Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating peptide (PACAP) are the inhibitory neurotransmitters in the gut wall. The mechanisms of the non-genomic effects of these neurotransmitters in smooth muscle relaxation have been investigated extensively over the last several decades. The genomic effects of these neurotransmitters on smooth muscle function are not known. VIP and PACAP, on binding to their receptors on smooth muscle cells, activate adenylate cyclase to produce cyclic 3'-5' adenosine monophosphate (cAMP) that mediates smooth muscle relaxation. However, cAMP is also a well known mediator of gene expression through the binding of transcription factor CRE binding protein (CREB) to the cAMP response element (CRE) on the promoters of its target genes. We have obtained substantial preliminary data that suggest an important novel function of the classic neurotransmitters VIP and PACAP to induce gene expression of the pore-forming alpha1C subunit of L-type Ca2+ channels in human colonic circular smooth muscle cells (HCCSMC). Ca2+ influx through these channels is an immediate early step in the signaling cascade for excitation-contraction coupling. Our preliminary data indicate that VIP/PACAP may also be anti-inflammatory neuropeptides that counter the initiation of the signaling cascade that activates the transcription factor NF-KB resulting in the suppression of cell contractility during inflammation. Based on these preliminary data our specific aims are to investigate: 1) VIP/PACAP-induced enhancement of alpha1C gene expression through cAMP/PKA signaling pathway in HCCSMC. 2) The cis- and trans-regulation of human ?1C promoter by VIP/PACAP-induced phosphorylation of the transcription factor CREB. 3) The interactions between cAMP/PKA, MAPK, PKC and CaMKII signaling pathways for the induction of alpha1C gene by VIP and PACAP. 4) The molecular and epigenetic mechanisms of the rnyo-protective role of VIP/PACAP in HCCSMC. This grant proposal presents a novel direction of research in the genomic regulation of smooth muscle function by two prominent and abundant neurotransmitters (VIP and PACAP) of the enteric inhibitory motor neurons. The findings will provide genomic and molecular insights into regulation of the expression of L-type calcium channels that play a critical role in excitation-contraction coupling in the normal state and during inflammation.
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