The long term goal of these studies is to elucidate the physiological role of the fibroblast growth factor (FGF) signaling pathway in the pancreatic islet. The pancreatic islet is a functional unit that secretes insulin, glucagon and other hormones in a regulated manner, processes that are modulated by extensive cell-cell (paracrine) communication. Pancreatic islet beta-cell dysfunction is a hallmark of Type II diabetes, and understanding the function of these cells in the context of a whole islet will enhance modeling of the disease process. Our preliminary data and the results of others indicate that FGFs and FGF receptors (FGFRs) are synthesized in beta-cells. Perturbation of this signaling pathway in the mouse pancreas using dominant-negative receptor expression has been shown to modulate insulin secretion and resulted in a diabetic phenotype. Regulated secretion of FGF can activate receptor to cause cell signaling by a number of mechanisms, including the release of internal Ca2+-stores and the activation of phosphatidylinositol 3-kinase (PI3K). FGF has varied roles in many different cell types including proliferation, cell survival, and angiogenesis.
Three specific aims have been proposed to examine this diverse signaling pathway in the pancreatic islet: 1) Determine the role of paracrine stimulation (FGF, insulin, glucagons, somatostatin, ATP) in the propagation of glucose-stimulated pancreatic islet Ca2+ oscillations. 2) Identify the subcellular route of fibroblast growth factor (FGF) secretion from pancreatic islet beta-cells. 3) Determine whether FGF activates the beta-cell PI3K/Akt pathway and whether this activation leads to enhanced cell survival.
The first aim will use a two channel microfluidic device to treat FGF stimulated islets with a glucose gradient, in combination with quantitative fluorescence microscopy to observe the metabolic and Ca2+-responses. More specifically, we will determine whether stimulated release of internal Ca2+-stores modifies the glucose-stimulated metabolic response. The second specific aim will examine the cellular trafficking routes involved in FGF secretion from beta-cells and determine whether its secretion is up-regulated during glucose-stimulation. The third specific aim will use a dominant-negative receptor isoform to examine the activation of PI3K in beta-cells. Activation of PI3K and downstream Akt has been shown to enhance cell survival. These studies will determine whether FGFR signaling is activated in beta-cells, and involved in maintenance of glucose-stimulated insulin secretion. Lay language summary: The proposed work will examine the regulation of insulin secretion. Preliminary evidence shows that fibroblast growth factor (FGF) may be involved in this regulation. These studies will examine whether FGF is involved in regulating insulin secretion, and whether FGF enhances the survival of insulin secreting beta-cells.
| Rocheleau, Jonathan V; Piston, David W (2008) Chapter 4: Combining microfluidics and quantitative fluorescence microscopy to examine pancreatic islet molecular physiology. Methods Cell Biol 89:71-92 |
| Kilkenny, Dawn M; Rocheleau, Jonathan V (2008) Fibroblast growth factor receptor-1 signaling in pancreatic islet beta-cells is modulated by the extracellular matrix. Mol Endocrinol 22:196-205 |
