GIT1 activates p21-activated kinase through a mechanism independent of p21 binding.
p21-activated kinases (PAKs) associate with a guanine nucleotide exchange factor, Pak-interacting exchange factor (PIX), which in turn binds the paxillin-associated adaptor GIT1 that targets the complex to focal adhesions. Here, a detailed structure-function analysis of GIT1 reveals how this multidomain adaptor also participates in activation of PAK. Kinase activation does not occur via Cdc42 or Rac1 GTPase binding to PAK. The ability of GIT1 to stimulate alphaPAK autophosphorylation requires the participation of the GIT N-terminal Arf-GAP domain but not Arf-GAP activity and involves phosphorylation of PAK at residues common to Cdc42-mediated activation. Thus, the activation of PAK at adhesion complexes involves a complex interplay between the kinase, Rho GTPases and protein partners that provide localization cues.
Loo
Tsui-Han
TH
GSK-IMCB Group, Institute of Molecular and Cell Biology, Singapore 117609, Singapore.
Ng
Yuen-Wai
YW
Lim
Louis
L
Manser
Ed
E
D048868:Adaptor Proteins, Signal Transducing; D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins / Q000378:metabolism*; D004789:Enzyme Activation; D022001:Focal Adhesions / Q000378:metabolism; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism*; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation; D041681:NIH 3T3 Cells; D010750:Phosphoproteins; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D064067:Rho Guanine Nucleotide Exchange Factors; D013347:Subcellular Fractions / Q000378:metabolism; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism*; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C485647:GIT1 protein, human; D020690:GTPase-Activating Proteins; C120766:Git1 protein, mouse; D020662:Guanine Nucleotide Exchange Factors; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein