Integrin alpha 2 cytoplasmic domain deletion effects: loss of adhesive activity parallels ligand-independent recruitment into focal adhesions.
Integrin alpha 2 cytoplasmic domain deletion effects: loss of adhesive activity parallels ligand-independent recruitment into focal adhesions.
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DOI：
10.1091/mbc.5.9.977
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发表时间：
1994-09
影响因子：
3.3
通讯作者：
S. Kawaguchi;J. Bergelson;R. Finberg;M. Hemler
中科院分区：
文献类型：
--
作者：
S. Kawaguchi;J. Bergelson;R. Finberg;M. Hemler
用整合素α 2亚基转染的中国仓鼠卵巢（CHO）细胞形成稳定的VLA-2异源二聚体，介导细胞与胶原的粘附。在CHO细胞内，胶原蛋白而不是纤连蛋白上散布，野生型α 2亚基定位于粘着斑复合物（FAC）中。相比之下，无论CHO细胞是否铺展在胶原蛋白或纤连蛋白上，具有缺失的胞质结构域的α 2都被募集到FACs中。因此，如先前对于其他整联蛋白所见，α 2胞质结构域充当负调节剂，防止整联蛋白不加选择地募集到FACs中。值得注意的是，如果α 2胞质结构域中仅存在一个或两个氨基酸（超出保守的GFFKR基序），则VLA-2 α 2亚基在FACs中的配体非依赖性定位被部分阻止，并且被4至7个氨基酸完全阻止。添加两个丙氨酸残基（添加到GFFKR）也部分阻止了配体非依赖性定位。在一个惊人的负相关，相同的突变体显示增加配体非依赖性招募到FACs表现出减少α 2依赖性粘附胶原。因此，VLA-2定位的控制可能与抑制细胞与胶原的粘附密切相关。与FAC定位和胶原粘附结果相反，VLA-2依赖性结合和埃可病毒感染不受α 2胞质结构域缺失或与其他胞质结构域交换的影响。
Chinese hamster ovary (CHO) cells transfected with the integrin alpha 2 subunit formed a stable VLA-2 heterodimer that mediated cell adhesion to collagen. Within CHO cells spread on collagen, but not fibronectin, wild-type alpha 2 subunit localized into focal adhesion complexes (FACs). In contrast, alpha 2 with a deleted cytoplasmic domain was recruited into FACs whether CHO cells were spread on collagen or fibronectin. Thus, as previously seen for other integrins, the alpha 2 cytoplasmic domain acts as a negative regulator, preventing indiscriminate integrin recruitment into FACs. Notably, ligand-independent localization of the VLA-2 alpha 2 subunit into FACs was partially prevented if only one or two amino acids were present in the alpha 2 cytoplasmic domain (beyond the conserved GFFKR motif) and was completely prevented by four to seven amino acids. The addition of two alanine residues (added to GFFKR) also partially prevented ligand-independent localization. In a striking inverse correlation, the same mutants showing increased ligand-independent recruitment into FACs exhibited diminished alpha 2-dependent adhesion to collagen. Thus, control of VLA-2 localization may be closely related to the suppression of cell adhesion to collagen. In contrast to FAC localization and collagen adhesion results, VLA-2-dependent binding and infection by echovirus were unaffected by either alpha 2 cytoplasmic domain deletion or exchange with other cytoplasmic domains.