title: A calmodulin-sensitive adenylate cyclase in the prothoracic glands of the tobacco hornworm, Manduca sexta.
abstract: The Ca2+/calmodulin (CaM) dependence of adenylate cyclase activity in Manduca sexta prothoracic glands was investigated. Membrane fractions from two developmental stages were used, day 3 of the last larval instar and day 0 of the pupal stage, both of which respond to the neuropeptide prothoracicotropic hormone (PTTH) with increased cAMP production dependent on extracellular Ca2+. The data revealed that both larval and pupal prothoracic gland membrane fractions have a Ca2+/CaM-dependent adenylate cyclase which is inhibited by CaM antagonists and EGTA. The larval adenylate cyclase shows a multiphasic response to Ca2+/CaM, with a 2-fold stimulation between 0.02 and 0.01 microM, a further increase in adenylate cyclase activity at concentrations greater than 2 microM and a potentiation of NaF-stimulated activity at doses greater than 0.1 microM Ca2+/CaM. Pupal prothoracic gland membrane fractions exhibit only the second phase of stimulation. Stimulation by the GTP analogs GTP-gamma-S and Gpp(NH)p is dependent on CaM in larval, but not in pupal membrane fractions, suggesting a role for CaM in Gs protein-mediated regulation of adenylate cyclase. However, adenylate cyclase activity in glands from both stages is dependent on CaM, supporting our initial premise that Ca2+ is required for cAMP synthesis in the prothoracic glands.
authors.affiliation: Department of Biology, University of North Carolina, Chapel Hill 27599-3280.
authors.forename: V H
authors.initials: VH
authors.lastname: Meller
authors.forename: W L
authors.initials: WL
authors.lastname: Combest
authors.forename: W A
authors.initials: WA
authors.lastname: Smith
authors.forename: L I
authors.initials: LI
authors.lastname: Gilbert
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism; D002147:Calmodulin / Q000032:analysis / Q000494:pharmacology* / Q000502:physiology; D000242:Cyclic AMP / Q000096:biosynthesis; D006160:Guanosine Triphosphate / Q000031:analogs & derivatives; D007093:Imidazoles / Q000494:pharmacology; D007301:Insect Hormones / Q000378:metabolism / Q000502:physiology; D007313:Insecta; D013909:Thorax / Q000032:analysis / Q000201:enzymology*; D014268:Trifluoperazine / Q000494:pharmacology
chemical_list: D015220:Calcium Channels; D002147:Calmodulin; D007093:Imidazoles; D007301:Insect Hormones; D014268:Trifluoperazine; C031938:calmidazolium; C009089:prothoracicotropic hormone; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D000262:Adenylyl Cyclases; D002118:Calcium