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Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state


Polyglutamine (polyQ)-expansion proteins cause neurodegenerative disorders including Huntington's disease, Kennedy's disease and various ataxias. The cytotoxicity of these proteins is associated with the formation of aggregates or other conformationally toxic species. Here, we show that the cytosolic chaperonin CCT (also known as TRiC) can alter the course of aggregation and cytotoxicity of huntingtin (Htt)–polyQ proteins in mammalian cells. Disruption of the CCT complex by RNAi-mediated knockdown enhanced Htt–polyQ aggregate formation and cellular toxicity. Analysis of the aggregation states of the Htt–polyQ proteins by fluorescence correlation spectroscopy revealed that CCT depletion results in the appearance of soluble Htt–polyQ aggregates. Similarly, overexpression of all eight subunits of CCT suppressed Htt aggregation and neuronal cell death. These results indicate that CCT has an essential role in protecting against the cytotoxicity of polyQ proteins by affecting the course of aggregation.

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Figure 1: Knockdown of CCT subunits stimulates aggregate formation of expanded polyQ repeats transiently expressed in HEK293 cells.
Figure 2: CCT is required for preventing Htt aggregation in stable transformants of HeLa cells.
Figure 3: Depletion of CCT subunits stimulates formation of soluble aggregates of polyQ-expansion proteins.
Figure 4: CCT prevents Htt toxicity and aggregation in neuronal cells.


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We thank M. Kadota for technical assistance and R. Tsien for providing the mRFP1 plasmid. We are grateful to I. Wada, T. Haraguchi, H. Taguchi, Y. Nagai, T. Shimi, K. Kabayama, K. Saito and H. Fujii for helpful discussion. G.M. was supported by a Human Frontiers Fellowship at Northwestern University and R.I.M. is supported by grants from the National Institutes of Health (National Institute for Medical Science, NIGMS; National Institute for Neurological Diseases and Stroke, NINDS; and National Institute for Aging, NIA), the Huntington Disease Coalition for the Cure, and the Daniel F. and Ada L. Rice Foundation. A.K. and C.P. were supported by fellowships from the Japan Society for Promotion of Science. H.K., M.K. and K.N. were supported by the Grants-in-Aid for Scientific Research programmes in Japan.

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Correspondence to Hiroshi Kubota.

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Kitamura, A., Kubota, H., Pack, CG. et al. Cytosolic chaperonin prevents polyglutamine toxicity with altering the aggregation state. Nat Cell Biol 8, 1163–1169 (2006).

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