Hsp90 is regulated by a switch point in the C‐terminal domain

Abstract

Heat shock protein 90 (Hsp90) is an abundant, dimeric ATPdependent molecular chaperone, and ATPase activity is essential for its in vivo functions. S-nitrosylation of a residue located in the carboxy-terminal domain has been shown to affect Hsp90 activity in vivo. To understand how variation of a specific amino acid far away from the amino-terminal ATP-binding site regulates Hsp90 functions, we mutated the corresponding residue and analysed yeast and human Hsp90 variants both in vivo and in vitro. Here, we show that this residue is a conserved, strong regulator of Hsp90 functions, including ATP hydrolysis and chaperone activity. Unexpectedly, the variants alter both the C-terminal and N-terminal association properties of Hsp90, and shift its conformational equilibrium within the ATPase cycle. Thus, S-nitrosylation of this residue allows the fast and efficient fine regulation of Hsp90.

Nitric Oxide and Heat Shock Protein 90 Activate Soluble Guanylate Cyclase by Driving Rapid Change in Its Subunit Interactions and Heme Content

“…We saw that the heme-independent sGC activator BAY 60-2770 could mimic the effect of NO in promoting hsp90 dissociation, whereas the heme-dependent sGC activator BAY 41-2272 could not. The ability of BAY 60-2770 to do so is perhaps the best indicator that the mechanism of NO action does not necessarily require any NO-based protein modifications such as protein S-nitrosation or tyrosine nitration, which can otherwise occur in hsp90 and sGC proteins when cells are exposed to NO (23)(24)(25). Rather, our results suggest a mechanism of action that involves fundamental changes in the apo-sGC-␤1 subunit.…”

“…3, B and E). In particular, there emerged a lower M r subpopulation of sGC-␤1 that clearly had no hsp90 associated with it (lanes [23][24][25][26]. This subpopulation existed only transiently in the cells because it was no longer present in cells that underwent a longer SNAP exposure for 30 min (Fig.…”

“…Gel filtration analysis of the heme-deficient RFL-6 cell supernatant (Fig. 6E) revealed that the BAY 60-2770 treatment shifted the apparent M r distribution of sGC-␤1 to cause significant buildup of the low M r , hsp90-free sGC-␤1 subpopulation in the cells (fractions [22][23][24][25]. Similar results were obtained with RFL-6 cells that had not been made heme-deficient prior to the BAY 60-2770 treatment (data not shown), consistent with their containing some apo-sGC-␤1 under normal culture conditions.…”

Heat Shock Protein 90-α Mediates Aldo-Keto Reductase 1B10 (AKR1B10) Protein Secretion through Secretory Lysosomes

“…Expression Vectors and Transfection-pcDNA3.1/FLAG/ HSP90␣ was provided by Dr. Johannes Buchner (Technische Universität München, Department Chemie, LS Biotechnologie, München, Germany) (32). The EGFP-AKR1B10 vector has been produced previously (14).…”

Fungal Hsp90: a biological transistor that tunes cellular outputs to thermal inputs

“…Also, phosphorylation at Thr22 by casein kinase 2 modulates Hsp90 interactions with the cochaperones Cdc37 and Aha1 65 . In addition, yeast Hsp90 is S-nitrosylated, which affects its dimerization dynamics and activity 68 , and by analogy with its mammalian counterpart 69 , yeast Hsp90 might also be acetylated.…”