The focus of our laboratory is on understanding the structure, function and regulation of a novel family of ATP-dependent proton pumps called the vacuolar ATPases (or V-ATPases). Acidification of intracellular compartments by V-ATPases is important for such processes as receptor-mediated endocytosis, intracellular membrane traffic, protein processing and degradation and coupled transport of small molecules, such as neurotransmitters. Acidic compartments also provide an entry point for disease causing agents like influenza virus and anthrax toxin. V-ATPases in the plasma membrane of certain cells function in such processes as bone resorption, renal acidification and tumor metastasis. Our laboratory is interested in both the basic biochemistry and cell physiology of the V-ATPases as well as the V-ATPase as a potential therapeutic target in treating human diseases such as cancer and bone disease.

The V-ATPases are large, multisubunit complexes composed of two domains. The peripheral V1 domain carries out ATP hydrolysis while the integral V0 domain is responsible for proton translocation. We are employing a variety biochemical, genetic and ultrastructural approaches in both yeast and mammalian systems to probe the structure and mechanism of the V-ATPases. Among the central issues that we are addressing are the structural organization of the V-ATPase subunits, the mechanism of coupling of proton transport and ATP hydrolysis and the mechanism of intracellular targeting of V-ATPases. We are also investigating how V-ATPase activity is controlled in vivo. Regulatory mechanisms include changes in coupling efficiency, changes in assembly of the V1 and V0 domains and differential targeting of V-ATPases. We are employing yeast 2-hybrid and genetic approaches to identify novel cellular partners involved in controlling reversible dissociation of the complex in vivo. Finally, we have begun to address the role of V-ATPases in tumor cell invasiveness and to develop genetic screens to identify inhibitors specific for particular isoforms of the V-ATPase that would be useful therapeutic agents in treating tumor metastasis and osteoporosis.