p21-Activated kinase 5 (Pak5) localizes to mitochondria and inhibits apoptosis by phosphorylating BAD.
Pak5 is the most recently identified and least understood member of the p21-activated kinase (Pak) family. This kinase is known to promote neurite outgrowth in vitro, but its localization, substrates, and effects on cell survival have not been reported. We show here that Pak5 has unique properties that distinguish it from all other members of the Pak family. First, Pak5, unlike Pak1, cannot complement an STE20 mutation in Saccharomyces cerevisiae. Second, Pak5 binds to the GTPases Cdc42 and Rac, but these GTPases do not regulate Pak5 kinase activity, which is constitutive and stronger than any other Pak. Third, Pak5 prevents apoptosis induced by camptothecin and C2-ceramide by phosphorylating BAD on Ser-112 in a protein kinase A-independent manner and prevents the localization of BAD to mitochondria, thereby inhibiting the apoptotic cascade that leads to apoptosis. Finally, we show that Pak5 itself is constitutively localized to mitochondria, and that this localization is independent of kinase activity or Cdc42 binding. These features make Pak5 unique among the Pak family and suggest that it plays an important role in apoptosis through BAD phosphorylation.
Cotteret
Sophie
S
Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA.
Jaffer
Zahara M
ZM
Beeser
Alexander
A
Chernoff
Jonathan
J
D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D019556:COS Cells; D002166:Camptothecin / Q000494:pharmacology; D002470:Cell Survival; D006224:Cricetinae; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D018076:DNA, Complementary / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005690:Galactose / Q000494:pharmacology; D005816:Genetic Complementation Test; D005982:Glutathione Transferase / Q000378:metabolism; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D020930:MAP Kinase Kinase Kinases; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation; D010766:Phosphorylation; D010957:Plasmids / Q000378:metabolism; D011233:Precipitin Tests; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D013110:Sphingosine / Q000031:analogs & derivatives* / Q000494:pharmacology; D013347:Subcellular Fractions; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D054462:p21-Activated Kinases
D018076:DNA, Complementary; D047908:Intracellular Signaling Peptides and Proteins; C064769:N-acetylsphingosine; D029701:Saccharomyces cerevisiae Proteins; D005982:Glutathione Transferase; C486708:Pak7 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020930:MAP Kinase Kinase Kinases; C078754:STE20 protein, S cerevisiae; D020764:cdc42 GTP-Binding Protein; D013110:Sphingosine; D005690:Galactose; D002166:Camptothecin