title: Eukaryotic translation initiation factor 3 subunit e controls intracellular calcium homeostasis by regulation of cav1.2 surface expression.
abstract: Inappropriate surface expression of voltage-gated Ca(2+)channels (CaV) in pancreatic ß-cells may contribute to the development of type 2 diabetes. First, failure to increase intracellular Ca(2+) concentrations at the sites of exocytosis impedes insulin release. Furthermore, excessive Ca(2+) influx may trigger cytotoxic effects. The regulation of surface expression of CaV channels in the pancreatic β-cells remains unknown. Here, we used real-time 3D confocal and TIRFM imaging, immunocytochemistry, cellular fractionation, immunoprecipitation and electrophysiology to study trafficking of L-type CaV1.2 channels upon β-cell stimulation. We found decreased surface expression of CaV1.2 and a corresponding reduction in L-type whole-cell Ca(2+) currents in insulin-secreting INS-1 832/13 cells upon protracted (15-30 min) stimulation. This internalization occurs by clathrin-dependent endocytosis and could be prevented by microtubule or dynamin inhibitors. eIF3e (Eukaryotic translation initiation factor 3 subunit E) is part of the protein translation initiation complex, but its effect on translation are modest and effects in ion channel trafficking have been suggested. The factor interacted with CaV1.2 and regulated CaV1.2 traffic bidirectionally. eIF3e silencing impaired CaV1.2 internalization, which resulted in an increased intracellular Ca(2+) load upon stimulation. These findings provide a mechanism for regulation of L-type CaV channel surface expression with consequences for β-cell calcium homeostasis, which will affect pancreatic β-cell function and insulin production.
authors.affiliation: Lund University Diabetes Center, Malmö, Sweden.
authors.forename: Pawel
authors.initials: P
authors.lastname: Buda
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinbothe
authors.forename: Vini
authors.initials: V
authors.lastname: Nagaraj
authors.forename: Taman
authors.initials: T
authors.lastname: Mahdi
authors.forename: Cheng
authors.initials: C
authors.lastname: Luan
authors.forename: Yunzhao
authors.initials: Y
authors.lastname: Tang
authors.forename: Annika S
authors.initials: AS
authors.lastname: Axelsson
authors.forename: Daiqing
authors.initials: D
authors.lastname: Li
authors.forename: Anders H
authors.initials: AH
authors.lastname: Rosengren
authors.forename: Erik
authors.initials: E
authors.lastname: Renström
authors.forename: Enming
authors.initials: E
authors.lastname: Zhang
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000378:metabolism*; D002460:Cell Line; D004705:Endocytosis / Q000187:drug effects; D039621:Eukaryotic Initiation Factor-3 / Q000378:metabolism*; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000494:pharmacology; D006706:Homeostasis / Q000187:drug effects; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D050417:Insulin-Secreting Cells / Q000166:cytology; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism*; D057054:Molecular Imaging; D021122:Protein Subunits / Q000378:metabolism*; D021381:Protein Transport / Q000187:drug effects; D051381:Rats
chemical_list: D020746:Calcium Channels, L-Type; D039621:Eukaryotic Initiation Factor-3; D007328:Insulin; C419385:L-type calcium channel alpha(1C); D021122:Protein Subunits; D005947:Glucose; D002118:Calcium