Eukaryotic translation initiation factor 3 subunit e controls intracellular calcium homeostasis by regulation of cav1.2 surface expression

PLoS One. 2013 May 30;8(5):e64462. doi: 10.1371/journal.pone.0064462. Print 2013.

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium / metabolism*
  • Calcium Channels, L-Type / metabolism*
  • Cell Line
  • Endocytosis / drug effects
  • Eukaryotic Initiation Factor-3 / metabolism*
  • Gene Expression Regulation* / drug effects
  • Glucose / pharmacology
  • Homeostasis* / drug effects
  • Insulin / metabolism
  • Insulin Secretion
  • Insulin-Secreting Cells / cytology
  • Intracellular Space / drug effects
  • Intracellular Space / metabolism*
  • Molecular Imaging
  • Protein Subunits / metabolism*
  • Protein Transport / drug effects
  • Rats

Substances

  • Calcium Channels, L-Type
  • Eukaryotic Initiation Factor-3
  • Insulin
  • L-type calcium channel alpha(1C)
  • Protein Subunits
  • Glucose
  • Calcium

Grants and funding

This work was supported by grants from the Swedish Research Council, NovoNordisk Foundation, Region Skåne and Albert Påhlsson Foundation to ER and AR, and a Tianjin Major Scientific and Technological Project Grant (09ZCZDSF04500) to DL. The fellowships of EZ, PB and TR were given by the Early Stage Training network CaVNet funded by the European Union. ER was a Senior Scientist and AR holds a Junior Researcher position at the SRC. This project is also supported by grants from the Juvenile Diabetes Research Foundation and the Swedish Strategic Research area in diabetes EXODIAB (ER PI and EZ co-PI). This work was done using imaging setups and real-time PCR equipment financed by the Knut and Alice Wallenberg foundation. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.