Silencing the cochaperone CDC37 destabilizes kinase clients and sensitizes cancer cells to HSP90 inhibitors

Abstract

The cochaperone CDC37 promotes association of HSP90 with the protein kinase subset of client proteins to maintain their stability and signalling functions. HSP90 inhibitors induce depletion of clients, which include several oncogenic kinases. We hypothesised that the targeting of CDC37 using siRNAs would compromise the maturation of these clients and increase the sensitivity of cancer cells to HSP90 inhibitors. Here we show that silencing of CDC37 in human colon cancer cells diminished association of kinase clients with HSP90 and reduced levels of the clients ERBB2, CRAF, CDK4 and CDK6, as well as phosphorylated AKT. CDC37 silencing promoted the proteasome-mediated degradation of kinase clients, suggesting a degradation pathway independent from HSP90 binding. Decreased cell signalling through kinase clients was also demonstrated by reduced phosphorylation of downstream substrates and colon cancer cell proliferation was subsequently reduced by inhibition of the G1/S-phase transition. Furthermore, combining CDC37 silencing with the HSP90 inhibitor 17-AAG induced more extensive and sustained depletion of kinase clients and potentiated cell cycle arrest and apoptosis. These results support an essential role for CDC37 in concert with HSP90 in maintaining oncogenic protein kinase clients and endorse the therapeutic potential of targeting CDC37 in cancer.

Correlation between PDZK1, Cdc37, Akt and Breast Cancer Malignancy: The Role of PDZK1 in Cell Growth through Akt Stabilization by Increasing and Interacting with Cdc37

“…down reduces Akt levels (10). Consistent with these reports and as shown in Figure 4B, partial knockdown of Cdc37 using two different siRNAs in PDZK1-overexpressing MCF-7 cells reduced the levels of Akt, suggesting a potential connection between PDZK1 and Cdc37.…”

“…It appears that PDZK1 reduces Akt ubiquitination and thus its degradation by the proteasome system ( Figure 6). Cdc37 is critical for the stability of numerous growth-promoting kinases, including Akt, and a reduction in the cochaperone drastically reduces the levels of client proteins (10).…”

“…TMA slides were processed essentially as recently described (17). Stained slides were scanned using the ×40 objective, and immunoreactivity was analyzed by using Image-Pro Plus software (version 6.0) (Media Cybernetics Inc., Rockville, MD, USA) as described previously (9,10). The measurement parameters included density mean, area sum and integrated optical density.…”

“…The efficiency of Hsp90 in promoting the stability of client proteins is mediated by cochaperones such as cell division cycle 37 (Cdc37) (9). Cdc37 is primarily responsible for securing the integrity of protein kinases such as Akt and EGFR (7,10). Akt, a serine/threonine kinase, is critical for the mediation of cell signaling initiated by growth factors, cytokines and other cellular stimuli (11).…”

Split Renilla Luciferase Protein Fragment-assisted Complementation (SRL-PFAC) to Characterize Hsp90-Cdc37 Complex and Identify Critical Residues in Protein/Protein Interactions

“…Cdc37, originally named as p50, was reported as an accessory factor to load the subset of protein kinases to Hsp90 in the intermediate Hsp90 superchaperone complex (13)(14)(15). Silencing Cdc37 reduces expression of the Hsp90 clients ERBB2, CRAF, CDK4, CDK6, and phosphorylated AKT, which are highly relevant to cancer progression (16). The involvement of the Hsp90-Cdc37 complex in the maturation and activity of oncogenic protein kinases makes the complex a potential therapeutic target for cancer chemotherapy.…”