Carlier E, Mabrouk K, Moulard M, Fajloun Z, Rochat H, De Waard M, Sabatier J M
INSERM U464, Laboratoire de Neurobiologie des Canaux Ioniques, Faculté de Médicine Nord, Marseille, France.
J Pept Res. 2000 Dec;56(6):427-37. doi: 10.1034/j.1399-3011.2000.00815.x.
SPC3 is a multibranched peptide containing eight identical GPGRAF motifs which are derived from the human immunodeficiency virus (HIV)-1 gp120 V3 loop consensus sequence. This molecule was reported to prevent the infection of CD4+ cells by various HIV-1 and HIV-2 strains. However, the molecular mode of action of SPC3 remains unclear. Here, we investigated the possibility that SPC3 could interact with alpha/beta-chemokine receptors following observations that, first, the V3 loop is likely to be involved in alpha/beta-chemokine receptor-dependent HIV entry and, second, natural ligands of these receptors are potent inhibitors of cell infection. To address this point, we examined the effects of SPC3 on Xenopus oocytes either uninjected or expressing exogenous human CXCR4 alpha-chemokine receptors. Extracellular applications of micromolar concentrations of SPC3 onto Xenopus oocytes trigger potent inward chloride currents which can be inhibited by increasing extracellular Ca2+ concentration. This effect can be blocked by chloride channel antagonists and is highly specific to SPC3 as it is not triggered by structural analogs of SPC3. The SPC3-induced chloride conductance in oocytes is alpha/beta-chemokine receptor dependent because: (i) SPC3 alters the sensitivity of this channel to external applications of human recombinant MIP-1alpha, a natural ligand of human CCR5 receptor, and (ii) the amplitude of the inward current could be increased by the expression of exogenous human CXCR4 chemokine receptor. The effect of SPC3 appears to rely on the activation of a phospholipase A2 signaling pathway, but is not affected by changes in cytosolic Ca2+ concentration, or by alterations in Gi/Go protein, adenylate cyclase, phospholipase C or protein kinase C activity. Altogether, the data indicate that SPC3 is capable of activating a surface alpha/beta-chemokine-like receptor-mediated signaling pathway in competent cells, thereby triggering, either directly or indirectly, a Ca2+-inactivated chloride conductance.
SPC3是一种多分支肽，包含八个相同的GPGRAF基序，这些基序源自人类免疫缺陷病毒（HIV）-1 gp120 V3环共有序列。据报道，该分子可预防多种HIV-1和HIV-2毒株对CD4 +细胞的感染。然而，SPC3的分子作用模式仍不清楚。在此，我们进行了研究，鉴于以下观察结果，SPC3可能与α/β趋化因子受体相互作用：首先，V3环可能参与α/β趋化因子受体依赖性HIV进入；其次，这些受体的天然配体是细胞感染的有效抑制剂。为了解决这一问题，我们研究了SPC3对未注射或表达外源性人类CXCR4α趋化因子受体的非洲爪蟾卵母细胞的影响。在非洲爪蟾卵母细胞上胞外施加微摩尔浓度的SPC3会引发强烈的内向氯离子电流，增加细胞外Ca2 +浓度可抑制该电流。这种效应可被氯离子通道拮抗剂阻断，并且对SPC3具有高度特异性，因为SPC3的结构类似物不会引发这种效应。卵母细胞中SPC3诱导的氯离子电导依赖于α/β趋化因子受体，原因如下：（i）SPC3改变了该通道对人重组MIP-1α（人CCR5受体的天然配体）胞外应用的敏感性；（ii）外源性人类CXCR4趋化因子受体的表达可增加内向电流的幅度。SPC3的作用似乎依赖于磷脂酶A2信号通路的激活，但不受胞质Ca2 +浓度变化或Gi / Go蛋白、腺苷酸环化酶、磷脂酶C或蛋白激酶C活性改变的影响。总之，数据表明SPC3能够在感受态细胞中激活表面α/β趋化因子样受体介导的信号通路，从而直接或间接触发Ca2 +失活的氯离子电导。
