title: Specific mitochondrial calcium overload induces mitochondrial fission in prostate cancer cells.
abstract: Mitochondria are structurally complex organelles that undergo fragmentation or fission in apoptotic cells. Mitochondrial fission requires the cytoplasmic dynamin-related protein, Drp1, which translocates to the mitochondria during apoptosis and interacts with the mitochondrial protein, Fis1. Finely tuned changes in cellular calcium modulate a variety of intracellular functions; in resting cells, the level of mitochondrial calcium is low, while it is higher during apoptosis. Mitochondria take up Ca(2+) via the Uniporter and extrude it to the cytoplasm through the mitochondrial Na+/Ca(2+) exchanger. Overload of Ca(2+) in the mitochondria leads to their damage, affecting cellular function and survival. The mitochondrial Na+/Ca2+ exchanger was blocked by benzodiazepine, CGP37157 (CGP) leading to increased mitochondrial calcium and enhancing the apoptotic effects of TRAIL, TNFalpha related apoptosis inducing ligand. In the present study, we observed that increasing mitochondrial calcium induced mitochondrial fragmentation, which correlated with the presence of Drp1 at the mitochondria in CGP treated cells. Under these conditions, we observed interactions between Drp1 and Fis1. The importance of Drp1 in fragmentation was confirmed by transfection of dominant negative Drp1 construct. However, fragmentation of the mitochondria was not sufficient to induce apoptosis, although it enhanced TRAIL-induced apoptosis. Furthermore, oligomerization of Bak was partially responsible for the increased apoptosis in cells treated with both CGP and TRAIL. Thus, our results show that combination of an apoptogenic agent and an appropriate calcium channel blocker provide therapeutic advantages.
authors.affiliation: Charlie Norwood VA Medical Center, Augusta, GA 30904, USA.
authors.forename: Ismail
authors.initials: I
authors.lastname: Kaddour-Djebbar
authors.forename: Vivek
authors.initials: V
authors.lastname: Choudhary
authors.forename: Craig
authors.initials: C
authors.lastname: Brooks
authors.forename: Taghreed
authors.initials: T
authors.lastname: Ghazaly
authors.forename: Vijayabaskar
authors.initials: V
authors.lastname: Lakshmikanthan
authors.forename: Zheng
authors.initials: Z
authors.lastname: Dong
authors.forename: M Vijay
authors.initials: MV
authors.lastname: Kumar
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000502:physiology; D015153:Blotting, Western; D002118:Calcium / Q000378:metabolism*; D045744:Cell Line, Tumor; D002998:Clonazepam / Q000031:analogs & derivatives / Q000494:pharmacology; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008297:Male; D008565:Membrane Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D046529:Microscopy, Electron, Transmission; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure*; D024101:Mitochondrial Proteins / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D019831:Sodium-Calcium Exchanger / Q000037:antagonists & inhibitors / Q000187:drug effects; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology; D013841:Thiazepines / Q000494:pharmacology; D014162:Transfection; D050998:bcl-2 Homologous Antagonist-Killer Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism
chemical_list: C494772:BAK1 protein, human; C476525:FIS1 protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D024101:Mitochondrial Proteins; D019831:Sodium-Calcium Exchanger; D053221:TNF-Related Apoptosis-Inducing Ligand; D013841:Thiazepines; D050998:bcl-2 Homologous Antagonist-Killer Protein; D002998:Clonazepam; C079032:CGP 37157; D020558:GTP Phosphohydrolases; C110768:DNM1L protein, human; D034281:Dynamins; D002118:Calcium