title: Caveolin-1 tyrosine phosphorylation enhances paclitaxel-mediated cytotoxicity.
abstract: Caveolin-1 (CAV1), a highly conserved membrane-associated protein, is a putative regulator of cellular transformation. CAV1 is localized in the plasmalemma, secretory vesicles, Golgi, mitochondria, and endoplasmic reticulum membrane and associates with the microtubule cytoskeleton. Taxanes such as paclitaxel (Taxol) are potent anti-tumor agents that repress the dynamic instability of microtubules and arrest cells in the G(2)/M phase. Src phosphorylation of Tyr-14 on CAV1 regulates its cellular localization and function. We report that phosphorylation of CAV1 on Tyr-14 regulates paclitaxel-mediated apoptosis in MCF-7 breast cancer cells. Befitting its role as a multitasking molecule, we show that CAV1 sensitizes cells to apoptosis by regulating cell cycle progression and activation of the apoptotic signaling molecules BCL2, p53, and p21. We demonstrate that phosphorylated CAV1 triggers apoptosis by inactivating BCL2 and increasing mitochondrial permeability more efficiently than non-phosphorylated CAV1. Furthermore, expression of p21, which correlates with taxane sensitivity, is regulated by CAV1 phosphorylation in a p53-dependent manner. Collectively, our findings underscore the importance of CAV1 phosphorylation in apoptosis and suggest that events that negate CAV1 tyrosine phosphorylation may contribute to anti-microtubule drug resistance.
authors.affiliation: Department of Oncology, Lombardi Comprehensive Cancer Center, and Departments of Physiology and Biophysics, Georgetown University, College of Medicine, Washington, D. C. 20057, USA.
authors.forename: Ayesha N
authors.initials: AN
authors.lastname: Shajahan
authors.forename: Aifen
authors.initials: A
authors.lastname: Wang
authors.forename: Markus
authors.initials: M
authors.lastname: Decker
authors.forename: Richard D
authors.initials: RD
authors.lastname: Minshall
authors.forename: Minetta C
authors.initials: MC
authors.lastname: Liu
authors.forename: Robert
authors.initials: R
authors.lastname: Clarke
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001943:Breast Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D051242:Caveolin 1 / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002463:Cell Membrane Permeability / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008870:Microtubules / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism / Q000473:pathology; D017239:Paclitaxel / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D011499:Protein Processing, Post-Translational / Q000187:drug effects* / Q000235:genetics; D050257:Tubulin Modulators / Q000494:pharmacology*; D014443:Tyrosine / Q000378:metabolism
chemical_list: D051017:Apoptosis Regulatory Proteins; D051242:Caveolin 1; D050257:Tubulin Modulators; D014443:Tyrosine; D017239:Paclitaxel