title: AHR38, a homolog of NGFI-B, inhibits formation of the functional ecdysteroid receptor in the mosquito Aedes aegypti.
abstract: In anautogenous mosquitoes, vitellogenesis, the key event in egg maturation, requires a blood meal. Consequently, mosquitoes are vectors of numerous devastating human diseases. After ingestion of blood, 20-hydroxyecdysone activates yolk protein precursor (YPP) genes in the metabolic tissue, the fat body. An important adaptation for anautogenicity is the previtellogenic developmental arrest (the state-of-arrest) preventing the activation of YPP genes in previtellogenic females prior to blood feeding. Here, we show that a retinoid X receptor homolog, Ultraspiracle (AaUSP), which is an obligatory partner in the functional ecdysteroid receptor, exists at the state-of-arrest as a heterodimer with the orphan nuclear receptor AHR38, a homolog of Drosophila DHR38 and nerve growth factor-induced protein B. Yeast two-hybrid and glutathione S-transferase pull-down assays demonstrate that AHR38 can interact strongly with AaUSP. AHR38 also disrupts binding of ecdysteroid receptor to ecdysone response elements. Cell co-transfection of AHR38 with AaEcR and AaUSP inhibits ecdysone-dependent activation of a reporter gene by the ecdysteroid receptor. Co-immunoprecipitation experiments indicate that AaUSP protein associates with AHR38 instead of AaEcR in fat body nuclei at the state-of-arrest.
authors.affiliation: Program in Genetics and Department of Entomology, Michigan State University, East Lansing, MI 488240-1115, USA.
authors.forename: J
authors.initials: J
authors.lastname: Zhu
authors.forename: K
authors.initials: K
authors.lastname: Miura
authors.forename: L
authors.initials: L
authors.lastname: Chen
authors.forename: A S
authors.initials: AS
authors.lastname: Raikhel
mesh_terms: D000330:Aedes / Q000235:genetics / Q000502:physiology*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002268:Carboxypeptidases / Q000235:genetics*; D002460:Cell Line; D003546:Cysteine Endopeptidases / Q000235:genetics*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D019281:Dimerization; D029721:Drosophila Proteins; D004441:Ecdysterone / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D017344:Genes, Insect; D006801:Humans; D019476:Insect Proteins; D008969:Molecular Sequence Data; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection; D014818:Vitellogenesis; D014819:Vitellogenins / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; C095176:Hr38 protein, Drosophila; D019476:Insect Proteins; C539821:NR4A1 protein, human; D057105:Nuclear Receptor Subfamily 4, Group A, Member 1; D018160:Receptors, Cytoplasmic and Nuclear; D011987:Receptors, Steroid; D011994:Recombinant Proteins; D014157:Transcription Factors; C066030:USP protein, Drosophila; D014819:Vitellogenins; C034808:ecdysteroid receptor; D004441:Ecdysterone; D002268:Carboxypeptidases; C071911:VCP protein, Aedes aegypti; D003546:Cysteine Endopeptidases