Insulin stimulates glucose uptake into muscle and adipose tissue through the translocation of the insulin-responsive glucose transporter type 4 (GLUT4) from an intracellular compartment to the cell surface. Although this translocation event requires the activation of phosphatidylinositol 3-kinase (PI 3-kinase) it is not sufficient, implicating a second signaling pathway. The PI 3-kinase-independent pathway involves the tyrosinc phosphorylation of the proto-oncogene c-cbl through the adaptor protein. cbl-associated protein (CAP). A downstream effector of the CAP/cbl pathway is teratocareinoma 10 (TC 10), a member of the Rho family of GTpases. Clone#38 was discovered as a protein that interacts with the syntaxin 4-interacting protein (synip) in a yeast two-hybrid screening. Synip is a negative regulator of syntaxin 4, the receptor for GLUT4 vesicle docking at the plasma membrane. Interestingly, this novel protein posses a RhoGAP domain that interacts with TC10. In addition, it also possesses a PX and SH3 protein interaction domains that are important for binding of signaling molecules. Thus, our hypothesis is that clone#38 is a scaffolding protein that recruits insulin signaling molecules to the site of GLUT4 vesicle docking. To test this hypothesis, I will first biochemically characterize clone#38 interaction with synip and TC10. Deletional mutants that fail to interact with synip or TC10 will be used in specific aim 2 to evaluate the role of clone#38 in insulin-stimulated glucose uptake and GLUT4 translocation.
In specific aim 3, I will search for proteins that bind to the PX and SH3 domains of clone#38. This approach may lead to new insights into the molecular mechanism of insulin action.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32DK061188-03
Application #
6698995
Study Section
Endocrinology Study Section (END)
Program Officer
Hyde, James F
Project Start
2002-02-12
Project End
2005-02-11
Budget Start
2004-02-12
Budget End
2005-02-11
Support Year
3
Fiscal Year
2004
Total Cost
$50,548
Indirect Cost
Name
University of Michigan Ann Arbor
Department
Internal Medicine/Medicine
Type
Schools of Medicine
DUNS #
073133571
City
Ann Arbor
State
MI
Country
United States
Zip Code
48109
Kanzaki, Makoto; Mora, Silvia; Hwang, Joseph B et al. (2004) Atypical protein kinase C (PKCzeta/lambda) is a convergent downstream target of the insulin-stimulated phosphatidylinositol 3-kinase and TC10 signaling pathways. J Cell Biol 164:279-90
Liu, Jun; DeYoung, Stephanie M; Hwang, Joseph B et al. (2003) The roles of Cbl-b and c-Cbl in insulin-stimulated glucose transport. J Biol Chem 278:36754-62