title: Host-cell specific effects of the nicotinic acetylcholine receptor chaperone RIC-3 revealed by a comparison of human and Drosophila RIC-3 homologues.
abstract: RIC-3 is a transmembrane protein which enhances maturation (folding and assembly) of neuronal nicotinic acetylcholine receptors (nAChRs). In this study, we report the cloning and characterisation of 11 alternatively spliced isoforms of Drosophila melanogaster RIC-3 (DmRIC-3). Heterologous expression studies of alternatively spliced DmRIC-3 isoforms demonstrate that nAChR chaperone activity does not require a predicted coiled-coil domain which is located entirely within exon 7. In contrast, isoforms containing an additional exon (exon 2), which is located within a proline-rich N-terminal region, have a greatly reduced ability to enhance nAChR maturation. The ability of DmRIC-3 to influence nAChR maturation was examined in co-expression studies with human alpha7 nAChRs and with hybrid nAChRs containing both Drosophila and rat nAChR subunits. When expressed in a Drosophila cell line, several of the DmRIC-3 splice variants enhanced nAChR maturation to a significantly greater extent than observed with human RIC-3. In contrast, when expressed in a human cell line, human RIC-3 enhanced nAChR maturation more efficiently than DmRIC-3. The cloning and characterisation of 11 alternatively spliced DmRIC-3 isoforms has helped to identify domains influencing RIC-3 chaperone activity. In addition, studies conducted in different expression systems suggest that additional host cell factors may modulate the chaperone activity of RIC-3.
authors.affiliation: Department of Pharmacology, University College London, London, UK.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Lansdell
authors.forename: Toby
authors.initials: T
authors.lastname: Collins
authors.forename: Arisa
authors.initials: A
authors.lastname: Yabe
authors.forename: Veronica J
authors.initials: VJ
authors.lastname: Gee
authors.forename: Alasdair J
authors.initials: AJ
authors.lastname: Gibb
authors.forename: Neil S
authors.initials: NS
authors.lastname: Millar
mesh_terms: D000818:Animals; D002460:Cell Line; D029721:Drosophila Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D004331:Drosophila melanogaster; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D018832:Molecular Chaperones / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D020033:Protein Isoforms / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology; D051381:Rats; D011978:Receptors, Nicotinic / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D029721:Drosophila Proteins; D047908:Intracellular Signaling Peptides and Proteins; D018832:Molecular Chaperones; D020033:Protein Isoforms; C496701:RIC3 protein, human; D011978:Receptors, Nicotinic