The conserved RIC-3 coiled-coil domain mediates receptor-specific interactions with nicotinic acetylcholine receptors.
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.
Biala
Yoav
Y
Department of Physiology, Hebrew University, Hadassah Medical School, Jerusalem, 91120, Israel.
Liewald
Jana F
JF
Ben-Ami
Hagit Cohen
HC
Gottschalk
Alexander
A
Treinin
Millet
M
D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D017173:Caenorhabditis elegans / Q000378:metabolism; D029742:Caenorhabditis elegans Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D017124:Conserved Sequence; D007150:Immunohistochemistry; D018408:Patch-Clamp Techniques; D025941:Protein Interaction Mapping; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism / Q000502:physiology; D017434:Protein Structure, Tertiary; D011978:Receptors, Nicotinic / Q000378:metabolism*; D017384:Sequence Deletion
D029742:Caenorhabditis elegans Proteins; C487508:Eat-2 protein, C elegans; D020033:Protein Isoforms; D011978:Receptors, Nicotinic; C529480:UNC-29 protein, C elegans; C099378:acr-16 protein, C elegans; C454141:ric-3 protein, C elegans