Label‐Free Quantitative Proteomics Identify Global Protein Interactors for the Androgen Receptor Associated Cochaperone SGTA

Abstract

Molecular chaperones facilitate proper folding and regulation of steroid hormone receptors (SHRs). Upon proper folding, SHRs bind ligand with high affinity, translocate to the nucleus and initiate gene expression accordingly. A novel cochaperone, human small glutamine rich TPR (tetratricopeptide repeat) containing protein alpha (SGTA), is a down‐regulator of androgen (AR), glucocorticoid (GR), and progesterone (PR) receptors. It binds to heat shock protein (Hsp) 70 and 90 kDa. Additionally, SGTA plays a role in cellular processes such as cell cycle progression and apoptosis. Therefore, label‐free quantitative proteomics was utilized to determine novel interactors in LNCaP human prostate cancer cells. Unknown protein interactions were purified using a Nickel resin and further analyzed with liquid chromatography mass spectrometry (LC‐MS/MS). To determine if interactions were transient or strong, a comparison of a 3‐hour versus an overnight incubation was used. Preliminary studies using rigorous statistical analysis have identified a broad range of proteins involved in different pathways other than the chaperoning pathway. Thus, future studies aim to validate these interactions with SGTA using nickel purification and assess their functional relevance, which will contribute to the understanding of the role SGTA plays within the chaperoning pathway and any cross‐talk with other pathways.