Ca2+ influx through L-type Ca2+ channels and Ca2+-induced Ca2+ release regulate cAMP accumulation and Epac1-dependent ERK 1/2 activation in INS-1 cells

  • Mol Cell Endocrinol. 2016 Jan 5;419:60-71. doi: 10.1016/j.mce.2015.09.034.
Evan P S Pratt  1 ,  Amy E Salyer  2 ,  Marcy L Guerra  2 ,  Gregory H Hockerman  3
Affiliations
  • 1. Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA; Purdue University Life Sciences Graduate Program, Purdue University, West Lafayette, IN, USA.
  • 2. Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA.
  • 3. Department of Medicinal Chemistry and Molecular Pharmacology, Purdue University, West Lafayette, IN, USA. Electronic address: [email protected].
PMID: 26435461 DOI: 10.1016/j.mce.2015.09.034
Abstract

We previously reported that INS-1 cells expressing the intracellular II-III loop of the L-type CA(2+) channel Cav1.2 (Cav1.2/II-III cells) are deficient in CA(2+)-induced CA(2+) release (CICR). Here we show that glucose-stimulated ERK 1/2 phosphorylation (GSEP) is slowed and reduced in Cav1.2/II-III cells compared to INS-1 cells. This parallels a decrease in glucose-stimulated cAMP accumulation (GS-cAMP) in Cav1.2/II-III cells. Influx of CA(2+) via L-type CA(2+) channels and CICR play roles in both GSEP and GS-cAMP in INS-1 cells since both are inhibited by nicardipine or ryanodine. Further, the Epac1-selective inhibitor CE3F4 abolishes glucose-stimulated ERK activation in INS-1 cells, as measured using the FRET-based sensor EKAR. The non-selective Epac antagonist ESI-09 but not the Epac2-selective antagonist ESI-05 nor the PKA Antagonist Rp-cAMPs inhibits GSEP in both INS-1 and Cav1.2/II-III cells. We conclude that L-type CA(2+) channel-dependent cAMP accumulation, that's amplified by CICR, activates Epac1 and drives GSEP in INS-1 cells.

Keywords
Ca(2+)-induced Ca(2+) release; Ca(v)1.2; Exchange protein directly activated by cAMP; Extracellular signal regulated kinase 1/2; L-type Ca(2+) channel; Pancreatic beta-cell; cAMP.
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