PRECURSOR POLYPROTEIN FOR MULTIPLE NEUROPEPTIDES SECRETED FROM THE SUBESOPHAGEAL GANGLION OF THE SILKWORM BOMBYX-MORI - CHARACTERIZATION OFTHE CDNA-ENCODING THE DIAPAUSE HORMONE PRECURSOR AND IDENTIFICATION OF ADDITIONAL PEPTIDES
Y. Sato et al., PRECURSOR POLYPROTEIN FOR MULTIPLE NEUROPEPTIDES SECRETED FROM THE SUBESOPHAGEAL GANGLION OF THE SILKWORM BOMBYX-MORI - CHARACTERIZATION OFTHE CDNA-ENCODING THE DIAPAUSE HORMONE PRECURSOR AND IDENTIFICATION OF ADDITIONAL PEPTIDES, Proceedings of the National Academy of Sciences of the United Statesof America, 90(8), 1993, pp. 3251-3255
Peptidergic neurons, which serve as source of various endocrine neurop
eptides, were identified in the suboesophageal ganglion (SG) and brain
of insects. In the silkworm Bombyx mori, SG is known to secrete two n
europeptides, diapause hormone (DH) responsible for induction of embry
onic diapause and pheromone biosynthesis-activating neuropeptide, whic
h share a pentapeptide amide, Phe-Xaa-Pro-Arg-Leu-NH2 (Xaa = Gly or Se
r), at the C terminus. We have isolated cDNA clones for DH from the cD
NA library of SG by using oligonucleotide probes. The molecular charac
terization of the cDNA reveals that the mRNA encodes an open reading f
rame consisting of 192 aa residues in which the 24-aa DH peptide is lo
calized at the N-terminal region just after the signal peptide. A homo
logy search proposed that the cDNA encodes pheromone biosynthesis-acti
vating neuropeptide and three other neuropeptides [alpha-, beta-, and
gamma-SG neuropeptide (SGNP)] in the region following DH, all of which
are flanked by possible tryptic cleavage sites and share the Phe-Xaa-
Pro-Arg-Leu-Gly sequence at the C terminus. Northern hybridization ana
lysis clearly showed that the gene expression was limited to SG. We ch
emically synthesized alpha-, beta-, and gamma-SGNP and used them to id
entify components in extracts of SG and to examine biological function
s. Alpha- and gamma-SGNP were identified in extracts of SG, and the sy
nthetic beta- and gamma-SGNP expressed weak DH activity. These results
indicate that DH, along with four other neuropeptides, is generated f
rom a common precursor polyprotein that is encoded by a single mRNA tr
anscribed in neurosecretory cells of SG.