Members of the protein tyrosine phosphatase (PTP) superfamily, all contain the highly conserved active site motif, Cys-x5- Arg (Cx5R), and are key mediators of a variety of cellular processes including growth, differentiation, motility, metabolism and programmed cell death. This proposal focuses on two novel PTPs whose functions are potentially linked to energy metabolism in the cell. The first two specific aims are directed at understanding laforin, a phosphatase mutated in the most severe form of progressive myoclonus epilepsy, Lafora's disease (LD). The hallmark of LD is the accumulation of starch-like polyglucosans called Lafora bodies. My laboratory has recently shown that malin, an E3 ligase also mutated in a subset of LD patients, interacts with and ubiquitinates laforin.
Specific Aim 1 outlines our intentions to fully characterize laforin's phosphatase activity. We have optimized bacterial expression and purification of laforin for use in these kinetic analyses as well as for crystallization efforts to determine the first structure of laforin.
Specific Aim 2 focuses on the modification of laforin by malin and the cellular consequences of this modification. Successful completion of these specific aims will give us a better understanding of the etiology of LD. The remaining three specific aims are designed to characterize FLIP, the first known mitochondrial PTP. Given the absence of precedent for PTPs in this organelle, and a nearly complete lack of known mitochondrial signaling pathways involving reversible phosphorylation, we will first perform a thorough characterization of PLIP in Specific Aim 3.
This aim i ncludes pinpointing PLIP to a specific submitochondrial compartment, establishing its mechanism of import, and determining a tissue expression profile.
Specific Aim 4 is an effort to elucidate the mitochondrial function(s) of PLIP using RNAi strategies in tissue culture cells and conditional knock-out strategies in mice. PLIP's potential function in cell culture will be evaluated with respect to glucose stimulated insulin secretion (GSIS), apoptosis, and the general - bioenergetic status of mitochondria. Our Cre-lox knockout mouse strategy will afford us the opportunity of ablating PLIP expression in a variety of different tissues enabling us to evaluate our cell culture data in the context of the whole animal.
Specific Aim 5 is designed to identify the cellular substrate(s) for PLIP, in part through leveraging our powerful RNAi technique in Drosophila S2 cells. Successful completion of Specific Aims 3-5 will give us a better understanding of PLIP's role in mitochondrial function and help to reveal mitochondria as important centers for cell signaling.

Agency
National Institute of Health (NIH)
Institute
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Type
Research Project (R01)
Project #
5R01DK018849-35
Application #
7599219
Study Section
Macromolecular Structure and Function A Study Section (MSFA)
Program Officer
Silva, Corinne M
Project Start
1991-10-01
Project End
2010-09-29
Budget Start
2009-05-01
Budget End
2010-09-29
Support Year
35
Fiscal Year
2009
Total Cost
$330,432
Indirect Cost
Name
University of California San Diego
Department
Pharmacology
Type
Schools of Medicine
DUNS #
804355790
City
La Jolla
State
CA
Country
United States
Zip Code
92093
Banerjee, Sourav; Ji, Chenggong; Mayfield, Joshua E et al. (2018) Ancient drug curcumin impedes 26S proteasome activity by direct inhibition of dual-specificity tyrosine-regulated kinase 2. Proc Natl Acad Sci U S A 115:8155-8160
Zhang, Hui; Zhu, Qinyu; Cui, Jixin et al. (2018) Structure and evolution of the Fam20 kinases. Nat Commun 9:1218
Qiu, Yimin; Poppleton, Erik; Mekkat, Arya et al. (2018) Enzymatic Phosphorylation of Ser in a Type I Collagen Peptide. Biophys J 115:2327-2335
Pollak, Adam J; Haghighi, Kobra; Kunduri, Swati et al. (2017) Phosphorylation of serine96 of histidine-rich calcium-binding protein by the Fam20C kinase functions to prevent cardiac arrhythmia. Proc Natl Acad Sci U S A 114:9098-9103
Cui, Jixin; Zhu, Qinyu; Zhang, Hui et al. (2017) Structure of Fam20A reveals a pseudokinase featuring a unique disulfide pattern and inverted ATP-binding. Elife 6:
Wang, Xiaorong; Cimermancic, Peter; Yu, Clinton et al. (2017) Molecular Details Underlying Dynamic Structures and Regulation of the Human 26S Proteasome. Mol Cell Proteomics 16:840-854
Nguyen, Kim B; Sreelatha, Anju; Durrant, Eric S et al. (2016) Phosphorylation of spore coat proteins by a family of atypical protein kinases. Proc Natl Acad Sci U S A 113:E3482-91
Guo, Xing; Wang, Xiaorong; Wang, Zhiping et al. (2016) Site-specific proteasome phosphorylation controls cell proliferation and tumorigenesis. Nat Cell Biol 18:202-12
Tagliabracci, Vincent S; Wiley, Sandra E; Guo, Xiao et al. (2015) A Single Kinase Generates the Majority of the Secreted Phosphoproteome. Cell 161:1619-32
He, Yantao; Guo, Xing; Yu, Zhi-Hong et al. (2015) A potent and selective inhibitor for the UBLCP1 proteasome phosphatase. Bioorg Med Chem 23:2798-809

Showing the most recent 10 out of 83 publications