Gluzincin aminopeptidases such as the mammalian Insulin Responsive Aminopeptidase (IRAP) and CD13 (APN) are dual function proteins that play essential roles in the cellular trafficking of membrane components. Defects in gluzincin function are thought to contribute to type II diabetes and altered uptake of dietary cholesterol. A plant gluzincin, APM1 appears to regulate cellular mechanisms that control the movement of the phytohormone auxin, which is required for the establishment and maintenance of plant polarity. Like IRAP and APN, APM1 is a bifunctional protein with both enzymatic and trafficking functions. APM1 functions in the cellular trafficking of Multiple Drug Resistance/ P-glycoproteins and appears to modulate other important developmental mechanisms as well. Arabidopsis apm1 mutants exhibit severe developmental defects that that can be only partially ameliorated by auxin treatment. A mechanistic function for APM1 is suggested by the regulation of sterol-dependent endocytotic cycling by mammalian IRAP and APN. The goal of the proposed research is to identify the mechanisms of APM1 action and determine their impact on auxin transport. The proposed project will 1. Determine where and when APM1 functions in growth and development. APM1 regulation of auxin dependent and independent developmental processes will be examined. 2. Map the membrane topology of APM1 and elucidate the mechanisms underlying APM1 function. APM1 regulation of sterol-dependent cycling of membrane transport proteins including those that transport auxin will be studied. 3. Assign APM1 functions to enzymatic and trafficking domains and identify the membrane domains responsible for trafficking activity. Interactions of specific APM1 protein domains with membrane transporters will be determined.
The proposed project is innovative as it explores a previously undescribed mechanism of protein trafficking and hormonal regulation in plants. Further, the proposed research is likely to provide new insights into gluzincin protein function in both plants and animals.
Broader Impacts: Manipulation of APM1 function can be used to alter plant form and productivity. As such, the proposed project can potentially increase the value of agricultural and ornamental crops. Further, enhanced understanding of gluzincin regulation derived from this project can lead to the development of new therapies for type II diabetes, obesity, and sterol metabolism. The results will be promulgated by publication in scientific journals and on the laboratory website. Important advances will be publicized in popular scientific literature.
The project will also train at least one PhD student in integrated approaches to membrane biology, physiology, molecular biology, and cell biology. Further, the project will recruit and train one summer undergraduate intern each year in the same techniques in order to encourage those students to pursue a graduate research education and research career. Interns will be recruited from institutions serving traditionally under-represented populations in basic biological research.
