Remold-O'Donnell E, Parent D
Center for Blood Research, Harvard Medical School, Boston, MA.
Blood. 1995 Sep 15;86(6):2395-402.
CD43 (sialophorin, leukosialin), an O-glycosylated and sialylated membrane protein (surface sialomucin) with antiadhesive properties, is thought to protect circulating leukocytes by preventing cell surface interactions. Although it is resistant to several proteases, the granule enzyme elastase was recently implicated in loss of extracellular CD43 regions from incubated neutrophils. Flow cytometry showed that neutrophil CD43 is cleaved by low levels of neutrophil elastase with half-maximal cleavage at 5 micrograms/mL; pancreatic elastase, in contrast, did not cleave CD43. Related neutrophil granule proteases proteinase-3 and cathepsin-G did not cleave CD43 or required greater than 10-fold higher enzyme levels, respectively. The 115-kD CD43 isoform on T-lymphoid cells, which differs in glycosylation from 135-kD neutrophil CD43, was equally sensitive to neutrophil elastase, suggesting that cleavage susceptibility extends to various leukocytes. Enzymatic removal of sialic acid did not facilitate CD43 cleavage by neutrophil elastase, a feature that distinguishes the action of neutrophil elastase from other proteases. Western blots of elastase-treated neutrophils detected an 83-kD CD43 fragment that, together with the released 52-kD fragment and 40-kD subfragment, accounts for the entire molecule and indicates that CD43 is cleaved at two sites only, releasing the distal approximately 40% of the sialomucin region. The specificity of the CD43 cleaving reaction was shown by the insensitivity of other neutrophil and lymphoid surface proteins to elastase levels that deplete CD43. Exceptions were P-selectin glycoprotein ligand-1 on neutrophils, also a surface mucin, and CD16 (Fc gamma RIII), which was previously characterized as elastase sensitive. The sensitivity and specificity of CD43 cleavage by neutrophil elastase, the very high levels of elastase in human neutrophils and its ready release by stimulating conditions suggest important physiologic/pathologic roles for this CD43 cleaving reaction.
CD43（唾液酸糖蛋白，白细胞唾液酸蛋白）是一种具有抗黏附特性的O-糖基化和唾液酸化膜蛋白（表面唾液黏蛋白），被认为可通过阻止细胞表面相互作用来保护循环中的白细胞。尽管它对几种蛋白酶具有抗性，但颗粒酶弹性蛋白酶最近被认为与孵育的中性粒细胞细胞外CD43区域的丢失有关。流式细胞术显示，中性粒细胞弹性蛋白酶的低水平可切割中性粒细胞CD43，半最大切割浓度为5微克/毫升；相比之下，胰腺弹性蛋白酶不会切割CD43。相关的中性粒细胞颗粒蛋白酶蛋白酶-3和组织蛋白酶-G分别不会切割CD43或需要高于10倍的酶水平。T淋巴细胞上的115-kD CD43同工型，其糖基化与135-kD中性粒细胞CD43不同，对中性粒细胞弹性蛋白酶同样敏感，这表明切割敏感性扩展到各种白细胞。酶促去除唾液酸不会促进中性粒细胞弹性蛋白酶对CD43的切割，这一特征将中性粒细胞弹性蛋白酶的作用与其他蛋白酶区分开来。弹性蛋白酶处理的中性粒细胞的蛋白质印迹检测到一个83-kD的CD43片段，该片段与释放的52-kD片段和40-kD亚片段一起构成了整个分子，并表明CD43仅在两个位点被切割，释放出唾液黏蛋白区域远端约40%的片段。其他中性粒细胞和淋巴细胞表面蛋白对耗尽CD43的弹性蛋白酶水平不敏感，这表明了CD43切割反应的特异性。例外情况是中性粒细胞上的P-选择素糖蛋白配体-1，它也是一种表面黏蛋白，以及CD16（FcγRIII），其先前被鉴定为对弹性蛋白酶敏感。中性粒细胞弹性蛋白酶对CD43切割的敏感性和特异性、人类中性粒细胞中弹性蛋白酶的非常高的水平及其在刺激条件下的易释放性表明该CD43切割反应具有重要的生理/病理作用。
