The skeletal muscle LIM protein 1 (SLIM1) is highly expressed in skeletal and 
cardiac muscle, and its expression is downregulated significantly in dilated 
human cardiomyopathy. However, the function of SLIM1 is unknown. In this study, 
we investigated the intracellular localization of SLIM1. Endogenous and 
recombinant SLIM1 localized to the nucleus, stress fibers, and focal adhesions 
in skeletal myoblasts plated on fibronectin, collagen, or laminin. However, 
after inhibition of integrin signaling either by plating on poly-l-lysine or by 
soluble RGD peptide, SLIM1 localized diffusely in the cytosol, with decreased 
nuclear expression. Disruption of the actin cytoskeleton by cytochalasin D did 
not inhibit nuclear localization of SLIM1 in integrin-activated cells. Green 
fluorescent protein-tagged SLIM1 shuttled in the nucleus of untransfected NIH 
3T3 cells, in a heterokaryon fusion assay. Overexpression of SLIM1 in Sol8 
myoblasts inhibited cell adhesion and promoted cell spreading and migration. 
These studies show SLIM1 localizes in an integrin-dependent manner to the 
nucleus and focal adhesions where it functions downstream of integrin activation 
to promote cell spreading and migration.