The tissue specifier element (TSE) functions as a Ca2+ response element for Ca2+ and cAMP synergistic signaling to the human vasoactive intestinal polypeptide (VIP) gene

Vasoactive intestinal polypeptide (VIP) is a pleiotropic neurotransmitter with roles in development, circadian function, immune regulation, and pain sensation. VIP gene expression is synergistically activated by elevation of cAMP and Ca 2+ (Hamelink et al., J. Neurosci. 22:, 2002). The effects of these two signaling pathways on VIP gene regulation were examined in NBFL human neuroblastoma cells, which endogenously express VIP. Treatment with forskolin or the Ca 2+ ionophore A23187, alone modestly (10‐fold) increased VIP mRNA, but together caused a synergistic (75‐fold) increase in NBFL cells. Although stimulation of neuroendocrine genes by both cAMP and Ca 2+ via convergence on a common cis‐active element, the cyclic AMP‐response element (CRE) is common, we found, unexpectedly, that the CRE of a full‐length VIP luciferase reporter gene, while essential for cAMP‐stimulated transcription and synergistic stimulation with cAMP and Ca 2+ , was dispensable for activation by Ca 2+ alone. Instead, Ca 2+ activation required a single element of 280 bases located 4 kb upstream from the VIP proximal promoter that was previously identified as a tissue specifier element (TSE; Hahm et al., JBC 273:,1998). The TSE of the VIP gene is a novel calcium response element in a neuron‐specific gene that is independent of the CRE, but acts together with it to enable synergistic cAMP and Ca 2+ signaling.