Table 1:

Class C GPCR Members

Member	Pharmacological Modulators	Dimerization	Roles in Lung
Metabotropic GABA: GABABR1, GABABR2	Ligand: GABA Agonist: Baclofen, CGP27492 Antagonist: Phaclofen, Saclofen, CGP36742, CGP35348, CGP55845 PAM: CGP7930	Heterodimer	ASM and epithelium ↑ airway contractility ↑ mucus production
CaSR	Ligand: Ca2+, spermine Agonist: Ca2+, Mg2+, polyvalent cations, β-amyloid, aminoglycoside antibiotics PAM: pH, L-α-amino acids, NPS R467, NPS R568, cinacalcet NAM: NPS 2143, Calhex 231	Homodimer Heterodimer (mGlu Grp I)	ASM and epithelium ↑ airway and pulmonary vascular contractility ↑ cell proliferation ↑ airway fluid secretion ↑ epithelial inflammation
GPRC6A	Ligand: L-α-amino acid	Homodimer	Unkno ‘n
Sweet/Umami Taste: T1R1, T1R2, T1R3	Ligand: T1R1/T1R3: L-glutamate; T1R2/T1R3: Sugars	Homodimer Heterodir er (T1R1/T1R3, T1R2/T1R3)	Unknown (potential airway immune modulation)
Metabotropic Glutamate Grp I: mGluR1, mGluR5	Ligand: Glutamate, ACPD Agonist: DHPG, CHPG, LY339764 Antagonist: CPPCOEt, BAY36–7620, Ro 674853	Homodimer PHetei’dimer (‘rp |’, III)	Unknown
Metabotropic Glutamate Grp II: mGluR2, mGluR3	Ligand: Glutamate, ACPD Agonist: LY341495, LY354740 Antagonist: Ro 64–5229, LY487379	Homodimer	Unknown
Metabotropic Glutamate Grp III mGluR4, mGluR6, mGluR7, mGluR8	Ligand: Glutamate, ACPD Agonist: MAP4, DCPG Antagonist: PHCCC	Homodimer	Unknown
RAIG Orphan: GPRC5A, GPRC5B, GPRC5C, GPRC5D	Unknown	Unknown	Unknown (GPRC5A may be most relevant)
Other Orphan: GPR156, GPR158, GPR179	Unkno n	Unknown	Unknown