Research - Institute of Biochemistry - Membrane and Stress Biology Unit - Laboratory of Conformational Diseases

Ervin WELKER
scientific adviser

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Elfrieda AYAYDIN-FODOR research associate
Tamás SZLANKA research associate
Eszter Erika VIRÁGH research associate
Andrea PAPDINÉ MOROVICZ scientific administrator
Divya Teja DONDAPATI Ph.D. student
Sudheer Babu SANGEETHAM Ph.D. student
Nóra WEINHARDT Ph.D. student
Mária ÁDÁMNÉ MESZLÉNYI laboratory assistant

LABORATORY OF CONFORMATIONAL DISEASES

Transmissible spongiform encephalopathies (TSEs) are deadly neuro-degenerative disorders among humans and mammals. The infectiousness is the most alarming feature of these diseases. It can be transmitted to humans from animals through the food chain and from humans by blood or organ donation or by infected medical devices. There is no cure or sufficient sensitive early detection for TSEs. The infectious agent, called prion, is believed to be a normal cell protein, the prion protein, with an unknown conformation that is different from its normal conformation. Our aim is to understand the conformational transition of the prion protein to disease-associated forms at the molecular level by combining the results of biochemical and biophysical measurements, cell-free conversion reactions, and experiments in cell and animal model systems.


The group carries out its research activity in both the Biochemistry and the Enzimology Institutes.

An ever-increasing number of diseases have been shown to originate from protein misfolding. Among them, there are more than 20 diseases [including Alzheimer's, Parkinson's, Huntington's and transmissible spongiform encephalopathies (TSEs)] that are characterized by amyloidal protein deposits and thought to share common structural features and mechanism of action. (The amyloidal deposits usually consist of fibres that contain misfolded proteins with a β-sheet conformation.) TSEs, which we chose as a model for the study of these conformational diseases, have drawn special attention due to the outbreak of a new variant of Creutzfeldt-Jakob disease (nvCJD) in the United Kingdom that seemed to be associated with eating beef from TSE-infected cattle.

TSE in humans may result from infection (nvCJD, iatrogenic CJD, kuru); can be inherited when a germ line mutation exists in the PRNP gene that encodes the prion protein [familial CJD, GerstmannStreüssler-Scheinker Syndrome (GSSS), Fatal Familial Insomnia]; and can be sporadic (sporadic CJD) when the origin of the disease is neither determined nor understood. TSEs are also observed in other mammals including sheep, goats, deer, elk, cattle, mink, cats and zoo animals.

The primary symptoms of TSEs usually include progressive dementia and ataxia, associated with spongiform degeneration of the brain and accumulation of an abnormal protease-resistant form of the prion protein (PrPres) in the central nervous system. (The normal, cellular form of this protein is denoted as PrPc.) After symptoms are first manifested, the progression of the disease can be dramatically rapid, leading inevitably to the death of the affected individual.

PrPc is a mainly α-helical, protease-sensitive, soluble monomer protein with a disordered N-terminus (approximate residues 23-127) and a structured C-terminal domain (residues 128-228, Figure 1.).



Figure 1. PrP is a 208 amino-acid residue glycosylated protein, which is connected to the cell surface by a glycosyl phosphatidyl inositol (GPI) anchor. However, only 110 residues (121-231) of the PrP domain are shown here. The two glycosylation sites are Asn 181 and Asn 197, which are both shown in yellow. One disulfide bond is present in the protein (colored gold here) connecting the second and third helices via Cys179-Cys214. The protein is colored by secondary structure. Alpha helices=magenta, beta sheets=blue



By contrast, PrPres has a very compact structure, which is high in both α and β conformations, exists as oligomers and can be dissolved only by denaturing in GdnHCl or detergents. The disease-associated protein (PrPres) has partial protease-resistance; its N-terminal ~6 kDa fragment is digested under conditions in which the highly compact C-terminal domain remains intact. Both forms of the protein contain a single disulfide bond and two glycosylation sites. The generally accepted assertion that the difference between the cellular and disease-associated forms of the prion protein is purely conformational with respect to its disulfide bond patterns is based on our earlier experiments.

There is no cure for the disease, and early diagnosis is not available to discriminate between TSE-infected unsymptomatic and uninfected individuals. Such a sensitive, rapid, economical and non-invasive screening test is vital with respect to animals destined for the human food chain, and to humans, who may participate in tissue and blood donation programs. As with any other disease, a detailed mechanistic understanding of pathogenesis is the most effective approach for the development of sensitive predictive diagnostic and efficacious therapeutic regimens.

Our aim is to understand TSEs at molecular and cellular levels as well as at the level of the whole organism as a model for the formation of amyloid fibrils in conformational diseases.

Selected publications

Welker, E., Narayan, M., Volles, M.J. and Scheraga, H.A. (1999). Two new structured intermediates in the oxidative folding of RNase A. FEBS Lett. 460: 477-479.

Narayan, M., Welker, E., Wedemeyer, W. J. and Scheraga, H. A. (2000). Oxidative folding of proteins. Acc. Chem. Res. 33: 805-812.

Welker, E., Narayan, M., Wedemeyer, W. J. and Scheraga, H. A. (2001). Structural determinants of oxidative folding in proteins. Proc. Natl. Acad. Sci. U.S.A. 98: 2312-2316.

Welker, E., Wedemeyer, W.J. and Scheraga, H.A. (2001). A role for Intermolecular Disulfide Bonds in Prion Diseases? Proc. Natl. Acad. Sci. U.S.A. 98: 4334-4336.

Welker, E., Wedemeyer, W.J., Narayan, M. and Scheraga, H.A. (2001). Coupling of conformational folding and disulfide-bond reactions in oxidative folding of proteins. Biochemistry 40: 9059-9064.

Saito, K., Welker, E. and Scheraga, H.A. (2001). Folding of a disulfide-bonded protein species with free thiol(s): Competition between conformational folding and disulfide reshuffling in an intermediate of bovine pancreatic ribonuclease A. Biochemistry 40: 15002-15008.

Welker, E., Raymond, L.D., Scheraga, H.A. and Caughey, B. (2002). Intramolecular versus intermolecular disulfide bonds in prion proteins. J. Biol. Chem. 277: 33477-33481.

Wedemeyer, W.J., Welker, E. and Scheraga, H.A. (2002). Proline cis-trans isomerization and protein folding. Biochemistry 41: 14637-14645.

Welker, E., Hathaway, L. and Scheraga, H.A. (2004). A new method for rapid characterization of the folding pathways of multi-disulfide-containing proteins. J. Am. Chem. Soc. 126: 3720-3721.

Welker, E., Maki, K., Shastry, M.C.R., Juminaga, D., Bhat, R., Scheraga, H.A. and Roder, H. (2004). Ultra-rapid mixing experiments shed new light on the characteristics of the initial conformational ensemble during the folding of ribonuclease A. Proc. Natl. Acad. Sci. U.S.A. 101: 17681-17686.

Narayan, M., Welker, E., Zhai, H., Han, X., Xu, G., McLafferty, F.W. and Scheraga, H.A. (2008). Detecting native-folds in mixtures of disulfide-bond-containing proteins. Nature Biotechnology 26: 427-429.

An, S. S., Lim, K. T., Oh, H. J., Lee, B. S., Zukic, E., Ju, Y. R., Yokoyama, T., Kim, S, Y., Welker, E. Differentiating blood samples from scrapie infected and non-infected hamsters by detecting disease-associated prion proteins using Multimer Detection System. 2010. Biochem Biophys Res Commun 392: 505-509.

Ferencz C, Petrovszki P, Kóta Z, Fodor-Ayaydin E, Haracska L, Bóta A, Varga Z, Dér A, Marsh D, Páli T: Estimating the rotation rate in the vacuolar proton-ATPase in native yeast vacuolar membranes, EUR BIOPHYS J. 42: (2-3) pp. 147-158 (2013)

Zencir S, Banerjee M, Dobson MJ, Ayaydin F, Fodor EA, Topcu Z, Mohanty S: New partner proteins containing novel internal recognition motif for human glutaminase interacting protein (hGIP), BIOCHEM BIOPHYS RES COMMUN. 432: (1) pp. 10-15 (2013)

Szalontai B, Nagy G, Krumova S, Fodor E, Páli T, Taneva SG, Garab G, Peters J, Dér A: Hofmeister ions control protein dynamics, BIOCHIM BIOPHYS ACTA-GENERAL SUBJECTS 1830: (10) pp. 4564-4572 (2013)

van Bon BWM, Oortveld MAW, Nijtmans LG, Fenckova M, Nijhof B, Besseling J, Vos M, Kramer JM, de Leeuw N, Castells-Nobau A, Asztalos L, Viragh E, Ruiter M, Hofmann F, Eshuis L, Collavin L, Huynen MA, Asztalos Z, Verstreken P, Rodenburg RJ, Smeitink JA, de Vries BBA, Schenck A CEP89 is required for mitochondrial metabolism and neuronal function in man and fly HUM MOL GENET 22: (15)3138-3151 (2013)

Willemsen MH, Nijhof B, Fenckova M, Nillesen WM, Bongers EMHF, Castells-Nobau A, Asztalos L, Viragh E, van Bon BWM, Tezel E, Veltman JA, Brunner HG, de Vries BBA, de Ligt J, Yntema HG, van Bokhoven H, Isidor B, Le Caignec C, Lorino E, Asztalos Z, Koolen DA, Vissers LELM, Schenck A, Kleefstra T GATAD2B loss-of-function mutations cause a recognisable syndrome with intellectual disability and are associated with learning deficits and synaptic undergrowth in Drosophila J MED GENET 50: (8)507-514 (2013)

E. Tóth, P.I. Kulcsár, E. Fodor, F. Ayaydin, L. Kalmár, A.É. Borsy, L. László, E. Welker. The highly conserved, N-terminal (RXXX)8 motif of mouse Shadoo mediates nuclear accumulation. 2013. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH, 1833 2013 1199–1211.

Orsolits B, Borsy A, Madarász E, Mészáros Z, Kőhidi T, Markó K, Jelitai M, Welker E, Környei Z. Retinoid machinery in distinct neural stem cell populations with different retinoid responsiveness. 2013. STEM CELLS AND DEVELOPMENT, 22: 2777-2793.

Balázs Schäfer†, Erika Orbán‡, Attila Borics†, Krisztina Huszár§, Antal Nyeste, Ervin Welker§, Csaba Tömböly†* Preparation of Semisynthetic Lipoproteins with Fluorescent Cholesterol Anchor and their Introduction to the Cell Membrane without Detergents and Surplus Lipids BIOCONJUGATE CHEMISTRY24:(10) 1684-1697.