Myosin-Is are the single-headed and membrane-associated members of the myosin superfamily that are found in nearly all eukaryotic cells. Myosin-Is comprise the largest unconventional myosin family found in humans (eight genes), and the large size and expression profile of the family distinguishes it as one of the most diverse. Myosin-Is play crucial roles in regulating membrane dynamics, cytoskeletal structure, and endosomal processing. However, the details of myosin-l molecular functions are still largely unknown. A widely-expressed myosin-I isoform, myo1c, has been shown to facilitate the fusion of vesicles containing glucose-transporter-4 (GLUT4) with the plasma membrane in response to insulin stimulation. This crucial step regulates the cellular uptake of glucose by controlling the number of glucose transporters present on the cell surface. Decreasing the expression of myo1c via siRNA knockdowns inhibits GLUT4 movement to the plasma membrane, and over expression of myo1c overrides PI3-kinase inhibitor blockage of membrane Fusion. While it is clear that insulin enhances the localization of GLUT4 vesicles with myo1c and actin and away from microtubules, the molecular role of myo1c in membrane fusion is not known. Our goal is to use the GLUT4 transport as a model system for determining the molecular role of myosin-l in membrane transport. We will investigate the cellular dynamics of myo1c movements using high-resolution microscopy, we will investigate how myo1c coordinates with microtubule motors, and we will investigate how the physical properties of myo1c mediate membrane delivery.
Our specific aims are as follows: 1. Dynamics and distribution of GLUT4 and the cytoskeleton. We will determine the organization and spatial kinetics of the actin and microtubule cytoskeletons during GLUT4 transport and fusion, and we will determine the specific role of myo1c during this process. 2. Mechanical role of myo1c in GLUT4 dynamics. We will determine the mechanical role of myo1c in GLUT4 dynamics. We will determine what a protein with transport and mechano-sensing activities is required for GLUT4 movements. 3. Myo1c regulation and GLUT4 recruitment. We will investigate the mechanical linkage between myo1c and a putative cargo-receptor, and we will investigate myo1c motor regulation.

Public Health Relevance

Insulin stimulates the uptake of glucose in fat cells through the translocation of the glucose transporter, GLUT4, from intracellular storage sites to the plasma membrane. It is this movement of GLUT4 that is largely responsible for removal of glucose from circulating blood after a meal and is crucial for glucose homeostasis. Our study will provide key details of the molecular regulation of insulin-stimulated glucose uptake by determining the roles of actin-based motors in vesicular transport.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Program Projects (P01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-CB-P)
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Pennsylvania
United States
Zip Code
Hendricks, Adam G; Goldman, Yale E; Holzbaur, Erika L F (2014) Reconstituting the motility of isolated intracellular cargoes. Methods Enzymol 540:249-62
Zajac, Allison L; Goldman, Yale E; Holzbaur, Erika L F et al. (2013) Local cytoskeletal and organelle interactions impact molecular-motor- driven early endosomal trafficking. Curr Biol 23:1173-80
Greenberg, Michael J; Ostap, E Michael (2013) Regulation and control of myosin-I by the motor and light chain-binding domains. Trends Cell Biol 23:81-9
Hendricks, Adam G; Lazarus, Jacob E; Perlson, Eran et al. (2012) Dynein tethers and stabilizes dynamic microtubule plus ends. Curr Biol 22:632-7
Wang, Yu-Hsiu; Collins, Agnieszka; Guo, Lin et al. (2012) Divalent cation-induced cluster formation by polyphosphoinositides in model membranes. J Am Chem Soc 134:3387-95
Sun, Yujie; Goldman, Yale E (2011) Lever-arm mechanics of processive myosins. Biophys J 101:1-11
Collins, Agnieszka; Warrington, Anthony; Taylor, Kenneth A et al. (2011) Structural organization of the actin cytoskeleton at sites of clathrin-mediated endocytosis. Curr Biol 21:1167-75
Schroeder 3rd, Harry W; Mitchell, Chris; Shuman, Henry et al. (2010) Motor number controls cargo switching at actin-microtubule intersections in vitro. Curr Biol 20:687-96
Arsenault, Mark E; Purohit, Prashant K; Goldman, Yale E et al. (2010) Comparison of Brownian-dynamics-based estimates of polymer tension with direct force measurements. Phys Rev E Stat Nonlin Soft Matter Phys 82:051923
Holzbaur, Erika L F; Goldman, Yale E (2010) Coordination of molecular motors: from in vitro assays to intracellular dynamics. Curr Opin Cell Biol 22:4-13