Mast cell-specific receptor for basic secretagogues (PubMed:25517090). Basic secretagogues are a set of cationic amphiphilic drugs, as well as endo- and exogenous peptides, which share basic head group combined with a hydrophobic core of the molecule. Recognizes and binds small molecules containing a cyclized a tetrahydroisoquinoline (THIQ), such as non-steroidal neuromuscular blocking drugs (NMBDs), including tubocurarine and atracurium (By similarity). Mediates mast cell responsiveness and side effects of small-molecule therapeutic drugs by acting as a specific receptor for basic secretagogues drugs in mast cells: binding to drugs induces pseudo-allergic reactions characterized by histamine release, inflammation and airway contraction (By similarity). Acts as a receptor for a number of ligands, including peptides: acts as a receptor of cortistatin-14, a regulator of sleep regulation locomotor activity, and cortical function (PubMed:12915402). Acts as a receptor for proadrenomedullin N- terminal peptides PAMP-12, and atlower extent PAMP-20 (PubMed:15823563). Acts as a receptor for antibacterial protein LL-37, promoting chemotaxis, degranulation and chemokine production in mast cells (PubMed:22069323). Acts as a receptor for PMX-53 peptide, a potent antagonist of C5AR1/CD88 (PubMed:21441599). Acts as a receptor for beta-defensins (PubMed:23698749). Acts as a receptor for complanadine A, an alkaloid (PubMed:24930830). {ECO:0000250|UniProtKB:Q3UG50, ECO:0000269|PubMed:15823563, ECO:0000269|PubMed:21441599, ECO:0000269|PubMed:22069323, ECO:0000269|PubMed:23698749, ECO:0000269|PubMed:24930830, ECO:0000269|PubMed:25517090, ECO:0000305|PubMed:12915402}.