The calcium sensor protein visinin-like protein-1 modulates the surface expression and agonist sensitivity of the α4β2 nicotinic acetylcholine receptor

Abstract

The calcium sensor protein visinin-like protein-1 (VILIP-1) was isolated from a brain cDNA yeast twohybrid library using the large cytoplasmic domain of the α4 subunit as a bait. VILIP-1 is a myristoylated calcium sensor protein that contains three functional calcium binding EF-hand motifs. The α4 subunit residues 302-339 were found to be essential for the interaction with VILIP-1. VILIP-1 coimmunopurified with detergent-solubilized recombinant α4β2 acetylcholine receptors (AChRs) expressed in tsA201 cells and with native α4 AChRs isolated from brain. Coexpression of VILIP-1 with recombinant α4β2 AChRs up-regulated their surface expression levels ∼2-fold and increased their agonist sensitivity to acetylcholine ∼3-fold. The modulation of the recombinant α4β2 AChRs by VILIP-1 was attenuated in VILIP-1 mutants that lacked the ability to be myristoylated or to bind calcium. Collectively, these results suggest that VILIP-1 represents a novel modulator of α4β2 AChRs that increases their surface expression levels and agonist sensitivity in response to changes in the intracellular levels of calcium.