The FNIP co-chaperones decelerate the Hsp90 chaperone cycle and enhance drug binding.

Mark R Woodford,Dante Capriotti,Timothy A Haystead,Dimitra Bourboulia,Stewart N Loh,Diana M Dunn,Chrisostomos Prodromou,W Marston Linehan,Barry Panaretou,Adam R Blanden,Laura S Schmidt,Aaron Smith,Philip F Hughes,Gennady Bratslavsky,David Loiselle,Mehdi Mollapour,Wendi Ackerman

doi:10.1038/ncomms12037

Abstract

Heat shock protein-90 (Hsp90) is an essential molecular chaperone in eukaryotes involved in maintaining the stability and activity of numerous signalling proteins, also known as clients. Hsp90 ATPase activity is essential for its chaperone function and it is regulated by co-chaperones. Here we show that the tumour suppressor FLCN is an Hsp90 client protein and its binding partners FNIP1/FNIP2 function as co-chaperones. FNIPs decelerate the chaperone cycle, facilitating FLCN interaction with Hsp90, consequently ensuring FLCN stability. FNIPs compete with the activating co-chaperone Aha1 for binding to Hsp90, thereby providing a reciprocal regulatory mechanism for chaperoning of client proteins. Lastly, downregulation of FNIPs desensitizes cancer cells to Hsp90 inhibitors, whereas FNIPs overexpression in renal tumours compared with adjacent normal tissues correlates with enhanced binding of Hsp90 to its inhibitors. Our findings suggest that FNIPs expression can potentially serve as a predictive indicator of tumour response to Hsp90 inhibitors.

Highlights

Heat shock protein-90 (Hsp90) is an essential molecular chaperone in eukaryotes involved in maintaining the stability and activity of numerous signalling proteins, known as clients
We examined the effects of FNIP1 and FNIP2 knockdown on Hsp[90] binding to ATP and drug. small interfering RNA (siRNA) knockdown of FNIP1, FNIP2 or both in human embryonic kidney 293 (HEK293) cells did not have an impact on Hsp[90] binding to ATP (Fig. 7g) but significantly decreased Hsp[90] binding to GB (Fig. 7h)
We further demonstrated that FLCN binding partners FNIP1 and FNIP2 function as co-chaperones of Hsp[90]

Summary

Introduction

Heat shock protein-90 (Hsp90) is an essential molecular chaperone in eukaryotes involved in maintaining the stability and activity of numerous signalling proteins, known as clients. We show that the tumour suppressor FLCN is an Hsp[90] client protein and its binding partners FNIP1/FNIP2 function as co-chaperones. The molecular chaperone heat shock protein-90 (Hsp90) is responsible for folding, stability and activity of many proteins known as ‘client proteins’, including many responsible for tumour initiation, progression and metastasis[1]. This makes the chaperone Hsp[90] an attractive target for cancer therapy[2]. Small molecule inhibitors bind to the ATP-binding pocket of Hsp[90] and inhibit its chaperone function This prevents Hsp[90] interaction with client proteins, leading to their degradation by the proteasome. FNIPs enhance the binding of Hsp[90] to its inhibitors such as ganetespib (GB); overexpression of FNIPs in specific tumours can be an indicator of their response to Hsp[90] inhibitors

Methods

Results

Conclusion