Lysophosphatidic acid-induced nuclear localization of protein kinase C δ in bovine theca cells stimulated with luteinizing hormone

Abstract

The amounts of lysophospholipase D (LPLD) and the ovarian protein kinase C δ (PKCδ) increase during the course of pregnancy. Because LPLD is involved in the production of the bioactive phospholipid lysophosphatidic acid (LPA), we examined whether stimulation with LPA would influence PKCδ in the ovary. We used immunoblotting and immunohistochemical methods to show that stimulation of bovine theca cells with LPA leads to an unexpected redistribution of PKCδ from the cytosol to the perinuclear area and that in the presence of LH, LPA induces a complete nuclear translocation of PKCδ. These effects of LPA are dose dependent, can be mimicked by phorbol ester, and are inhibited by a PKCδ inhibitor, rottlerin. Concomitantly, under the same experimental conditions both LPA and the phorbol ester PMA (4β-phorbol-12-myristate-13-acetate) augment LH-stimulated progesterone accumulation in this cell system. This functional effect of LPA and PMA is abolished in cells pretreated with rottlerin. It is unclear whether the nuclear localization of PKCδ indicates a specific function of the enzyme in the bovine ovary. Because PKCδ supports a luteotropic function in rodent models, a similar role in the bovine ovary is also likely.