Journal of Neuroscience, Vol 9, 996-1003, Copyright © 1989 by Society for Neuroscience
Biosynthesis of adipokinetic hormones (AKHs): further characterization of precursors and identification of novel products of processing
S Hekimi and M O'Shea
Laboratoire de Neurobiologie, Geneve 4, Switzerland.
Two adipokinetic hormones (AKH I: pGlu-Leu-Asn-Phe-Thr-Pro-Asn-Trp-Gly-
Thr-NH2, and AKH II: pGlu-Leu-Asn-Phe-Ser-Thr-Gly-Trp-NH2) are synthesized
by the neurosecretory cells of the corpora cardiaca (CC) of the locust
Schistocerca gregaria. Both AKHs are released into the blood during flight
and serve to regulate lipid metabolism and other physiological processes
involved in flight. By in vitro "pulse-chase" experiments we show that 2
precursors (P1 and P2) are involved in AKH biosynthesis. These are about
8.4 kDa polypeptides which are AKH immunoreactive but also contain an amino
acid (tyrosine) not present in the AKH peptides. By following the fate of
14C-tyrosine incorporated into P1 and P2, we have identified 2 novel
products of precursor processing. These are called AKH-Precursor Related
Peptides or APRP 1 and APRP 2. Size exclusion chromatography shows that the
APRPs are about 6.5 kDa large and therefore represent major fragments of
the precursors. The optical density peaks corresponding to P1, P2, APRP 1,
and APRP 2 on a reverse-phase chromatogram are identified. The precursors
being metabolic intermediates are represented by minor optical density
peaks that disappear when de novo protein synthesis is blocked by
cycloheximide. In contrast, the APRPs are represented by major optical
density peaks consistent with their being accumulating end products of AKH
precursor processing. The function of the APRPs is as yet unknown. They
are, however, co-synthesized and also co-released with the AKHs, and may
therefore also have hormonal functions related to flight.