Meeting Abstract

P1.62  Wednesday, Jan. 4  Role of mTOR and TGFβ in Y-organ activation during the crustacean molting cycle ABUHAGR , A. M.*; CHANG, E. S.; MYKLES, D. L.; Colorado State Univ.; UC Davis Bodega Marine Lab; Colorado State Univ.

Molting in decapod crustaceans is controlled by molt-inhibiting hormone (MIH), an eyestalk neuropeptide that suppresses production of ecdysteroids by a pair of molting glands (Y-organs or YOs). In the blackback land crab, Gecarcinus lateralis, molting is induced by eyestalk ablation (ESA) or autotomy of 5 or more walking legs. The YO transitions through four physiological states during the molting cycle: “basal” state at postmolt and intermolt; “activated” state at early premolt (D0); “committed” state at mid premolt (D1,2); and “repressed” state at late premolt (D3,4). The basal to activated state transition is triggered by a transient reduction in MIH; the YOs hypertrophy, but remain sensitive to MIH, as premolt is suspended by MIH injection or by limb bud autotomy (LBA). Metazoan Target of Rapamycin (mTOR), which controls global translation of mRNA into protein, appears to be involved in YO activation in early premolt. Rapamycin (1 µM) inhibited YO ecdysteroidogenesis in vitro. Injection of rapamycin (10 µM final) lowered hemolymph ecdysteroid titer in 1, 3, 7, and 14 day post-ESA animals. At the activated to committed state transition, the animal becomes committed to molt, as the YO is less sensitive to MIH and premolt is not suspended by LBA. YO commitment involves a putative transforming growth factor-beta (TGFβ)-like factor. Injection of SB431542 (10 µM final), a TGFβ receptor antagonist, lowered hemolymph ecdysteroid titers in 7 and 14 day post-ESA animals, but had no effect on ecdysteroid titers at 1 and 3 days post-ESA. The goal now is to determine the effects of molting, rapamycin, and SB431542 on the expression of mTOR signaling components (mTOR, Rheb, Akt, and S6K) using quantitative PCR. Supported by NSF (IOS-0745224).