MP88-13 TUMOR SUPPRESSOR TSC1 IS A NEW HSP90 COCHAPERONE THAT FACILITATES FOLDING OF KINASE AND NON-KINASE CLIENTS

Abstract

You have accessJournal of UrologyKidney Cancer: Basic Research & Pathophysiology III1 Apr 2018MP88-13 TUMOR SUPPRESSOR TSC1 IS A NEW HSP90 COCHAPERONE THAT FACILITATES FOLDING OF KINASE AND NON-KINASE CLIENTS Mark Woodford, Rebecca Sager, Adam Blanden, Stewart Loh, David Gutmann, Oleg Shapiro, Dimitra Bourboulia, Michael Wong, Gennady Bratslavsky, and Mehdi Mollapour Mark WoodfordMark Woodford More articles by this author , Rebecca SagerRebecca Sager More articles by this author , Adam BlandenAdam Blanden More articles by this author , Stewart LohStewart Loh More articles by this author , David GutmannDavid Gutmann More articles by this author , Oleg ShapiroOleg Shapiro More articles by this author , Dimitra BourbouliaDimitra Bourboulia More articles by this author , Michael WongMichael Wong More articles by this author , Gennady BratslavskyGennady Bratslavsky More articles by this author , and Mehdi MollapourMehdi Mollapour More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2018.02.2933AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Mutation of either TSC1 or TSC2 causes tuberous sclerosis, a multisystem genetic syndrome that can lead to formation of benign tumors in the kidneys, lungs, and other organs and has also been linked to epilepsy and autism. The tumor suppressors Tsc1 and Tsc2 form the tuberous sclerosis complex (TSC), a regulator of mTOR activity. Tsc1 stabilizes Tsc2; however the precise mechanism remains elusive. Molecular chaperones such as heat shock protein-90 (Hsp90) are essential for the stability and activation of numerous signaling proteins, including tumor suppressors. The objective of this work was to determine the role of Hsp90 in the stability and activity of TSC. We hypothesize that Hsp90 mediates TSC formation and thus is essential for the stability of Tsc2. METHODS Tsc1-FLAG and Tsc2-FLAG were transiently expressed and isolated from HEK293 cells. Interacting proteins were identified by co-immunoprecipitation. Hsp90 chaperone function is coupled to its ATPase activity. We have developed an assay to measure this activity by determining the rate of ATP breakdown and inorganic phosphate production. Hsp90 was isolated from WT and TSC1-/- mice and assayed for ATPase activity in vitro. RESULTS Tsc2 interacts with the molecular chaperone Hsp90 both in vitro and in vivo. Treatment of HEK293 cells with Hsp90 inhibitors such as ganetespib or SNX2112 caused ubiquitination and proteasomal degradation of Tsc2; therefore Tsc2 is a new client of Hsp90. However, Tsc1 stability does not depend on Hsp90. Tsc1 potently decelerates Hsp90 ATPase activity and facilitates the interaction of Tsc2 and other clients with Hsp90. We also showed that Tsc1 competes with the activating co-chaperone Aha1 for binding to Hsp90, providing a reciprocal regulatory mechanism for chaperoning of kinase and non-kinase clients. CONCLUSIONS Tsc1 interacts with Tsc2 and protects Tsc2 from degradation. Many pathogenic mutations of Tsc2 destabilize the protein. Our data suggest that lack of interaction of pathogenic Tsc2 mutants with Tsc1 and consequently Hsp90 lead to their degradation. Further, these newly elucidated roles of Tsc1 and Tsc2 suggest a potential mechanism for the observed differences between TSC1 and TSC2 mutant disease. In the absence of Tsc2, Tsc1 will still perform its critical role as a co-chaperone of Hsp90. However when Tsc1 is lost, the stability of both Tsc2 and many other Hsp90 clients is dramatically reduced, leading to a different phenotypic manifestation. © 2018FiguresReferencesRelatedDetails Volume 199Issue 4SApril 2018Page: e1202 Advertisement Copyright & Permissions© 2018MetricsAuthor Information Mark Woodford More articles by this author Rebecca Sager More articles by this author Adam Blanden More articles by this author Stewart Loh More articles by this author David Gutmann More articles by this author Oleg Shapiro More articles by this author Dimitra Bourboulia More articles by this author Michael Wong More articles by this author Gennady Bratslavsky More articles by this author Mehdi Mollapour More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...