RESUMO
Osteopontin (OPN) is a multifunctional protein that has been linked to various intractable inflammatory diseases. One way by which OPN induces inflammation is the production of various functional fragments by enzyme cleavage. It has been well appreciated that OPN is cleaved by thrombin, and/or matrix metalloproteinase-3 and -7 (MMP-3/7). Although the function of thrombin-cleaved OPN is well characterized, little is known about the function of MMP-3/7-cleaved OPN. In this study, we found a novel motif, LRSKSRSFQVSDEQY, in the C-terminal fragment of MMP-3/7-cleaved mouse OPN binds to α9ß1 integrin. Importantly, this novel motif is involved in the development of anti-type II collagen antibody-induced arthritis (CAIA). This study provides the first in vitro and in vivo evidence that OPN cleavage by MMP-3/7 is an important regulatory mechanism for CAIA.
Assuntos
Artrite Experimental/metabolismo , Colágeno Tipo II/imunologia , Integrinas/metabolismo , Metaloproteinase 3 da Matriz/metabolismo , Metaloproteinase 7 da Matriz/metabolismo , Osteopontina/química , Osteopontina/metabolismo , Motivos de Aminoácidos , Sequência de Aminoácidos , Animais , Anticorpos/farmacologia , Artrite Experimental/patologia , Artrite Experimental/prevenção & controle , Células CHO , Movimento Celular/efeitos dos fármacos , Cricetinae , Cricetulus , Ligantes , Melanoma Experimental , Camundongos , Dados de Sequência Molecular , Células NIH 3T3 , Peptídeos/metabolismo , Ligação Proteica/efeitos dos fármacos , Cicatrização/efeitos dos fármacosRESUMO
Integrins affect the motility of multiple cell types to control cell survival, growth, or differentiation, which are mediated by cell-cell and cell-extracellular matrix interactions. We reported previously that the α9 integrin splicing variant, SFα9, promotes WT α9 integrin-dependent adhesion. In this study, we introduced a new murine α4 integrin splicing variant, α4B, which has a novel short cytoplasmic tail. In inflamed tissues, the expression of α4B, as well as WT α4 integrin, was up-regulated. Cells expressing α4B specifically bound to VCAM-1 but not other α4 integrin ligands, such as fibronectin CS1 or osteopontin. The binding of cells expressing WT α4 integrin to α4 integrin ligands is inhibited by coexpression of α4B. Knockdown of α4B in metastatic melanoma cell lines results in a significant increase in lung metastasis. Expression levels of WT α4 integrin are unaltered by α4B, with α4B acting as a regulatory subunit for WT α4 integrin by a dominant-negative effect or inhibiting α4 integrin activation.
