Relationship of p21-activated kinase (PAK) and filopodia to persistence and oncogenic transformation.
Previously, we found that oncogenically transformed cells had fewer filopodia and more large, p21-activated kinase (PAK)-dependent features than normal cells. These large protrusions (LPs) were increased in cells expressing RhoA(N19) with Cdc42-associated kinase (ACK). Here, we determine how GTPase-mediated mechanisms of focal contact (FC) regulation affect these protrusions. Constructs encoding various proteins were introduced into cells which were then studied by microscopy and computerized image processing and analysis. Constructs that prevented PAK recruitment by PAK-interacting exchange factor (PIX) or restricted PAK residence time on FCs decreased both protrusions. Thus, filopodia were also PAK-dependent. A comparison of FC distribution in cells expressing PAK in the presence or absence of PAK kinase inhibitor domain (KID) suggested that PAK enlarged FCs without affecting the prevalence of either protrusion. KID or Nck expression increased LPs but not filopodia. Nck failed to synergize with KID or ACK and RhoA(N19) in enhancing LPs. Nck and KID synergistically enhanced filopodia, possibly because Nck recruited PAK to FCs while KID prevented their dissociation by PAK-mediated autophosphorylation. Coexpression of Nck, ACK, and RhoA(N19) abrogated filopodia and replicated the transformed phenotype. Since Nck recruitment of PAK is implicated in persistence of directional movement, we studied the PAK-Nck interface. Filopodia were eliminated by the Nck PAK-binding domain and LPs by the PAK Nck-binding domain. The results suggested that filopodia formation has more stringent requirements than LP formation, and Nck and PAK are used differently in the protrusions. Loss of filopodia in transformed cells may reflect defective regulation of GTPase mechanisms.
Heckman
Carol A
CA
Department of Biological Sciences, Bowling Green State University, Bowling Green, Ohio 43403-0212, USA. heckman@bgsu.edu
Demuth
John G
JG
Deters
Donald
D
Malwade
Santosh R
SR
Cayer
Marilyn L
ML
Monfries
Clinton
C
Mamais
Adamantios
A
D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D002283:Carcinoma, Bronchogenic / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002448:Cell Adhesion; D002460:Cell Line; D002465:Cell Movement; D002471:Cell Transformation, Neoplastic / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D020848:Chimerin 1 / Q000378:metabolism; D020662:Guanine Nucleotide Exchange Factors / Q000378:metabolism; D007091:Image Processing, Computer-Assisted; D008175:Lung Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D008856:Microscopy, Fluorescence; D009154:Mutation; D015513:Oncogene Proteins / Q000378:metabolism; D009857:Oncogenes; D010766:Phosphorylation; D021381:Protein Transport; D011554:Pseudopodia / Q000201:enzymology* / Q000473:pathology; D051381:Rats; D011916:Rats, Inbred F344; D064067:Rho Guanine Nucleotide Exchange Factors; D014162:Transfection; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D054462:p21-Activated Kinases / Q000235:genetics / Q000378:metabolism*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D048868:Adaptor Proteins, Signal Transducing; D020848:Chimerin 1; D020662:Guanine Nucleotide Exchange Factors; C078332:Nck protein; D015513:Oncogene Proteins; D064067:Rho Guanine Nucleotide Exchange Factors; D054462:p21-Activated Kinases; D020764:cdc42 GTP-Binding Protein; D020830:rac1 GTP-Binding Protein; D020742:rhoA GTP-Binding Protein