Abstract
cGMP-dependent protein kinase II (cGKII; encoded by PRKG2) is a serine/threonine kinase that is critical for skeletal growth in mammals; in mice, cGKII deficiency results in dwarfism. Using radiographic analysis, we determined that this growth defect was a consequence of an elongated growth plate and impaired chondrocyte hypertrophy. To investigate the mechanism of cGKII-mediated chondrocyte hypertrophy, we performed a kinase substrate array and identified glycogen synthase kinase-3beta (GSK-3beta; encoded by Gsk3b) as a principal phosphorylation target of cGKII. In cultured mouse chondrocytes, phosphorylation-mediated inhibition of GSK-3beta was associated with enhanced hypertrophic differentiation. Furthermore, cGKII induction of chondrocyte hypertrophy was suppressed by cotransfection with a phosphorylation-deficient mutant of GSK-3beta. Analyses of mice with compound deficiencies in both protein kinases (Prkg2(-/-)Gsk3b(+/-)) demonstrated that the growth retardation and elongated growth plate associated with cGKII deficiency were partially rescued by haploinsufficiency of Gsk3b. We found that beta-catenin levels decreased in Prkg2(-/-) mice, while overexpression of cGKII increased the accumulation and transactivation function of beta-catenin in mouse chondroprogenitor ATDC5 cells. This effect was blocked by coexpression of phosphorylation-deficient GSK-3beta. These data indicate that hypertrophic differentiation of growth plate chondrocytes during skeletal growth is promoted by phosphorylation and inactivation of GSK-3beta by cGKII.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Alkaline Phosphatase / genetics
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Animals
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Axin Protein
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Cell Differentiation*
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Cell Line
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Cells, Cultured
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Chondrocytes / cytology*
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Chondrocytes / metabolism
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Collagen Type X / genetics
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Collagen Type X / metabolism
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Cyclic GMP-Dependent Protein Kinase Type II
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Cyclic GMP-Dependent Protein Kinases / genetics
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Cyclic GMP-Dependent Protein Kinases / metabolism*
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Gene Expression / drug effects
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Glycogen Synthase Kinase 3 / deficiency
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Glycogen Synthase Kinase 3 / genetics
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Glycogen Synthase Kinase 3 / metabolism*
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Glycogen Synthase Kinase 3 beta
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Growth Plate / abnormalities
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Growth Plate / metabolism
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HeLa Cells
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High Mobility Group Proteins / genetics
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High Mobility Group Proteins / metabolism
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Humans
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Lithium Chloride / pharmacology
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Matrix Metalloproteinase 13 / genetics
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Mice
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Mice, Inbred C57BL
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Mice, Knockout
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Mice, Transgenic
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Models, Biological
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Phosphorylation
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Repressor Proteins / genetics
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Repressor Proteins / metabolism
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SOX9 Transcription Factor
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Signal Transduction / drug effects
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Transcription Factors / genetics
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Transcription Factors / metabolism
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beta Catenin / metabolism
Substances
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Axin Protein
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Collagen Type X
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High Mobility Group Proteins
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Repressor Proteins
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SOX9 Transcription Factor
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SOX9 protein, human
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Sox9 protein, mouse
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Transcription Factors
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beta Catenin
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GSK3B protein, human
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Glycogen Synthase Kinase 3 beta
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Gsk3b protein, mouse
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Cyclic GMP-Dependent Protein Kinase Type II
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Cyclic GMP-Dependent Protein Kinases
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PRKG2 protein, human
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Prkg2 protein, mouse
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Glycogen Synthase Kinase 3
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Alkaline Phosphatase
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Matrix Metalloproteinase 13
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Lithium Chloride