title: Camptothecin induces nuclear export of prohibitin preferentially in transformed cells through a CRM-1-dependent mechanism.
abstract: Prohibitin is a growth-suppressive protein that has multiple functions in the nucleus and the mitochondria. Our earlier studies had shown that prohibitin represses the activity of E2F transcription factors while enhancing p53-mediated transcription. At the same time, prohibitin has been implicated in mediating the proper folding of mitochondrial proteins. We had found that treatment of cells with camptothecin, a topoisomerase 1 inhibitor, led to the export of prohibitin and p53 from the nucleus to the mitochondria. Here we show that the camptothecin-induced export of prohibitin occurs preferentially in transformed cell lines, but not in untransformed or primary cells. Cells that did not display the translocation of prohibitin were refractive to the apoptotic effects of camptothecin. The translocation was mediated by a putative nuclear export signal at the C-terminal region of prohibitin; fusion of the nuclear export signal (NES) of prohibitin to green fluorescence protein led to its export from the nucleus. Leptomycin B could inhibit the nuclear export of prohibitin showing that it was a CRM-1-dependent event driven by Ran GTPase. Confirming this, prohibitin was found to physically interact with CRM-1, and this interaction was significantly higher in transformed cells. Delivery of a peptide corresponding to the NES of prohibitin prevented the export of prohibitin to cytoplasm and protected cells from apoptosis. These results suggest that the regulated translocation of prohibitin from the nucleus to the mitochondria facilitates its pleiotropic functions and might contribute to its anti-proliferative and tumor suppressive properties.
authors.affiliation: Drug Discovery Program, Department of Interdisciplinary Oncology, H. Lee Moffitt Cancer Center and Research Institute, University of South Florida, Tampa, Florida 33612, USA.
authors.forename: Shipra
authors.initials: S
authors.lastname: Rastogi
authors.forename: Bharat
authors.initials: B
authors.lastname: Joshi
authors.forename: Gina
authors.initials: G
authors.lastname: Fusaro
authors.forename: Srikumar
authors.initials: S
authors.lastname: Chellappan
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects*; D000972:Antineoplastic Agents, Phytogenic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D002166:Camptothecin / Q000494:pharmacology*; D002461:Cell Line, Transformed; D045744:Cell Line, Tumor; D006801:Humans; D028884:Karyopherins / Q000502:physiology*; D008928:Mitochondria / Q000378:metabolism; D049790:Nuclear Export Signals; D009687:Nuclear Proteins; D000091402:Prohibitins; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology*; D012097:Repressor Proteins / Q000187:drug effects / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein
chemical_list: D000972:Antineoplastic Agents, Phytogenic; D002166:Camptothecin; D028884:Karyopherins; D049790:Nuclear Export Signals; D009687:Nuclear Proteins; D000091402:Prohibitins; D018160:Receptors, Cytoplasmic and Nuclear; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53; D020931:ran GTP-Binding Protein; D000097606:Exportin 1 Protein; C120587:RAN protein, human