α-Actinin 4 (Tyr-4), Phosphospecific Antibody

α-Actinins are widely expressed cytoskeletal proteins that cross-link actin filaments through anti-parallel homodimers of the rod domains. Four α-actinin genes have been discovered in humans with α-actinin 1 and 4 being widely expressed in non-muscle cells. α-Actinins contain three conserved domains that include an N-terminal actin binding domain, four spectrin-like repeats in the central region, and a C-terminal calmodulin binding domain. α-Actinin cross-links the actin filament networks and associates the network to focal adhesion sites through binding of talin and vinculin. α-Actinin 1 is phosphorylated at Tyr-12 by FAK, while α-actinin 4 can be phosphorylated at Tyr-4 and Tyr-31 after EGF treatment. Tyr-4 and Tyr-31 phosphorylation inhibit actin binding and reduces actin-filament driven multi-nucleation in rat kidney cells. Thus, phosphorylation in α-actinins may be important for regulating actin binding and actin cytoskeletal remodeling.

The antibody detects a 100 kDa* protein corresponding to the molecular mass of α-actinin 4 on SDS-PAGE immunoblots of human A431 cells treated with pervanadate, but is not observed after akaline phosphatase treatment. This sequence is well conserved in rat and mouse α-actinin 4, but is not conserved in other α-actinins.