Requirement for PAK4 in the anchorage-independent growth of human cancer cell lines.
p21-activated protein kinase (PAK) serine/threonine kinases are important effectors of Rho family GTPases and have been implicated in the regulation of cell morphology and motility, as well as in cell transformation. To further investigate the possible involvement of PAK kinases in tumorigenesis, we analyzed the expression of several family members in tumor cell lines. Here we demonstrate that PAK4 is frequently overexpressed in human tumor cell lines of various tissue origins. We also have identified serine (Ser-474) as the likely autophosphorylation site in the kinase domain of PAK4 in vivo. Mutation of this serine to glutamic acid (S474E) results in constitutive activation of the kinase. Phosphospecific antibodies directed against serine 474 detect activated PAK4 on the Golgi membrane when PAK4 is co-expressed with activated Cdc42. Furthermore, expression of the active PAK4 (S474E) mutant has transforming potential, leading to anchorage-independent growth of NIH3T3 cells. A kinase-inactive PAK4 (K350A,K351A), on the other hand, efficiently blocks transformation by activated Ras and inhibits anchorage-independent growth of HCT116 colon cancer cells. Taken together, our data strongly implicate PAK4 in oncogenic transformation and suggest that PAK4 activity is required for Ras-driven, anchorage-independent growth.
Callow
Marinella G
MG
SUGEN Inc., South San Francisco, California 94080-4811, USA.
Clairvoyant
Felix
F
Zhu
Shirley
S
Schryver
Brian
B
Whyte
David B
DB
Bischoff
James R
JR
Jallal
Bahija
B
Smeal
Tod
T
D016475:3T3 Cells; D000328:Adult; D000595:Amino Acid Sequence; D000818:Animals; D002471:Cell Transformation, Neoplastic; D011905:Genes, ras; D006056:Golgi Apparatus / Q000737:chemistry; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000502:physiology*; D014407:Tumor Cells, Cultured; D054462:p21-Activated Kinases
C116367:PAK4 protein, human; C492065:Pak4 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases