title: Splice isoforms of phosducin-like protein control the expression of heterotrimeric G proteins.
abstract: Heterotrimeric G proteins play an essential role in cellular signaling; however, the mechanism regulating their synthesis and assembly remains poorly understood. A line of evidence indicates that the posttranslational processing of G protein β subunits begins inside the protein-folding chamber of the chaperonin containing t-complex protein 1. This process is facilitated by the ubiquitously expressed phosducin-like protein (PhLP), which is thought to act as a CCT co-factor. Here we demonstrate that alternative splicing of the PhLP gene gives rise to a transcript encoding a truncated, short protein (PhLPs) that is broadly expressed in human tissues but absent in mice. Seeking to elucidate the function of PhLPs, we expressed this protein in the rod photoreceptors of mice and found that this manipulation caused a dramatic translational and posttranslational suppression of rod heterotrimeric G proteins. The investigation of the underlying mechanism revealed that PhLPs disrupts the folding of Gβ and the assembly of Gβ and Gγ subunits, events normally assisted by PhLP, by forming a stable and apparently inactive tertiary complex with CCT preloaded with nascent Gβ. As a result, the cellular levels of Gβ and Gγ, which depends on Gβ for stability, decline. In addition, PhLPs evokes a profound and rather specific down-regulation of the Gα transcript, leading to a complete disappearance of the protein. This study provides the first evidence of a generic mechanism, whereby the splicing of the PhLP gene could potentially and efficiently regulate the cellular levels of heterotrimeric G proteins.
authors.affiliation: From the Departments of Ophthalmology and.
authors.forename: Xueli
authors.initials: X
authors.lastname: Gao
authors.affiliation: From the Departments of Ophthalmology and.
authors.forename: Satyabrata
authors.initials: S
authors.lastname: Sinha
authors.affiliation: From the Departments of Ophthalmology and.
authors.forename: Marycharmain
authors.initials: M
authors.lastname: Belcastro
authors.affiliation: Biochemistry, West Virginia University, Morgantown, West Virginia 26506.
authors.forename: Catherine
authors.initials: C
authors.lastname: Woodard
authors.affiliation: From the Departments of Ophthalmology and; Biochemistry, West Virginia University, Morgantown, West Virginia 26506.
authors.forename: Visvanathan
authors.initials: V
authors.lastname: Ramamurthy
authors.affiliation: Biochemistry, West Virginia University, Morgantown, West Virginia 26506.
authors.forename: Peter
authors.initials: P
authors.lastname: Stoilov
authors.affiliation: From the Departments of Ophthalmology and; Biochemistry, West Virginia University, Morgantown, West Virginia 26506. Electronic address: sokolovm@wvuhealthcare.com.
authors.forename: Maxim
authors.initials: M
authors.lastname: Sokolov
mesh_terms: D017398:Alternative Splicing / Q000502:physiology*; D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D057809:HEK293 Cells; D020962:Heterotrimeric GTP-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D006801:Humans; D008822:Mice, Transgenic; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D055550:Protein Stability
chemical_list: D002352:Carrier Proteins; D018832:Molecular Chaperones; D009419:Nerve Tissue Proteins; C098789:PDCL protein, human; C498319:Pdcl protein, mouse; D020033:Protein Isoforms; D020962:Heterotrimeric GTP-Binding Proteins
keywords: Chaperone; Chaperonin; Heterotrimeric G Proteins; Phosducin-like Protein; Photoreceptors; Protein Assembly; RNA Splicing; Retina