title: Calpain-mediated processing of p53-associated parkin-like cytoplasmic protein (PARC) affects chemosensitivity of human ovarian cancer cells by promoting p53 subcellular trafficking.
abstract: Resistance to cisplatin (CDDP)-based therapy is a major hurdle to the successful treatment of human ovarian cancer (OVCA), and the chemoresistant phenotype in OVCA cells is associated with Akt-attenuated p53-mediated apoptosis. Pro-apoptotic functions of p53 involve both transcription-dependent and -independent signaling pathways, and dysfunctional localization and/or inactivation of p53 contribute to the development of chemoresistance. PARC is a cytoplasmic protein regulating p53 subcellular localization and subsequent function. Little is known about the molecular mechanisms regulating PARC. Although PARC contains putative caspase-3 cleavage sites, and CDDP is known to induce the activation of caspases and calpains and induce proteasomal degradation of anti-apoptotic proteins, if and how PARC is regulated by CDDP in OVCA are unknown. Here, we present evidence that CDDP promotes calpain-mediated PARC down-regulation, mitochondrial and nuclear p53 accumulation, and apoptosis in chemosensitive but not resistant OVCA cells. Inhibition of Akt is required to sensitize chemoresistant cells to CDDP in a p53-dependent manner, an effect enhanced by PARC down-regulation. CDDP-induced PARC down-regulation is reversible by inhibition of calpain but not of caspases or the 26 S proteasome. Furthermore, in vitro experiments confirm the ability of calpain in mediating Ca(2+)-dependent PARC down-regulation. The role of Ca(2+) in PARC down-regulation was further confirmed as ionomycin-induced PARC down-regulation in both chemosensitive and chemoresistant ovarian cancer cells. The data presented here implicate the regulation of p53 subcellular localization and apoptosis by PARC as a contributing factor in CDDP resistance in OVCA cells and Ca(2+)/calpain in PARC post-translational processing and chemosensitivity.
authors: Reproductive Biology Unit and Division of Gynecologic Oncology, Department of Obstetrics and Gynecology, University of Ottawa, Ottawa, Ontario K1Y 4E9, Canada.
authors: Michael G
authors: MG
authors: Woo
authors: Kai
authors: K
authors: Xue
authors: Jiayin
authors: J
authors: Liu
authors: Heidi
authors: H
authors: McBride
authors: Benjamin K
authors: BK
authors: Tsang
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D002118:Calcium / Q000378:metabolism; D061207:Calcium Ionophores / Q000494:pharmacology; D002154:Calpain / Q000235:genetics / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D053148:Caspase 3 / Q000235:genetics / Q000378:metabolism; D045744:Cell Line, Tumor; D002945:Cisplatin / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects / Q000235:genetics; D019008:Drug Resistance, Neoplasm; D004789:Enzyme Activation / Q000187:drug effects / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D015759:Ionomycin / Q000494:pharmacology; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D046988:Proteasome Endopeptidase Complex / Q000235:genetics / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D021381:Protein Transport / Q000187:drug effects; D014166:Transferases; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D061207:Calcium Ionophores; D002352:Carrier Proteins; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D015759:Ionomycin; C400192:Cul9 protein, human; D014166:Transferases; C505407:CASP3 protein, human; D002154:Calpain; D053148:Caspase 3; D046988:Proteasome Endopeptidase Complex; C061553:ATP dependent 26S protease; D002945:Cisplatin; D002118:Calcium