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

Abstract

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.