Regulation of vasoactive intestinal peptide receptor expression in developing nervous systems

Vasoactive intestinal peptide (VIP) is a 28-amino acid peptide that has several functions, including the regulation of water and electrolyte secretion, hormone and cytokine release, bronchodilitation, and neurogenesis. VIP effects are mediated by specific G-protein coupled receptors. Three distinct receptor subtypes, with differing affinity for VIP, have been cloned and characterized as receptors 1 and 2 (VPAC1 and VPAC2) and pituitary adenylate cyclase activating polypeptide receptor (PAC1). Our laboratory has demonstrated that upregulation of VPAC1 in SK-N-SH neuroblastoma cells results in marked shift in cell type to the glial lineage with a corresponding loss of neuronal lineage and suppression of xenograft tumor growth. To understand the molecular mechanisms responsible for regulation of the VPAC1 gene in neuronal lineage, we have cloned and sequenced 2.6-kb of the 5'-flanking sequences of the human VPAC1 gene. Sequence analysis demonstrated that the human VPAC1 promoter sequence contains putative binding sites for several known transcription factors, including Sp1, NFkB, and cETS-1. To study the temporal and spatial expression pattern of human VPAC1 promoter sequences, we have generated transgenic mice expressing the bacterial beta-galactosidase gene under the control of the 2.6-kb 5'-flanking and promoter sequence of the human VPAC1 gene. Transgene expression was detected in brain, spinal cord, and lung in 14-day-old animals. Taken together, these results demonstrate that VPAC1 may play an important role in the nervous system, and suggest a role for VIP in neuronal differentiation.