Signalling functions of α-tocopherol in smooth muscle cells

Abstract

α-Tocopherol but not β-tocopherol, activates protein phosphatase 2A, decreases protein kinase C activity and attenuates smooth muscle cell proliferation at physiological concentrations. β-Tocopherol prevents the effects of α-tocopherol. Inhibition of protein kinase Cα, but not of the other isoforms, by the inhibitor Go6976 prevents the effect of α-tocopherol. Protein kinase Cα, immunoprecipitated from α-tocopherol treated cells, is less phosphorylated and inactive. It is proposed that the specific activation of protein phosphatase 2A by α-tocopherol results in dephosphorylation and inactivation of protein kinase Cα. Finally, this cascade of events leads to smooth muscle cell proliferation inhibition.