Tensin plays critical roles in renal function, muscle regeneration, and cell migration. It binds to actin filaments and interacts with the cytoplasmic tails of beta-integrin via its PTB domain, allowing tensin to link actin filaments to integrin receptors. Tensin functions as a platform for assembly and disassembly of signaling complexes at focal adhesions by recruiting tyrosine-phosphorylated signaling molecules, and also by providing interaction sites for other proteins. In addition to its PTB domain, it contains a C-terminal SH2 domain. PTB domains have a common PH-like fold and are found in various eukaryotic signaling molecules. This domain was initially shown to binds peptides with a NPXY motif with differing requirements for phosphorylation of the tyrosine, although more recent studies have found that some types of PTB domains can bind to peptides lack tyrosine residues altogether. In contrast to SH2 domains, which recognize phosphotyrosine and adjacent carboxy-terminal residues, PTB-domain binding specificity is conferred by residues amino-terminal to the phosphotyrosine. PTB domains are classified into three groups: phosphotyrosine-dependent Shc-like, phosphotyrosine-dependent IRS-like, and phosphotyrosine-independent Dab-like PTB domains.
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