Members of the protein tyrosine phosphatase (PTP) super family 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 the mitochondrial phosphatase, PTPMT1 (formerly PLIP), the first resident mitochondrial phosphatase to be identified and functionally linked to energy metabolism in the cell. PTPMT1 is a highly conserved phosphatase with over 60 orthologs throughout the Animalia, Plantae, Protista, and Eubacteria kingdoms. There is no precedent for PTPs in the mitochondrion, and no known mitochondrial signaling pathways involving reversible phosphorylation. We, therefore, performed several analyses of cells in which PTPMT1 had been ablated. A lipidomic analysis comparing the lipid profile of PTPMTI-ablated versus wild type cells pointed to phosphatidylglycerol phosphate (PGP) as the in vivo substrate for PTPMT1. PGP is an intermediate in cardiolipin biosynthesis, a key component of inner mitochondrial membranes. We propose to: 1) Synthesize PGP for in vitro analyses to demonstrate that PTPMT1 is a PGP phosphatase. We will also use this substrate with a variety of other phosphatases to determine if the ability to convert PGP to PG is an enzymatic activity unique to PTPMT1. Conversely, the ability of PTPMT1 to utilize other lipid phosphate substrates will also be assessed. 2) Address whether PGP phosphatase activity is conserved in selected orthologues. 3) Address the function of PTPMT1 in the inner mitochondrial membrane. We propose to quantitate the effects of PTPMT1 expression on rates of cardiolipin biosynthesis, as well as examine the mitochondrial morphology and bioenergetic status of PTPMT1 deficient cells. 4) Determine the structure of PTPMT1 itself and in combination with PGP. These experiments will allow a detailed understanding of how PTPMT1 exhibits such unusual phospholipid substrate specificity. Our results will shed light on the possible roles of PTPMT1 in various diseases where reduced cardiolipin has been reported, such as ischemia, heart failure and diabetes, and provide insight into novel points of therapeutic intervention for these diseases.

Public Health Relevance

This project is focused on the mitochondrial phosphatase, PTPMT1. We have proposed that its endogenous substrate is phosphatidylglycerol phosphate, an important intermediate in cardiolipin biosynthesis, a key component of mitochondrial membranes. Thus, PTPMT1 function is intimately linked to mitochondrial function, which plays a critical role in ageing and diseases such as diabetes.

National Institute of Health (NIH)
National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK)
Research Project (R01)
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Molecular and Integrative Signal Transduction Study Section (MIST)
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Silva, Corinne M
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University of California San Diego
Schools of Medicine
La Jolla
United States
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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

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