Modulation of gain-of-function ?6*-nicotinic acetylcholine receptor by ?3 subunits.

ABSTRACT: We previously have shown that ?3 subunits either eliminate (e.g. for all-human (h) or all-mouse (m) ?6?4?3-nAChR) or potentiate (e.g. for hybrid m?6h?4h?3- or m?6m?4h?3-nAChR containing subunits from different species) function of ?6*-nAChR expressed in Xenopus oocytes, and that nAChR h?6 subunit residues Asn-143 and Met-145 in N-terminal domain loop E are important for dominant-negative effects of nAChR h?3 subunits on h?6*-nAChR function. Here, we tested the hypothesis that these effects of ?3 subunits would be preserved even if nAChR ?6 subunits harbored gain-of-function, leucine- or valine-to-serine mutations at 9' or 13' positions (L9'S or V13'S) in their second transmembrane domains, yielding receptors with heightened functional activity and more amenable to assessment of effects of ?3 subunit incorporation. However, coexpression with ?3 subunits potentiates rather than suppresses function of all-human, all-mouse, or hybrid ?6((L9'S or V13'S))?4*- or ?6(N143D+M145V)(L9'S)?2*-nAChR. This contrasts with the lack of consistent function when ?6((L9'S or V13'S)) and ?2 subunits are expressed alone or in the presence of wild-type ?3 subunits. These results provide evidence that gain-of-function h?6h?2*-nAChR (i.e. h?6(N143D+M145V)(L9'S)h?2h?3 nAChR) could be produced in vitro. These studies also indicate that nAChR ?3 subunits can be assembly partners in functional ?6*-nAChR and that 9' or 13' mutations in the nAChR ?6 subunit second transmembrane domain can act as gain-of-function and/or reporter mutations. Moreover, our findings suggest that ?3 subunit coexpression promotes function of ?6*-nAChR.

SUBMITTER: Dash B 

PROVIDER: S-EPMC3340145 | biostudies-literature | 2012 Apr

REPOSITORIES: biostudies-literature