Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01275 (glucagon)
 26,492 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Specific receptors for pituitary adenylate cyclase-activating polypeptide (PACAP), a novel peptide with neuroregulatory and neurotrophic functions, have recently been identified in the retinas of different mammalian species. In the present study, expression of PACAP receptors and PACAP was investigated in the retinas of 12-18-week human embryos. Radioligand binding studies showed that the two forms of PACAP with 38 and 27 amino acids (PACAP 38 and PACAP 27, respectively) displaced the binding of 125I-PACAP 27 with IC50 values in the picomolar range, whereas functional receptor assays demonstrated that the two peptides were potent and effective stimulators of adenylyl cyclase activity. In contrast, vasoactive intestinal peptide (VIP) and human peptide histidine-isoleucine, which are homologous to PACAP, displayed lower affinities for the 125I-PACAP 27 binding site and were much less potent stimulators of cyclic AMP formation. Glucagon and secretin were inactive in both receptor assays. The expression of specific PACAP receptors was further investigated by reverse transcription-polymerase chain reaction technique, which showed the presence of mRNAs coding for PACAP type I and for nonselective PACAP type II (both VIP1 and VIP2) receptors. By the same technique, expression of PACAP mRNA was also detected. These data indicate that the developing human retina synthesizes PACAP and that the peptide may act on retinal cells by predominantly stimulating PACAP type I receptors coupled to cyclic AMP formation.
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PMID:Expression of pituitary adenylate cyclase-activating polypeptide (PACAP) receptors and PACAP in human fetal retina. 928 45

Since many isoforms of adenylyl cyclase and adenosine 3', 5'-monophosphate (cAMP) phosphodiesterase have been cloned, it is likely that receptors of each hormone have a specific combination of these isoforms. Types I, III and VIII adenylyl cyclases are reported to be stimulated by Ca(2+)-calmodulin, type I phosphodiesterase by Ca(2+)-calmodulin, but types IV and VII (cAMP-specific) phosphodiesterases by Co2+. In the present study, we examined different effects of Ca2+ and Co2+ on hormone-induced cAMP response in the isolated perfused rat liver.The removal of Ca2+ from the perfusion medium (0 mM CaCl(2 ) + 0.5 mM EGTA) did not affect glucagon (0.1 nM)-responsive cAMP but reduced secretin (1 nM)-, vasoactive intestinal polypeptide (VIP, 1-10 nM)- and forskolin (1 microM)-responsive cAMP considerably. The addition of 1 mM CoCl2 reduced glucagon- and secretin-responsive cAMP considerably, forskolin-responsive cAMP partly, did not affect 1 nM VIP-responsive cAMP, but enhanced 10 nM VIP-responsive cAMP. Forskolin- and VIP-responsive cAMP was greater in the combination (0 mM CaCl(2) + 0.5 mM EGTA + 3 mM CoCl2) than in the Ca(2+)-free perfusion alone. These results suggest that secretin, VIP1 and VIP2 receptors are linked to Ca(2+)-calmodulin-sensitive adenylyl cyclase; glucagon receptor to Ca(2+)-calmodulin-insensitive adenylyl cyclase; VIP1 receptor to Ca(2+)-calmodulin-dependent phosphodiesterase; glucagon, secretin and VIP2 receptors to cAMP-specific phosphodiesterase, respectively, in the rat liver.
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PMID:Hormone-specific combinations of isoforms of adenylyl cyclase and phosphodiesterase in the rat liver. 1125 14