Type of Binding Sites | Binding Affinity (Kd) | Receptor Subtypes | Splice Variants | Transduction Mechanisms | ||
---|---|---|---|---|---|---|
Adenylyl Cyclase | PLC | Others | ||||
Type I | PACAP38 ≈ PACAP27 ≈ Maxadilan ≈ 0.5 nM VIP > 500 mM | PAC1-R | S Hop1 Hop2 Hip-Hop | Stimulates cAMP production PACAP38 ≈ PACAP27 ≫ VIP | Stimulates IP turnover PACAP38 > PACAP27 ≫ VIP | Stimulates calcium levels Stimulates phospholipase D |
Hip | – | |||||
Vs | Stimulates IP turnover PACAP38 ≈ PACAP27 ≫ VIP | |||||
TM4 | − | Activates L-type channel | ||||
Type II | PACAP38 ≈ PACAP27 ≈ VIP≈ 1 nM > PHI > secretin | VPAC1-R | − | Stimulates cAMP production PACAP38 > PACAP27 > VIP | + ? | Sometimes stimulates calcium levels Stimulates phospholipase D |
Helodermin > PACAP38 ≈ PACAP27 ≈ VIP ≈ 1 nM > PHI | VPAC2-R | − | Stimulates cAMP production PACAP38 ≈ PACAP27 ≈ VIP | − | Sometimes stimulates calcium levels Stimulates phospholipase D |
S, PAC1-R short variant; TM4, PAC1-R short variant with discrete deletions in transmembrane domains II and IV; Vs, PAC1-R with a 21-amino acid deletion in the N-terminal extracellular domain; −, no activation; +, activation.