Regulated CD44 cleavage under the control of protein kinase C, calcium influx, and the Rho family of small G proteins
Regulated CD44 cleavage under the control of protein kinase C, calcium influx, and the Rho family of small G proteins
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DOI：
10.1074/jbc.274.36.25525
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发表时间：
1999-09-03
影响因子：
4.8
通讯作者：
Saya, H
中科院分区：
文献类型：
--
作者：
Okamoto, I;Kawano, Y;Saya, H
CD44 是多种细胞外基质成分的细胞表面受体，与肿瘤细胞侵袭和转移有关。我们之前的研究表明，癌细胞中表达的 CD44 通过膜相关金属蛋白酶在细胞外结构域进行蛋白水解切割，并且 CD44 切割在 CD44 介导的肿瘤细胞迁移中起着关键作用（Okamoto, I.、Kawano, Y.、Tsuiki, H.、Sasaki, J.、Nakao, M.、Matsumoto, M.、Suga, M,、Ando, M., Nakajima, M. 和 Saya, H. (1999) Oncogene 18, 1435-1446)。在本研究中，我们首先证明了膜束缚的 CD44 裂解产物通过细胞内蛋白水解途径快速降解，并且仅在 CD44 细胞外裂解后发生。为了解决细胞外结构域 CD44 裂解的调节机制，我们发现 12-O-十四烷酰佛波醇 13-乙酸酯 (TPA) 和钙离子载体离子霉素分别通过蛋白激酶 C 依赖性和非依赖性途径快速增强 U251MG 细胞中金属蛋白酶介导的 CD44 裂解，表明存在多种不同的 CD44 裂解调节途径。伴随着 TPA 诱导的 CD44 裂解，TPA 处理诱导 CD44 和 ERM 蛋白（ezrin、radixin 和 moesin）重新分布到新生成的膜波纹区域。已知溶血磷脂酸可激活 Rho 依赖性途径，治疗可抑制 TPA 诱导的 CD44 重新分布和 CD44 裂解。此外，Rac显性活性突变体的过度表达导致CD44重新分布到Rac诱导的褶皱区域并增强CD44裂解。这些结果表明Rho家族蛋白在调节CD44分布和裂解中发挥作用。
CD44 is a cell surface receptor for several extracellular matrix components and is implicated in tumor cell invasion and metastasis. Our previous studies have shown that CD44 expressed in cancer cells is proteolytically cleaved at the extracellular domain through membrane-associated metalloproteases and that CD44 cleavage plays a critical role in CD44-mediated tumor cell migration (Okamoto, I., Kawano, Y., Tsuiki, H., Sasaki, J., Nakao, M., Matsumoto, M., Suga, M,, Ando, M., Nakajima, M., and Saya, H. (1999) Oncogene 18, 1435-1446). In the present study, we first demonstrate rapid degradation of the membrane-tethered CD44 cleavage product through intracellular proteolytic pathways, and it occurs only after CD44 extracellular cleavage. To address the mechanisms regulating CD44 cleavage at the extracellular domain, we show that 12-O-tetradecanoylphorbol 13-acetate (TPA) and the calcium ionophore ionomycin rapidly enhance metalloprotease-mediated CD44 cleavage in U251MG cells via protein kinase C-dependent and -independent pathways, respectively, suggesting the existence of multiple distinct pathways for regulation of CD44 cleavage. Concomitant with TPA-induced CD44 cleavage, TPA treatment induces redistribution of CD44 and ERM proteins (ezrin, radixin, and moesin) to newly generated membrane ruffling areas. Treatment with lysophosphatidic acid, which is known to activate the Rho-dependent pathway, inhibits TPA-induced CD44 redistribution and CD44 cleavage. Furthermore, overexpression of Rac dominant active mutants results in the redistribution of CD44 to the Rac-induced ruffling areas and the enhancement of CD44 cleavage, These results suggest that the Rho family proteins play a role in regulation of CD44 distribution and cleavage.