Fig. 2
From: Neuropeptides in asthma, chronic obstructive pulmonary disease and cystic fibrosis
Simplified schematic of select neuropeptide and their proposed receptor mechanisms mediating mucus secretion. Receptors coupled to Gs increase cAMP through adenylyl cyclase (not shown). cAMP then increases intracellular Ca2+ through downstream mediators, such as protein kinase A (not shown). Receptors coupled to Gq lead to breakdown to inositol 1,4,5-phosphate (IP3) and subsequent mobilization of Ca2+ from intracellular stores. Ca2+ serves as a common mediator of mucus granule discharge and exocytosis [231]. Additional details regarding receptor and effector mechanisms are shown in Table 3. Abbreviations: SubP, substance P; NKA, neurokinin A; VIP, vasoactive intestinal peptide; CGRP, calcitonin gene-related peptide; NPY, neuropeptide Y; GRP, gastrin-releasing peptide; NMB, neuromedin B; IP3, inositol 1,4,5-trisphosphate; VPAC2, vasoactive intestinal peptide receptor 2; bombesin subtype-1 receptor (BB1); bombesin subtype-2 receptor (BB2)