Descoteaux A, Matlashewski G, Turco S J
Department of Biochemistry, University of Kentucky Medical Center, Lexington 40536.
J Immunol. 1992 Nov 1;149(9):3008-15.
The cell surface lipophosphoglycan (LPG) from Leishmania donovani promastigotes is a potent inhibitor of purified protein kinase C (PKC) activity in vitro. In this study, we have investigated the effect of LPG on the activation process of PKC in murine bone marrow-derived macrophages. The extent and kinetics of calcium ionophore A23187-induced [3H] phorbol dibutyrate binding to macrophages were not affected by LPG pretreatment or infection with either wild-type or LPG-deficient promastigotes, indicating no effect on the association of calcium-dependent PKC with the plasma membrane. In contrast, LPG inhibited the phosphorylation of both the PKC-specific VRKRTRLLR substrate peptide and MARCKS, and endogenous PKC substrate, in 1-oleoyl-2-acetyl-glycerol-stimulated macrophages. These observations provide direct evidence that LPG effectively inhibits PKC activity in intact macrophages. Finally, depletion of PKC rendered macrophages more permissive for the proliferation of L. donovani, suggesting that inhibition of PKC-dependent events contributes to the survival of this parasite within its host cell.
来自杜氏利什曼原虫前鞭毛体的细胞表面脂磷壁酸聚糖（LPG）在体外是纯化蛋白激酶C（PKC）活性的有效抑制剂。在本研究中，我们研究了LPG对小鼠骨髓来源巨噬细胞中PKC激活过程的影响。钙离子载体A23187诱导的[3H]佛波醇二丁酸酯与巨噬细胞结合的程度和动力学不受LPG预处理或野生型或LPG缺陷型前鞭毛体感染的影响，表明对钙依赖性PKC与质膜的结合没有影响。相反，LPG抑制了1-油酰-2-乙酰甘油刺激的巨噬细胞中PKC特异性VRKRTRLLR底物肽和MARCKS（一种内源性PKC底物）的磷酸化。这些观察结果提供了直接证据，表明LPG有效地抑制了完整巨噬细胞中的PKC活性。最后，PKC的缺失使巨噬细胞对杜氏利什曼原虫的增殖更具易感性，这表明抑制PKC依赖性事件有助于该寄生虫在其宿主细胞内的存活。
