Analysis on β1 integrin and its associating molecules in the pathophysiology of Rheumatoid Arthritis and Progressive Systemic Sclerosis.

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β1 integrin is key adhesion molecule possibly involving in pathogenesis of autoimmune inflammatory diseases such as rheumatoid arthritis (RA) and progressive systemic sclerosis (PSS). The aim of this study is investigating the biological roles of β1 integrin and its associating molecules Crk-associated substrate lymphocyte type (Cas-L) and tetraspanins (CD9 and CD82).1) We showed that Cas-L localize in lipid raft through its c-terminal half domains, and that reduction of Cas-L expression by shRNAi retroviral vector resulted in significantly reduced cellular migration and IL-2 production, suggesting that localization of Cas-L in lipid raft is necessary for cellular migration and cytokine production.2) We showed that Cas-L associated with IKK-α/β and TRAF6 that are important signaling molecules in NF-κB system. The associating domain of Cas-L for IKKs are tentatively determined as HLH domain. We further analyzed osteoclast differentiation using RAW264.7 cells, and find that mRNA of p130Cas, a Cas-L homologue, was up-regulated whereas that of Cas-L was down-regulated during RANKL-induced osteoclast differentiation.3) By Two-Hybrid screening, we identified Smad6 and 7 as Cas-L binding molecules. We showed that Cas-L and Smad 6, 7 associate and co-localize each other in the cytoplasm. Furthermore, analysis on siRNA of Cas-L revealed that Cas-L positively regulates TGF-β-mediated signaling pathway.4) To artificially regulate immune system in future, we generated potent shRNAi retroviral vector for Cas-L and recombinant extracellular loops of CD9 or CD82-IgG-Fc fusion proteins.