James G. Burchfield

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The protein kinase Akt mediates several metabolic and mitogenic effects of insulin, whereas activation of protein kinase C (PKC) isoforms has been implicated in the inhibition of insulin action. We have previously shown that both PKC and PKCepsilon are activated in skeletal muscle of insulin-resistant high fat-fed rats, and to identify potential substrates(More)
OBJECTIVE Insufficient insulin secretion is a hallmark of type 2 diabetes, and exposure of beta-cells to elevated lipid levels (lipotoxicity) contributes to secretory dysfunction. Functional ablation of protein kinase C epsilon (PKCepsilon) has been shown to improve glucose homeostasis in models of type 2 diabetes and, in particular, to enhance(More)
In type 2 diabetes, pancreatic beta cells fail to secrete sufficient insulin to overcome peripheral insulin resistance. Intracellular lipid accumulation contributes to beta cell failure through poorly defined mechanisms. Here we report a role for the lipid-regulated protein kinase C isoform PKCepsilon in beta cell dysfunction. Deletion of PKCepsilon(More)
Vesicle transport in eukaryotic cells is regulated by SNARE proteins, which play an intimate role in regulating the specificity of vesicle fusion between discrete intracellular organelles. In the present study we investigated the function and plasticity of v-SNAREs in insulin-regulated GLUT4 trafficking in adipocytes. Using a combination of knockout mice,(More)
The regulated trafficking or exocytosis of cargo-containing vesicles to the cell surface is fundamental to all cells. By coupling the technology of fluorescently tagged fusion proteins with total internal reflection fluorescence microscopy (TIRFM), it is possible to achieve the high spatio-temporal resolution required to study the dynamics of sub-plasma(More)
The insulin-stimulated trafficking of GLUT4 to the plasma membrane in muscle and fat tissue constitutes a central process in blood glucose homeostasis. The tethering, docking, and fusion of GLUT4 vesicles with the plasma membrane (PM) represent the most distal steps in this pathway and have been recently shown to be key targets of insulin action. However,(More)
Regulated GLUT4 trafficking is a key action of insulin. Quantitative stepwise analysis of this process provides a powerful tool for pinpointing regulatory nodes that contribute to insulin regulation and insulin resistance. We describe a novel GLUT4 construct and workflow for the streamlined dissection of GLUT4 trafficking; from simple high throughput(More)
Exercise is essential in regulating energy metabolism and whole-body insulin sensitivity. To explore the exercise signaling network, we undertook a global analysis of protein phosphorylation in human skeletal muscle biopsies from untrained healthy males before and after a single high-intensity exercise bout, revealing 1,004 unique exercise-regulated(More)
This paper presents a novel computer vision system for automated identification of vesicle-plasma membrane fusion events in image sequences obtained from Total Internal Reflection Fluorescence (TIRF) microscopes. Identification of such events is important in order to better understand the process of exocytosis in cells. Manual analysis of thousands of(More)
This study aimed to determine whether protein kinase C (PKC) δ plays a role in the glucose intolerance caused by a high-fat diet, and whether it could compensate for loss of PKCε in the generation of insulin resistance in skeletal muscle. Prkcd −/−, Prkce −/− and wild-type mice were fed high-fat diets and subjected to glucose tolerance tests. Blood glucose(More)