title: Down-regulation of mammalian sterile 20-like kinase 1 by heat shock protein 70 mediates cisplatin resistance in prostate cancer cells.
abstract: Mammalian sterile 20-like kinase 1 (Mst1) is an ubiquitously expressed serine/threonine kinase, and its activation results in cell apoptosis. Recent studies suggest that Mst1 may function as a tumor suppressor. Here, we reported that heat shock protein 70 (Hsp70), which is thought to protect cells against cellular stress, has been identified as an Mst1-interacting protein, in a yeast two-hybrid screen of human adult prostate cDNA library with a dominant-negative Mst1 (K59R) as bait. The interaction of Mst1 with Hsp70 was confirmed by coimmunoprecipitation in both cotransfected HEK293 cells and prostate cancer cells. Hsp70 colocalized with Mst1 in the cytoplasm of LNCaP cells. The interaction sites with Mst1 consisted of NH(2)-terminal ATPase domain in Hsp70, whereas the inhibitory domain of Mst1 mediates the binding of Hsp70 in Mst1. Overexpression of Hsp70 mediates proteasomal degradation of Mst1 in a Hsp70 interacting protein (CHIP)-dependent manner. Furthermore, the proapoptotic effect of Mst1 was markedly inhibited by overexpression of Hsp70 or CHIP. Most strikingly, in response to the treatment of anticancer drug cisplatin, the induction of Hsp70 expression is higher in the androgen-independent DU145 cells compared with the androgen-dependent LNCaP cells. The higher levels of Hsp70 induction and subsequent Mst1 degradation mediate cisplatin resistance in prostate cancer DU145 cells. Moreover, overexpression of Mst1 sensitizes prostate cancer cells to cisplatin treatment. These findings implicate that Mst1, a downstream target of Hsp70, may be developed as a target for sensitizing hormone-refractory prostate cancers to chemotherapy.
authors.affiliation: Department of Cell Biology and Molecular Medicine, University of Medicine and Dentistry of New Jersey, New Jersey Medical School, Newark, NJ 07103, USA.
authors.forename: Aixia
authors.initials: A
authors.lastname: Ren
authors.forename: Guijun
authors.initials: G
authors.lastname: Yan
authors.forename: Bei
authors.initials: B
authors.lastname: You
authors.forename: Jianxin
authors.initials: J
authors.lastname: Sun
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology*; D015536:Down-Regulation; D019008:Drug Resistance, Neoplasm; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis / Q000378:metabolism*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008297:Male; D011471:Prostatic Neoplasms / Q000188:drug therapy* / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D015398:Signal Transduction; D014162:Transfection; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism; D000099317:Hippo Kinases
chemical_list: D000970:Antineoplastic Agents; D002945:Cisplatin; D018840:HSP70 Heat-Shock Proteins; D047908:Intracellular Signaling Peptides and Proteins; D017346:Protein Serine-Threonine Kinases; D044767:Ubiquitin-Protein Ligases; C467728:STUB1 protein, human; C095566:STK4 protein, human; D000099317:Hippo Kinases