Institute of Marine and Environmental Technology, University of Maryland Center for Environmental Science, 701 E. Pratt Street, Columbus Center, Baltimore, MD 21202, USA.
Gene. 2013 Sep 15;527(1):139-53. doi: 10.1016/j.gene.2013.05.035. Epub 2013 Jun 10.
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.
甲壳动物蜕皮被认为主要受蜕皮激素和甲壳动物高血糖激素（CHH）神经肽家族调节，包括蜕皮抑制激素（MIH）和 CHH。20-OH 蜕皮甾酮和/或 Ponasterone A 的激增通过与保守的异二聚体核受体：蜕皮激素受体（EcR）和超螺旋体（USP）/视黄酸受体（RXR）结合来启动蜕皮过程。为了更好地了解蜕皮激素在蜕皮调节中的作用，从 Y 器官中分离出了蓝蟹 Callinectes sapidus EcR1 和 RXR1 的全长 cDNA，并在不同蜕皮阶段的 Y 器官和眼柄中测定了它们的表达水平。Y 器官显示出四种假定的 CasEcRs 和 CasRXRs 的表达，它们在开放阅读框的长度上有所不同，但具有与典型核受体相同的结构域结构：AF1、DBD、HR、LBD 和 AF2。假定的 CasEcR 异构体是由 HR 中的 27-aa 插入和 LBD 中的 49-aa 残基取代衍生而来。相比之下，DBD 和 LBD 中的 5-aa 和/或 45-aa 插入会导致 CasRXR 异构体的产生。眼柄和 Y 器官显示出 CasEcRs 和 CasRXRs 的共表达，但水平不同。在眼柄中，CasRXRs 的表达水平比 CasEcRs 高 3-5 倍，而在 Y 器官中，CasRXRs 比 CasEcRs 高 2.5-4 倍。组织对血淋巴中蜕皮激素水平变化的特异性反应表明，这些组织可能在对蜕皮激素的敏感性或反应性上存在差异。通过计算机分析，在蓝蟹和其他节肢动物 EcR/RXR/USP 的 5'UTR 序列中存在上游开放阅读框和内部核糖体进入位点，表明这些受体的翻译可能受到强有力的控制。
