title: Ecdysone and retinoid-X receptors of the blue crab, Callinectes sapidus: cloning and their expression patterns in eyestalks and Y-organs during the molt cycle.
abstract: Crustacean molting is known to be regulated largely by ecdysteroids and crustacean hyperglycemic hormone (CHH) neuropeptide family including molt-inhibiting hormone (MIH) and CHH. The surge of 20-OH ecdysone and/or ponasterone A initiates the molting process through binding to its conserved heterodimeric nuclear receptor: Ecdysone Receptor (EcR) and Ultraspiracle (USP)/Retinoid-X Receptor (RXR). To better understand the role of ecdysteroids in the molt regulation, the full-length cDNAs of the blue crab, Callinectes sapidus EcR1 and RXR1 were isolated from the Y-organs and their expression levels were determined in both Y-organs and eyestalks at various molt stages. Y-organs show the expression of four putative isoforms of CasEcRs and CasRXRs which differ in the length of the open reading frame but share the same domain structures as in typical nuclear receptors: AF1, DBD, HR, LBD, and AF2. The putative CasEcR isoforms are derived from a 27-aa insert in the HR and a 49-aa residue substitution in the LBD. In contrast, an insertion of a 5-aa and/or a 45-aa in the DBD and LBD gives rise to CasRXR isoforms. The eyestalks and Y-organs show the co-expression of CasEcRs and CasRXRs but at the different levels. In the eyestalks, the expression levels of CasRXRs are 3-5 times higher than those of CasEcRs, while in Y-organs, CasRXRs are 2.5-4 times higher than CasEcRs. A tissue-specific response to the changes in the levels of hemolymphatic ecdysteroids indicates that these tissues may have differences in the sensitivity or responsiveness to ecdysteroids. The presence of upstream open reading frame and internal ribosome entry site in 5' UTR sequences of C. sapidus and other arthropod EcR/RXR/USP analyzed by in silico indicates a plausible, strong control(s) of the translation of these receptors.
authors.affiliation: Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 E. Pratt Street, Columbus Center, Baltimore, MD 21202, USA.
authors.forename: Sirinart
authors.initials: S
authors.lastname: Techa
authors.forename: J Sook
authors.initials: JS
authors.lastname: Chung
mesh_terms: D020121:5' Untranslated Regions; D000595:Amino Acid Sequence; D000818:Animals; D060829:Arthropod Proteins / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D003386:Brachyura / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism; D003001:Cloning, Molecular; D017124:Conserved Sequence; D026461:Ecdysteroids / Q000097:blood; D005123:Eye / Q000254:growth & development / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D008969:Molecular Sequence Data; D018978:Molting; D009928:Organ Specificity; D010802:Phylogeny; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D011987:Receptors, Steroid / Q000235:genetics* / Q000378:metabolism; D047488:Retinoid X Receptors / Q000235:genetics* / Q000378:metabolism; D017422:Sequence Analysis, DNA; D059467:Transcriptome
chemical_list: D020121:5' Untranslated Regions; D060829:Arthropod Proteins; D026461:Ecdysteroids; D020033:Protein Isoforms; D011987:Receptors, Steroid; D047488:Retinoid X Receptors; C055469:ecdysone receptor
keywords: AF1; AF2; AK; C(4); CHH; CPE; CW; D(0); D(2); DBD; DNA-binding domain; EcR; Ecd(s); Ecd-RIA; Ecdysone Receptor; Ecdysteroids; Eyestalk; FXR; HR; IRES; Isoforms; LBD; MIH; ORF; RACE; RXR; Retinoid X Receptor; USP; UTR; Y-organs; aa; activation function-1; activation function-2; amino acid; arginine kinase; carapace width; crustacean hyperglycemic hormone; cytoplasmic polyadenylation element; early premolt stage; ecdysone receptor; ecdysteroid(s); ecdysteroid-radioimmunoassay; farnesoid X receptor; hinge region; intermolt stage; internal ribosome entry site; late premolt stage; ligand-binding domain; mORF; major open reading frame; molt-inhibiting hormone; open reading frame; rapid amplification of cDNA ends; retinoid-X receptor; uORF; ultraspiracle; untranslated region; upstream open reading frame