In Silico Screening Identified Novel Small-molecule Antagonists of PAC1 Receptor

Abstract

Pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptors are present in the spinal dorsal horn and dorsal root ganglia, suggesting an important role of PACAP signaling systems in the modulation of spinal nociceptive transmission. Previously, we found that intrathecal injection of PACAP or maxadilan, a selective PACAP type I (PAC1) receptor agonist, induced transient aversive responses followed by a long-lasting mechanical allodynia in mice, suggesting that PACAP-PAC1 receptor systems are involved in chronic pain and that selective PAC1 antagonists may become a new class of analgesics. Although several PAC1 antagonists, such as PACAP 6-38, have been reported, all of them are peptide compounds. In the present study, we identified new small-molecule antagonists of the PAC1 receptor using in silico screening and in vitro/vivo pharmacological assays. The identified small-molecule compounds, named PA-8 and PA-9, dose dependently inhibited the phosphorylation of CREB induced by PACAP in PAC1-, but not VPAC- or VPAC-receptor-expressing CHO cells. PA-8 and PA-9 also dose dependently inhibited PACAP-induced cAMP elevation with an IC of 2.0 and 5.6 nM, respectively. In vivo pharmacological assays showed that intrathecal injection of these compounds blocked the induction of PACAP-induced aversive responses and mechanical allodynia in mice. In contrast, the compounds when administered alone exerted neither agonistic nor algesic actions in the in vitro/vivo assays. The compounds identified in the present study are new and the first small-molecule antagonists of the PAC1 receptor; they may become seed compounds for developing novel analgesics.

Molecular and cellular correlates of human nerve regeneration: ADCYAP1/PACAP enhance nerve outgrowth

“…In fact, function blocking antibodies to PAC1 are undergoing clinical testing for migraine treatment (Amgen) and given our findings, care will need to be taken that such treatments do not impair sensory neuron function in the context of co-existing neuropathy. One means of optimizing delivery to promote neurite outgrowth of small fibres would be to develop small molecule agonists of PAC1 that can be given locally, as has been achieved for PAC1 antagonists ( Takasaki et al , 2018 ) and other growth promoting molecules, such as GDNF ( Sidorova et al , 2017 ).…”

Peptide receptors as cancer drug targets

“…Addition of 100 nM PACAP‐27 or PACAP‐38 to NSCLC cells significantly increases tyrosine phosphorylation of EGFR and HER2 within 1 minute . EGFR and HER2 transactivation are inhibited upon addition of PACAP, gefitinib (EGFR tyrosine kinase inhibitor (TKI)), PP2 (Src inhibitor), TGF‐α antibody, or GM6001 (matrix metalloprotease inhibitor (MMP) inhibitor) (Fig. ).…”

“…The PACAP gene ( ADCYAP1 ) is hypermethylated in cervical cancer. 15 PACAP‐27 and PACAP‐38 bind with high affinity to PAC1, VPAC1, and VPAC2, however PACAP is an antagonist for PAC1 . Selective agonists for VPAC1, VPAC2, and PAC1 are (Lys 15 , Arg 16 , Leu 17 ) VIP 1–7 GRF 8–27 , Ro 25–1553, and (Iaa 1 , Ala 16,17 , d ‐Lys 38 (IAAD)) PACAP‐38, respectively .…”

“…Selective agonists for VPAC1, VPAC2, and PAC1 are (Lys 15 , Arg 16 , Leu 17 ) VIP 1–7 GRF 8–27 , Ro 25–1553, and (Iaa 1 , Ala 16,17 , d ‐Lys 38 (IAAD)) PACAP‐38, respectively . Recently, small molecule PAC1 antagonists PA‐8 and PA‐9 were discovered . It remains to be determined if PA‐8 or PA‐9 inhibits the proliferation of cancer cells.…”

“…cAMP increases protein kinase (PK) A activity resulting in phosphorylation of cAMP response element binding protein (CREB), followed by altered gene expression and increased proliferation. The growth of lung cancer cells is inhibited by VIPhyb, which blocks VPAC1 and VPAC2, and by PACAP, which antagonizes PAC1 …”