Carrageenan Inhibits Insulin Signaling through GRB10-mediated Decrease in Tyr(P)-IRS1 and through Inflammation-induced Increase in Ser(P)307-IRS1

J Biol Chem. 2015 Apr 24;290(17):10764-74. doi: 10.1074/jbc.M114.630053. Epub 2015 Mar 17.

Abstract

Inflammation induced by exposure to the common food additive carrageenan leads to insulin resistance by increase in Ser(P)(307)-insulin receptor substrate 1 (IRS1) and subsequent decline in the insulin-stimulated increase in Ser(P)(473)-AKT. Inhibition of carrageenan-induced inflammation reversed the increase in Ser(P)(307)-IRS1 but did not completely reverse the carrageenan-induced decline in Ser(P)(473)-AKT. To identify the additional mechanism responsible for the decrease in Ser(P)(473)-AKT, studies were performed in human HepG2 cells and in C57BL/6J mice. Following carrageenan, expression of GRB10 (growth factor receptor-bound 10 protein), an adaptor protein that binds to the insulin receptor and inhibits insulin signaling, increased significantly. GRB10 silencing blocked the carrageenan-induced reduction of the insulin-stimulated increase in Tyr(P)-IRS1 and partially reversed the decline in Ser(P)(473)-AKT. The combination of GRB10 silencing with BCL10 silencing and the reactive oxygen species inhibitor Tempol completely reversed the decline in Ser(P)(473)-AKT. After carrageenan, GRB10 promoter activity was enhanced because of activation by GATA2. A direct correlation between Ser(P)(473)-AKT and Ser(P)(401)-GATA2 was evident, and inhibition of AKT phosphorylation by the PI3K inhibitor LY294002 blocked Ser(401)-GATA2 phosphorylation and the increase in GRB10 expression. Studies indicated that carrageenan inhibited insulin signaling by two mechanisms: through the inflammation-mediated increase in Ser(P)(307)-IRS1, a negative regulator of insulin signaling, and through a transcriptional mechanism leading to increase in GRB10 expression and GRB10-inhibition of Tyr(P)-IRS1, a positive regulator of insulin signaling. These mechanisms converge to inhibit the insulin-induced increase in Ser(P)(473)-AKT. They provide internal feedback, mediated by Ser(P)(473)-AKT, Ser(P)(401)-GATA2, and nuclear GATA2, which links the opposing effects of serine and tyrosine phosphorylations of IRS1 and can modulate insulin responsiveness.

Keywords: Akt PKB; Carrageenan; GATA Transcription Factor; GRB10; Inflammation; Insulin Receptor Substrate 1 (IRS-1); Insulin Resistance.

MeSH terms

  • Animals
  • Carrageenan / toxicity*
  • GATA2 Transcription Factor / metabolism
  • GRB10 Adaptor Protein / chemistry
  • GRB10 Adaptor Protein / genetics
  • GRB10 Adaptor Protein / metabolism*
  • Gene Expression / drug effects
  • Hep G2 Cells
  • Humans
  • Inflammation / chemically induced
  • Inflammation / metabolism
  • Insulin / metabolism*
  • Insulin Receptor Substrate Proteins / chemistry
  • Insulin Receptor Substrate Proteins / metabolism*
  • Insulin Resistance
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Models, Statistical
  • Phosphorylation
  • Promoter Regions, Genetic
  • Proto-Oncogene Proteins c-akt / chemistry
  • Proto-Oncogene Proteins c-akt / metabolism
  • RNA, Small Interfering / genetics
  • Serine / chemistry
  • Signal Transduction
  • Tyrosine / chemistry

Substances

  • GATA2 Transcription Factor
  • GATA2 protein, human
  • GRB10 protein, human
  • Gata2 protein, mouse
  • Grb10 protein, mouse
  • IRS1 protein, human
  • Insulin
  • Insulin Receptor Substrate Proteins
  • Irs1 protein, mouse
  • RNA, Small Interfering
  • GRB10 Adaptor Protein
  • Tyrosine
  • Serine
  • Carrageenan
  • Proto-Oncogene Proteins c-akt