Loss of Egr-1 sensitizes pancreatic β-cells to palmitate-induced ER stress and apoptosis

Mun Wai Cheong, Li Hua Kuo, Yi Ning Cheng, Pei-Jane Tsai, Li Chun Ho, Haw Chih Tai, Wen-Tai Chiu, Shun-hua Chen, Pei-Jung Lu, Yan-Shen Shan, Lee Ming Chuang, Yau-Sheng Tsai

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Abstract: Pancreatic β-cells are particularly susceptible to fatty-acid-induced endoplasmic reticulum (ER) stress and apoptosis. To understand how β-cells sense fatty acid stimuli and translate into a long-term adaptive response, we investigated whether palmitic acid (PA) regulates early growth response-1 (Egr-1), an immediate-early transcription factor, which is induced by many environmental stimuli and implicated in cell proliferation, differentiation, and apoptosis. We found that Egr-1 was rapidly and transiently induced by PA in MIN6 insulinoma cells, which was accompanied by calcium influx and ERK1/2 phosphorylation. Calcium chelation and MEK1/2 inhibition blocked PA-induced Egr-1 upregulation, suggesting that PA induces Egr-1 expression through a calcium influx-MEK1/2-ERK1/2 cascade. Knockdown of Egr-1 increased PA-induced caspase-3 activation and ER stress markers and decreased PA-induced Akt phosphorylation and insulin secretion and signaling. Akt replenishment and insulin supplementation rescued PA-induced apoptosis in Egr-1 knockdown cells. These results suggest that the absence of Egr-1 loses its ability to couple the short-term insulin/Akt pathway to long-term survival adaptation. Finally, Egr-1-deficient mouse islets are more susceptible to ex vivo stimuli of apoptosis. In human pancreatic tissues, EGR1 expression correlated with expression of ER stress markers and anti-apoptotic gene. In conclusion, Egr-1 is induced by PA and further attempts to rescue β-cells from ER stress and apoptosis through improving insulin/Akt signaling. Our study underscores Egr-1 as a critical early sensor in pancreatic β-cells to translate fatty acid stimuli into a cellular adaptation mechanism. Key Message: PA stimulates Egr-1 expression via a calcium influx-MEK1/2-ERK1/2-Elk-1 cascade.Egr-1 attenuates PA-induced ER stress and apoptosis.Egr-1 maintains Akt survival pathway to protect β-cells from PA-induced apoptosis.Egr-1-deficient islets are prone to ex vivo stimuli of apoptosis.Human EGR1 expression correlates with genes for ER stress and anti-apoptosis.

Original languageEnglish
Pages (from-to)807-818
Number of pages12
JournalJournal of Molecular Medicine
Volume93
Issue number7
DOIs
Publication statusPublished - 2015 Jul 22

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Drug Discovery
  • Genetics(clinical)

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