Tyrosine hydroxylase phosphorylation in bovine adrenal chromaffin cells: the role of MAPKs after angiotensin II stimulation

Angiotensin II (All, 100 nm) stimulation of bovine adrenal chromaffin cells (BACCs) produced angiotensin II receptor subtype 1 (AT(1))-mediated increa ses in extracellular regulated protein kinase 1/2 (ERK1/2) and stress-activ ated p38MAPK (p38 kinase) phosphorylation over a period of 10 min. ERK1/2 a nd p38 kinase phosphorylation preceded Ser31 phosphorylation on tyrosine hy droxylase (TOH). The inhibitors of mitogen-activated protein kinase kinase 1/2 (MEK1/2) activation, PD98059 (0.1-50 muM) and UO126 (0.1-10 muM), dose- dependently inhibited both ERK2 and Ser31 phosphorylation on TOH in respons e to All, suggesting MEK1/2 involvement. The p38 kinase inhibitor SB203580 (20 muM, 30 min) abolished Ser31 and Ser19 phosphorylation on TOH and parti ally inhibited ERK2 phosphorylation produced by All. In contrast, 1 muM SB2 03580 did not affect All-stimulated TOH phosphorylation, but fully inhibite d heat shock protein 27 (HSP27) phosphorylation produced by All. Also, 1 tm SB203580 fully inhibited Ser19 phosphorylation on TOH and HSP27 phosphoryl ation in response to anisomycin (30 min, 10 mug/mL). The results suggest th at ERKs mediate Ser31 phosphorylation on TOH in response to All, but p38 ki nase is not involved. Previous studies suggesting a role for p38 kinase in the phosphorylation of Ser31 are explained by the non-specific effects of 2 0 muM SB203580 in BACCs. The p38 kinase pathway is able to phosphorylate Se r19 on TOH in response to anisomycin, but does not do so in response to AII .