Characterization of Acyl-CoA synthetase isoforms in pancreatic beta cells: Gene silencing shows participation of ACSL3 and ACSL4 in insulin secretion

Arch Biochem Biophys. 2017 Mar 15;618:32-43. doi: 10.1016/j.abb.2017.02.001. Epub 2017 Feb 11.

Abstract

Long-chain acyl-CoA synthetases (ACSLs) convert fatty acids to fatty acyl-CoAs to regulate various physiologic processes. We characterized the ACSL isoforms in a cell line of homogeneous rat beta cells (INS-1 832/13 cells) and human pancreatic islets. ACSL4 and ACSL3 proteins were present in the beta cells and human and rat pancreatic islets and concentrated in insulin secretory granules and less in mitochondria and negligible in other intracellular organelles. ACSL1 and ACSL6 proteins were not seen in INS-1 832/13 cells or pancreatic islets. ACSL5 protein was seen only in INS-1 832/13 cells. With shRNA-mediated gene silencing we developed stable ACSL knockdown cell lines from INS-1 832/13 cells. Glucose-stimulated insulin release was inhibited ∼50% with ACSL4 and ACSL3 knockdown and unaffected in cell lines with knockdown of ACSL5, ACLS6 and ACSL1. Lentivirus shRNA-mediated gene silencing of ACSL4 and ACSL3 in human pancreatic islets inhibited glucose-stimulated insulin release. ACSL4 and ACSL3 knockdown cells showed inhibition of ACSL enzyme activity more with arachidonate than with palmitate as a substrate, consistent with their preference for unsaturated fatty acids as substrates. ACSL4 knockdown changed the patterns of fatty acids in phosphatidylserines and phosphatidylethanolamines. The results show the involvement of ACLS4 and ACLS3 in insulin secretion.

Keywords: Acyl-CoA synthetases; Gene silencing; Human pancreatic islets; Insulin secretion; Insulin secretory vesicles; Phosphatidylethanolamine; Phosphatidylserine.

MeSH terms

  • Animals
  • Arachidonic Acid / chemistry
  • Coenzyme A Ligases / genetics
  • Coenzyme A Ligases / metabolism*
  • Gene Silencing
  • Glucose / chemistry
  • Humans
  • Insulin / metabolism*
  • Insulin Secretion
  • Insulin-Secreting Cells / enzymology*
  • Islets of Langerhans / cytology*
  • Palmitic Acid / chemistry
  • Phosphatidylethanolamines / chemistry
  • Phosphatidylserines / chemistry
  • Protein Isoforms
  • Rats

Substances

  • Insulin
  • Phosphatidylethanolamines
  • Phosphatidylserines
  • Protein Isoforms
  • Arachidonic Acid
  • Palmitic Acid
  • phosphatidylethanolamine
  • Coenzyme A Ligases
  • ACSL1 protein, human
  • long-chain-fatty-acid-CoA ligase
  • Glucose