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The conserved NxNNWHW motif in Aha-type co-chaperones modulates the kinetics of Hsp90 ATPase stimulation.

ABSTRACT: Hsp90 is a dimeric molecular chaperone that is essential for the folding and activation of hundreds of client proteins. Co-chaperone proteins regulate the ATP-driven Hsp90 client activation cycle. Aha-type co-chaperones are the most potent stimulators of the Hsp90 ATPase activity but the relationship between ATPase regulation and in vivo activity is poorly understood. We report here that the most strongly conserved region of Aha-type co-chaperones, the N terminal NxNNWHW motif, modulates the apparent affinity of Hsp90 for nucleotide substrates. The ability of yeast Aha-type co-chaperones to act in vivo is ablated when the N terminal NxNNWHW motif is removed. This work suggests that nucleotide exchange during the Hsp90 functional cycle may be more important than rate of catalysis.

SUBMITTER: Mercier R

PROVIDER: S-EPMC6426937 | biostudies-literature | 2019 Mar

REPOSITORIES: biostudies-literature

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The conserved NxNNWHW motif in Aha-type co-chaperones modulates the kinetics of Hsp90 ATPase stimulation.

Mercier Rebecca R Wolmarans Annemarie A Schubert Jonathan J Neuweiler Hannes H Johnson Jill L JL LaPointe Paul P

Nature communications 20190320 1

Hsp90 is a dimeric molecular chaperone that is essential for the folding and activation of hundreds of client proteins. Co-chaperone proteins regulate the ATP-driven Hsp90 client activation cycle. Aha-type co-chaperones are the most potent stimulators of the Hsp90 ATPase activity but the relationship between ATPase regulation and in vivo activity is poorly understood. We report here that the most strongly conserved region of Aha-type co-chaperones, the N terminal NxNNWHW motif, modulates the app ...[more]

PMID: 30894538

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Hsp90 and Associated Co-Chaperones of the Malaria Parasite.

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Project description: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.

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Project description:The molecular chaperone heat shock protein 90 (Hsp90) is required for the folding and activation of numerous essential signaling proteins. Hsp90 is generally thought to transition between an open (apo) and a closed (ATP) conformation in response to nucleotide. Here, 3D single-particle reconstructions of Escherichia coli and yeast Hsp90 homologs establish the existence of two distinct nucleotide-stabilized conformations (ATP, ADP) in addition to an apo extended state, supporting previous structural work. However, single-particle matching methods reveal that, rather than being irreversibly determined by nucleotide, a species-dependent dynamic conformational equilibrium exists between states. Using crosslinking methods, we trap transient nucleotide-specific states of yeast and human Hsp90 and establish that the apo, ATP, and ADP states are universal. These data support a conserved three-state chaperone cycle where the conformational equilibrium varies between species, implicating evolutionary tuning to meet the particular client protein and metabolic environment of an organism.

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