligands, whereas the corresponding domain within caveolin-2 fails to recognize these ligands under the same conditions. These results serve to further demonstrate the specificity of this interaction. The implications of our current findings are discussed regarding other caveolin- and caveolae-associated proteins.

[Prion protein has periodic aromatics and is associated with caveolae-like domain -- webmaster}:

PQGGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQ

MANLGCWMLVLFVATWSDLGLCKKRPKPGGWNTGGSRYPGQGSP GGNRYPPQGGGGWGQPHGGGWGQPHGGGWGQPHGGGWGQGGGTHSQWNKPSKPKTNMK HMAGAAAAGAVVGGLGGYMLGSAMSRPIIHFGSDYEDRYYRENMHRYPNQVYYRPMDE YSNQNNFVHDCVNITIKQHTVTTTTKGENFTETDVKMMERVVEQMCITQYERESQAYY QRGSSMVLFSSPPVILLISFLIFLIVG

COOH-terminal sequence of the cellular prion protein directs subcellular trafficking and controls conversion into the scrapie isoform

Proc Natl Acad Sci U S A 94 (6): 2333-2338 (1997) 
Kaneko K, Vey M, Scott M, Pilkuhn S, Cohen FE, Prusiner SB
Efficient formation of scrapie isoform of prion protein (PrP(Sc)) requires targeting PrP(Sc) by glycophosphatidyl inositol (GPI) anchors to caveolae-like domains (CLDs). Redirecting the cellular isoform of prion protein (PrP(C)) to clathrin-coated pits by creating chimeric PrP molecules with four different COOH-terminal transmembrane domains prevented the formation of PrP(Sc). To determine if these COOH-terminal transmembrane segments prevented PrP(C) from refolding into PrP(Sc) by altering the structure of the polypeptide, we fused the 28-aa COOH termini from the Qa protein. Two COOH-terminal Qa segments differing by a single residue direct the transmembrane protein to clathrin-coated pits or the GPI form to CLDs; PrP(Sc) was formed from GPI-anchored PrP(C) but not from transmembrane PrP(C). Our findings argue that PrP(Sc) formation is restricted to a specific subcellular compartment and as such, it is likely to involve auxiliary macromolecules found within CLDs.

Prion protein with amino-proximal deletions restore susceptibility of PrP knockout mice to scrapie.

EMBO J 15 (6): 1255-1264 (1996) 
Fischer M, Rulicke T, Raeber A, Sailer A, Moser M, Oesch B, Brandner S, Aguzzi A, Weissmann C
The 'protein only' hypothesis postulates that the prion, the agent causing transmissible spongiform encephalopathies, is PrP(Sc), an isoform of the host protein PrP(C). Protease treatment of prion preparations cleaves off approximately 60 N-terminal residues of PrP(Sc) but does not abrogate infectivity. Disruption of the PrP gene in the mouse abolishes susceptibility to scrapie and prion replication. We have introduced into PrP knockout mice transgenes encoding wild-type PrP or PrP lacking 26 or 49 amino-proximal amino acids which are protease susceptible in PrP(Sc). Inoculation with prions led to fatal disease, prion propagation and accumulation of PrP(Sc) in mice expressing both wild-type and truncated PrPs. Within the framework of the 'protein only' hypothesis, this means that the amino-proximal segment of PrP(C) is not required either for its susceptibility to conversion into the pathogenic, infectious form of PrP or for the generation of PrP(Sc).

Metal-dependent alpha-helix formation promoted by the glycine-rich octapeptide region of prion protein.

FEBS Lett 396 (2-3): 248-252 (1996) 
Miura T, Hori-i A, Takeuchi H
Prion diseases share a common feature in that the normal cellular prion protein (PrP(C)) converts to a protease-resistant isoform PrP(Sc). The alpha-helix-rich C-terminal half of PrP(C) is partly converted into beta-sheet in PrP(Sc). We have examined by Raman spectroscopy the structure of an octapeptide PHGGGWGQ that appears in the N-terminal region of PrP(C) and a longer peptide containing the octapeptide region. The peptides do not assume any regular structure without divalent metal ions, whereas Cu(II) binding to the HGGG segment induces formation of alpha-helical structure on the C-terminal side of the peptide chain. The N-terminal octapeptide of prion protein may be a novel structural motif that acts as a promoter of alpha-helix formation.

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