As the epidemic of insulin resistance and type 2 diabetes emerges worldwide, there is an urgent need to understand how insulin maintains blood glucose homeostasis at the molecular level. A major function of insulin is to promote glucose uptake into muscle and adipose tissues, a process mediated by the glucose transporter GLUT4. Upon insulin stimulation, GLUT4 is relocated from intracellular storage vesicles to the cell surface through regulated exocytosis. The exocytosis of GLUT4 vesicles requires the SNARE proteins as the core fusion machinery, as well as a group of fusion regulators. Loss-of-function mutations of the SNAREs or fusion regulators abrogate insulin-triggered GLUT4 exocytosis and disrupt blood glucose homeostasis. Moreover, imbalances in the GLUT4 vesicle fusion proteins have been implicated in obesity-associated insulin resistance. While the physiological importance of the SNAREs and fusion regulators is clear, it remains poorly understood how they act in concert to mediate and regulate GLUT4 vesicle fusion. The overall goal of this proposal is to answer this key question using novel and complementary approaches. We will first define the molecular mechanisms and functional interactions of the vesicle fusion proteins using a novel reconstituted fusion system. We will use both recombinant proteins and native proteins isolated from mouse adipocytes. We will then characterize GLUT4 vesicle fusion proteins in 3T3-L1 adipocytes and in adipocytes isolated from knockout mice. Finally, we will determine whether and how the activities of the vesicle fusion proteins are impaired in insulin resistance, using hig fat diet-fed mice as a model system. If successfully accomplished, this research will substantially broaden our knowledge about the regulatory mechanisms of GLUT4 exocytosis. The findings will also shed light upon the diseases associated with glucose imbalances such as insulin resistance and type 2 diabetes, and will facilitate the development of novel strategies for therapeutic intervention.

Public Health Relevance

Insulin-triggered exocytosis of the glucose transporter GLUT4 plays a key role in maintaining blood glucose homeostasis. Imbalances in the GLUT4 pathway can give rise to insulin resistance and type 2 diabetes. Knowledge of the protein-protein networks that mediate and regulate GLUT4 exocytosis will shed light upon the pathogenesis of type 2 diabetes and will likely identify novel targets for therapeutic intervention.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
Project #
Application #
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Haft, Carol R
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Colorado at Boulder
Schools of Arts and Sciences
United States
Zip Code
Menasche, Bridget L; Crisman, Lauren; Gulbranson, Daniel R et al. (2018) Fluorescence Activated Cell Sorting (FACS) in Genome-Wide Genetic Screening of Membrane Trafficking. Curr Protoc Cell Biol :e68
Yu, Haijia; Shen, Chong; Liu, Yinghui et al. (2018) SNARE zippering requires activation by SNARE-like peptides in Sec1/Munc18 proteins. Proc Natl Acad Sci U S A 115:E8421-E8429
Shen, Chong; Liu, Yinghui; Yu, Haijia et al. (2018) The N-peptide-binding mode is critical to Munc18-1 function in synaptic exocytosis. J Biol Chem 293:18309-18317
Guan, Xiaoyang; Chaffey, Patrick K; Wei, Xiuli et al. (2018) Chemically Precise Glycoengineering Improves Human Insulin. ACS Chem Biol 13:73-81
Gulbranson, Daniel R; Davis, Eric M; Demmitt, Brittany A et al. (2017) RABIF/MSS4 is a Rab-stabilizing holdase chaperone required for GLUT4 exocytosis. Proc Natl Acad Sci U S A 114:E8224-E8233
Yu, Haijia; Liu, Yinghui; Gulbranson, Daniel R et al. (2016) Extended synaptotagmins are Ca2+-dependent lipid transfer proteins at membrane contact sites. Proc Natl Acad Sci U S A 113:4362-7
Zhang, Conggang; Lee, Schuyler; Peng, Yinghua et al. (2015) A chemical genetic approach to probe the function of PINK1 in regulating mitochondrial dynamics. Cell Res 25:394-7
Yu, Haijia; Rathore, Shailendra S; Shen, Chong et al. (2015) Reconstituting Intracellular Vesicle Fusion Reactions: The Essential Role of Macromolecular Crowding. J Am Chem Soc 137:12873-83
Shen, Chong; Rathore, Shailendra S; Yu, Haijia et al. (2015) The trans-SNARE-regulating function of Munc18-1 is essential to synaptic exocytosis. Nat Commun 6:8852
Davis, Eric M; Kim, Jihye; Menasche, Bridget L et al. (2015) Comparative Haploid Genetic Screens Reveal Divergent Pathways in the Biogenesis and Trafficking of Glycophosphatidylinositol-Anchored Proteins. Cell Rep 11:1727-36

Showing the most recent 10 out of 14 publications