Hepatocyte growth factor-induced ectodomain shedding of cell adhesion molecule L1 -: Role of the L1 cytoplasmic domain
Hepatocyte growth factor-induced ectodomain shedding of cell adhesion molecule L1 -: Role of the L1 cytoplasmic domain
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DOI：
10.1074/jbc.m403587200
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发表时间：
2004-07-23
影响因子：
4.8
通讯作者：
Novak-Hofer, I
中科院分区：
文献类型：
--
作者：
Heiz, M;Grünberg, J;Novak-Hofer, I
L1细胞粘附分子及其可溶性形式是肿瘤相关蛋白和肿瘤分期的潜在标志物以及治疗干预的靶点。可溶性L1由金属蛋白酶介导的L1胞外结构域脱落产生。我们研究了肝细胞生长因子（HGF）的影响，一种生长因子，增加肾癌细胞的侵袭力，对L1从这些细胞的胞外域脱落。所有测试的L1阳性肾癌细胞系释放180 kDa形式的L1到培养基中。在存在血清的情况下，加入HGF导致L1脱落的剂量依赖性增加，在5 ng/ml时达到最大值。相反，L1脱落被胶质细胞源性神经营养因子（GDNF）抑制。酪氨酸激酶抑制剂金雀异黄素减少基础和HGF刺激的L1脱落，表明蛋白磷酸化参与其中。为了研究L1胞内结构域的作用，构建了L1胞质部分的两个突变体。L1 trun缺乏完整的细胞内结构域表现出增强的基底脱落。在一个L1 YH突变体，含有突变酪氨酸1229组氨酸，删除锚蛋白结合基序的L1，基础脱落减少。细胞松弛素D破坏肌动蛋白组装也减少了L1的脱落。这些结果表明，胞质结构域调节L1的基底脱落，并通过L1锚蛋白结合位点与细胞骨架相关。在两种突变体中，HGF刺激L1脱落，表明HGF刺激脱落不需要L1胞质结构域中受体介导的磷酸化。
The L1 cell adhesion molecule and its soluble form are tumor-associated proteins and potential markers for tumor staging as well as targets for therapeutic intervention. Soluble L1 is produced by metalloprotease-mediated ectodomain shedding of L1. We investigated effects of hepatocyte growth factor (HGF), a growth factor shown to increase invasiveness of renal carcinoma cells, on ectodomain shedding of L1 from these cells. All of the tested L1-positive renal carcinoma cell lines released a 180-kDa form of L1 into the medium. In the presence of serum, addition of HGF led to a dose-dependent increase in L1 shedding with a maximum reached at 5 ng/ml. In contrast, L1 shedding was inhibited by glial cell line-derived neurotrophic factor ( GDNF). The tyrosine kinase inhibitor Genistein reduced basal and HGF-stimulated L1 shedding, indicating that protein phosphorylation is involved. To investigate the role of the L1 intracellular domain, two mutants of the L1 cytoplasmic part were constructed. L1trun lacking the complete intracellular domain showed enhanced basal shedding. In a L1YH mutant, containing the mutation tyrosine 1229 to histidine that deletes the ankyrin binding motif of L1, basal shedding was reduced. Disruption of actin assembly by cytochalasin D also reduced shedding of L1. These results indicate that the cytoplasmic domain regulates basal shedding of L1, and association with the cytoskeleton through the L1 ankyrin binding site is involved. HGF stimulated L1 shedding in both mutants, indicating that receptor-mediated phosphorylation in the L1 cytoplasmic domain is not required for HGF-stimulated shedding.