Approaches for defining the Hsp90-dependent proteome

Abstract

Hsp90 is the target of ongoing drug discovery studies seeking new compounds to treat cancer, neurodegenerative diseases, and protein folding disorders. To better understand Hsp90’s roles in cellular pathologies and in normal cells, numerous studies have utilized proteomics assays and related high-throughput tools to characterize its physical and functional protein partnerships. This review surveys these studies, and summarizes the strengths and limitations of the individual attacks. We also include downloadable spreadsheets compiling all of the Hsp90-interacting proteins identified in more than 23 studies. These tools include cross-references among gene aliases, human homologues of yeast Hsp90-interacting proteins, hyperlinks to database entries, summaries of canonical pathways that are enriched in the Hsp90 interactome, and additional bioinformatic annotations. In addition to summarizing Hsp90 proteomics studies performed to date and the insights they have provided, we identify gaps in our current understanding of Hsp90-mediated proteostasis.

The expanding proteome of the molecular chaperone HSP90

“…This is a large body of work, and is important to help the multitude of other affected protein classes lends further weight to the developing view that HSP90 should not be regarded only as a chaperone of signaling proteins, as originally thought, 36 but rather has substantially more far-reaching cellular roles, including, for example, glucose metabolism, ribonucleoprotein (RNP) assembly and the DNA damage response. 7 Indeed, aside from "protein kinase activity," Sharma et al identified "DNA metabolic processes," including proteins involved in DNA repair, as the other most significantly downregulated functional category from their bioinformatic analysis, an observation that is consistent with the preclinical findings that HSP90 inhibitors sensitize cancer cells to radiation through inhibition of base excision repair. 37 Whether these various far-reaching effects exemplified above can all be explained as downstream consequences of client protein signaling will remain an area for future research.…”

“…Putative protein clients have also been detected by observing their depletion following the treatment of cells with HSP90 inhibitors, typically using western blotting. Hartson and Matts 7 have recently reviewed more basis for this interest is HSP90's ability to facilitate both the activation and stabilization, through physical interaction, of a wide range of "client" proteins, many of which are involved in oncogenesis and malignant progression. 1 Inhibition of HSP90 leads to the loss of this physical interaction and to ubiquitination and degradation of clients via the 26S proteasome (Fig.…”

“…These studies have commonly involved genetic, chemical genetic and physical interaction screens performed in yeast [8][9][10][11][12][13][14] as well as large-scale analyses, commonly utilizing affinity purification of HSP90, of proteins present in HSP90 complexes. 7,[15][16][17][18][19][20] Only a few efforts have been made previously toward characterizing the global cellular effects of HSP90 inhibition in mammalian cells. The first published report by Clarke et al 21 used mRNA expression profiling, by cDNA microarray, to characterize in an unbiased fashion the effects in a panel of human colon cancer cell lines of treatment with the first clinically evaluated HSP90 inhibitor, the geldanamycin analog 17-AAG (tanespimicin).…”

“…7,41,42 The biological and clinical significance of the effects on particular biological pathways and candidate proteins identified by Sharma and colleagues will also need to be explored further (e.g., see Fig. 2).…”

System Level Mechanisms of Adaptation, Learning, Memory Formation and Evolvability: The Role of Chaperone and Other Networks

“…The involvement of Hsp90 in immune functions is supported by the recent finding of its association with STAT3 [68]. Recently an extensive review summarized the potential human Hsp90 sub-interactome compiling the results of more than 23 studies [69]. Their assessment identified RNAprocessing, glucose metabolism, the cytoskeleton and extracellular transport as major human Hsp90 network-related functions.…”