Our laboratory focuses on two major areas: 1) understanding the molecular mechanism of action and of insulin and related growth factors at a molecular level, as well as their alterations in pathologic states; and 2) defining at a molecular and physiologic level the defects that underlie human diabetes mellitus. To achieve these goals, we use a wide variety of methods ranging from basic cell biology and biochemistry to analysis in the yeast two-hybrid system and tissue-specific knockouts in mammalian animals.
The molecular mechanism of insulin action represents one of the most important of the receptor tyrosine kinases in control of metabolism and growth. Following stimulation, the insulin receptor phosphorylates as many as six different intracellular substrate proteins, each of which dock to a number of other intracellular proteins through SH2 and non-SH2 mediated interactions. This results in stimulation of both the PI 3-kinase pathway and the Ras-MAP kinase pathway, as well as activation of many serine and threonine kinases and stimulation of protein trafficking. To understand the complementarity and redundancy between these various complex pathways, we have utilized cellular transfection models, mouse knockout models and cells derived from knockout mice. We have focused primarily on the IRS proteins and various regulatory subunits of PI 3-kinase. These studies indicate that the insulin signaling network is a finely tuned circuit with multiple interactions which allows signaling to proceed to a wide variety of downstream targets including glucose transporter translocation, stimulation of glycogen, lipid and protein synthesis, and regulation of gene expression, cell growth and differentiation. Through the use of tissue-specific knockouts with the Cre-lox system of recombination, the role of each of these pathways in specific insulin actions in specific tissues is being determined. These genetic modifications also are further modulated by acquired alterations secondary to changes in levels of important metabolic intermediates.
The second major focus of the laboratory is defining the molecular defects that may cause non-insulin dependent (Type 2) diabetes. This study is being approached by studying the structure and function of proteins known to be involved in the insulin action cascade, as well as identification of novel genes involved in diabetes and insulin resistance through subtraction cloning, PCR differential display, and DNA Chip technology. As each of these candidate genes for diabetes is identified, studies are conducted to determine its relationship to human diabetes, as well as to create cellular and animal models of disease based on these new candidate genes. This includes production of overexpressing cell lines, as well as transgenic and knockout animals.
|
References:
- Kulkarni RN, Bruning JC, Winnay JN, Postic C, Magnuson MA, Kahn CR. 1999 Tissue-specific knockout of the insulin receptor in pancreatic b cells creates an insulin secretory defect similar to that in Type 2 diabetes. Cell 96:329-339
- Bruening J, Winnay J, Bonner-Weir S, Taylor SI, Accili D, Kahn CR. 1997 Development of a novel polygenic model of non-insulin-dependent diabetes mellitus in mice heterozygous for insulin receptor and IRS-1 null alleles. Cell 88(4):561-572
- Inoue, G, Cheatham, B, Kahn, CR 1999 Development of an in vitro reconstitution assay for glucose transporter 4 translocation. Proc. Natl. Acad. Sci. USA 96(26):14919-14924
|
Harvard University Home / GSAS Home / HMS Home 
