Nesprin-1α self-associates and binds directly to emerin and lamin A in vitro

Nesprin-1α is a spectrin repeat (SR)-containing, transmembrane protein of the inner nuclear membrane, and is highly expressed in muscle cells. A yeast two-hybrid screen for nesprin-1α-interacting proteins showed that nesprin-1α interacted with itself. Blot overlay experiments revealed that nesprin-1α's third SR binds the fifth SR. The carboxy-terminal half of nesprin-1α directly bound lamin A, a nuclear intermediate filament protein. Biochemical analysis demonstrated that nesprin-1α dimers bind directly to the nucleoplasmic domain of emerin, an inner nuclear membrane protein, with an affinity of 4 nM. Binding was optimal for full nucleoplasmic dimers of nesprin-1α, since nesprin fragments SR1-5 and SR5-7 bound emerin as monomers with affinities of 53 nM and 250 mM, respectively. We propose that membrane-anchored nesprin-1α antiparallel dimers interact with both emerin and lamin A to provide scaffolding at the inner nuclear membrane.