Signaling Mechanisms in the Crustacean Molting Gland

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Growth in crustaceans requires the periodic shedding of the shell, a process called molting, which is controlled by an endocrine center in the eyestalks. The center secretes two peptide hormones, molt-inhibiting hormone (MIH) and crustacean hyperglycemic hormone (CHH), which inhibit a pair of molting glands (Y-organs or YOs) located in the body. It is the YO, when activated by a drop in MIH, that makes the hormone (ecdysteroid) required for molting. Coordination of molting processes involves a complex interaction between the YO and the eyestalk endocrine center that is poorly understood. It is thought that binding of MIH and CHH to membrane receptors activates separate signaling pathways that converge at cyclic nucleotide-dependent inhibition of enzymes that make ecdysteroid. The YO is a dynamic tissue responsive to changing hormonal conditions. Thus, it is the integration of the hormonal signals by the YO that ultimately determines when an animal molts. Using a comparative approach that incorporates a variety of biochemical and molecular techniques, the project will determine the components of the MIH and CHH signaling pathways and how molting and limb regeneration affect YO sensitivity to MIH and CHH. Understanding the hormonal regulation of crustacean molting and growth is essential to manage fisheries, develop effective aquaculture practices, and mitigate potential effects of pollutants, such as endocrine disruptors. Despite intense effort, very little is known about the molting gland responds to varying hormonal stimuli. Now that methods to express large amounts of active MIH and CHH are available, the signaling pathways can be elucidated and potential interactions with other hormones and pollutants can be determined. The potential role of nitric oxide in MIH signaling constitutes an entirely novel and exciting line of investigation. The project will train a postdoctoral fellow, two graduate students, and four undergraduates in advanced molecular biological techniques.