Purification and characterization of the prothoracicotropic hormone of
            <i>Drosophila melanogaster</i>

The molecular mechanisms by which dietary cholesterol is trafficked within cells are poorly understood. Previous work indicates that the NPC1 family of proteins plays an important role in this process, although the precise functions performed by this protein family remain elusive. We have taken a genetic approach to further explore the NPC1 family in the fruit fly Drosophila melanogaster. The Drosophila genome encodes two NPC1 homologs, designated NPC1a and NPC1b, that exhibit 42% and 35% identity to the human NPC1 protein, respectively. Here we describe the results of mutational analysis of the NPC1a gene. The NPC1a gene is ubiquitously expressed, and a null allele of NPC1a confers early larval lethality. The recessive lethal phenotype of NPC1a mutants can be partially rescued on a diet of high cholesterol or one that includes the insect steroid hormone 20-hydroxyecdysone. We also find that expression of NPC1a in the ring gland is sufficient to rescue the lethality associated with the loss of NPC1a and that cholesterol levels in NPC1a mutant larvae are unchanged relative to controls. Our results suggest that NPC1a promotes efficient intracellular trafficking of sterols in many Drosophila tissues including the ring gland where sterols must be delivered to sites of ecdysone synthesis. S TEROLS are critical in eukaryotic biology as structural components of all membranes and as precursors for the synthesis of the large eukaryotic family of steroid hormones (Mouritsen and Zuckermann 2004;Payne and Hales 2004;Becher and McIlhinney 2005). While sterols are essential due to the important biological functions they serve, an overabundance of the primary mammalian sterol, cholesterol, is toxic and contributes to a variety of prevalent diseases including heart disease and stroke (Choy et al. 2004;Saini et al. 2004). Accumulating evidence also suggests that alterations in cholesterol homeostasis may contribute to neurodegenerative disorders such as Alzheimer's disease, although the mechanisms by which alterations in cholesterol metabolism affect neuronal integrity remain unclear (Burns and Duff 2002;Reiss et al. 2004;Wellington 2004).The importance of sterols in eukaryotic biology and disease pathogenesis has stimulated intensive investigation of cholesterol homeostasis in vertebrates. This body of work has clarified many features of cholesterol metabolism, including its de novo synthesis from acetate in the endoplasmic reticulum (ER) (Bloch 1965;Lynen 1966), its packaging into and transport within lipoprotein particles (Oncley 1954;Fredrickson 1957), and the receptor-mediated uptake of these particles by cells (Brown and Goldstein 1986). While these advances have fostered the development of treatment strategies that affect the etiology of hypercholesterolemia, this disorder remains a major source of morbidity, and our knowledge of cholesterol metabolism and the health consequences associated with altered cholesterol homeostasis is far from complete. In particular, the molecular mechanisms by which cholesterol is ab...

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“…prothoracicotropic hormone, a neurosecretory peptide hormone secreted by the brain (Henrich et al 1987;Kim et al 1997;Zitnan et al 1993).…”

Section: Npc1amentioning

confidence: 99%

Mutations of a Drosophila NPC1 Gene Confer Sterol and Ecdysone Metabolic Defects

2006

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“…On the other hand, our data indicate that the expression of Start1 itself depends on ecdysone, implying that in Drosophila ecdysone might be involved in the regulation of its own synthesis. This possibility seems especially attractive to us, because for Drosophila a PTTH similar to Bombyx PTTH has not yet been identified, and the role of a Drosophila protein with PTTH-like activity (10) remains open.…”

mentioning

confidence: 99%

The Drosophila gene Start1 : A putative cholesterol transporter and key regulator of ecdysteroid synthesis

Roth

Gierl

Vollborn

et al. 2004

Proc. Natl. Acad. Sci. U.S.A.

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“…7D), contrasting with the case of the bombyxin immunoreactive nerves. By in situ hybridization for PTTH mRNA using 35 S-labeled cRNA as a probe, the same two dorsolateral neurosecretory cells of Bombyx brain were radiolabeled, confirming that PTTH is actually synthesized in these cells.…”

Section: )16)mentioning

confidence: 82%

“…No reliable sequence information from purified PTTH has been reported for any insect other than Bombyx mori, though a considerable degree of purification was achieved with PTTH of Manduca sexta 34) and Drosophila melanogaster. 35) Molecular biological approach to infer the PTTH primary structure has accumulated recently, however.…”

Section: )33)mentioning

confidence: 99%

Molecular characterization of the brain secretory peptides, prothoracicotropic hormone (PTTH) and bombyxin, of the silkmoth <i>Bombyx mori</i>

Ishizaki

2004

Proceedings of the Japan Academy. Ser. B: Physical and Biologic

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Molecular characterization of the brain secretory peptides, PTTH and bombyxin, of Bombyx mori is reviewed. PTTH is a 30-kDa homodimeric glycoprotein, the monomer of which consists of 109 amino acids. Two monomers are held together by a disulfide bond. cDNA and gene coding for PTTH were cloned and the precursor protein for PTTH monomer was deduced. A novel 5-kD brain secretory peptide named bombyxin has been discovered from Bombyx brain. Bombyxin is highly homologous to vertebrate insulin-family peptides and possesses the prothoracicotropic activity when injected into brain-removed pupae of a heterologous moth, Samia cynthia ricini, though inactive to Bombyx from which it was derived. cDNA and gene coding for bombyxin were cloned, preprobombyxin protein was deduced, and posttranslational processing to generate mature bombyxin was suggested. The Bombyx genome contains highly multiple copies of the gene coding for bombyxins. Immunohistochemically, PTTH-and bombyxin-producing brain neurosecretory cells were identified.

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Purification and characterization of the prothoracicotropic hormone of Drosophila melanogaster

Cited by 37 publications

References 27 publications

Mutations of a Drosophila NPC1 Gene Confer Sterol and Ecdysone Metabolic Defects

Mutations of a Drosophila NPC1 Gene Confer Sterol and Ecdysone Metabolic Defects

The Drosophila gene Start1 : A putative cholesterol transporter and key regulator of ecdysteroid synthesis

Molecular characterization of the brain secretory peptides, prothoracicotropic hormone (PTTH) and bombyxin, of the silkmoth <i>Bombyx mori</i>

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