PAK promotes morphological changes by acting upstream of Rac.
The serine/threonine kinase p21-activated kinase (PAK) has been implicated as a downstream effector of the small GTPases Rac and Cdc42. While these GTPases evidently induce a variety of morphological changes, the role(s) of PAK remains elusive. Here we report that overexpression of betaPAK in PC12 cells induces a Rac phenotype, including cell spreading/membrane ruffling, and increased lamellipodia formation at growth cones and shafts of nerve growth factor-induced neurites. These effects are still observed in cells expressing kinase-negative or Rac/Cdc42 binding-deficient PAK mutants, indicating that kinase- and p21-binding domains are not involved. Furthermore, lamellipodia formation in all cell lines, including those expressing Rac binding-deficient PAK, is inhibited significantly by dominant-negative RacN17. Equal inhibition is achieved by blocking PAK interaction with the guanine nucleotide exchange factor PIX using a specific N-terminal PAK fragment. We conclude that PAK, via its N-terminal non-catalytic domain, acts upstream of Rac mediating lamellipodia formation through interaction with PIX.
Glaxo-IMCB Group, Institute of Molecular and Cell Biology, Singapore.
A
A
Obermeier
S
S
Ahmed
E
E
Manser
S C
SC
Yen
C
C
Hall
L
L
Lim
D000818:Animals; D017871:Calcium-Calmodulin-Dependent Protein Kinases / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics / Q000502:physiology; D002462:Cell Membrane / Q000502:physiology; D002465:Cell Movement / Q000235:genetics / Q000502:physiology; D011232:Chemical Precipitation; D019204:GTP-Binding Proteins / Q000235:genetics / Q000502:physiology*; D005822:Genetic Vectors; D006150:Guanine Nucleotides / Q000378:metabolism; D048031:JNK Mitogen-Activated Protein Kinases; D008845:Microinjections; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D016297:Mutagenesis, Site-Directed; D016501:Neurites / Q000502:physiology; D016716:PC12 Cells; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D051381:Rats; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology*; D013347:Subcellular Fractions / Q000378:metabolism / Q000502:physiology; D013379:Substrate Specificity; D054462:p21-Activated Kinases; D020744:rac GTP-Binding Proteins
D006150:Guanine Nucleotides; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D017871:Calcium-Calmodulin-Dependent Protein Kinases; D048031:JNK Mitogen-Activated Protein Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D019204:GTP-Binding Proteins; D020744:rac GTP-Binding Proteins