Thy-1 binds to integrin β₃ on astrocytes and triggers formation of focal contact sites

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• 作者：Lisette Leyton ; Pascal Schneider ; Cecilia V. Labra ; Curzio R&#xfc ; egg ; Claudio A. Hetz ; Andrew F. G. Quest ; Claude Bron
• 关键词：Biochemistry ; Cell Biology ; Genetics
• 刊名：Current Biology
• 出版年：2001
• 出版时间：10 July 2001
• 年：2001
• 卷：11
• 期：13
• 页码：1028-1038
• 全文大小：495 K

文摘

Background: Thy-1 is an abundant neuronal glycoprotein in mammals. Despite such prevalence, Thy-1 function remains largely obscure in the absence of a defined ligand. Astrocytes, ubiquitous cells of the brain, express a putative Thy-1 ligand that prevents neurite outgrowth. In this paper, a ligand molecule for Thy-1 was identified, and the consequences of Thy-1 binding for astrocyte function were investigated.

Results: Thy-1 has been implicated in cell adhesion and, indeed, all known Thy-1 sequences were found to contain an integrin binding, RGD-like sequence. Thy-1 interaction with β3 integrin on astrocytes was demonstrated in an adhesion assay using a thymoma line (EL-4) expressing high levels of Thy-1. EL-4 cells bound to astrocytes five times more readily than EL-4^−f, control cells lacking Thy-1. Binding was blocked by either anti-Thy-1 or anti-β3 antibodies, by RGD-related peptides, or by soluble Thy-1-Fc chimeras. However, neither RGE/RLE peptides nor Thy-1(RLE)-Fc fusion protein inhibited the interaction. Immobilized Thy-1-Fc, but not Thy-1(RLE)-Fc fusion protein supported the attachment and spreading of astrocytes in a Mn²⁺-dependent manner. Binding to Thy-1-Fc was inhibited by RGD peptides. Moreover, vitronectin, fibrinogen, denatured collagen (dcollagen), and a kistrin-derived peptide, but not fibronectin, also mediated Mn²⁺-dependent adhesion, suggesting the involvement of β3 integrin. The addition of Thy-1 to matrix-bound astrocytes induced recruitment of paxillin, vinculin, and focal adhesion kinase (FAK) to focal contacts and increased tyrosine phosphorylation of proteins such as p130^Cas and FAK. Furthermore, astrocyte binding to immobilized Thy-1-Fc alone was sufficient to promote focal adhesion formation and phosphorylation on tyrosine.

Conclusions: Thy-1 binds to β3 integrin and triggers tyrosine phosphorylation of focal adhesion proteins in astrocytes, thereby promoting focal adhesion formation, cell attachment, and spreading.