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 Ca2+channels (CaV) in pancreatic ß-cells may contribute to the development of type 2 diabetes. First, failure to increase intracellular Ca2+ concentrations at the sites of exocytosis impedes insulin release. Furthermore, excessive Ca2+ 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 Ca2+ 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 Ca2+ 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.

Identification of Differentially Expressed Proteins from Leishmania amazonensis Associated with the Loss of Virulence of the Parasites

“…a ) Spots match ID number obtained from ImageMaster Platinum;b ) Name of the identified protein;c ) Uniprot identification code;d ) Experimentally predicted and expected isoelectric point ( pI );e ) Experimentally predicted and expected molecular weight ( Mr , in kDa);f ) Number of identified peptides by MS;g ) Percentage of the protein sequence covered by identified peptides;h ) Normalized data from R0 represented by mean values of each condition divided by R30 value;i ) Fold represents the maximum spot intensity mean value of the conditions divided by the smallest value;j ) One-way ANOVA ( P <0.01) obtained from spot analysis;k ) Biological functions according to NCBI, UniProt, and Gene Ontology databases;l ) Biological activity and/or immunological application described in other studies: [22] Tull et al, 2010; [23] Oliveira et al, 2006; [24] Daifalla et al, 2011; [25] Iyer et al, 2008; [26] Hunger-Glaser et al, 1999; [27] Werbovetz et al, 1999; [28] Feng et al, 2011; [29] Niemirowicz et al, 2007; [30] Hunger-Glaser et al, 1997; [31] Alcolea et al, 2009; [32] Bhaskar et al, 2012; [33] Khanra et al, 2012; [34] Berberich et al, 2003; [35] Moore et al, 1996; [36] Swenerton et al, 2011; [37] Hummadi et al, 2006; [38] Martins et al, 2006; [39] Burns et al, 1993; [40] Kushawaha et al, 2011; [41] Misra et al, 2005; [42] Bringaud et al, 1995; [43] Eggleson et al, 1999; [44] Mureev et al, 2007; [45] Steiner et al, 2007; [46] Martínez-Rodríguez et al, 2012; [47] Drummelsmith et al, 2004; [48] Achour et al, 2002; [49] Buda et al, 2013; [50] Alcolea et al, 2011; [51] Martín et al, 2009; [52] Silva et al, 2012. The proteins were identified through the data included in ...…”

Mathematical modelling of local calcium and regulated exocytosis during inhibition and stimulation of glucagon secretion from pancreatic alpha‐cells

“…3 (Dai et al 2014). Another possibility could be regulation by L-type Ca 2+ channel trafficking to and from the cell membrane as in insulin-secreting cells (Buda et al 2013). It may be speculated that this increment will facilitate formation of Ca 2+ channel clusters able to trigger exocytosis.…”

The role of eIF3 and its individual subunits in cancer

“…eIF3e also has been shown to promote the binding of the kinase Mnk1 to eIF4G and its subsequent phosphorylation of eIF4E [107]. In addition to binding to eIF4G, 3e interacts with the stress-and interferon-inducible translation inhibitory protein P56 [108], with the MIF4GD/SLIP12 proteins involved in the translation of histone mRNAs that lack the poly(A) tail [109], with the Ca ++ voltage-gated channel protein CaV1.2 [110], with the DNA damage protein ATM [111] and with the cell growth proteins, TID1 and Patched [112]. eIF3e also is involved in nonsense mediated decay of mRNAs [113], and reduced levels appear to specifically down-regulate the synthesis of Hypoxia-inducible factors (HIFs) [104].…”