Regulation of anchorage-dependent signal transduction by protein kinase A and p21-activated kinase.
Activation of the canonical mitogen-activated protein kinase (MAPK) cascade by soluble mitogens is blocked in non-adherent cells. It is also blocked in cells in which the cAMP-dependent protein kinase (PKA) is activated. Here we show that inhibition of PKA allows anchorage-independent stimulation of the MAPK cascade by growth factors. This effect is transient, and its duration correlates with sustained tyrosine phosphorylation of paxillin and focal-adhesion kinase (FAK) in non-adherent cells. The effect is sensitive to cytochalasin D, implicating the actin cytoskeleton as an important factor in mediating this anchorage-independent signalling. Interestingly, constitutively active p21-activated kinase (PAK) also allows anchorage-independent MAPK signalling. Furthermore, PKA negatively regulates PAK in vivo, and whereas the induction of anchorage-independent signaling resulting from PKA suppression is blocked by dominant negative PAK, it is markedly prolonged by constitutively active PAK. These observations indicate that PKA and PAK are important regulators of anchorage-dependent signal transduction.
Howe
A K
AK
Department of Pharmacology, University of North Carolina at Chapel Hill, North Carolina 27599-7365, USA. alanhowe@med.unc.edu
Juliano
R L
RL
D016475:3T3 Cells; D000818:Animals; D002448:Cell Adhesion; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics / Q000378:metabolism*; D015638:Cytochalasin D / Q000494:pharmacology; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004789:Enzyme Activation; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D020935:MAP Kinase Signaling System; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019384:Nucleic Acid Synthesis Inhibitors / Q000494:pharmacology; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*; D014443:Tyrosine / Q000378:metabolism; D054462:p21-Activated Kinases
D003598:Cytoskeletal Proteins; D019384:Nucleic Acid Synthesis Inhibitors; D051419:Paxillin; D010750:Phosphoproteins; C496062:Pxn protein, mouse; D011993:Recombinant Fusion Proteins; D015638:Cytochalasin D; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D017346:Protein Serine-Threonine Kinases; D054462:p21-Activated Kinases; D017868:Cyclic AMP-Dependent Protein Kinases; D020928:Mitogen-Activated Protein Kinases