Phosphorylation of Forkhead Protein FoxO1 at S253 Regulates Glucose Homeostasis in Mice.
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The transcription factor forkhead box O1 (FoxO1) is a key mediator in the insulin signaling pathway and controls multiple physiological functions, including hepatic glucose production (HGP) and pancreatic -cell function. We previously demonstrated that S256 in human FOXO1 (FOXO1-S256), equivalent to S253 in mouse FoxO1 (FoxO1-S253), is a key phosphorylation site mediating the effect of insulin as a target of protein kinase B on suppression of FOXO1 activity and expression of target genes responsible for gluconeogenesis. Here, we investigated the role of FoxO1-S253 phosphorylation in control of glucose homeostasis in vivo by generating global FoxO1-S253A/A knockin mice, in which FoxO1-S253 alleles were replaced with alanine (A substitution) blocking FoxO1-S253 phosphorylation. FoxO1-S253A/A mice displayed mild increases in feeding blood glucose and insulin levels but decreases in fasting blood glucose and glucagon concentrations, as well as a reduction in the ratio of pancreatic -cells/-cells per islet. FoxO1-S253A/A mice exhibited a slight increase in energy expenditure but barely altered food intake and glucose uptake among tissues. Further analyses revealed that FoxO1-S253A/A enhances FoxO1 nuclear localization and promotes the effect of glucagon on HGP. We conclude that dephosphorylation of S253 in FoxO1 may reflect a molecular basis of pancreatic plasticity during the development of insulin resistance.
author list (cited authors)
Zhang, K., Guo, X., Yan, H., Wu, Y., Pan, Q., Shen, J. Z., ... Guo, S.
complete list of authors
Zhang, Kebin||Guo, Xiaoqin||Yan, Hui||Wu, Yuxin||Pan, Quan||Shen, James Zheng||Li, Xiaopeng||Chen, Yunmei||Li, Ling||Qi, Yajuan||Xu, Zihui||Xie, Wei||Zhang, Weiping||Threadgill, David||He, Ling||Villarreal, Daniel||Sun, Yuxiang||White, Morris F||Zheng, Hongting||Guo, Shaodong