Trimeric G proteins in crustacean (Callinectes sapidus) Y-organs: occurrence and functional link to protein synthesis.
Crustacean Y-organs produce ecdysteroid molting hormones. Regulation of ecdysteroidogenesis appears to be complex, involving regulatory ligands (including but not limited to molt-inhibiting hormone, an eyestalk neurohormone) and the capacity of the Y-organs to respond to those ligands. Available data indicate cell signaling pathways involving cAMP, cGMP, or both may be involved in regulation of Y-organ function. Trimeric G proteins link receptor occupancy to regulation of intracellular cAMP levels. In studies reported here, we have assessed the occurrence of G proteins in blue crab (Callinectes sapidus) Y-organs, and the link of G proteins to Y-organ function. Bacterial toxin-catalyzed ADP-ribosylation revealed a PTX-sensitive (alpha i-like) protein in Y-organ membranes, but failed to reveal a CTX-sensitive (alpha s-like) protein in Y-organ membranes. Western blotting with primary antibodies raised against conserved regions of mammalian G proteins detected an alpha i-immunoreactive protein (approximately 40 kDa) and two alpha s-immunoreactive proteins (approximately 50 and approximately 57 kDa) in Y-organ membrane preparations. Incubation of Y-organ membrane fractions with cholera toxin significantly suppressed incorporation of [35S]-methionine into TCA-precipitable Y-organ proteins, but had no detectable effect on ecdysteroidogenesis in short-term (6 h) incubations. The combined results indicate that C. sapidus Y-organs possess both Gi and Gs proteins, and that alpha s is functionally linked to regulation of glandular protein synthesis.
Han
Deug-Woo
DW
Department of Biology, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
Watson
R Douglas
RD
D000818:Animals; D015153:Blotting, Western; D003386:Brachyura / Q000378:metabolism*; D002772:Cholera Toxin / Q000633:toxicity; D000242:Cyclic AMP / Q000378:metabolism; D026461:Ecdysteroids / Q000378:metabolism; D004702:Endocrine Glands / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism* / Q000502:physiology; D008715:Methionine / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology*
D026461:Ecdysteroids; D008565:Membrane Proteins; D002772:Cholera Toxin; D008715:Methionine; D000242:Cyclic AMP; D019204:GTP-Binding Proteins