Multiple intracellular signal transduction pathways mediating inward current produced by the neuropeptide, achatin-I.
The effects of intracellular signal transduction system inhibitors on the inward current (Iin) caused by achatin-I (Gly-D-Phe-Ala-Asp), an Achatina endogenous tetrapeptide having a D-phenylalanine residue, applied locally onto the neurone tested, were examined under voltage clamp using two identifiable Achatina giant neurone types, v-RCDN (ventral-right cerebral distinct neurone) and PON (periodically oscillating neurone). H-89 (N-[2-(p-bromocinnamylamino)-ethyl]-5-isoquinolinesulfonamide) (adenosine-3',5'-cyclic monophosphate (cyclic AMP)-dependent protein kinase inhibitor) markedly suppressed the achatin-I-induced Iin on PON, whereas this drug was ineffective on the Iin of v-RCDN. Dose (pressure duration)-response study of achatin-I on PON in a physiological solution and in the presence of H-89, and Lineweaver-Burk plot of these data, indicated that H-89 inhibited the Iin in a noncompetitive manner. KT5823 (N-methyl-(8R*,9S*,11S*)-(-)-9-methoxy-9-methoxycarbonyl-8-methyl-2,3,9, 10-tetrahydro-8,11-epoxy-1H,8H,11H-2, 7b,11a-triazadibenzo[a,g]cycloocta[c,d,e]-trinden-1-on e) (guanosine-3',5'-cyclic monophosphate (cyclic GMP)-dependent protein kinase inhibitor) suppressed the achatin-I-induced Iin of v-RCDN in mainly noncompetitive and partly uncompetitive manners, but this drug had no effect on the Iin of PON. W-7 (N-(6-aminohexyl)-5-chloro-1-naphthalene-sulfonamide) (calmodulin inhibitor) suppressed noncompetitively the Iin of PON, but this drug had no effect on the Iin of v-RCDN. IBMX (3-isobutyl-1-methylxanthine) (cyclic nucleotide phosphodiesterase inhibitor) enhanced the achatin-I-induced Iin of v-RCDN, but this drug was ineffective on the Iin of PON. However, IBMX might have effects on the achatin-I receptor sites on v-RCDN. These findings suggest multiple intracellular signal transduction pathways mediating the achatin-I-induced Iin: the Iin of PON is via cyclic AMP-dependent and probably Ca2+/calmodulin-dependent protein kinases, and that of v-RCDN via cyclic GMP-dependent protein kinase. Other signal transduction system inhibitors including calphostin C (2-[12-[2-(benzyloxy)-propyl]-3, 10-dihydro-4,9-dihydroxy-2,6,7,11-tetramethoxy-3,10-dioxo-1-per yleny]-1 -methylethyl carbonic acid 4-hydroxyphenyl ester) (protein kinase C inhibitor) did not significantly affect the Iin of both v-RCDN and PON.
Emaduddin
M
M
Department of Physiology, Gifu University School of Medicine, Japan.
Liu
G J
GJ
Takeuchi
H
H
Munekata
E
E
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000470:Alkaloids / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002227:Carbazoles; D004305:Dose-Response Relationship, Drug; D007211:Indoles; D007546:Isoquinolines / Q000494:pharmacology; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009479:Neuropeptides / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D018377:Neurotransmitter Agents / Q000037:antagonists & inhibitors* / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D010726:Phosphodiesterase Inhibitors / Q000494:pharmacology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors; D047428:Protein Kinase Inhibitors; D015398:Signal Transduction / Q000187:drug effects*; D012908:Snails; D013449:Sulfonamides / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology
D000470:Alkaloids; D002227:Carbazoles; D007211:Indoles; D007546:Isoquinolines; D009281:Naphthalenes; D009479:Neuropeptides; D018377:Neurotransmitter Agents; D010726:Phosphodiesterase Inhibitors; D047428:Protein Kinase Inhibitors; D013449:Sulfonamides; D014665:Vasodilator Agents; C059927:achatin I; C073601:KT 5823; C017967:W 7; D011493:Protein Kinase C; C058819:calphostin C; C063509:N-(2-(4-bromocinnamylamino)ethyl)-5-isoquinolinesulfonamide; D015056:1-Methyl-3-isobutylxanthine