The conserved RIC-3 coiled-coil domain mediates receptor-specific interactions with nicotinic acetylcholine receptors

Mol Biol Cell. 2009 Mar;20(5):1419-27. doi: 10.1091/mbc.e08-08-0851. Epub 2008 Dec 30.

Abstract

RIC-3 belongs to a conserved family of proteins influencing nicotinic acetylcholine receptor (nAChR) maturation. RIC-3 proteins are integral membrane proteins residing in the endoplasmic reticulum (ER), and containing a C-terminal coiled-coil domain (CC-I). Conservation of CC-I in all RIC-3 family members indicates its importance; however, previous studies could not show its function. To examine the role of CC-I, we studied effects of its deletion on Caenorhabditis elegans nAChRs in vivo. Presence of CC-I promoted maturation of particular nAChRs expressed in body-wall muscle, whereas it was not required for other nAChR subtypes expressed in neurons or pharyngeal muscles. This effect is receptor-specific, because it could be reproduced after heterologous expression. Consistently, coimmunoprecipitation analysis showed that CC-I enhances the interaction of RIC-3 with a nAChR that requires CC-I in vivo; thus CC-I appears to enhance affinity of RIC-3 to specific nAChRs. However, we found that this function of CC-I is redundant with functions of sequences downstream to CC-I, potentially a second coiled-coil. Alternative splicing in both vertebrates and invertebrates generates RIC-3 transcripts that lack the entire C-terminus, or only CC-I. Thus, our results suggest that RIC-3 alternative splicing enables subtype specific regulation of nAChR maturation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Alternative Splicing
  • Amino Acid Sequence
  • Animals
  • Caenorhabditis elegans / metabolism
  • Caenorhabditis elegans Proteins / chemistry
  • Caenorhabditis elegans Proteins / metabolism
  • Caenorhabditis elegans Proteins / physiology*
  • Conserved Sequence
  • Immunohistochemistry
  • Patch-Clamp Techniques
  • Protein Interaction Mapping
  • Protein Isoforms / chemistry
  • Protein Isoforms / metabolism
  • Protein Isoforms / physiology
  • Protein Structure, Tertiary
  • Receptors, Nicotinic / metabolism*
  • Sequence Deletion

Substances

  • Caenorhabditis elegans Proteins
  • Eat-2 protein, C elegans
  • Protein Isoforms
  • Receptors, Nicotinic
  • UNC-29 protein, C elegans
  • acr-16 protein, C elegans
  • ric-3 protein, C elegans