1992 — 1996 |
Michaeli, Tamar H |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Signal Transduction Pathways of Ras Proteins
The long term objective of this grant proposal is to elucidate the function of RAS proteins. The RAS gene family has been implicated in the control of normal cell proliferation and differentiation, and in the development of various human cancers. The high degree of evolutionary conservation among RAS genes is exemplified by the structural and functional homology between yeast and mammalian RAS proteins. The goal of the proposed studies is to identify and characterize the proteins that constitute the RAS signalling pathway in yeast. For these purposes the studies utilize dominant interfering RAS mutants that block the transmission of RAS signals in yeast and in higher eukaryotes. These mutants provide a novel and powerful probe to examine RAS function. Two complementing experimental approaches will be employed in these studies. One approach is to identify and characterize the genes that can restore transmission of RAS signals in the presence of these interfering mutants. The second approach will involve the establishment of a direct biochemical assay to detect the physical interactions of these interfering RAS mutants with cellular proteins. These studies will be extended to higher eukaryotes by examining the effects yeast proteins that interact directly with RAS have on the function of RAS in amphibian oocytes and in cultured mammalian cells. Additionally, if time permits, mammalian homologs of yeast proteins that interact directly with RAS will be isolated. The identification of the proteins that mediate RAS function, and of proteins that associate directly with RAS will constitute an important contribution to the understanding of RAS signal transduction pathways in yeast and in higher eukaryotes.
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0.958 |
2003 |
Michaeli, Tamar H |
R01Activity Code Description: To support a discrete, specified, circumscribed project to be performed by the named investigator(s) in an area representing his or her specific interest and competencies. |
Phosphodiesterase Regulation of Glucose Hemeostasis
DESCRIPTION (provided by applicant): The objective of the proposed research is to elucidate the contribution of the camp phosphodiesterase, PDE7A, to the regulation of glucose homeostasis. Since cAMP antagonizes insulin action, cAMP phosphodiesterases can augment insulin signaling by reducing levels of cAMP pools relevant to insulin action. In particular, PDE3B augments insulin signaling in fat and liver. PDE3B, however, is not expressed in skeletal muscle. Our studies established PDE7A as a cAMP specific phosphodiesterase expressed to high levels in skeletal muscle as the particulate PDE7A2 splice variant. Our targeted disruption of the PDE7A gene in mice yielded PDE7KO mice with defects in glucose homeostasis - glucose intolerance and insulin resistance. PDE7KO mice, however, are not hyperinsulinemic and their insulin secretion in response to injected glucose is indistinguishable from that of wild type mice. Consistent with the abundant expression of PDE7A2 in skeletal muscle, and with the strong contribution of skeletal muscle to whole body glucose disposal, PDE7KO mice are impaired in insulin stimulated glucose uptake by skeletal muscle, but not by adipose tissue. Based on these observations, we hypothesize that a primary defect in PDE7KO mice is the disposal of glucose by skeletal muscle. The experimental program will examine in vivo defects of PDE7KO mice in glucose disposal, glucose and lipid metabolism, cAMP and insulin signaling, in skeletal muscle, and in liver and adipocytes. The contribution of pancreatic beta-cells to PDE7KO phenotypes will also be assessed. Thus, the aim of the proposal is to at understand the cross talk between the insulin and the cAMP signaling pathways and mechanisms underlying diabetogenic, metabolic perturbations in glucose homeostasis.
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0.958 |