Cross-talk between PKA and PKC in human fibroblasts: what are the pharmacotherapeutic implications?
BACKGROUND
The present study was designed to confirm or refute in human fibroblasts the hypothesized cross-talk elicited via neurotransmitter transduction cascades at the level of protein kinase mediated phosphorylation of the nuclear transcription factor CREB.


METHODS
Human fibroblasts from normal control subjects were subcultured and incubated at confluency after five growth passages with isoproterenol (stimulation of PKA mediated phosphorylation) and/or phorbol 12-myristate 13-acetate (PMA) (stimulation of PKC mediated phosphorylation) followed by the determination of nuclear CREB-P by immunoblotting, enhanced chemiluminescence and quantitation of the autoradiograms by laser densitometry.


RESULTS
Using the nuclear transcription factor CREB as a target, both the activation of the cyclic AMP-PKA pathway by isoproterenol and the activation of the PKC pathway by PMA caused phosphorylation of nuclear CREB. This phosphorylation is additive in nature and appears to occur at the same molecular site, serine133 of CREB.


CONCLUSIONS
The present results in human fibroblasts demonstrate that the hypothesized cross-talk at the level of protein kinase mediated phosphorylation of transcription factors is no longer hypothetical. Since it is the phosphorylation of nuclear CREB that determines its dimerization and transcriptional activation of programs of CRE containing genes, the results suggest that this convergence of the neurotransmitter signals may be the critical mechanism in gene expression following the administration of antidepressant drugs that affect noradrenergic, serotonergic or both transduction cascades. The results may also provide a rationale for the apparent superior clinical efficacy of dual uptake inhibitors.
Manier
D H
DH
Department of Psychiatry, Vanderbilt University Medical Center, Nashville, TN 37232-2647, USA.
Shelton
R C
RC
Sulser
F
F
D051698:Activating Transcription Factor 2; D000928:Antidepressive Agents / Q000494:pharmacology*; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics; D017868:Cyclic AMP-Dependent Protein Kinases / Q000235:genetics*; D005347:Fibroblasts / Q000187:drug effects / Q000201:enzymology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D006801:Humans; D010766:Phosphorylation; D011493:Protein Kinase C / Q000235:genetics*; D020239:Receptor Cross-Talk / Q000187:drug effects*; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
D051698:Activating Transcription Factor 2; D000928:Antidepressive Agents; D017362:Cyclic AMP Response Element-Binding Protein; D014157:Transcription Factors; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C