Abstract
Protein phosphorylation is a fundamental mechanism regulating nearly every aspect of cellular life. Several secreted proteins are phosphorylated, but the kinases responsible are unknown. We identified a family of atypical protein kinases that localize within the Golgi apparatus and are secreted. Fam20C appears to be the Golgi casein kinase that phosphorylates secretory pathway proteins within S-x-E motifs. Fam20C phosphorylates the caseins and several secreted proteins implicated in biomineralization, including the small integrin-binding ligand, N-linked glycoproteins (SIBLINGs). Consequently, mutations in Fam20C cause an osteosclerotic bone dysplasia in humans known as Raine syndrome. Fam20C is thus a protein kinase dedicated to the phosphorylation of extracellular proteins.
Publication types
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Research Support, N.I.H., Extramural
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Research Support, Non-U.S. Gov't
MeSH terms
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Abnormalities, Multiple / genetics
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Abnormalities, Multiple / metabolism
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Amino Acid Motifs
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Amino Acid Sequence
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Animals
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Calcification, Physiologic
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Casein Kinase I
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Casein Kinases / metabolism
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Caseins / metabolism*
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Cattle
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Cell Line, Tumor
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Cleft Palate / genetics
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Cleft Palate / metabolism
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Exophthalmos / genetics
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Exophthalmos / metabolism
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Extracellular Matrix Proteins / chemistry
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Extracellular Matrix Proteins / genetics
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Extracellular Matrix Proteins / metabolism*
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Glycoproteins / metabolism
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Golgi Apparatus / enzymology*
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HEK293 Cells
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HeLa Cells
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Humans
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Microcephaly / genetics
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Microcephaly / metabolism
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Milk / enzymology
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Molecular Sequence Data
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Mutation
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Osteopontin
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Osteosclerosis / genetics
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Osteosclerosis / metabolism
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Phosphorylation
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Protein Sorting Signals
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Recombinant Fusion Proteins / chemistry
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Recombinant Fusion Proteins / metabolism
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Secretory Pathway*
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Substrate Specificity
Substances
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Caseins
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Extracellular Matrix Proteins
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Glycoproteins
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Protein Sorting Signals
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Recombinant Fusion Proteins
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Osteopontin
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Casein Kinase I
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Casein Kinases
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FAM20C protein, human