Activation of Protein Kinase Cα in the Lysophosphatidic Acid-Induced Bovine Sperm Acrosome Reaction and Phospholipase D1 Regulation1

Abstract

Protein kinase C (PKC) has been implicated in the sperm acrosome reaction. In the present study, we demonstrate induction of the acrosome reaction and activation of sperm PKCalpha by lysophosphatidic acid (LPA), which is known to induce signal transduction cascades in many cell types via binding to specific cell-surface receptors. Under conditions by which LPA activates PKCalpha, there is significant stimulation of the acrosome reaction, which is inhibited by PKC inhibitors. Protein kinase Calpha belongs to the Ca(2+)-dependent classical PKC family of isoforms, and indeed we show that its activation depends upon the presence of Ca(2+) in the incubation medium. Protein kinase Calpha is a known regulator of phospholipase D (PLD). We investigated the possible regulatory relationships between PKCalpha and PLD1. Using specific antibodies against PLD1, we demonstrate for the first time its presence in bovine sperm. Furthermore, PLD1 coimmunoprecipitates with PKCalpha and the PKCalpha-PLD1 complex decomposes after treatment of the cells with LPA or 12-O:-tetradecanoyl phorbol-13-acetate, resulting in the translocation of PKCalpha to the plasma membrane and translocation of PLD1 to the particulate fraction. A possible bilateral regulation of PKCalpha and PLD1 activation during the sperm acrosome reaction is suggested.

Extracellular Adenosine Triphosphate Stimulates Acrosomal Exocytosis in Bovine Spermatozoa via P2 Purinoceptor1

“…Activation of PKC by ATPe was also found in CHO cells [56]. In recent papers, we showed that one of the cPKC isoforms, PKC␣, is involved in the bovine sperm AR [42,43]. Here, we provide further support for this notion by showing that ATPe activates PKC␣, and that the AR induced by ATPe is inhibited by a PKC-specific inhibitor.…”

“…In our recent publications, we showed that the Ca 2ϩ -dependent PKC␣ isoform is involved in the mechanism of bovine sperm AR [42,43]. The involvement of the P 2y receptor suggests that the activation of PLC results in the hydrolysis of phosphatidyl inositol to produce diacylglycerol (DAG) and inositol 1,4,5-tris-phosphate (IP 3 ).…”

LPA receptor signaling: pharmacology, physiology, and pathophysiology

“…One study demonstrated that LPP-1 overexpression resulted in impaired spermatogenesis (264), suggesting that the presence of LPA may be important in sperm development. There is also evidence for LPA involvement in sperm motility (265), although triple genetic deletion of LPA [1][2][3] showed no detectable defi cits in sperm motility. However, deletion of LPA 1-3 did result in decreased germ cell survival and increased prevalence of azoospermia in aging mice (264).…”

Phospholipase C and D regulation of Src, calcium release and membrane fusion during Xenopus laevis development

“…PLD1 (not PLD2) is localized in the outer acrosome membrane “suggesting its possible involvement in the AR” (Garbi et al, 2000). The authors also suggest that acrosomal PLD1 is involved in PKCα activation and that PA is “a fusogenic compound that may stimulate the fusion between the outer acrosomal and the plasma membrane leading to acrosomal exocytosis.”…”