Tetrahydrobiopterin Cofactor Biosynthesis: GTP Cyclohydrolase I mRNA Expression in Rat Brain and Superior Cervical Ganglia

Abstract

GTP cyclohydrolase I (GTPCH) is the rate-limiting enzyme in the biosynthesis of tetrahydrobiopterin, the reduced pteridine cofactor required for catecholamine (CA), indoleamine, and nitric oxide biosynthesis. We have used the reverse transcription-polymerase chain reaction technique, based on the published cDNA sequence for rat liver GTPCH, to clone a portion of the GTPCH transcript from rat adrenal gland mRNA and have used this clone for the analysis of GTPCH mRNA in brain and other tissues of the rat by northern blot, nuclease protection assay, and in situ hybridization. Two GTPCH mRNA transcripts of 1.2 and 3.8 kb in length were detected by northern blot, with the 1.2-kb form predominating in the liver and the 3.8-kb form in the pineal gland, adrenal gland, brainstem, and hypothalamic neurons maintained in culture. In situ hybridization studies localized GTPCH mRNA to CA-containing perikarya in the locus ceruleus, ventral tegmental area, and substantia nigra, pars compacta. Levels of GTPCH mRNA in central and peripheral catecholamine neurons determined by nuclease protection assay were increased twofold 24 h after a single injection of the CA-depleting drug reserpine; both the 1.2- and 3.8-kb transcripts were increased in the adrenal gland. Low levels of GTPCH mRNA were also detected by nuclease protection assay in the striatum, hippocampus, and cerebellum, brain regions that do not contain monoaminergic perikarya.

Coexpression of Tyrosine Hydroxylase, GTP Cyclohydrolase I, Aromatic Amino Acid Decarboxylase, and Vesicular Monoamine Transporter 2 from a Helper Virus-Free Herpes Simplex Virus Type 1 Vector Supports High-Level, Long-Term Biochemical and Behavioral Correction of a Rat Model of Parkinson's Disease

“…However, GTP CH I RNA is found only in monoaminergic neurons and has not been detected in striatal cells (Hirayama et al, 1993). Nigrostriatal dopaminergic neurons contain lower levels of GTP CH I RNA and protein than are found in either noradrenergic or serotonin neurons (Hirayama et al, 1993;Hirayama and Kapatos, 1998). Using a different antibody, GTP CH I-IR was reported in nigrostriatal neuron cell bodies in the SNc, but was not detected in striatal processes (Hirayama and Kapatos, 1998), similar to our results ( Fig.…”

“…The human AADC antibody is human specific and does not recognize rat AADC. The GTP CH I antibody is panspecific and also recognizes rat GTP CH I (Pluss et al, 1996); however, GTP CH I is expressed in monoamine-producing cells and is not expressed in fibroblasts (Hirayama et al, 1993;Hirayama and Kapatos, 1998). Also, 1 day after infection with the 3-gene-vector, we detected the three predicted IRs, FLAG-IR, GTP CH I-IR, and human AADC-IR (data not shown).…”

“…This antibody is panspecific and also recognizes the endogenous rat GTP CH I (Pluss et al, 1996). However, GTP CH I RNA is found only in monoaminergic neurons and has not been detected in striatal cells (Hirayama et al, 1993). Nigrostriatal dopaminergic neurons contain lower levels of GTP CH I RNA and protein than are found in either noradrenergic or serotonin neurons (Hirayama et al, 1993;Hirayama and Kapatos, 1998).…”

The eNOS cofactor tetrahydrobiopterin improves endothelial dysfunction in livers of rats with CCl4 cirrhosis

“…[24][25][26] All of them were identical at their central and 5Ј-regions, but diverged at their 3Ј-ends. This heterogeneity might be the result of alternative splicing of pre-mRNA, alternative transcription initiation sites, or multiple polyadenylation signals.…”

Tetrahydrobiopterin‐dependent stabilization of neuronal nitric oxide synthase dimer reduces susceptibility to phosphorylation by protein kinase C in vitro

“…When both stabilized and non-stabilized dimers coexist, the phosphorylation of stabilized dimers was negligible. The rate limiting enzyme of H R B biosynthesis [5], GTP cyclohydrolase-I [20], and the enzyme catalyzing the second step of H R B biosynthesis, 6-pyruvoyl tetrahydropterin synthase [21], are expressed in catecholamine-negative neurons in the cerebellum. Reduced nNOS activity was observed in the cerebellum of hph-1 mice lacking 90% of the activity of GTP cyclohydrolase-1 [22].…”