Activation of mitogen-activated protein kinases is required for alpha(1)-adrenergic agonist-induced cell scattering in transfected HepG2 cells

Activation of alpha(1B)-adrenergic receptors (alpha(1B)AR) by phenylephrine (PE) induces scattering of HepG2 cells stably transfected with the alpha(1 B)AR (TFG2 cells). Scattering was also observed after stimulation of TFG2 c ells with phorbol myristate acetate (PMA) but not with hepatocyte growth fa ctor/scatter factor, epidermal growth factor, or insulin. PMA but not pheny lephrine rapidly activated PKC alpha in TFG2 cells, and the highly selectiv e PKC inhibitor bisindolylmaleimide (GFX) completely abolished PMA-induced but not PE-induced scattering PE rapidly activated p44/42 mitogen-activated protein kinase (MAPK), p38 MAPK, c-Jun N-terminal kinase (JNK), and AP1 (c -fos/c-jun), Selective blockade of p42/44 MAPK activity by PD98059 or by tr ansfection of a MEK1 dominant negative adenovirus significantly inhibited t he PE-induced scattering of TFG2 cells. Selective inhibition of p38 MAPK by SB203850 or SB202190 also blocked PE-induced scattering, whereas treatment of TFG2 cells with the PI3 kinase inhibitors LY294002 or wortmannin did no t inhibit PE-induced scattering. Blocking JNK activation with a dominant ne gative mutant of JNK or blocking AP1 activation with a dominant negative mu tant of c-jun (TAM67) significantly inhibited PE-induced cell scattering Th ese data indicate that PE-induced scattering of TFG2 cells is mediated by c omplex mechanisms, including activation of p42/44 MAPK, p38 MAPK, and JNK, Cell spreading has been reported to play important roles in wound repair, t umor invasion, and metastasis, Therefore, catecholamines acting via the alp ha(1)AR may modulate these physiological and pathological processes. (C) 20 00 Academic Press.