Structural determinants for binding to CGRP receptors expressed by human SK-N-MC and Col 29 cells: studies with chimeric and other peptides.
Structure-activity relationships for the binding of human alpha-calcitonin gene-related peptide 8-37 (halphaCGRP8-37) have been investigated at the CGRP receptors expressed by human SK-N-MC (neuroblastoma) and Col 29 (colonic epithelia) cells by radioligand binding assays and functional assays (halphaCGRP stimulation of adenylate cyclase). On SK-N-MC cells the potency order was halphaCGRP8-37 > halphaCGRP19-37 = AC187 > rat amylin8-37 > halpha[Tyr0]-CGRP28-37 (apparent pKBs of 7.49+/-0.25, 5.89+/-0.20, 6.18+/-0.19, 5.85+/-0.19 and 5.25+/-0.07). The SK-N-MC receptor appeared CGRP1-like. On Col 29 cells, only halphaCGRP8-37 of the above compounds was able to antagonize the actions of halphaCGRP (apparent pKB=6.48+/-0.28). Its receptor appeared CGRP2-like. halpha[Ala11,18]-CGRP8-37, where the amphipathic nature of the N-terminal alpha-helix has been reduced, bound to SK-N-MC cells a 100 fold less strongly than halphaCGRP8-37. On SK-N-MC cells, halphaCGRP8-18,28-37 (M433) and mastoparan-halphaCGRP28-37 (M432) had apparent pKBs of 6.64+/-0.16 and 6.42+/-0.26, suggesting that residues 19-27 play a minor role in binding. The physico-chemical properties of residues 8-18 may be more important than any specific side-chain interactions. M433 was almost as potent as halphaCGRP8-37 on Col 29 cells (apparent pKB=6.17+/-0.20). Other antagonists were inactive.
Pharmaceutical Sciences Institute, Aston University, Birmingham, UK.
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Poyner
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Soomets
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Howitt
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Langel
D000262:Adenylyl Cyclases / Q000378:metabolism; D000595:Amino Acid Sequence; D000682:Amyloid / Q000737:chemistry / Q000378:metabolism; D000818:Animals; D015740:Calcitonin Gene-Related Peptide / Q000494:pharmacology; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D002460:Cell Line; D055598:Chemical Phenomena; D002627:Chemistry, Physical; D000242:Cyclic AMP / Q000378:metabolism; D006801:Humans; D058228:Islet Amyloid Polypeptide; D008969:Molecular Sequence Data; D009479:Neuropeptides / Q000737:chemistry* / Q000378:metabolism*; D010446:Peptide Fragments / Q000494:pharmacology; D011869:Radioligand Assay; D051381:Rats; D018015:Receptors, Calcitonin Gene-Related Peptide / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000737:chemistry* / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014407:Tumor Cells, Cultured
D000682:Amyloid; D000077221:Calcitonin Gene-Related Peptide Receptor Antagonists; D058228:Islet Amyloid Polypeptide; D009479:Neuropeptides; D010446:Peptide Fragments; D018015:Receptors, Calcitonin Gene-Related Peptide; D011993:Recombinant Fusion Proteins; C058636:calcitonin gene-related peptide (8-37); D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D015740:Calcitonin Gene-Related Peptide