?-Synuclein in central nervous system and from erythrocytes, mammalian cells, and Escherichia coli exists predominantly as disordered monomer.

ABSTRACT: Since the discovery and isolation of ?-synuclein (?-syn) from human brains, it has been widely accepted that it exists as an intrinsically disordered monomeric protein. Two recent studies suggested that ?-syn produced in Escherichia coli or isolated from mammalian cells and red blood cells exists predominantly as a tetramer that is rich in ?-helical structure (Bartels, T., Choi, J. G., and Selkoe, D. J. (2011) Nature 477, 107-110; Wang, W., Perovic, I., Chittuluru, J., Kaganovich, A., Nguyen, L. T. T., Liao, J., Auclair, J. R., Johnson, D., Landeru, A., Simorellis, A. K., Ju, S., Cookson, M. R., Asturias, F. J., Agar, J. N., Webb, B. N., Kang, C., Ringe, D., Petsko, G. A., Pochapsky, T. C., and Hoang, Q. Q. (2011) Proc. Natl. Acad. Sci. 108, 17797-17802). However, it remains unknown whether or not this putative tetramer is the main physiological form of ?-syn in the brain. In this study, we investigated the oligomeric state of ?-syn in mouse, rat, and human brains. To assess the conformational and oligomeric state of native ?-syn in complex mixtures, we generated ?-syn standards of known quaternary structure and conformational properties and compared the behavior of endogenously expressed ?-syn to these standards using native and denaturing gel electrophoresis techniques, size-exclusion chromatography, and an oligomer-specific ELISA. Our findings demonstrate that both human and rodent ?-syn expressed in the central nervous system exist predominantly as an unfolded monomer. Similar results were observed when human ?-syn was expressed in mouse and rat brains as well as mammalian cell lines (HEK293, HeLa, and SH-SY5Y). Furthermore, we show that ?-syn expressed in E. coli and purified under denaturing or nondenaturing conditions, whether as a free protein or as a fusion construct with GST, is monomeric and adopts a disordered conformation after GST removal. These results do not rule out the possibility that ?-syn becomes structured upon interaction with other proteins and/or biological membranes.

SUBMITTER: Fauvet B 

PROVIDER: S-EPMC3346117 | biostudies-literature | 2012 May

REPOSITORIES: biostudies-literature