Protein kinase A expression and its possible roles in regulating tooth eruption genes in the dental follicle

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BACKGROUND: Tooth eruption requires the chronological expression of a series of genes in the dental follicle (DF). Protein kinase A (PKA) is a major phosphorylation pathway in the cells, and may regulate the expression of tooth eruption genes. MATERIAL/METHODS: In vivo, we studied the expression of the regulatory (R) and catalytic (C) subunits of PKA in the DF of newborn rats. In vitro, dental follicle cells (DFC) were treated with a specific PKA inhibitor, and then the gene expression of monocyte chemotactic protein-1 (MCP-1), colony-stimulating factor-1 (CSF-1) and parathyroid hormone-related protein receptor (PTHrP-R) was determined. Cells also were treated with either phorbol-12-myristate-13-acetate or dibutyryl-cAMP, and the gene expression for RI alpha, RI beta, RII alpha and RII beta of PKA was examined. RESULTS: The results indicate that RI alpha of PKA is the predominant subunit in the DF with steady expression from days 1 to 11 postnatally. In contrast, expression of the RI beta, RII alpha, RII beta subunits are progressively reduced over this time period. However, there is a sharp decline of RI beta expression at postnatal day 3. The expression of the C subunits slightly decreases at days 3 and 5 with a greater decrease at day 7 postnatally. The specific PKA inhibitor reduces MCP-1 gene expression and translation, as well as moderately reducing CSF-1 and PTHrP-R expression. CONCLUSIONS: The reduction of the RI beta subunit in the rat DF at day 3 may result in an elevated PKA activity to trigger the maximal burst of gene expression of MCP-1 and CSF-1 seen at this time.

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Medical science monitor : international medical journal of experimental and clinical research

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