Characterization of the rapid proteolytic shedding of murine L-selectin.
Characterization of the rapid proteolytic shedding of murine L-selectin.
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DOI：
10.1155/2001/91831
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Dailey, M O
中科院分区：
文献类型：
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作者：
Zhao, L C;Edgar, J B;Dailey, M O
研究了l -选择素在小鼠白细胞中脱落的结构要求。激活后，淋巴细胞和中性粒细胞上的l -选择素被膜金属蛋白酶裂解，产生可溶性外结构域和膜保留的6kd片段。放射化学测序显示，在R321和S322之间的膜近端区（MPR）有一个与人类同源的切割位点。虽然完整的中性粒细胞l -选择素较大，但它在相同或非常接近的位置被切割。对几种表达l -选择素点突变和嵌合结构的转染物的分析表明，与人类脱落一样，蛋白质水解过程对底物位点具有相对松散的序列特异性。此外，一些结构体易受缓慢本构分裂的影响，但它们的脱落在PMA刺激下不会增加，这表明基础脱落和激活脱落是可分离的过程。将15个氨基酸的MPR插入到小鼠B7.2中，使该分子对组成性脱落具有敏感性。PMA刺激导致很少或没有加速该分子的下调。这些结果表明，识别膜近端切割位点和远离MPR的位点是最大程度诱导l -选择素脱落的必要条件。
The structural requirements for L-selectin shedding were studied in murine leukocytes. Upon activation, L-selectin on both lymphocytes and neutrophils undergoes cleavage by a membrane metalloprotease, resulting in the generation of a soluble ectodomain and a membrane- retained 6 kD fragment. Radiochemical sequencing demonstrated a cleavage site in the membrane-proximal region (MPR) between R321 and S322, which is homologous to the human site. Although intact neutrophil L-selectin is larger, it is cleaved at the same, or very close, site. Analysis of several transfectants expressing L-selectin point mutations and chimeric constructs suggest that, like human shedding, the proteolytic process has relatively loose sequence specificity for the substrate site. In addition, some constructs are susceptible to slow constitutive cleavage, but their shedding does not increase upon PMA stimulation, showing that basal and activated shedding are separable processes. Insertion of the 15 amino acid MPR into murine B7.2 conferred upon this molecule susceptibility to constitutive shedding. PMA stimulation results in little or no acceleration of down regulation of this molecule. These results suggest that recognition of both the membrane-proximal cleavage site and of a site distant from the MPR are required for maximal induction of L-selectin shedding.