Project Summary: This application proposes to transition the candidate (Peter Piermarini) from a postdoctoral scientist to an independent researcher. Fostering this transition are his mentors Professors Klaus Beyenbach and Michael Kotlikoff, and two external consultants (Boron, Yale and Harrison, Arizona State). In the proposed study, the candidate will (i) expand his experimental repertoire of molecular and genomic biology, (ii) acquire powerful methods in renal physiology, such as in vitro microperfusion of tubular epithelia, and (iii) gain a solid knowledge of electrophysiology. In addition to research, the candidate will have opportunities to (i) give formal lectures to the upper-level course 'Mammalian Physiology', and (ii) mentor an undergraduate student through a research project. In the candidate's proposed research, he will explore the mechanisms of acid-base transport in the Malpighian (renal) tubules of the yellow-fever mosquito, Aedes aegypti. He will determine if these tubules represent a valid model system for understanding V-type H+ATPase-driven acid secretion in (-intercalated cells of the mammalian, renal collecting tubule. In years 1 and 2 of the proposed study, the candidate will use molecular approaches to clone and localize acid-base transporters in Malpighian tubules, and will also characterize the function of these transporters in a heterologous expression system (Xenopus oocytes), as well as in the native tubule epithelium. In year 3, the candidate will measure the effects of an acid load on the physiology of isolated tubules, and determine if the acid-base transporters identified in years 1 and 2 contribute to transepithelial acid secretion. Funding from the K01 award will allow the candidate to establish an independent program and to be nominated for a research-track assistant professor position at Cornell. He also will be well positioned to apply for independent positions at other universities. Relevance: The V-type H+ATPase (proton pump) is a protein of vital importance to human health. For example, humans with genetic defects in the proton pump often have impaired acid secretion by the kidney, weakened bones, deafness, and sterility (in males). The goal of the proposed study is to develop a model system for better understanding the function of the proton pump in the human kidney. This model system is the 'kidney'of an insect, the yellow-fever mosquito. Although mosquitoes are quite different than humans, the cells that compose the kidneys of mosquitoes (i) closely resemble acid-secreting cells of the mammalian kidney, and (ii) are energized entirely by the proton pump. Moreover, mosquito kidneys are much more accessible and easier to study in the laboratory than mammalian kidneys, making the former an ideal experimental model system for studying the latter.