αII-Spectrin Is Critical for Cell Adhesion and Cell Cycle

Spectrins are ubiquitous scaffolding components of the membrane skeleton that organize and stabilize microdomains on both the plasma membrane and the intracellular organelles. By way of their numerous interactions with diverse protein families, they are implicated in various cellular functions. Using small interfering RNA strategy in the WM-266 cell line derived from human melanoma, we found that αII-spectrin deficiency is associated with a defect in cell proliferation, which is related to a cell cycle arrest at the G 1 phase (first gap phase), as evaluated by DNA analysis and Rb phosphorylation. These observations coincided with elevated expression of the cyclin-dependent kinase inhibitor, p21 Cip . Concomitantly, spectrin loss impaired cell adhesion and spreading. These cell adhesion defects were associated with modifications of the actin cytoskeleton, such as loss of stress fibers, alterations of focal adhesions, and modified expression of some integrins. Our results provide novel insights into spectrin functions by demonstrating the involvement of αII-spectrin in cell cycle regulation and actin organization.