GRM1 and cystic fibrosis: mGluR1 and its downstream signaling cascade in PCs, consisting of Gαq (Offermanns et al. 1997), phospholipase Cβ3 and β4 (PLCβ3, PLCβ4) (Kano et al. 1998; Rai et al. 2021), and protein kinase Cγ (PKCγ) (Kano et al. 1995), are involved mainly in the late phase of CF elimination.