The subcellular localization and protein stability of mouse alpha-actinin 2 is controlled by its nuclear receptor binding motif in C2C12 cells.

Alpha actinin (ACTN) has emerged as a multitasking protein, whose roles range from bundling actin filaments to functioning as a versatile protein interaction platform for proteins involved in structural or signaling aspects. We report here that ACTN2, one of the four ACTN isoforms, may shuttle between the cytoplasm and nucleus where the nuclear exportation takes place in a CRM1-dependent manner. The majority of ACTN2 was found to localize in the cytoplasm and exhibit a lower stability which was demonstrated using either mutants carrying mutated nuclear receptor binding motif or inhibitors against the ubiquitin- and calpain-dependent degradation pathways. Horse serum induced differentiation of C2C12 cells also caused the redistribution of nuclear ACTN2 to the cytoplasm, which subcellular compartment the ACTN2 behaves as an unstable protein. Our data indicated that the model in which ACTN2 functions as a multi-talented coregulator may be controlled by the differential protein stability modulated via nucleo-cytoplasmic trafficking in C2C12 cells.