ER and prion topology: the plot thickens
Dealler to lead blood monoclonal effort
Serious caveolin
Microdomains of GPI-anchored proteins
Diagnostics news
Mule deer on hold: AF009180, U97331, AF009181 undergoing revision
Obtaining obscure symposium proceedings
Solvent extraction as an adjunct to rendering
Mid-year nvCJD statistics
Chlamydia pneumoniae in Alzheimer glial cells
Mol Cell 1998 Jul;2(1):85-91 online but costs $95 even with a subscription already to Cell Hegde RS, Voigt S, Lingappa VRIn mammalian cells, the Sec61 complex and translocating chain-associated membrane protein (TRAM) are necessary and sufficient to direct the biogenesis, in the appropriate topology, of all secretory and membrane proteins examined thus far. We demonstrate here that the proper translocation of the prion protein (PrP), a substrate that can be synthesized in more than one topologic form, requires additional factors. In the absence of these additional factors, PrP is synthesized exclusively in the transmembrane topology (termed the CtmPrP form) associated with the development of neurodegenerative disease. Thus, translocation accessory factors, acting on some but not other substrates, can function as molecular switches to redirect nascent proteins toward divergent topologic fates with different functional consequences.
Comment (webmaster):
This looks to be a signficant development towards understanding natural and transgenic disease alleles. It does not sound from the abstract like they have actually identified or characterized the 'additional factors' necessary to shift prion topology away from the default (neurodegenerative) one -- one hopes this is not another shaggy dog story like 'protein x.' One wonders just what percentage of secretory and membrane proteins have had their requirements determined; the implication here is that others must use the same factors as prion protein, otherwise they would have shown up by now as CJD mutations at some other locus.
See also new ER article in 18 Aug 98 PNAS:
Newly synthesized thyroglobulin, the major secretory glycoprotein of the thyroid gland, folds and homodimerizes in the endoplasmic reticulum (ER) before its export to the site of iodination, where it serves as the precursor for thyroid hormone synthesis....
For trafficking through the eukaryotic secretory pathway, exportable proteins must achieve a certain level of conformational maturity to be competent for intracellular transport as well as for their ultimate biological function. An increasing number of genetically transmitted metabolic diseases involving intracellular retention of exportable proteins have been recognized, caused by mutations that lead to tertiary and quaternary structural defects (1).
In a family of disorders of protein trafficking known as endoplasmic reticulum storage diseases (ERSDs; ref. 2), mutations as small as a single amino acid change can lead to failure of protein export from the ER (an essential step in overall protein export), such as in cystic fibrosis [mutant CFTR (3)], juvenile pulmonary emphysema [mutant -L-antitrypsin (4)], osteogenesis imperfecta [mutant type I procollagen (5)], juvenile diabetes insipidus [mutant vasopressin precursor (6)], and hypercholesterolemia [mutant low density lipoprotein receptor (7)]. Because export of the mutant protein from the ER is prevented, it never reaches the destination at which its physiologic function normally takes place.
Tue, Aug 18, 1998 By John von Radowitz, Medical Correspondent, PA NewsThe Government is backing the development of a new CJD blood-screening test devised by one of its fiercest former critics, it was disclosed today. Up to 500,000 has been pledged by the Department of Health to set up a research facility within the Public Health Laboratory Service in Leeds. Microbiologist Stephen Dealler (correct) is at the heart of the project to produce a simple test which will show whether donated blood carries a risk of new variant CJD -- the brain disease linked to infected beef.
Until recently Dr Dealler, who has warned of possible CJD epidemics involving hundreds of thousands of victims, was a thorn in the side of the Government. But now he has rejoined the establishment and is employed as an adviser to the Department of Health. He has joined forces with the biotechnology company Proteus International to work on the screening test.
Preliminary results from the research, beginning in October, are expected within six months. Dr Dealler admitted today: "It feels very odd to be on the inside again." The project highlights the misgivings of officials and scientists over the use of leucodepletion -- removal of white blood cells -- to ensure blood supplies are safe.
The process, recently introduced by the Government in the wake of fears over blood safety, is not only expensive -- possibly costing tens of millions of pounds -- but is not 100% effective. It is widely recognised that a reliable blood test would be better if one was available.
The new test would use antibodies to identify the modified "rogue" form of prion protein that is believed to cause CJD, BSE and other related diseases such as scrapie in sheep. Proteus has already employed the same technology to develop a BSE diagnostic test now being used for the slaughterhouse monitoring of beef by one supermarket chain in Ireland. The test has yet to be validated by trials now under way in Europe.
Dr Arthur Rushton, development director at Proteus, said the technology was offered to the Ministry of Agriculture several years ago but rejected. The company was told that the Ministry had its own equivalent antibody technology, although nothing appears to have come from it. Dr Rushton said: "I think there has been a sea change in the attitude of the Government, and quite rightly."
About 2.5 million blood donations are made each year in the UK. Dr Dealler said one in 250 blood donors -- one in 125 transfusions -- may be infected with new variant CJD. Detecting perhaps 1,000 molecules of infectious prion protein per millilitre of blood would require a highly sensitive test. Achieving this level of sensitivity had never been done before.
Dr Dealler said funding was offered by the Department of Health after the project was approved by the Spongiform Encephalopathy Advisory Committee, the body that advises the Government on BSE and CJD. This was an indication that ministers had faith in the research.
"The Department of Health virtually needs things nailed on its forehead before it will approve money for anything" said Dr Dealler. An initial 390,000 will be given, with a further 110,000 after two years.
Comment ">Charles Arthur, science reporter:
"A couple of things perhaps to add to the wire stories (PA News is the prime source of stories for most national papers in the UK) and my own.
1) It's not going to be monoclonal - Proteus took a lot of care to explain that they are developing polyclonal antibodies, because they reckon monoclonal is not specific enough.
2) The test, if it works, will not differentiate between the various forms of CJD.
3) Dealler and Proteus would not say what method they're using; it's not the Collinge-type glocosylation, nor Western blot, nor does it use protease. The suggestion seems to be that it'll identify the misfolding, but that's just my interpolation of what they said."
PNAS Vol. 95, Issue 17, 10257-10262, August 18, 1998 Ferruccio Galbiati et al.Caveolae are cholesterol/sphingolipid-rich microdomains of the plasma membrane that have been implicated in signal transduction and vesicular trafficking. Caveolins are a family of caveolae-associated integral membrane proteins. Caveolin-1 and -2 show the widest range of expression, whereas caveolin-3 expression is restricted to muscle cell types.
It has been previously reported that little or no caveolin mRNA species are detectable in the brain by Northern blot analyses or in neuroblastoma cell lines. However, it remains unknown whether caveolins are expressed within neuronal cells. Here we demonstrate the expression of caveolin-1 and -2 in differentiating PC12 cells and dorsal root ganglion (DRG) neurons by using mono-specific antibody probes. ... These findings demonstrate that neuronal cells express caveolins.
Caveolae are 50- to 100-nm vesicular organelles that are located at or near the plasma membrane. It has been proposed that caveolae play a pivotal role in a number of essential cellular functions, including signal transduction, lipid metabolism, cellular growth control, and apoptotic cell death.
The principal protein components of caveolae are the caveolin family of proteins, termed caveolin-1, -2, and -3. Caveolin-2 shows the same tissue distribution as caveolin-1, colocalizes with caveolin-1, and forms a hetero-oligomeric complex with caveolin-1 in vivo . In contrast, caveolin-3 is a muscle-specific caveolin-related protein that is primarily expressed in striated muscle cell types (cardiac and skeletal) (5-7).
It has been proposed that caveolin family members function as scaffolding proteins (8) to organize and concentrate specific lipids [cholesterol and glyco-sphingolipids ] and lipid-modified signaling molecules within caveolae membranes. Caveolins interact directly with a number of caveolae-associated signaling molecules, such as H-Ras, hetero-trimeric G-proteins, epidermal growth factor receptor, protein kinase C, Src-family tyrosine kinases, and nitric oxide synthase isoforms). In many of these cases, it has been documented that caveolin-binding can effectively inhibit the enzymatic activity of these signaling molecules in vitro.
...
Based on these and other observations, we and others have proposed the "caveolae signaling hypothesis," which states that caveolar localization of certain inactive signaling molecules could provide a compartmental basis for their regulated activation and explain cross-talk between different signaling pathways Thus, we have suggested that caveolin may function as a negative regulator of many different classes of signaling molecules through the recognition of specific caveolin-binding motifs.
Are these findings relevant to neuronally based signal transduction? Caveolin mRNAs and proteins have been shown to be virtually undetectable in brain tissue by Northern and Western blot analyses by several independent investigators, which initially suggested that neurons do not express caveolin proteins. In addition, it has been shown that caveolin-1 is not expressed within neuroblastoma cell lines (29). However, this could be secondary to their transformed phenotype, as both caveolin-1 and caveolae are down-regulated in response to cell transformation.
Here we demonstrate the expression of caveolin-1 and -2 in differentiating PC12 cells and dorsal root ganglion (DRG) neurons by using mono-specific antibody probes. In support of our current findings, it has been previously shown that caveolae-like domains can be purified from neuronal cell plasma membranes and that they contain receptor tyrosine kinases [including insulin and the neurotrophin receptors, Trk-B and p75 nerve growth factor (NGF) receptors], as well as other signaling molecules, and the scrapie prion protein . However, these investigators were unable to detect the presence of caveolin proteins (32, 33). Also, it has been shown that the p75 NGF receptor is associated with caveolae membranes when heterologously expressed in NIH 3T3 cells and is observed to coimmunoprecipitate with caveolin-1.
...Thus, induction of caveolins 1 and 2 during NGF-induced differentiation of PC12 cells is consistent with the idea that caveolins are generally induced during differentiation processes and that caveolin expression is highest in terminally differentiated nondividing cells.
32. Wu, C., Butz, S., Ying, Y. & Anderson, R. G. W. (1997) J. Biol. Chem. 272, 3554-3559. 33. Vey, M., Pilkuhn, S., Holger, W., Nixon, R., DeArmond, S. J., Smart, E. J., Anderson, R. G. W., Taraboulos, A. & Prusiner, S. B. (1996) Proc. Natl. Acad. Sci. USA 93, 14945-14949
McConville JP, Craig JJ BMJ 1998 Aug 15;317(7156):472 free fulltextBack-and-forth by critics and authors on S100 test; Collinge writes on tonsil test for nvCJD.
Vet Rec 1998 Jul 11;143(2):50-51 Robey WG, Jackson R, Walters RL, Brackett JM, Harrington CA, Killian WR Abbott Diagnostics Division, Department 9RB, Abbott Laboratories, North Chicago, IL 60064, USA.No abstract, first item from Abbott Labs entry into field. Project manager "Katherine Wortley"
April, 1998 issue of Biopharm Intergen Company (Purchase, NY, USA)"Intergen has begun to sell various forms of bovine products that have been 'tested' for the presence of BSE via Protease K resistence PrPsc Western Blot analyis. They published the validation scheme in the April, 1998 issue of Biopharm. That along with their bovine source documentation, they claim, will minimize potential for BSE contamination in their bovine products."
Results were controlled by comparison with Alzheimer-type changes in sections from the same cortical areas in 110 sex- and age-matched non-demented control patients. For comparison, the control patients were also classified according to the CERAD neuropathology criteria as if they had been demented. Alzheimer-type tissue changes as in definite and probable CERAD AD occur in 10.9% of the CJD patients and 19.1% of control patients (P=0.11). The median age of CJD and control patients with CERAD AD is 72 and 68 years, respectively, which differs significantly from the median ages of 64 and 63 years, respectively, in the non-AD/CJD and non-AD control patients.
Since CERAD criteria include "presence of other neuropathological lesions likely to cause dementia", an AD diagnosis in CJD patients (all of whom are demented) is solely based on densities of neuritic plaques. Similar Alzheimer-type changes in even higher frequency, however, are also present in elderly non-demented controls.
Thus, the coexistence of Alzheimer-type pathology in CJD most likely represents an age-related change. Deposits of prion protein (PrP) frequently accumulate at the periphery of beta/A4 plaques. The presence of beta/A4 amyloid in the brain may influence PrP morphogenesis.
15 Aug 98 webmaster correspondenceSome mix-ups got into the mule deer sequences posted to GenBank this week and sent out on prion sequence alerting services. These will be corrected shortly; don't use as is.
13 Aug 1998 webmasterI have just recently discovered that amazon.com carries quite obscure TSE symposium proceedings, and even better, has the table of contents for them online. These sometimes have excellent information in them that will never surface in the regular indexed literature. However, this source does not carry Elsevier proceedings or special journal supplements.
Table of Contents
Introduction -- Guide to the Talks
Douglas R. O. Morrison
Polymorphic Genotype Matching in Acquired Creutzfeldt-Jakob Disease: An
Analysis of Donor/Recipient Case Pairs
Paul Brown
Human Prion Protein Gene Mutation at Codon 183 Associated with an Atypical
Form of Prion Disease
Ricardo Nitrini
Fatal Familial Insomnia: A Human Model ofPrion Disease
Elio Lugaresi
Mechanisms of Phenotypic Heterogeneity inHuman Prion Diseases
Pierluigi Gambetti
Transgenic Mice with Neuron-Specific Expression of a Hamster Prion Protein
Minigene Are Susceptible to Hamster Scrapie Agent
Bruce Chesebro
The Use of Transgenic Mice in the Investigation of Transmissible Spongiform
Encephalopathies
Charles Weissmann
Large-Scale Sequencing of Human, Mouse, and Sheep Prion Protein Genes
Inyoul Lee
Electron Microscopy in Prion Research: Tubulovesicular Structures Are Not Composed
of Prion Protein (PrP) but They May BeIntimately Associated with PrP Amyloid Fibrils
P.P. Liberski
Familial Prion Diseases Modeled in Cell Culture
David A. Harris Sylvain Lehmann Nathalie Daude
Yeast Approach to Protein "Prionization": SUP35-[PSI] System
S. G. Inge-Vechtomov
Prions of Yeast: Genetic Evidence that the Non-Mendelian Elements, [PSI]
and [URE3] Are Altered Self-Replicating Forms of Sup35p andUre2p, Respectively
Reed B. Wickner
Early Clinical Detection of Brain Diseases in Animals
B.F. Semenov
Prion Biology and Diseases -- Fatal Conformations of Proteins during a Journey from
Heresy to Orthodoxy
Stanley B. Prusiner
New Variant Creutzfeldt-Jakob Disease
Robert Will
The Molecular Basis of Cellular Dysfunction in Prion Diseases
Randal R. Nixon
Presenilin Proteins and the Pathogenesis ofEarly-Onset Familial Alzheimer's Disease:
Beta-Amyloid Production and Parallels toPrion Diseases
David Westaway
Polyene Antibiotics in Experimental Transmissible Subacute SpongiformEncephalopathies
Vincent Beringue
Scrapie Pathogenesis in Brain Grafts Adriano Aguzzi
Sebastian Brandner
Structural Properties of Recombinant Human Prion Protein
Graham Jackson
Autonomous Folding and Three-DimensionalStructure of the Carboxy-Terminal Domain of
the Mouse Prion Protein, PrP (121-231
Rudi Glockshuber
Protease-Resistant Prion Protein Formation
Byron Caughey Gregory J. Raymond
Biophysical Studies on Structure StructuralTransitions and
Infectivity of the Prion Protein
Detlev Riesner Klaus Kellings
Amyloidogenesis in Transmissible Spongiform Encephalopathies
Franco Cardone Maurizio Pocchiari
Neuronal Degeneration and Cell Death in Prion Disease
Hans A. Kretzschmar
Clinical, Pathological, and Molecular Characterization of GSS in the Indiana Kindred (PRNP F198S) B. Ghetti
Studies on the Pathogenesis of Scrapie and the Purification of Scrapie Agent in the
Hamster Model
Heino Diringer
PrP Peptides as a Tool to Investigate the Pathogenesis of Prion ProteinAmyloidoses
Fabrizio Tagliavini
Properties of the Prion Proteins in CJD Patients Heterozygous for the E200K Mutation
Ruth Gabizon
Transmission Studies of Fatal FamilialInsomnia
Katie Sidle
Molecular, Genetic, and Transgenetic Studies of Human Prion Disease
J. Collinge
Molecular Biology of Prion Propagation
Stanley B. Prusiner
Ultrastructural and Immunocytochemical Studies on Prion Pathogenesis
Lajos Laszlo
Overview of the BSE Epidemic
John Wilesmith
Assessing Risks of BSE Transmission to Humans
John Collinge
Human Activities Are Causing Selection of Pathogenic Agents
Luc Montagnier
Pathogenic Similarity of Slow Infections, Induced by Prions and Virions
V. A. Zouev
Protein Floding and Misfolding
A. R. Clarke
CJD Risk Factors: Analysis of 104 Patients
Eva Mitrova
Names and Addresses of Participants
2. Prion Diseases
by John Collinge (Editor), Mark S. Palmer (Editor)
Price: $57.50 Special Order Hardcover - (March 1997)
1. Prion diseases: an introduction By Mark S. Palmer, John Collinge
2. Human prion diseases By John Collinge, Mark S. Palmer
3. Pathology of prion diseases By James W. Ironside, Jeanne E.Bell
4. Animal prion diseases By Ray Bradley
5. Cell biology and transgenic models of prion diseases By Stanley B. Pruisner
6. Neurophysiology of prion disease By John G. R. Jefferys
7. Structural properties of the prion protein By Corinne Smith, Anthony R. Clarke
Appendix. Alignment of amino acids of the prion protein from eleven species
3. Bovine Spongiform Encephalopathy: The Bse Dilemma
(Proceedings in the Serono Symposia)
by Clarence J., Jr Gibbs (Editor)
Price: $140.00 Special Order Hardcover - (October 1996)
1. The Potential Risk to Humans of Amyloids in
Animals By D. Carleton Gajdusek
2. Bovine Spongiform Encephalopathy Distribution
and Update on Some Transmission and Decontamination Studies
By Ray Bradley
3. Preliminary Observations on the Pathogenesis
of Experimental Bovine Spongiform Encephalopathy
By Gerald A. H. Wells, Michael Dawson,
Stephen A. C. Hawkins, Anthony R. Austin, Robert B. Green, Ian
Dexter, Mark W. Horigan, Marion M. Simmons
4. Recent Observations on the Epidemiology of
Bovine Spongiform Encephalopathy By John W. Wilesmith
5. Scrapie: Studies on Vertical and Horizontal
Transmission By James L. Hourrigan, Albert L. Klingsporn
6. Transmission of Sheep and Goat Strains of
Scrapie from Experimentally Infected Cattle to Hamsters and Mice
By Clarence J. Gibbs, Jr., Jiri Safar,
Michael P. Sulima, Alfred E. Bacote, R. Andres San Martin
7. Experimental Transmission of Scrapie to Cattle
By Randall C. Cutlip, Janice M. Miller,
Richard E. Race, Allen L. Jenny, Howard D. Lehmkuhl, Mark M. Robinson
8. An Assessment of Transmissible Mink
Encephalopathy as an Indicator of Bovine Scrapie in U.S. Cattle
By Mark M. Robinson
9. Experimental Infections of Cattle and Mink
with the Agents of Transmissible Mink Encephalopathy, Scrapie, and
Bovine Spongiform EncephalopathBy Mark M. Robinson
10. BSE-Free Status: What Does It Mean?
By Richard F. Marsh
11. Differing Neurohistologic Images of Scrapie,
Transmissible Mink Encephalopathy, and Chronic Wasting Disease
of Mule Deer and Elk By William J. Hadlow
12. Analysis of Risk Factors and Active
Surveillance for BSE in Argentina By A. A. Schudel, B. J. Carrillo, E. L.
Weber, J. Blanco Viera, E. J. Gimeno, C. Van Gelderen, E. Ulloa, A.
Nader, B. G. Cane, R. H. Kimberlin
13. Speculations on the Origin of BSE and the
Epidemiology of CJD By Richard H. Kimberlin
14. Structure and Biologic Characteristics of
Prion Protein (Scrapie Amyloid): Implications for the Safety of
Naturally Derived Biologics By Jiri Safar
15. Prion Strains and Neuromuscular Disease in
PrP Transgenic Mice By George A. Carlson
16. Deciphering Prion Diseases with Transgenic Mice
By Glenn C. Telling, Michael Scott, Stanley B. Prusiner
17. Posttranslational Modifications and
Conformational Changes of PrP{-63}superscript Sc and Their Relationship
to Infectivity
By Richard Rubenstein
18. Amyloidosis: The Key to the Epidemiology and
Pathogenesis of Transmissible Spongiform Encephalopathies
By Heino Diringer, Michael Beekes,
Elizabeth Baldauf, Sven Cassens, Muhsin Ozel
19. Effect of Amphotericin B on Different
Experimental Strains of Spongiform Encephalopathy Agents
By Maurizio Pocchiari, Loredana Ingrosso,
20. Genetics of Human Spongiform
Encephalopathies: Current Status
By Lev G. Goldfarb
21. PrP Allelic Variants Associated with Natural
Scrapie
By Peter B. G. M. Belt, Alex Bossers,
Bram E. C. Schreuder, Mari A. Smits
22. The Formation of Scrapie-Associated Prion
Protein In Vitro
By Byron Caughey, Suzette Priola, David
Chesebro, Peter Lansbury
23. Proteinase K-Resistant Prion Protein
Detection in Animal Tissues and In Vitro
By Richard E. Race, Darwin Ernst
24. Elimination of Scrapie-Agent Infectivity in
Naturally Derived Biologics
By Alessandro Di Martino
25. Cellular and Scrapie Prion Protein
Immunolocalization and In Vitro Amyloid Formation
By Mauro Ceroni, Jiri Safar, Pedro
Piccardo, Paul P. Liberski, Paola Pergami, Clarence J. Gibbs, Jr.
26. Real and Theoretical Threats to Human Health
Posed by the Epidemic of Bovine Spongiform Encephalopathy
By Richard T. Johnson
27. Incidence of Creutzfeldt-Jakob Disease in
the European Community
By R. G. Will
28. Problems in the Evaluation of Theoretical
Risks for Humans to Become Infected with BSE-Contaminated
Bovine-Derived Pharmaceutical Products
By Maurizio Pocchiari
29. Evaluation of BSE Risk Factors Among
European Countries
By Beat Hornlimann, Dagmar Heim,
Christian Griot
4. Transmissible Subacute Spongiform Encephalopathies: Prion Diseases
Edited by L. Court and B. Dodet
These are the proceedings of the IIIrd International Symposium, which was
held in Paris 18-20 March 1996. It includes opening lectures by Carleton Gajdusek and Stanley Prusiner, and texts from the most prominent scientists in the field, and covers the epidemiology of TSE in animals and humans, genetic susceptibility, neuropathology, pathogenesis, experimental transmission, transgenic and in vitro models, molecular biology. New data on the conformation of the normal and the pathological protein, non proteic
models, transmission risks and control are also presented.
1996 Paperback
ISBN: 2-906077-91-7
508 pages
Price: US$ 139.00
Vet Rec 1998 Jul 4;143(1):6-9 Taylor DM, Fernie K, McConnell I, Ferguson CE, Steele PJSolvent extraction as an adjunct to rendering: the effect on BSE and scrapie agents of hot solvents followed by dry heat and steam.
The study was designed to determine the effect on bovine spongiform encephalopathy (BSE) and scrapie agents of the solvent extraction processes used in the past by British renderers. The raw material was mouse spleen infected with either the 22A strain of scrapie agent or the 301V strain of BSE agent. Samples were exposed to hexane, heptane, petroleum spirit or perchlorethylene at the relevant temperatures for the appropriate times. Control samples were exposed to the same range of temperatures for the same range of times in saline. Other samples were exposed to the hot solvents, followed by treatment with dry heat at 100 degrees C for 30 minutes and steam at 100 degrees C for 30 minutes. Further samples were exposed only to the dry heat and steam cycles.
No single complete process was significantly more effective than any of the others, and they all produced only slight inactivation, less than one log on average for both strains of agent. The average degree of inactivation produced by exposure to hot saline was generally comparable to that produced by exposure to the hot solvents. This was also true for the samples exposed only to dry heat and steam compared with those exposed to hot solvent before treatment with dry heat and steam, and suggests that the slight inactivation was caused by the heat rather than by the solvents.
It is concluded that the solvent extraction processes used by renderers in Britain had little capacity to inactivate BSE and scrapie agents.
UK Dept of Health, next release Sept 727 cases of nvCJD plus 1 in France:
| - | Referrals | Sporadic | Iatrogenic | Familial | GSS | nvCJD | Total |
| 1995 | 86 | 34 | 4 | 2 | 3 | 3 | 46 |
| 1996 | 134 | 41 | 4 | 2 | 4 | 10 | 61 |
| 1997 | 157 | 55 | 6 | 3 | 0 | 10 | 74 |
| 1998* | 116 | 26 | 0 | 2 | 0 | 8 | 36 |
Comment (webmaster):
One thing that is apparent from the totals column, which averages 41 over the last 14 years, is that intense surveillance in 1996-97 gave a surge of detection of sporadic cases and possibly nvCJD, leaving a bit of a totals deficit for this year. nvCJD thus remains flat with no explanation for the victim set and no clues except met/met and relative youth.
One fast and informative thing to do would be sequencing the upstream and downstream parts of the prion gene. This might take the Sanger Centre an hour to do all of them. The idea would be that the victim class might have regulatory variations leading to higher prion protein expression levels.
Most irresponsibly, prion researchers have failed to establish a central DNA bank for the thousands of dementia cases and controls with the ORF sequenced. Thus, it is difficult to re-study promoter regions in, say, sporadic CJD or deletions with dementia. Exon 1 is quite short and trivial to sequence. Another common blunder is not to sequence the intron/exon boundary that lies only a dozen bases or so upstream of the ATG start codon. Few researchers post their mutant alleles to GenBank; for deletions, only 2 of 19 studies did this, meaning only 2 of the 5 classes of deletions are available for resources such as SwissProt and OMIM.
By DAVID MORGAN, Reuters August 11, 1998 [Aug 98 issue of Medical Microbiology and Immunology]Research into the cause of Alzheimer's disease has for the first time identified a possible link with bacterial infection, health experts said Tuesday.The bacteria Chlamydia pneumoniae, a known cause of common respiratory ailments such as sinusitis and bronchitis, was found in the brains of 17 out of 19 Alzheimer victims examined by a team of university biologists in Philadelphia, Detroit and Baltimore. The same organism showed up in the brain of only one of 19 patients who had died of other diseases.
Chlamydia infection was most pronounced in regions of the brain that had sustained damage typical of Alzheimer's disease, a form of dementia that strikes one in 10 elderly people and leads to forgetfulness, disorientation and confusion. There is no known cure.Up to now, suspected causes of Alzheimer's disease have ranged from environmental toxins and genetic predisposition to abnormal protein levels in the brain.British researchers caused a stir early in 1997 when they presented evidence of a link between the disorder and the virus which causes cold sores.
"People have been looking at viruses. They haven't been looking at bacteria," said Zaven Khachaturian, director of the Alzheimer Association's Ronald and Nancy Reagan Institute. "This study needs to be looked at with great care, and replicated."
The three-year study by researchers from Allegheny University of the Health Sciences, Wayne State University and Johns Hopkins University could shed light on the cause of inflammation which has been found in the brains of victims of Alzheimer's.
"What we have here is an organism that can get inside (brain) cells and can potentially trigger them to cause inflammation," said Brian Balin, an Allegheny University neurobiologist who helped lead the research.Describing the Chlamydia bacteria as a possible new risk factor for Alzheimer's, researchers said they hoped their efforts would lead to new treatments for victims.The study's results appeared in this month's issue of the journal, Medical Microbiology and Immunology.
Alzheimer's disease, a leading cause of death in industrialized countries, is expected to afflict nearly five million people in the United States alone by 2000. Experts say the number of American sufferers could jump to 14.5 million by the middle of the next century. With the cost of care estimated at $174,000 over the average lifetime of an Alzheimer sufferer, the disease could pose a financial nightmare for the federal government's ailing Medicare insurance program in coming decades unless a cure can be found.
People often carry the Chlamydia pneumoniae bacteria from childhood without ill-effects. The bacteria are believed to infect as much as 70 percent of populations in some parts of the world, including the U.S. Pacific Northwest and Scandanavia.Alan Hudson, microbiologist at Wayne State University, said researchers came to suspect Chlamydia after reports of a link between Alzheimer's and atherosclerosis, in which the bacteria was believed to play a role. Atherosclerosis, a condition which leads to cardiovascular disease and strokes, is marked by inflammation and a buildup of fatty substances in the blood vessels.
Research found Chlamydia in the brain's glial cells, which support nerve cells and function like an immune system in the brain. When infected, they cause inflammation.Balin said a main goal of the research team now was to figure out how Chlamydia bacteria slipped >from the respiratory system to the brain.
Nature 394, 802 - 805 (1998) Tim Friedrichson and Teymuras V. KurzchaliaThere is some discussion as to whether glycosyl-phosphatidylinositol(GPI)-anchored proteins occur in microdomains in the cell membrane. These putative microdomains have been implicated in processes such as sorting in polarized cells and signal transduction. Complexes enriched in GPI-anchored proteins, cholesterol and glycosphingolipids have been isolated from cell membranes by using non-ionic detergents: these complexes were thought to represent a clustered arrangement of GPI-anchored proteins. However, results obtained when clustering of GPI-anchored proteins induced by antibodies or by detergents was prevented support the idea of a dispersed surface distribution of GPI-anchored proteins at steady state.
Here we use chemical crosslinking to show that membrane microdomains of a GPI-anchored protein exist at the surface in living cells. This clustering is specific for the GPI-anchored form, as two transmembrane forms bearing the same ectodomain do not form oligomers. Depletion of membrane cholesterol causes the clustering of GPI-anchored proteins to break up, whereas treatment of cells with detergent substantially increases the size of the complexes. We find that in living cells these GPI-anchored proteins reside in microdomains consisting of at least 15 molecules, which are much smaller than those seen after detergent extraction.