Absence of coupling between release and biosynthesis of peptide hormones in insect neuroendocrine cells.
Adipokinetic hormone (AKH)-producing cells in the corpus cardiacum of the insect Locusta migratoria represent a neuroendocrine system containing large quantities of stored secretory peptides. In the present study we address the question whether the release of AKHs from these cells induces a concomitant enhancement of their biosynthesis. The effects of hormone release in vivo (by flight activity) and in vitro (using crustacean cardioactive peptide, locustamyoinhibiting peptide, and activation of protein kinase A and C) on the biosynthetic activity for AKHs were measured. The intracellular levels of prepro-AKH mRNAs, the intracellular levels of pro-AKHs, and the rate of synthesis of (pro-)AKHs were used as parameters for biosynthetic activity. The effectiveness of in vitro treatment was assessed from the amounts of AKHs released. Neither flight activity as the natural stimulus for AKH release, nor in vitro treatment with the regulatory peptides or signal transduction activators appeared to affect the biosynthetic activity for AKHs. This points to an absence of coupling between release and biosynthesis of AKHs. The strategy of the AKH-producing cells to cope with variations in secretory stimulation seems to rely on a pool of secretory material that is readily releasable and continuously replenished by a process of steady biosynthesis.
Harthoorn
L F
LF
Department of Biochemical Physiology, Utrecht University, The Netherlands. L.F.Harthoorn@bio.uu.nl
Oudejans
R C
RC
Diederen
J H
JH
Van de Wijngaart
D J
DJ
Van der Horst
D J
DJ
D000818:Animals; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D005426:Flight, Animal / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects / Q000502:physiology; D006110:Grasshoppers / Q000502:physiology*; D066298:In Vitro Techniques; D007301:Insect Hormones / Q000235:genetics* / Q000378:metabolism*; D019476:Insect Proteins / Q000494:pharmacology; D008297:Male; D009479:Neuropeptides / Q000494:pharmacology; D009490:Neurosecretory Systems / Q000187:drug effects / Q000378:metabolism; D009842:Oligopeptides / Q000235:genetics* / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism; D011498:Protein Precursors / Q000235:genetics; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction / Q000502:physiology; D014158:Transcription, Genetic / Q000187:drug effects / Q000502:physiology
D007301:Insect Hormones; D019476:Insect Proteins; D009479:Neuropeptides; D009842:Oligopeptides; D011498:Protein Precursors; D012333:RNA, Messenger; C044833:adipokinetic hormone; C058620:crustacean cardioactive peptide; C073324:locustamyoinhibiting peptide, Locusta migratoria; D017868:Cyclic AMP-Dependent Protein Kinases; D011493:Protein Kinase C; D011761:Pyrrolidonecarboxylic Acid