Lysophosphatidic acid‐induced activation of protein Ser/Thr kinases in cultured rat 3Y1 fibroblasts Possible involvement in rhop21‐mediated signalling

Renaturation kinase assay was used to detect protein kinases activated by lysophosphatidic acid (LPA) in cultured rat 3Y1 fibroblasts. LPA activated several Ser/Thr protein kinases with apparent molecular weights of 145K, 85K, 64-65K (a doublet), and 60K (each named p145, p85, p64165 and p60, respectively) in addition to p43 mitogen activated protein (MAP)-kinase. Experiments using pertussis toxin and botulinum C3 exoenzyme showed that p145, p85, and p64165 kinases were activated by a pertussis toxin-insensitive rho p21-dependent pathway and that the activation of MAP-kinase was mediated by both the pertussis toxin-sensitive rho p21-independent and the pertussis toxin-insensitive rho p21-dependent pathways.