title: p21-activated Kinase 1 (Pak1)-dependent phosphorylation of Raf-1 regulates its mitochondrial localization, phosphorylation of BAD, and Bcl-2 association.
abstract: Raf-1 protects cells from apoptosis, independently of its signals to MEK and ERK, by translocating to the mitochondria where it binds Bcl-2 and displaces BAD. However, the answer to the question of how Raf-1 is normally lured to the mitochondria and becomes activated remains elusive. p21-activated protein kinases (Paks) are serine/threonine protein kinases that phosphorylate Raf-1 at Ser-338 and Ser-339. Here we elucidate the molecular mechanism through which Pak1 signals to BAD through a Raf-1-activated pathway. Upon phosphorylation by Pak1, Raf-1 translocates to mitochondria and phosphorylates BAD at Ser-112. Moreover, the mitochondrial translocation of Raf-1 and the interaction between Raf-1 and Bcl-2 are regulated by Raf-1 phosphorylation at Ser-338/Ser-339. Notably, we show that formation of a Raf-1-Bcl-2 complex coincides with loss of an interaction between Bcl-2 and BAD. These signals are specific for Pak1, because Src-activated Raf-1 only stimulates the MAP kinase cascade. Thus, our data identify the molecular connections of a Pak1-Raf-1-BAD pathway that is involved in cell survival signaling.
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Shenghao
authors.initials: S
authors.lastname: Jin
authors.forename: Ya
authors.initials: Y
authors.lastname: Zhuo
authors.forename: Weining
authors.initials: W
authors.lastname: Guo
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Field
mesh_terms: D000818:Animals; D017209:Apoptosis; D002352:Carrier Proteins / Q000378:metabolism*; D002460:Cell Line; D002470:Cell Survival; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D020935:MAP Kinase Signaling System; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D041681:NIH 3T3 Cells; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism / Q000502:physiology*; D021381:Protein Transport; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism*; D019908:Proto-Oncogene Proteins c-raf / Q000378:metabolism*; D012694:Serine / Q000737:chemistry; D015398:Signal Transduction; D013347:Subcellular Fractions; D014162:Transfection; D051025:bcl-Associated Death Protein; D054462:p21-Activated Kinases
chemical_list: C494819:BAD protein, human; C494820:Bad protein, mouse; D002352:Carrier Proteins; D010455:Peptides; D019253:Proto-Oncogene Proteins c-bcl-2; D051025:bcl-Associated Death Protein; D012694:Serine; C515903:PAK1 protein, human; C515905:Pak1 protein, mouse; D017346:Protein Serine-Threonine Kinases; D019908:Proto-Oncogene Proteins c-raf; D054462:p21-Activated Kinases