Membrane transduction pathway in the neuronal control of protein secretion by the albumen gland in Helisoma (Mollusca)

Abstract

The albumen gland in Helisoma secretes a perivitelline fluid which surrounds each egg and is made up of several 66 kDa protein subunits and polysaccharide complexes. Forskolin, an adenylate cyclase activator, stimulated the secretion and release of the perivitelline fluid. An acidic extract of the central nervous system increased the intracellular concentration of cAMP in the albumen gland and this results in the release of the 66 kDa molecule and other proteins. Digestion of the brain extract with proteases abolished this activity, suggesting that the factor is a peptide. Cyclic AMP analogues and [BMX also stimulated the protein secretion in dose-dependent manner. Forskolin when added with the brain factor had an additive response. SQ22536, a non-competitive inhibitor of adenylate cyclase, inhibited brain extract dependent adenylate cyclase activity whereas aluminum fluoride, a G protein activator, was found to stimulate adenylate cyclase. Dopamine also stimulates protein secretion by the albumen gland and through the application of various agonists and antagonists of dopamine, it was established that the neurotransmitter acts via D1-like receptors by stimulating adenylate cyclase.