The phosphoinositides PI4P, PI(4,5)P2, and PI(3,4,5)P3 orchestrate numerous physiological processes occurring at the plasma membrane, including exo/endocytosis, actin assembly, and several growth factor signaling pathways, and dysregulation of the metabolism of these lipids is causative of many diseases, including diabetes, numerous cancers, and several neurological disorders. The first committed step in the biosynthesis of these phosphoinositides is catalyzed by the PI 4-kinase Type III? (PI4KIII?). Despite the fundamental role that this enzyme plays in the phosphoinositide metabolic network, surprisingly little is known about its regulation. To understand how nature controls the subcellular localization and activity of PI4KIII? and hence regulates the phosphoinositide pools under its control, I have in my preliminary work characterized two PI4KIII? regulatory proteins and begun to study their molecular properties and physiological functions. I showed that the palmitoylated, peripheral membrane protein EFR3/Rolling blackout cooperates with a soluble tetratricopeptide adaptor, TTC7, to recruit PI4KIII? to the plasma membrane, its site of action. Recently, I identified a third potential PI4KIII? regulator, hyccin, a protein of unknown function implicated in a brain white matter disease termed hypomyelination and congenital cataracts (HCC). The overarching hypothesis guiding this work is that EFR3, TTC7, and hyccin form the core of a PI4KIII? protein-protein interaction network that controls PI4P synthesis at the plasma membrane.
Aim 1 describes studies to elucidate fundamental cellular functions of EFR3 and test the hypothesis that EFR3 is a master regulator of phosphoinositide metabolism at the neuronal synapse.
Aim 2 outlines biochemical and chemical biology experiments to define the principles governing the assembly of the PI4KIII?/TTC7/EFR3 complex and its spatiotemporal regulation at the plasma membrane.
Aim 3 describes studies to probe the physical and functional connection between hyccin and PI4KIII?, TTC7, and EFR3. In sum, these multidisciplinary studies will elucidate fundamental principles that regulate the PI4P synthetic machinery at the plasma membrane. More broadly, the approaches I develop and the principles that I elucidate will be applicable to the long-term goal of understanding how regulation of PI4P synthesis connects to the broader metabolic network (e.g., via coupling to downstream enzymes that generate PI(4,5)P2, PI(3,4,5)P3, IP3, and diacylglycerol). As well, my proposed studies to connect hyccin function to PI4P metabolism represent a first step toward the long-term goal of understanding the mechanisms of pathogenesis of HCC, which may shed light on potential therapies for this and other leukodystrophies.

Public Health Relevance

Phosphoinositides are an important class of signaling lipids whose dysregulation is causative of many diseases, including diabetes, numerous cancers, and several neurological disorders. The goal of this project is to understand the cellular mechanisms that regulate the synthesis of phosphoinositides at the plasma membrane. A key hypothesis to be tested is that impairment of this process is central to the pathogenesis of a disease of the brain white matter termed hypomyelination and congenital cataracts (HCC), a first step toward potential therapies for this and other leukodystrophies.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Research Transition Award (R00)
Project #
5R00GM110121-05
Application #
9333404
Study Section
Special Emphasis Panel (NSS)
Program Officer
Nie, Zhongzhen
Project Start
2014-04-01
Project End
2018-08-31
Budget Start
2017-09-01
Budget End
2018-08-31
Support Year
5
Fiscal Year
2017
Total Cost
Indirect Cost
Name
Cornell University
Department
Miscellaneous
Type
Organized Research Units
DUNS #
872612445
City
Ithaca
State
NY
Country
United States
Zip Code
14850
Bumpus, Timothy W; Liang, Felice J; Baskin, Jeremy M (2018) Ex Uno Plura: Differential Labeling of Phospholipid Biosynthetic Pathways with a Single Bioorthogonal Alcohol. Biochemistry 57:226-230
Lees, Joshua A; Zhang, Yixiao; Oh, Michael S et al. (2017) Architecture of the human PI4KIII? lipid kinase complex. Proc Natl Acad Sci U S A 114:13720-13725
Bumpus, Timothy W; Baskin, Jeremy M (2017) Clickable Substrate Mimics Enable Imaging of Phospholipase D Activity. ACS Cent Sci 3:1070-1077
Knopf, Kevin M; Murphy, Brendan L; MacMillan, Samantha N et al. (2017) In Vitro Anticancer Activity and in Vivo Biodistribution of Rhenium(I) Tricarbonyl Aqua Complexes. J Am Chem Soc 139:14302-14314
Baskin, Jeremy M; Aye, Yimon (2017) Meeting Proceedings, 2017 Cornell University Baker Symposium-Quo Vadis: The Boundless Trajectories of Chemical Biology. ACS Chem Biol 12:1445-1448
Baskin, Jeremy M; Aye, Yimon (2017) Meeting Proceedings, 2017 Cornell University Baker Symposium-Quo Vadis: The Boundless Trajectories of Chemical Biology. Biochemistry 56:2967-2970
Bumpus, Timothy W; Baskin, Jeremy M (2016) A Chemoenzymatic Strategy for Imaging Cellular Phosphatidic Acid Synthesis. Angew Chem Int Ed Engl 55:13155-13158
Baskin, Jeremy M; Wu, Xudong; Christiano, Romain et al. (2016) The leukodystrophy protein FAM126A (hyccin) regulates PtdIns(4)P synthesis at the plasma membrane. Nat Cell Biol 18:132-8