The broad objective of this research project is to explore the structure, functions, and modes of temporal and spatial regulation of the Na,K-ATPase (sodium pump) and the LAMP family of lysosome-associated membrane proteins (LAMPs). Research on the sodium pump is subdivided into several projects. (1) Mechanisms regulating vertebrate sodium pumps are being studied at multiple levels, including gene expression, subunit assembly. endocytosis, and protein degradation. (2) Molecular/genetic approaches are being taken to the study of sodium pump regulation in the fruit fly, Drosophila. One goal is to identify and characterize other genes involved in regulating the sodium pump. (3) The domains involved in subunit interactions within the sodium pump are being studied by analyzing the potential of mutant and chimeric subunits to assemble when expressed in cells and when combined in vitro. Subunit dissociation and rebinding tests are being developed for exploring the nature of subunit interactions. (4) Three-dimensional structures of small domains of the sodium pump are being analyzed by NMR methods, and attempts are underway to obtain crystals of larger domains for structural studies. (5) Expression systems are under development in tissue cultured kidney cells and in Dictyostelium, to provide better contexts in which to compare the ion transport properties of various sodium pump isoforms and to study structure-function relationships. Alterations in sodium pump regulation have been linked to a variety of diseases, including hypertension and polycystic kidney disease. Research exploring basic aspects of sodium pump structure, function and regulation will contribute to the foundation of information upon which rational studies of these disease states must rest. Research on the LAMPs has four goals: (1) to determine the genetic basis of molecular heterogeneity of LAMP proteins, (2) to describe the dynamics of LAMP behavior in the endocytic membrane system, (3) to study the regulation of LAMP expression at the cell surface, and (4) to determine the natural function of LAMP proteins. The LAMPs are not only the major lysosomal membrane proteins, but they are also tumor antigens, and their expression at the cell surface correlates with metastatic potential in some types of cancer. Research on the LAMPs may have a bearing upon mechanisms regulating metastatic potential of cancer cells.
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