Actin-binding proteins are essential for linear and branched actin filament dynamics
that control shape change, cell migration, and cell junction remodeling in vascular
endothelium (endothelial cells [ECs]). The epithelial protein lost in neoplasm (EPLIN)
is an actin-binding protein, expressed as EPLIN-α and EPLIN-β by alternative promoters;
however, the isoform-specific functions are not yet understood. Aortic compared to
cava vein ECs and shear stress-exposed cultured ECs express increased EPLIN-β levels
that stabilize stress fibers. In contrast, EPLIN-α expression is increased in growing
and migrating ECs, is targeted to membrane protrusions, and terminates their growth
via interaction with the Arp2/3 complex. The data indicate that EPLIN-α controls protrusion
dynamics while EPLIN-β has an actin filament stabilizing role, which is consistent
with FRAP analyses demonstrating a lower EPLIN-β turnover rate compared to EPLIN-α.
Together, EPLIN isoforms differentially control actin dynamics in ECs, essential in
shear stress responses, cell migration, and barrier function.