title: PHM is required for normal developmental transitions and for biosynthesis of secretory peptides in Drosophila.
abstract: To understand the roles of secretory peptides in developmental signaling, we have studied Drosophila mutant for the gene peptidylglycine alpha-hydroxylating monooxygenase (PHM). PHM is the rate-limiting enzyme for C-terminal alpha-amidation, a specific and necessary modification of secretory peptides. In insects, more than 90% of known or predicted neuropeptides are amidated. PHM mutants lack PHM protein and enzyme activity; most null animals die as late embryos with few morphological defects. Natural and synthetic PHM hypomorphs revealed phenotypes that resembled those of animals with mutations in genes of the ecdysone-inducible regulatory circuit. Animals bearing a strong hypomorphic allele contain no detectable PHM enzymatic activity or protein; approximately 50% hatch and initially display normal behavior, then die as young larvae, often while attempting to molt. PHM mutants were rescued with daily induction of a PHM transgene and complete rescue was seen with induction limited to the first 4 days after egg-laying. The rescued mutant adults produced progeny which survived to various stages up through metamorphosis (synthetic hypomorphs) and displayed prepupal and pupal phenotypes resembling those of ecdysone-response gene mutations. Examination of neuropeptide biosynthesis in PHM mutants revealed specific disruptions: Amidated peptides were largely absent in strong hypomorphs, but peptide precursors, a nonamidated neuropeptide, nonpeptide transmitters, and other peptide biosynthetic enzymes were readily detected. Mutant adults that were produced by a minimal rescue schedule had lowered PHM enzyme levels and reproducibly altered patterns of amidated neuropeptides in the CNS. These deficits were partially reversed within 24 h by a single PHM induction in the adult stage. These genetic results support the hypothesis that secretory peptide signaling is critical for transitions between developmental stages, without strongly affecting morphogenetic events within a stage. Further, they show that PHM is required for peptide alpha-amidating activity throughout the life of Drosophila. Finally, they define novel methods to study neural and endocrine peptide biosynthesis and functions in vivo.
authors.affiliation: Department of Anatomy & Neurobiology, Washington University School of Medicine, Saint Louis 63130, USA.
authors.forename: N
authors.initials: N
authors.lastname: Jiang
authors.forename: A S
authors.initials: AS
authors.lastname: Kolhekar
authors.forename: P S
authors.initials: PS
authors.lastname: Jacobs
authors.forename: R E
authors.initials: RE
authors.lastname: Mains
authors.forename: B A
authors.initials: BA
authors.lastname: Eipper
authors.forename: P H
authors.initials: PH
authors.lastname: Taghert
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D017931:DNA Primers; D004330:Drosophila / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism; D007150:Immunohistochemistry; D008675:Metamorphosis, Biological; D006899:Mixed Function Oxygenases / Q000235:genetics*; D009030:Mosaicism; D009097:Multienzyme Complexes; D010452:Peptide Biosynthesis; D016133:Polymerase Chain Reaction
chemical_list: D017931:DNA Primers; D009097:Multienzyme Complexes; D006899:Mixed Function Oxygenases; C035189:peptidylglycine monooxygenase