Lysophosphatidic acid stimulates tyrosine phosphorylation of focal adhesion kinase, paxillin, and p130. Signaling pathways and cross-talk with platelet-derived growth factor.
Addition of 1-oleoyl-lysophosphatidic acid (LPA) induces tyrosine phosphorylation of multiple substrates in Swiss 3T3 cells including bands of M(r) 110,000-130,000 and M(r) 70,000-80,000. An increase in tyrosine phosphorylation of the M(r) 110,000-130,000 cluster of bands was detected as soon as 30 s after LPA stimulation reaching a maximum within 1 min. LPA stimulated tyrosine phosphorylation of all bands in a concentration-dependent fashion; a half-maximal effect occurred at 30 nM. Immunoprecipitation of lysates of LPA-treated cells with monoclonal antibodies that specifically recognize focal adhesion kinase (p125FAK), paxillin, and p130 revealed that these proteins are prominent substrates for LPA-stimulated tyrosine phosphorylation. Down-regulation of protein kinase C (PKC) by prolonged pretreatment with phorbol 12,13-dibutyrate, selective inhibition of PKC by GF109203X, or depletion of the intracellular Ca2+ pool by thapsigargin had no effect on LPA-stimulated tyrosine phosphorylation. Thus, protein tyrosine phosphorylation by LPA is largely independent of either the PKC or Ca2+ pathways. In contrast, pretreatment of the cells with cytochalasin D, which selectively disrupts the network of the actin filaments, completely inhibited LPA-induced tyrosine phosphorylation. Furthermore, tyrosine phosphorylation of p125FAK induced by LPA was completely prevented when cells were stimulated in the presence of platelet-derived growth factor at a concentration (30 ng/ml) that causes disruption of actin stress fibers. This suggests that the integrity of the actin cytoskeleton is essential for LPA-induced tyrosine phosphorylation and reveals a novel cross-talk between LPA and platelet-derived growth factor on p125FAK tyrosine phosphorylation.
Seufferlein
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T
Imperial Cancer Research Fund, London, United Kingdom.
Rozengurt
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E
D016475:3T3 Cells; D008841:Actin Cytoskeleton / Q000502:physiology; D000199:Actins / Q000378:metabolism; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism*; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008246:Lysophospholipids / Q000494:pharmacology*; D051379:Mice; D051419:Paxillin; D010750:Phosphoproteins / Q000378:metabolism*; D019000:Phosphotyrosine; D010982:Platelet-Derived Growth Factor / Q000494:pharmacology*; D011493:Protein Kinase C / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction; D014443:Tyrosine / Q000031:analogs & derivatives* / Q000378:metabolism
D000199:Actins; D015815:Cell Adhesion Molecules; D003598:Cytoskeletal Proteins; D008246:Lysophospholipids; D051419:Paxillin; D010750:Phosphoproteins; D010982:Platelet-Derived Growth Factor; C496062:Pxn protein, mouse; D019000:Phosphotyrosine; D014443:Tyrosine; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D051416:Focal Adhesion Protein-Tyrosine Kinases; C496051:Ptk2 protein, mouse; D011493:Protein Kinase C; D002118:Calcium