Abstract
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). Eyestalk ablation (ESA) activates the YOs, which hypertrophy and increase ecdysteroid secretion. At mid premolt, which occurs 7–14 days post-ESA, the YO transitions to the committed state; hemolymph ecdysteroid titers increase further and the animal reaches ecdysis ~ 3 weeks post-ESA. Two conserved signaling pathways, mechanistic target of rapamycin (mTOR) and transforming growth factor-β (TGF-β), are expressed in the Gecarcinus lateralis YO. Rapamycin, an mTOR antagonist, inhibits YO ecdysteroidogenesis in vitro. In this study, rapamycin lowered hemolymph ecdysteroid titer in ESA G. lateralis in vivo; levels were significantly lower than in control animals at all intervals (1–14 days post-ESA). Injection of SB431542, an activin TGF-β receptor antagonist, lowered hemolymph ecdysteroid titers 7 and 14 days post-ESA, but had no effect on ecdysteroid titers at 1 and 3 days post-ESA. mRNA levels of mTOR signaling genes Gl-mTOR, Gl-Akt, and Gl-S6k were increased by 3 days post-ESA; the increases in Gl-mTOR and Gl-Akt mRNA levels were blocked by SB431542. Gl-elongation factor 2 and Gl-Rheb mRNA levels were not affected by ESA, but SB431542 lowered mRNA levels at Days 3 and 7 post-ESA. The mRNA level of an activin TGF-β peptide, Gl-myostatin-like factor (Mstn), increased 5.5-fold from 0 to 3 days post-ESA, followed by a 50-fold decrease from 3 to 7 days post-ESA. These data suggest that (1) YO activation involves an up regulation of the mTOR signaling pathway; (2) mTOR is required for YO commitment; and (3) a Mstn-like factor mediates the transition of the YO from the activated to the committed state.
Publication Date
8-1-2016
Journal Title
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology
Publisher
Elsevier
Digital Object Identifier (DOI)
Document Type
Article
Recommended Citation
Abuhagr, A.M., MacLea, K.S., Mudron, M.R., Chang, S.A., Chang, E.S., and Mykles, D.L. Roles of mechanistic target of rapamycin and transforming growth factor-B signaling in the molting gland (Y-organ) of the blackback land crab, Gecarcinus lateralis. Comp Biochem Physiol A Mol Integr Physiol, 198:15-21. doi: 10.1016/j.cbpa.2016.03.018, 2016.
Rights
© 2016 Elsevier Inc. All rights reserved.
Comments
This is an Author’s Original Manuscript of an article published by Elsevier in Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology in 2016, available online: https://dx.doi.org/10.1016/j.cbpa.2016.03.018. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/