PROJECT SUMMARY Dysregulation of pancreatic islet function is a hallmark of type 2 diabetes mellitus (T2DM) progression. Thus, understanding the exact mechanisms by which islet function can be preserved and regulated is crucial. It is increasingly evident that α-cells play an important role in the potentiation of glucose-stimulated insulin secretion (GSIS), thereby expanding their function beyond that of the traditional counterregulatory role. However, the regulation of intra-islet communication and its role in maintaining normal islet function remains incompletely defined. Endogenous potentiators of β-cell function include glucagon and glucagon-like peptide-1 (GLP-1). While GLP-1 and glucagon both potentiate GSIS by binding to the GLP-1 receptor (GLP-1R) on the β-cell, GLP-1 is 300-fold more potent at promoting GSIS than glucagon. Canonically, glucagon is produced by the α-cell, and GLP-1 is produced by the enteroendocrine L-cells in the gut. However, a growing body of literature reports that under pathophysiological conditions, α-cells can produce and secrete active GLP-1. Our lab has identified the signaling protein 14-3-3-ζ as a key regulator of α-cell endocrine profile. Specifically, we have found that β-cell 14-3-3-ζ ablation and inhibition increases GSIS and activates α-cell active GLP-1 production and secretion in mouse and human islets in vitro. How β-cell 14-3-3-ζ expression is regulated and the role of the α-cell in the impact of β-cell 14-3-3-ζ on islet function is unknown. Therefore, the driving hypothesis of this project is that β-cell 14-3-3-ζ is a crucial regulator of α-cell to β-cell crosstalk. I will pursue our hypothesis in the following aims: Aim 1 will define a new pathway regulating β-cell14-3-3-ζ expression. Specifically, our lab has found that enhanced β-cell GLP-1R signaling decreases 14-3-3-ζ expression in the β-cell. I will study β-cells and mouse and human islets to define the key signaling nodes by which β-cell GLP-1R signaling decreases 14-3-3-ζ expression. Aim 2 will determine the efficacy of targeting 14-3-3-ζ in the β-cell to improve islet function in high fat diet-fed mice. Aim 3 will determine the effect of β-cell 14-3-3-ζ ablation on bidirectional islet cell crosstalk. Through these carefully designed experiments, I aim to shed light on a new crosstalk mechanism between α- cells and β-cells, potentially opening new avenues for understanding and treating T2DM. The training plan will be facilitated by the mentorship of my sponsor, mentorship team and the exceptional facilities and graduate student support at UC Davis. This proposal describes an integrative and comprehensive training plan to support my scientific and professional development and propel me toward my long-term goal of becoming an independent researcher focused on the molecular underpinnings of metabolic disease.