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.
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.
Lee
Sung Gu
SG
Department of Biology, Colorado State University, Fort Collins, CO 80523, USA.
Bader
Brandon D
BD
Chang
Ernest S
ES
Mykles
Donald L
DL
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
D009479:Neuropeptides; D004441:Ecdysterone; D006162:Guanylate Cyclase