Roubey R A, Ross G D, Merrill J T, Walton F, Reed W, Winchester R J, Buyon J P
Department of Medicine, University of North Carolina, Chapel Hill 27599.
J Immunol. 1991 May 15;146(10):3557-62.
C receptor CR3 (iC3b-receptor, CD11b/CD18) plays an essential role in several phagocytic and adhesive neutrophil functions. Recent evidence suggests that stimulus-induced phosphorylation of the CR3 beta-chain, CD18, may mediate certain neutrophil functions by transiently converting the molecule to an activated state. Staurosporine, a protein kinase C inhibitor that blocks PMA-induced CD18 phosphorylation, was used to study the functional relevance of this event. Neutrophils adhered to glass were assayed for binding and phagocytosis of iC3b-opsonized sheep E (EC3bi) in the presence or absence of PMA and/or staurosporine. Binding of EC3bi was markedly increased, not only by PMA, but also by staurosporine and by a combination of both agents (three- to sevenfold). The enhancement of rosetting by staurosporine was likely caused by increased surface expression of CR3 via exocytosis of specific granular contents. In contrast, staurosporine alone did not stimulate phagocytosis of EC3bi and markedly inhibited PMA-induced phagocytosis. Staurosporine also inhibited phagocytosis of yeast beta glucan particles, a CR3 ligand that, in contrast to EC3bi, is bound and ingested without additional prior treatment with PMA. beta glucan phagocytosis was associated with a low level of CD18 phosphorylation. Staurosporine did not block phagocytosis in general, because this agent had relatively little effect on FcR-mediated phagocytosis. These data demonstrate that phagocytosis mediated by CR3 requires activation of CR3 via a staurosporine-sensitive pathway. Increased binding of EC3bi, a function of increased surface expression of CR3, does not require activation of CR3 by such a pathway, confirming previous evidence for the independence of these two phenomena. A direct role for CD18 phosphorylation in the activation of CR3 for phagocytosis is consistent with these data.
补体受体CR3（iC3b受体，CD11b/CD18）在中性粒细胞的多种吞噬和黏附功能中起关键作用。最近的证据表明，刺激诱导的CR3β链（CD18）磷酸化可能通过将该分子短暂转变为活化状态来介导某些中性粒细胞功能。星形孢菌素是一种蛋白激酶C抑制剂，可阻断佛波酯（PMA）诱导的CD18磷酸化，用于研究该事件的功能相关性。在有或没有PMA和/或星形孢菌素存在的情况下，检测黏附在玻璃上的中性粒细胞对iC3b调理的绵羊红细胞（EC3bi）的结合和吞噬作用。不仅PMA，而且星形孢菌素以及两种药物联合使用（增加三到七倍）均可使EC3bi的结合显著增加。星形孢菌素增强红细胞吸附作用可能是由于特定颗粒内容物的胞吐作用导致CR3表面表达增加所致。相比之下，单独的星形孢菌素不会刺激EC3bi的吞噬作用，反而会显著抑制PMA诱导的吞噬作用。星形孢菌素还抑制酵母β-葡聚糖颗粒的吞噬作用，β-葡聚糖颗粒是一种CR3配体，与EC3bi不同，它在无需预先用PMA处理的情况下即可被结合和摄取。β-葡聚糖吞噬作用与低水平的CD18磷酸化有关。星形孢菌素一般不会阻断吞噬作用，因为该药物对FcR介导的吞噬作用影响相对较小。这些数据表明，CR3介导的吞噬作用需要通过星形孢菌素敏感途径激活CR3。EC3bi结合增加是CR3表面表达增加的结果，不需要通过该途径激活CR3，这证实了先前关于这两种现象独立性的证据。CD18磷酸化在激活CR3进行吞噬作用中起直接作用与这些数据一致。
