Expression and functional analysis of a cytoplasmic domain variant of the beta 1 integrin subunit.
Expression and functional analysis of a cytoplasmic domain variant of the beta 1 integrin subunit.
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DOI：
10.1083/jcb.121.1.171
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发表时间：
1993-04
期刊：
影响因子：
--
通讯作者：
Tarone G
中科院分区：
文献类型：
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作者：
Balzac F;Belkin AM;Koteliansky VE;Balabanov YV;Altruda F;Silengo L;Tarone G
我们之前已经描述了整合素β 1亚基（β 1B）1的一种变体形式，其特征是细胞质结构域的序列改变。利用合成的与β 1B独特序列对应的多肽的多克隆抗体，我们分析了该分子在人体组织和培养细胞中的表达。Western blot分析显示，β 1B在皮肤和肝脏中表达，在骨骼肌和心肌中表达量较低。该蛋白在脑、肾和平滑肌中未检测到。体外培养的角化细胞和肝癌细胞呈阳性，而成纤维细胞、内皮细胞和平滑肌细胞呈阴性。从永生化胚胎星形细胞中提取的星形细胞细胞系表达β 1B。在这些细胞中β 1B占β 1的30%，并与α 1和α 5亚基形成异源二聚体。为了研究β 1B的功能特性，将编码该分子的全长cDNA转染CHO细胞。选择稳定的转染物，并通过区分转染的人蛋白和内源性仓鼠β 1A的单抗鉴定β 1B。免疫沉淀实验表明β 1B与内源性仓鼠α亚基一起在细胞表面输出。α 5/ β 1B复合物与纤维连接蛋白亲和基质结合，并被含rgd的肽特异性释放。因此β 1B和β 1A在α / β结合和纤维连接蛋白结合方面是相似的。然而，这两种蛋白的亚细胞定位不同。免疫荧光研究表明，事实上，与β 1A相比，β 1B并不局限于局灶性粘连。有限的组织分布和独特的亚细胞定位表明β 1B具有独特的功能特性。
We have previously described a variant form of the integrin beta 1 subunit (beta 1B)1 characterized by an altered sequence at the cytoplasmic domain. Using polyclonal antibodies to a synthetic peptide corresponding to the unique sequence of the beta 1B, we analyzed the expression of this molecule in human tissues and cultured cells. Western blot analysis showed that the beta 1B is expressed in skin and liver and, in lower amounts, in skeletal and cardiac muscles. The protein was not detectable in brain, kidney, and smooth muscle. In vitro cultured keratinocytes and hepatoma cells are positive, but fibroblasts, endothelial cells, and smooth muscle cells are negative. An astrocytoma cell line derived from immortalized fetal astrocytes was found to express beta 1B. In these cells beta 1B represent integral of 30% of the beta 1 and form heterodimers with alpha 1 and alpha 5 subunits. To investigate the functional properties of beta 1B, the full- length cDNA coding for this molecule was transfected into CHO cells. Stable transfectants were selected and the beta 1B was identified by a mAb that discriminate between the transfected human protein and the endogenous hamster beta 1A. Immunoprecipitation experiments indicated that the beta 1B was exported at the cell surface in association with the endogenous hamster alpha subunits. The alpha 5/beta 1B complex bound to a fibronectin-affinity matrix and was specifically released by RGD-containing peptides. Thus beta 1B and beta 1A are similar as far as the alpha/beta association and fibronectin binding are concerned. The two proteins differ, however, in their subcellular localization. Immunofluorescence studies indicated, in fact, that beta 1B, in contrast to beta 1A, does not localize in focal adhesions. The restricted tissue distribution and the distinct subcellular localization, suggest that beta 1B has unique functional properties.