English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Plus monthly

Global: Zendy Tools annual

Global: Zendy Tools monthly

Global: Zendy Free Plan

Insulin enhances the proliferation and survival of pancreatic β-cells, but its mechanisms remain unclear. We hypothesized that Raf-1, a kinase upstream of both ERK and Bad, might be a critical target of insulin in β-cells. To test this hypothesis, we treated human and mouse islets as well as MIN6 β-cells with multiple insulin concentrations and examined putative downstream targets using immunoblotting, immunoprecipitation, quantitative fluorescent imaging, and cell death assays. Low doses of insulin rapidly activated Raf-1 by dephosphorylating serine 259 and phosphorylating serine 338 in human islets, mouse islets, and MIN6 cells. The phosphorylation of ERK by insulin was eliminated by exposure to a Raf inhibitor (GW5074) or transfection with a dominant-negative Raf-1 mutant. Insulin also enhanced the interaction between mitochondrial Raf-1 and Bcl-2 agonist of cell death (Bad), promoting Bad inactivation via its phosphorylation on serine 112. Insulin-stimulated ERK phosphorylation was abrogated by calcium chelation, calcineurin and calmodulin-dependent protein kinase II inhibitors, and Ned-19, a nicotinic acid adenine dinucleotide phosphate receptor (NAADPR) antagonist. Blocking Raf-1 and Ca2+ signaling resulted in nonadditive β-cell death. Autocrine insulin signaling partly accounted for the effects of glucose on ERK phosphorylation. Our results demonstrate that Raf-1 is a critical target of insulin in primary β-cells. Activation of Raf-1 leads to both an ERK-dependent pathway that involves nicotinic acid adenine dinucleotide phosphate-sensitive Ca2+ stores and Ca2+-dependent phosphorylation events, and an ERK-independent pathway that involves Bad inactivation at the mitochondria. Together our findings identify a novel insulin signaling pathway in β-cells and shed light on insulin’s antiapoptotic and mitogenic mechanisms.

Acute Insulin Signaling in Pancreatic Beta-Cells Is Mediated by Multiple Raf-1 Dependent Pathways