Catecholaminergic (dopaminergic, noradrenergic, and adrenergic) transmitter phenotypes require the cooperative actions of four biosynthetic enzymes: tyrosine hydroxylase, aromatic L-amino acid decarboxylase, dopamine ␤-hydroxylase, and phenylethanolamine N-methyltransferase. Mechanisms that control expression of these enzymes in a transmitter phenotype-specific manner, however, are poorly understood. Here, we provide evidence that overexpression of a novel cdc10/ SWI6 motif-containing protein, V-1, elicits the coordinate up-regulation of tyrosine hydroxylase, aromatic Lamino acid decarboxylase, and dopamine ␤-hydroxylase mRNAs in the neuronal cell line PC12D, and as a result, catecholamine levels are increased. Furthermore, V-1 is strongly expressed in the cytoplasm of rat chromaffin cells of adrenal medulla. Thus, V-1 may act as a cytoplasmic protein/protein adapter and be involved in control of the catecholaminergic phenotype expression via an intracellular pathway signaling to the nucleus.Abnormalities in catecholamine biosynthesis and neurotransmission have been implicated as the cause of neurological and psychiatric diseases (1). Signal transduction pathways via protein kinase, including cAMP-dependent protein kinases, Ca 2ϩ /phospholipid-dependent protein kinase, and Ca 2ϩ /calmodulin-dependent protein kinase, that regulate the activity of TH 1 and the transcription of genes encoding catecholamine biosynthesizing enzymes have been identified and extensively characterized (2-17). In addition, Mash1 and Phox2 transcription factors have been recently shown by gene targeting to be required for development of subpopulations of central nervous system and peripheral nervous system catecholaminergic neurons (18,19). Little is known, however, about mechanisms that control expression of genes encoding the four enzymes that determine the catecholaminergic phenotype.V-1 is a novel soluble protein consisting of 117 amino acids that contains 2.5 tandem repeats of the cdc10/SWI6 motif, also known as the ankyrin repeat (see Fig. 1A) (20,21). This motif has been demonstrated to be crucial for protein-protein interactions (22,23). Our recent studies have revealed a characteristic temporal profile for the expression of the V-1 gene in developing murine brain. During embryonic stages, expression of the V-1 gene is detectable but weak. After birth, expression of V-1 mRNA gradually increases to reach a maximal level during the first to second postnatal weeks, declining thereafter to adult levels by postnatal day 28.2 However, strong expression of the V-1 gene persists in regions of synaptic plasticity even after the second postnatal week (24). We have established stable transfectants that overexpress V-1 using the catecholamine-producing neuronal cell line PC12D to examine functional roles of V-1 in neuronal cells and analyzed the neuronal phenotypes of these cells using techniques of molecular biology, neurochemistry, biochemistry, and electrophysiology. In this study, we also demonstrate that the V-1 protein is intensely co-e...

No abstract