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


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.
Yao
Shaomian
S
Department of Comparative Biomedical Sciences, School of Veterinary Medicine, Louisiana State University, Baton Rouge, Louisiana 70803, USA.
Wise
Gary E
GE
D000818:Animals; D000831:Animals, Newborn; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics / Q000378:metabolism; D017868:Cyclic AMP-Dependent Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D003795:Dental Sac / Q000254:growth & development / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D016173:Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D051381:Rats; D017207:Rats, Sprague-Dawley; D044168:Receptor, Parathyroid Hormone, Type 1 / Q000235:genetics / Q000378:metabolism; D014078:Tooth Eruption / Q000235:genetics*
D018932:Chemokine CCL2; D021122:Protein Subunits; D044168:Receptor, Parathyroid Hormone, Type 1; D016173:Macrophage Colony-Stimulating Factor; D017868:Cyclic AMP-Dependent Protein Kinases