Okadaic acid activates p42 mitogen-activated protein kinase (MAP kinase; ERK-2) in B-lymphocytes but inhibits rather than augments cellular proliferation: contrast with phorbol 12-myristate 13-acetate.

摘要: Ligation of the membrane immunoglobulin M receptor as well stimulation with protein kinase C agonist phorbol 12-myristate 13-acetate leads to a B-lymphocyte proliferation and differentiation. Both stimuli activate p42 mitogen-activated (MAP) in human B-lymphocytes [Casillas, Hanekom, Williams, Katz Nel (1991) J. Biol. Chem. 266, 19088-19094]. MAP activation is dependent on tyrosine threonine phosphorylation its activity inhibited by threonine/serine phosphatases. Okadaic acid, specific inhibitor type 1 2A serine/threonine phosphatases, induced potent dose-dependent fashion, but failed induce [3H]thymidine incorporation into normal tonsil B-cells. Moreover, combination ligation, okadaic acid decreased rather than increased incorporation. The kinetics differed from anti-membrane stimulation. 42 kDa 44 proteins which co-electrophoresed co-chromatographed ERK-2 ERK-1 respectively. Ramos cells also contained constitutively active 46 appeared separate peak chromatography could be immunoprecipitated an antiserum against rat fusion protein.