The major interest of our research centers on understanding the mechanisms of regulation of glycogen metabolism, and in particular those involved in signaling by insulin, epinephrine and muscle contraction. DESCRIPTION: The overall goal of the principal investigator's research program is to understand the role of protein phosphatases in signal transduction pathways. Protein phosphatase type 1 PP1 constitutes a major proportion of serinethreonine phosphataseactivity in the cell. Four PP1 holoenzymes have been identified and all contain a similarcatalytic subunit CS1 but differ in the associated regulatory subunits. The function of the latter components appear to be to target the enzyme to various cellular compartments, to confer substratespecificity and to control enzyme activity. Biochemical and genetic studies have provided evidence that PP1 is involved in several cell functions, including glycogen metabolism, calcium transport, muscle contraction, gene expression, cell cycle and cell growth. Although much has been learned about the participation of these enzymes in a variety of cellular processes, knowledge of their intracellular targets and regulation of their activity is quite limited. The objectives of this project are to understand the molecular basis of the interaction between catalytic and regulatory components, to elucidate the regulatory mechanisms and to define the role in specific cell functions of two forms of type 1 holoenzyme: the ATP-Mg-dependent and the glycogen sarcoplasmic reticulum-associated protein phosphatases. The ATP-dependent phosphatase is a cytosolic enzyme and contains inhibitor-2 as the regulatory subunit, whereas the glycogen SR- associated form interacts with both membranes and glycogen via its regulatory component RGL. Structure function studies will be directed at characterizing the functional domains of CS1 and the regions of interaction between CS1 and the regulatory subunits, I-2 and RGL, by utilizing the yeast two-hybrid system and in vitro reconstitution assays of bacterially expressed mutant proteins. Studies of the roles of the two phosphatases in cells will involve over expression of CS1 together with wild type or mutated regulatory subunits I-2 or RGL in mammaliancells to; analyze any modulation of cellular responses to extracellular signals. In addition, the control of the phosphatases will be probed by overexpressing active or dominant negative versions of putative upstream regulatory elements such as those in the MAP kinaseERK cascades. Success in this investigation should lead to improved understanding of the physiological role of some of the major type 1 phosphatases. The major interest of our research centers on structure-function relationship and physiological role of type 1 serine/threonine protein phosphatases (PP1) with a particular emphasis on glycogen metabolism and hence diabetes and obesity.
Biochemical Engineering, Biochemistry, Biochemistry, Carbohydrates, Biochemistry, Nucleic Acid, Biochemistry, Proteins, Bioengineering, Biology, Cellular, Biology, Molecular, Cancer Biology, Cancer/Carcinogenesis, Cardiovascular Diseases, Cell Components, Cell Lines