1. A secretory kinase complex regulates extracellular protein phosphorylation.
- Author
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Cui, Jixin, Xiao, Junyu, Tagliabracci, Vincent S, Wen, Jianzhong, Rahdar, Meghdad, and Dixon, Jack E
- Subjects
Mammary Glands ,Animal ,Cell Line ,Ameloblasts ,Animals ,Mice ,Inbred C57BL ,Humans ,Mice ,Lepidoptera ,Casein Kinase I ,Dental Enamel Proteins ,Recombinant Proteins ,Extracellular Matrix Proteins ,Sequence Alignment ,Signal Transduction ,Gene Expression ,Gene Expression Regulation ,Amino Acid Sequence ,Sequence Homology ,Amino Acid ,Phosphorylation ,Founder Effect ,Molecular Sequence Data ,Female ,biochemistry ,extracellular protein phosphorylation ,human ,kinase complex ,mouse ,pseudokinase ,secretory pathway phosphorylation ,tooth enamel formation ,Mammary Glands ,Animal ,Inbred C57BL ,Sequence Homology ,Amino Acid ,Biochemistry and Cell Biology - Abstract
Although numerous extracellular phosphoproteins have been identified, the protein kinases within the secretory pathway have only recently been discovered, and their regulation is virtually unexplored. Fam20C is the physiological Golgi casein kinase, which phosphorylates many secreted proteins and is critical for proper biomineralization. Fam20A, a Fam20C paralog, is essential for enamel formation, but the biochemical function of Fam20A is unknown. Here we show that Fam20A potentiates Fam20C kinase activity and promotes the phosphorylation of enamel matrix proteins in vitro and in cells. Mechanistically, Fam20A is a pseudokinase that forms a functional complex with Fam20C, and this complex enhances extracellular protein phosphorylation within the secretory pathway. Our findings shed light on the molecular mechanism by which Fam20C and Fam20A collaborate to control enamel formation, and provide the first insight into the regulation of secretory pathway phosphorylation.
- Published
- 2015