The function of ENSG00000006128 (TAC1, tachykinin precursor 1) is as follows. Tachykinins are active peptides which excite neurons, evoke behavioral responses, are potent vasodilators and secretagogues, and contract (directly or indirectly) many smooth muscles. [Substance P]: Is a ligand for TACR1, and triggers G protein- coupled receptor signaling via activation of phosphatidylinositol hydrolysis by phospholipase C. Substance P binding to TACR1 also triggers signaling via activation of adenylate cyclase activity which results in increased intracellular levels of cyclic AMP (cAMP) (By similarity). Is also a TACR3 agonist with low receptor affinity (PubMed:37391393). Basic secretagogue neuropeptide released from the terminals of specific sensory nerves (PubMed:30686732). Acts as a ligand for MRGPRX2 receptor in mast cells, initiating a signaling that mediates neurogenic inflammation and pain (PubMed:30686732, PubMed:34789875). Neurogenic inflammation includes mast cell activation, recruitment of immune cells and release of inflammatory mediators, such as cytokines and chemokines (By similarity). The inflammatory response can then activate or sensitize nociceptors, promoting pain (By similarity). {ECO:0000250|UniProtKB:P06767, ECO:0000250|UniProtKB:P41539, ECO:0000269|PubMed:30686732, ECO:0000269|PubMed:34789875, ECO:0000269|PubMed:37391393}. [Neurokinin A]: Is a ligand for TACR2, and triggers G protein-coupled receptor signaling via activation of G(q) and phosphatidylinositol hydrolysis by phospholipase C (PubMed:35882833). Binding to TACR2 also triggers signaling via activation of adenylate cyclase activity which results in increased intracellular levels of cyclic AMP (cAMP). {ECO:0000250|UniProtKB:P06767, ECO:0000269|PubMed:35882833}.