Meeting Abstract
10.2 Thursday, Jan. 3 Conserved role of cyclic nucleotides and nitric oxide in the molt-inhibiting pathway of Gecarcinus lateralis and Carcinus maenas COVI, Joseph A*; GOMEZ, Andrea M; CHANG, Sharon; CHANG, Ernie S; LEE, Kara J; MYKLES, Donald L; Colorado State University; Colorado State University; Bodega Bay Marine Lab; Bodega Bay Marine Lab; Colorado State University; Colorado State University joseph.covi@colostate.edu
The signaling pathway initiated by molt-inhibiting hormone (MIH) in the crustacean Y-organ (YO) is poorly understood. While it is well accepted that cGMP is a critical signaling molecule in the response of the YO to MIH, the guanylyl-cyclase responsible for its production remains elusive. Recent work has confirmed the presence of nitric oxide synthase and a nitric oxide (NO)-sensitive guanylyl cyclase (GC-I) in YO tissue of the blackback land crab. We employed an in vitro assay to investigate the role of NO and cyclic nucleotides in regulating ecdysteroidogenesis by the YOs of two species of Brachyuran crab: Gecarcinus lateralis and Carcinus maenas. Slowly hydrolysable analogs of cAMP and cGMP induced equivalent inhibition of ecdysteroid production. Incubation of cultured Y-organs with the non-specific phosphodiesterase inhibitor, IBMX, produced a profound and dose dependent inhibition of ecdysteroid secretion in C. maenas, but not G. lateralis. NO donors inhibited ecdysteroid secretion in both species of crab; C. maenas displayed greater sensitivity to SNAP while G. lateralis was affected only by SE175. Inclusion of IBMX enhanced inhibition of ecdysteroidogenesis by SNAP and SE175 in C. maenas YOs, but had no effect on secretion by G. lateralis YOs. Ecdysteroid secretion in both species was inhibited by a combination of NO donor, GC-I activator, and phosphodiesterase inhibitor. Together these data support the involvement of an NO-sensitive guanylyl-cyclase in MIH signaling, and confirm that PDE activity is a critical, though less conserved, component of ecdysteroidogenic regulation in the decapod YO. Supported by NSF (IBN-0342982)
