We have discovered a family of novel secreted kinases that are key mediators of a variety of cellular processes including differentiation, mineralization, and extracellular signaling. These kinases share little sequence identity with canonical kinases and function extracellularly and/or in the lumen of the secretory pathway. We have determined that Fam20C is the authentic Golgi casein kinase that phosphorylates casein and other secreted proteins involved in mineralization within Ser-x-Glu (S-x-E) motifs. Phosphoproteomic studies have established that greater than 75% of secreted phosphoproteins are phosphorylated on S-x-E motifs, thus making Fam20C an important potential regulator of numerous physiological functions. This proposal is focused on understanding the substrate specificity, evolution, and structure/function of Fam20C.
Specific Aim 1 is an in depth biochemical characterization of Fam20C, including a detailed kinetic analysis and identification of novel substrates.
Specific Aim 2 addresses the evolution and functional conservation of Fam20 kinases in Caenorhabditis elegans and Drosophila melanogaster, two organisms lacking mineralized tissue. Using bioinformatics we have identified potential substrates for C. elegans and Drosophila Fam20 enzymes that will shed new light on the evolutionary origins of secreted protein phosphorylation. The goal of Specific Aim 3 is to solve the crystal structure of Fam20C. We have made significant progress toward obtaining the structure of the C. elegans Fam20C ortholog and have obtained crystals that diffract to 2.6?. We propose to solve structures for C. elegans Fam20 complexed with its co-substrates. In addition, we will pursue the structure of Fam20B, a closely related family member that does not phosphorylate S-x-E, but utilizes a distinct proteoglycan substrate. Successful completion of these specific aims will result in a better understanding of this important family of novel secreted kinases.
This project is focused on novel secreted kinases, which add phosphate residues to numerous secreted proteins. These modifications are critical for many biological processes, playing essential roles in development, kidney function, tooth enamel, and bone mineralization.
|Guo, Xing; Wang, Xiaorong; Wang, Zhiping et al. (2016) Site-specific proteasome phosphorylation controls cell proliferation and tumorigenesis. Nat Cell Biol 18:202-12|
|Guo, Xing; Dixon, Jack E (2016) The 26S proteasome: A cell cycle regulator regulated by cell cycle. Cell Cycle 15:875-6|
|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|
|Cui, Jixin; Xiao, Junyu; Tagliabracci, Vincent S et al. (2015) A secretory kinase complex regulates extracellular protein phosphorylation. Elife 4:e06120|
|Cozza, Giorgio; Salvi, Mauro; Banerjee, Sourav et al. (2015) A new role for sphingosine: Up-regulation of Fam20C, the genuine casein kinase that phosphorylates secreted proteins. Biochim Biophys Acta 1854:1718-26|
|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|
|Wen, Jianzhong; Xiao, Junyu; Rahdar, Meghdad et al. (2014) Xylose phosphorylation functions as a molecular switch to regulate proteoglycan biosynthesis. Proc Natl Acad Sci U S A 111:15723-8|
|Bahmanyar, Shirin; Biggs, Ronald; Schuh, Amber L et al. (2014) Spatial control of phospholipid flux restricts endoplasmic reticulum sheet formation to allow nuclear envelope breakdown. Genes Dev 28:121-6|
|Worby, Carolyn A; Dixon, Jack E (2014) PTEN. Annu Rev Biochem 83:641-69|
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