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|Title: ||Crustacean Molt-inhibiting Hormone: Structure, Function, and Cellular Mode of Action|
|Authors: ||Nakatsuji, Teruaki;Lee, Chi-Ying;Watson, R. Douglas|
|Keywords: ||Molt-inhibiting hormone;MIH;Ecdysteroid;Y-organ;Molting;Crustacean hyperglycemic hormone family;Phosphodiesterase|
|Issue Date: ||2012-07-03T04:02:58Z
|Abstract: ||In Crustacea, secretion of ecdysteroid molting hormones by Y-organs is regulated, at least in part, by moltinhibiting|
hormone (MIH), a polypeptide neurohormone produced by neurosecretory cells of the eyestalks.
This article reviews current knowledge of MIH, with particular emphasis on recent findings regarding the (a)
structure of the MIH peptide and gene, (b) levels of MIH in eyestalks and hemolymph, (c) cellular mechanism
of action of MIH, and (d) responsiveness of Y-organs to MIH. At least 26 MIH/MIH-like sequences have been
directly determined by protein sequencing or deduced from cloned cDNA. Recent studies reveal the existence
of multiple forms of MIH/MIH-like molecules among penaeids and raise the possibility that molecular
polymorphism may exist more generally among MIH (type II) peptides. The hemolymphatic MIH titer has
been determined for two species, a crayfish (Procambarus clarkii) and a crab (Carcinus maenas). The data are
dissimilar and additional studies are needed. Composite data indicate cellular signaling pathways involving
cGMP, cAMP, or both may play a role in MIH-induced suppression of ecdysteroidogenesis. Data from the two
species studied in our laboratories (P. clarkii and Callinectes sapidus) strongly favor cGMP as the
physiologically relevant second messenger. Ligand-binding studies show an MIH receptor exists in Y-organ
plasma membranes, but the MIH receptor has not been isolated or fully characterized for any species. Such
studies are critical to understanding the cellular mechanism by which MIH regulates ecdysteroidogenesis.
Rates of ecdysteroid synthesis appear also to be influenced by stage-specific changes in the responsiveness of
Y-organs to MIH. The changes in responsiveness result, at least in part, from changes in glandular
phosphodiesterase (PDE) activity. The PDE isotype (PDE1) present in Y-organs of C. sapidus is calcium/
calmodulin dependent. Thus, calcium may regulate ecdysteroidogenesis through activation of glandular PDE.
|Relation: ||Comparative Biochemistry and Physiology-Part A, 152(2): 139-148|
|Appears in Collections:||[生物學系] 期刊論文|
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