It is known that activation of the PI 3-kinase - Akt2 pathway is required for insulin-stimulated glucose transporter GLUT4 translocation from intracellular storage to the plasma membrane (PM) although the molecular mechanism is not fully understood. To identify novel insulin signaling proteins required for glucose transport, we have successfully applied quantitative phosphoproteomic approaches and siRNA-based functional screening assays to cultured 3T3-L1 adipocytes, demonstrating unequivocally the requirement of a novel protein CDP138 for insulin stimulation of glucose transport and GLUT4 translocation. CDP138 is a 138 kDa previously unknown phosphoprotein encoded by KIAA0528. Interestingly, CDP138 is phosphorylated by both Akt2 and CaMKIId directly. CDP138 forms oligomers and is capable of binding calcium and membrane lipids. We demonstrated that both the C2 domain and Akt phosphorylation site Ser197 in CDP138 are critical for insulin-induced GLUT4 translocation and membrane fusion between the GLUT4 vesicles and the PM. We have also successfully developed the first CDP138 mutant mouse line. Our preliminary data shows that CDP138 null mice, but not their wild-type littermates, are hyperglycemic when challenged with a high- fat diet for only 4 weeks. The focus of this project is to study the molecular basis by which CDP138 regulates GLUT4 - PM fusion and to determine physiological significance of CDP138 in glucose metabolism using the loss-of-function animal model. First, we propose to determine if phosphorylation and oligomerization of CDP138 affect its intracellular distribution, interactions with calcium ion and lipid membranes, and GLUT4 translocation. Second, we wil identify lipid-binding sites in the C2 domain and test their role in GLUT4 translocation and GLUT4 vesicle - PM fusion in live cels. Third, we observed that CDP138 interacts with TBC1D4/TBC1D1 and RalBP1, GTPase activating proteins for Rab10/Rab8A/Rab13 and Rac1, respectively. Since those GTPases are known to be involved in the regulation of GLUT4 translocation, we will examine if CDP138 regulates their activities. Furthermore, we will determine the physiological significance of CDP138 in vivo, by comparing insulin sensitivity, glucose disposal, body composition and metabolic rate in CDP138 knockout mice and their wild-type littermates fed with a normal chow or a high-fat diet. State-of-the art hyperinsulinemic-euglycemic clamp technology will be used in this study. Finally, we will also examine if CDP138 is necessary for exercise- or contraction-induced glucose transport using the knockout mouse model. Together, this project will provide valuable and novel insight into the molecular mechanisms by which CDP138 acts as a point of convergence between kinase activation and glucose transport.

Public Health Relevance

We identified a novel phosphoprotein CDP138 as an essential factor for insulin-stimulated glucose transport and its protein level is significantly reduced in obese animals. This project is designed to understand how CDP138 regulates glucose transport in both cultured cells and a loss-of-function mouse model. In addition, this project will provide new insight into potential therapeutic targets for diabetes.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK094025-02
Application #
8466967
Study Section
Cellular Aspects of Diabetes and Obesity Study Section (CADO)
Program Officer
Sechi, Salvatore
Project Start
2012-07-01
Project End
2013-09-30
Budget Start
2013-06-01
Budget End
2013-09-30
Support Year
2
Fiscal Year
2013
Total Cost
$89,282
Indirect Cost
$43,497
Name
Sanford-Burnham Medical Research Institute
Department
Type
DUNS #
020520466
City
La Jolla
State
CA
Country
United States
Zip Code
92037
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Huang, Jun-Yuan; Zhou, Qiong Lin; Huang, Chun-Hong et al. (2017) Neutrophil Elastase Regulates Emergency Myelopoiesis Preceding Systemic Inflammation in Diet-induced Obesity. J Biol Chem 292:4770-4776
Mansuy-Aubert, Virginie; Zhou, Qiong L; Xie, Xiangyang et al. (2013) Imbalance between neutrophil elastase and its inhibitor ?1-antitrypsin in obesity alters insulin sensitivity, inflammation, and energy expenditure. Cell Metab 17:534-48