Temperature-dependent stimulation and inhibition of adenylate cyclase by Aplysia bag cell peptides.
The bag cell peptides (alpha-, beta-, and gamma-BCP) are secreted by the neuroendocrine bag cells of Aplysia, and provide feedback modulation of bag cell excitability and cAMP levels. We report here that if 200-500 mM NaCl is included in the assay buffer, the BCPs alter adenylate cyclase activity in a manner consistent with their effects on cAMP levels in intact bag cells. Specifically, beta-BCP and the related peptide A from the atrial gland stimulate the enzyme, while the effects of alpha-BCP(1-7) and gamma-BCP are temperature-dependent, stimulating at 30 degrees C and inhibiting at 15 degrees C. Both stimulation and inhibition require GTP, suggesting mediation by Gs and Gi. The ionic requirements of stimulation and inhibition differ: Cl- is necessary to support stimulation, but not inhibition. Moreover, pertussis toxin blocks inhibition, but does not affect stimulation. These results suggest that the temperature-sensitive mechanism lies upstream from the G-proteins in the signal transduction pathway.
Department of Cell Molecular and Structural Biology, Northwestern University, Chicago, IL 60611.
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Berry
D000067956:Adenylyl Cyclase Inhibitors; D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D001048:Aplysia / Q000502:physiology*; D002712:Chlorides / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism*; D005246:Feedback; D007447:Invertebrate Hormones / Q000502:physiology*; D012964:Sodium / Q000502:physiology; D013696:Temperature
D000067956:Adenylyl Cyclase Inhibitors; D002712:Chlorides; D007447:Invertebrate Hormones; C026880:egg-laying hormone, Mollusca; D012964:Sodium; D000242:Cyclic AMP; D000262:Adenylyl Cyclases