Sorting membrane proteins into intralumenal vesicles that form within late endosomes is a fundamental process that regulates many biological pathways that rely on maintaining appropriate levels of a given set of cell surface membrane proteins. This is the pathway that guides the delivery and degradation of proteins in lysosomes. This pathway is driven by ubiquitin, which works as a sorting signal when attached to membrane protein cargo. This process controls the degradation of almost all cell surface membrane proteins and understanding this degradative process is significant since it impacts a wide array of normal and pathogenic processes that rely on proper activity of particular membrane proteins such as transporters and signaling receptors at the cell surface. The long-term goal of the competitive renewal proposal is to understand how this ubiquitin-dependent sorting pathway is controlled, and will lead to insights into how disease states such as cancer might be achieved when this process goes awry. To accomplish this we have devised aims to 1) discover how the major family of Nedd4- related ubiquitin ligases are programed to target different cell surface membrane proteins; 2) discover how ubiquitinated membrane proteins are recognized by the endosomal sorting machinery and how that cargo plays an active role in organizing the sorting apparatus itself; and 3) discover new proteins that participate in the process of intralumenal vesicle formation using a series of genetic screens.

Public Health Relevance

The proposed research is relevant to public health because it focuses on how multiple cellular functions are regulated through the degradation of cell surface proteins that mediate growth, differentiation, signal- transduction, neuronal signaling, and nutrient uptake. Thus, the proposed research is relevant to mission of the NIH to increase understanding of fundamental life processes that in turn will lay the foundation for advances in disease diagnosis, treatment and prevention.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Study Section
Membrane Biology and Protein Processing Study Section (MBPP)
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Ainsztein, Alexandra M
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University of Iowa
Schools of Medicine
Iowa City
United States
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Krishnamani, Venkatramanan; Peterson, Tabitha A; Piper, Robert C et al. (2018) Informatic Analysis of Sequence Data from Batch Yeast 2-Hybrid Screens. J Vis Exp :
Peterson, Tabitha A; Stamnes, Mark A; Piper, Robert C (2018) A Yeast 2-Hybrid Screen in Batch to Compare Protein Interactions. J Vis Exp :
Xu, Peng; Hankins, Hannah M; MacDonald, Chris et al. (2017) COPI mediates recycling of an exocytic SNARE by recognition of a ubiquitin sorting signal. Elife 6:
MacDonald, Chris; Piper, Robert C (2017) Genetic dissection of early endosomal recycling highlights a TORC1-independent role for Rag GTPases. J Cell Biol 216:3275-3290
MacDonald, Chris; Winistorfer, Stanley; Pope, Robert M et al. (2017) Enzyme reversal to explore the function of yeast E3 ubiquitin-ligases. Traffic 18:465-484
MacDonald, Chris; Piper, Robert C (2016) Cell surface recycling in yeast: mechanisms and machineries. Biochem Soc Trans 44:474-8
Pashkova, Natasha; Peterson, Tabitha A; Krishnamani, Venkatramanan et al. (2016) DEEPN as an Approach for Batch Processing of Yeast 2-Hybrid Interactions. Cell Rep 17:303-315
MacDonald, Chris; Stamnes, Mark A; Katzmann, David J et al. (2015) Tetraspan cargo adaptors usher GPI-anchored proteins into multivesicular bodies. Cell Cycle 14:3673-8
MacDonald, Chris; Payne, Johanna A; Aboian, Mariam et al. (2015) A family of tetraspans organizes cargo for sorting into multivesicular bodies. Dev Cell 33:328-42
Peterson, Tabitha A; Yu, Liping; Piper, Robert C (2015) Backbone and side-chain NMR assignments for the C-terminal domain of mammalian Vps28. Biomol NMR Assign 9:21-4

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