title: Knockdown of MTP18, a novel phosphatidylinositol 3-kinase-dependent protein, affects mitochondrial morphology and induces apoptosis.
abstract: We identified a novel human cDNA encoding a mitochondrial protein, MTP18 (mitochondrial protein, 18 kDa) as a transcriptional downstream target of phosphatidylinositol (PI) 3-kinase signaling. We demonstrate that MTP18 mRNA as well as protein expression is dependent on PI 3-kinase activity. Confocal microscopy and biochemical fractionation revealed a mitochondrial localization of MTP18. Loss-of-function analysis employing antisense molecules revealed that MTP18 is essential for cell viability in PC-3 and HaCaT cells. We show that knockdown of MTP18 protein level results in a cytochrome c release from mitochondria and consequently leads to apoptosis. In addition, HaCaT cells with reduced levels of MTP18 become more sensitive to apoptotic stimuli. This effect is accompanied by dramatic subcellular alterations. Reduction of MTP18 impairs mitochondrial morphology resulting in the formation of a highly interconnected mitochondrial reticulum in COS-7 cells. Conversely, overexpression of MTP18 induces a punctuate morphology of mitochondria suggesting also a functional role of MTP18 in maintaining the mitochondrial integrity. Hence, our data indicate an unexpected connection of PI 3-kinase signaling, apoptosis and the morphology of mammalian mitochondria.
authors.affiliation: Atugen AG, Otto Warburg Haus (Nr. 80), Robert-Rössle-Strasse 10, 13125 Berlin, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Tondera
authors.forename: Ansgar
authors.initials: A
authors.lastname: Santel
authors.forename: Rolf
authors.initials: R
authors.lastname: Schwarzer
authors.forename: Sybille
authors.initials: S
authors.lastname: Dames
authors.forename: Klaus
authors.initials: K
authors.lastname: Giese
authors.forename: Anke
authors.initials: A
authors.lastname: Klippel
authors.forename: Jörg
authors.initials: J
authors.lastname: Kaufmann
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D019556:COS Cells; D002455:Cell Division; D002460:Cell Line; D016373:DNA, Antisense / Q000235:genetics; D018076:DNA, Complementary / Q000235:genetics; D006367:HeLa Cells; D006801:Humans; D008928:Mitochondria / Q000378:metabolism* / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction
chemical_list: D016373:DNA, Antisense; D018076:DNA, Complementary; D024101:Mitochondrial Proteins; D019869:Phosphatidylinositol 3-Kinases; D012333:RNA, Messenger; C490021:MTFP1 protein, human