title: Effects of elevated ecdysteroid on tissue expression of three guanylyl cyclases in the tropical land crab Gecarcinus lateralis: possible roles of neuropeptide signaling in the molting gland.
abstract: Two eyestalk (ES) neuropeptides, molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH), increase intracellular cGMP levels in target tissues. Both MIH and CHH inhibit ecdysteroid secretion by the molting gland or Y-organ (YO), but apparently through different guanylyl cyclase (GC)-dependent pathways. MIH signaling may be mediated by nitric oxide synthase (NOS) and NO-sensitive GC. CHH binds to a membrane receptor GC. As molting affects neuropeptide signaling, the effects of ecdysteroid on the expression of the land crab Gecarcinus lateralis beta subunit of a NO-sensitive GC (Gl-GC-Ibeta), a membrane receptor GC (Gl-GC-II) and a NO-insensitive soluble GC (Gl-GC-III) were determined. Gl-GC-Ibeta isoforms differing in the absence or presence of an N-terminal 32-amino acid sequence and Gl-GC-III were expressed at higher mRNA levels in ES ganglia, gill, hepatopancreas, ovary and testis, and at lower levels in YO, heart and skeletal muscle. Three Gl-GC-II isoforms, which vary in the length of insertions (+18, +9 and +0 amino acids) within the N-terminal ligand-binding domain, differed in tissue distribution. Gl-GC-II(+18) was expressed highly in striated muscle (skeletal and cardiac muscles); Gl-GC-II(+9) was expressed in all tissues examined (ES ganglia, YO, gill, hepatopancreas, striated muscles and gonads); and Gl-GC-II(+0) was expressed in most tissues and was the dominant isoform in ES and thoracic ganglia. ES ablation, which increased hemolymph ecdysteroid, increased Gl-GC-II(+18) mRNA level in claw muscle. Using real-time RT-PCR, ES ablation increased Gl-GC-Ibeta, Gl-GC-III and ecdysone receptor mRNA levels in the YOs approximately ten-, approximately four- and approximately twofold, respectively, whereas Gl-GC-II mRNA level was unchanged. A single injection of 20-hydroxyecdysone into intact animals transiently lowered Gl-GC-Ibeta in hepatopancreas, testis and skeletal muscle, and certain Gl-GC-II isoforms in some of the tissues. These data suggest that YO and other tissues can modulate responses to neuropeptides by altering GC expression.
authors.affiliation: Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
authors.forename: Sung Gu
authors.initials: SG
authors.lastname: Lee
authors.forename: Brandon D
authors.initials: BD
authors.lastname: Bader
authors.forename: Ernest S
authors.initials: ES
authors.lastname: Chang
authors.forename: Donald L
authors.initials: DL
authors.lastname: Mykles
mesh_terms: D000818:Animals; D003386:Brachyura / Q000187:drug effects / Q000378:metabolism*; D004441:Ecdysterone / Q000494:pharmacology*; D005786:Gene Expression Regulation; D006162:Guanylate Cyclase / Q000235:genetics* / Q000378:metabolism*; D006321:Heart / Q000187:drug effects; D018978:Molting / Q000502:physiology*; D018482:Muscle, Skeletal / Q000187:drug effects / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D009479:Neuropeptides / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology
chemical_list: D009479:Neuropeptides; D004441:Ecdysterone; D006162:Guanylate Cyclase