Ectopic expression of LIM-nebulette (LASP2) reveals roles in cell migration and spreading.

LIM-nebulette (LASP2) is a small focal adhesion protein and a member of the nebulin family of actin binding proteins. This recently identified splice variant of the nebulette locus is widely expressed and highly enriched in neuronal tissue. Other than that LIM-nebulette is a focal adhesion protein and interacts with zyxin, nothing is known about its function. Given that LIM-nebulette has an identical modular organization and overlapping tissue distributions to that of LASP1, we have analyzed the role of LIM-nebulette in comparison with that of LASP1. We find that LIM-nebulette is a dynamic focal adhesion protein that increases the rate of attachment and spreading of fibroblasts on fibronectin coated surfaces. Additionally, LIM-nebulette is recruited from the cortical cytoskeleton in non-motile cells to focal adhesions at the leading edge of stimulated cells. In confluent cultures of HeLa and NIH3T3 cells, LIM-nebulette co-localizes with alpha-catenin in putative adherens junctions, whereas LASP1 is devoid of these areas. Interestingly, overexpression of LIM-nebulette in PC6 cells inhibits neurite outgrowth in response to growth factors. Collectively, our data indicate that LIM-nebulette and LASP1 have distinct roles in the actin cytoskeleton.