Han, D.W.*; Watson, R.D.: Presence and potential roles of G-proteins in Y-organs of the blue crab.

The synthesis of ecdysteroid hormones by crustacean Y-organs is negatively regulated by molt-inhibiting hormone (MIH); a neuropeptide synthesized and released from eyestalk neurosecretory cells. Several lines of evidence suggest that the suppressive effect of MIH on Y-organ ecdysteroid synthesis is mediated by an increase in intracellular cAMP. To better understand the link between MIH receptor occupancy and Y-organ cAMP levels, we have assessed the presence of GTP-binding proteins (G-proteins) in Y-organs of the blue crab (Callinectes sapidus). We report here the presence of G-proteins in Y-organs and control (neural) tissue as determined by (1) ADP-ribosylation catalyzed by bacterial toxins and (2) western blot analysis using antibodies raised against mammalian G-proteins. A pertussis toxin (PTX)-sensitive G-protein (~ 45 kD) was detected in both thoracic ganglia and Y-organs. A cholera toxin (CTX)-sensitive G-protein (~ 49 kD) was detected in ganglia, but not in Y-organs. Western blot analysis, using antibodies raised against either G-alpha or G-alpha-s, revealed an immunoreactive protein of ~ 49 kD in both ganglia and Y-organs. The combined results indicate that Gi-like and Gs-like proteins exist in Y-organs and thoracic ganglia of blue crabs. We are currently assessing the functional role of G-proteins in ecdysteroidogenesis. Funded by MS/AL Sea Grant (NA86RG0039) and NSF (IBN-9419916).