David E. James

Learn More
Antibodies specific for the insulin-regulatable glucose transporter (GLUT 4) were used to immunolocalize this protein in brown adipose tissue from basal- and insulin-treated rats. Cryosections of fixed tissue were incubated with antibodies, which were subsequently labeled with Protein A/gold and examined by EM. Antibodies against albumin and cathepsin D(More)
In muscle and fat cells, insulin stimulates the delivery of the glucose transporter GLUT4 from an intracellular location to the cell surface, where it facilitates the reduction of plasma glucose levels. Understanding the molecular mechanisms that mediate this translocation event involves integrating our knowledge of two fundamental processes--the signal(More)
Berberine has been shown to have antidiabetic properties, although its mode of action is not known. Here, we have investigated the metabolic effects of berberine in two animal models of insulin resistance and in insulin-responsive cell lines. Berberine reduced body weight and caused a significant improvement in glucose tolerance without altering food intake(More)
Insulin-stimulated GLUT4 translocation is central to glucose homeostasis. Functional assays to distinguish individual steps in the GLUT4 translocation process are lacking, thus limiting progress toward elucidation of the underlying molecular mechanism. Here we have developed a robust method, which relies on dynamic tracking of single GLUT4 storage vesicles(More)
Insulin stimulates the translocation of the glucose transporter GLUT4 from intracellular vesicles to the plasma membrane. In the present study we have conducted a comprehensive proteomic analysis of affinity-purified GLUT4 vesicles from 3T3-L1 adipocytes to discover potential regulators of GLUT4 trafficking. In addition to previously identified components(More)
A major mechanism by which insulin stimulates glucose transport in muscle and fat is the translocation of glucose transporters from an intracellular membrane pool to the cell surface. The existence of a distinct insulin-regulatable glucose transporter was suggested by the poor cross-reactivity between antibodies specific for either the HepG2 or rat brain(More)
Munc-18, also known as n-Sec1 or rbSec1, is a syntaxin-binding protein thought to play a role in regulating synaptic vesicle exocytosis. Although a gene family of syntaxins has been identified, only a limited subset bind to Munc-18. This implicates the existence of other mammalian Munc-18 homologues that may be involved in a range of vesicle transport(More)
Sec1p-like/Munc-18 (SM) proteins bind to t-SNAREs and inhibit ternary complex formation. Paradoxically, the absence of SM proteins does not result in constitutive membrane fusion. Here, we show that in yeast cells lacking the SM protein Vps45p, the t-SNARE Tlg2p is down-regulated, to undetectable levels, by rapid proteasomal degradation. In the absence of(More)
Insulin stimulates the movement of two glucose transporter isoforms (GLUT1 and GLUT4) to the plasma membrane (PM) in adipocytes. To study this process we have prepared highly purified PM fragments by gently sonicating 3T3-L1 adipocytes grown on glass coverslips. Using confocal laser immunofluorescence microscopy we observed increased PM labeling for GLUT1(More)
The first differentiative event in mammalian development is segregation of the inner cell mass and trophectoderm (TE) lineages. The epithelial TE cells pump fluid into the spherical blastocyst to form the blastocyst cavity. This activity is fuelled by glucose supplied through facilitative glucose transporters. However, the reported kinetic characteristics(More)