This project studies neurochemical signal transduction and the control of tissue specific gene expression, using the pineal gland as a model. Efforts are directed at determining the details of the chemical and ionic components of transmembrane signalling processing and in the neural and tissue specific regulation of gene expression. Signal transduction in this system is of special interest because cAMP and cGMP are regulated by dual receptor mechanisms which appear to interact at the level of regulation of adenylyl and guanylyl cyclases. One leg of these pathways activates these enzymes via GTP binding regulatory proteins. similar to GS alpha. This leg is controlled by beta-adrenergic or VIP receptors: activation of this leg produces only partial stimulation of cAMP and cGMP accumulation. Activation of the other leg is via alpha1-adrenergic receptors. This activates protein kinase C which acts, perhaps on the regulatory or catalytic proteins, to increase the activation of adenylyl and guanylyl cyclase. Activation of protein kinase C occurs as a result of an increase in [Ca2+]i and in diacylglycerol production by phospholipase C. In addition, in the regulation cGMP, there appears to be a strong requirement for activation of phospholipase A and for an increase in [Ca2+]i. Current activities are focused on the role of MEKA in signal transduction. MEKA is a 33 kDa substrate of protein kinase A and exists as a cytoplasmic complex with GS(beta)gamma. Immunoprecipitation is being used to isolate and study the phosphorylation states of GS alpha, adenylyl cyclase and guanylyl cyclase complexes. In the area of the neural and developmental control of gene expression, advances have been made in purifying N-acetyltransferase and hydroxyindole-O-methyltransferase, and in isolating cDNA clones coding for these enzymes. A human hydroxyindole-O-methyltransferase cDNA clone has been sequenced and the gene has been located on the pseuodoautosomal region of the Y chromosome.
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