cDNA cloning and complete sequence of porcine choline acetyltransferase: in vitro translation of the corresponding RNA yields an active protein

Enzymatic and transcriptional regulation of the cytoplasmic acetyl-CoA hydrolase ACOT12

Acyl-CoA thioesterase 12 (ACOT12) is the major enzyme known to hydrolyze the thioester bond of acetyl-CoA in the cytosol in the liver. ACOT12 contains a catalytic thioesterase domain at the N terminus and a steroidogenic acute regulatory protein-related lipid transfer (START) domain at the C terminus. We investigated the effects of lipids (phospholipids, sphingolipids, fatty acids, and sterols) on ACOT12 thioesterase activity and found that the activity was inhibited by phosphatidic acid (PA) in a noncompetitive manner. In contrast, the enzymatic activity of a mutant form of ACOT12 lacking the START domain was not inhibited by the lipids. These results suggest that the START domain is important for regulation of ACOT12 activity by PA. We also found that PA could bind to thioesterase domain, but not to the START domain, and had no effect on ACOT12 dissociation. ACOT12 is detectable in the liver but not in hepatic cell lines such as HepG2, Hepa-1, and Fa2N-4. ACOT12 mRNA and protein levels in rat primary hepatocytes decreased following treatment with insulin. These results suggest that cytosolic acetyl-CoA levels in the liver are controlled by lipid metabolites and hormones, which result in allosteric enzymatic and transcriptional regulation of ACOT12.

Historical landmarks in the histochemistry of the cholinergic synapse: Perspectives for future researches

Nearly one hundred years ago, acetylcholine (ACh) was proposed as a chemical agent responsible for nerve transmission at the synapse, the junction area between one neuron and its target cell. Since it has been proved that ACh played, indeed, a major role in the functioning of the nerve system in the vertebrates, cholinergic nerve transmission became a basic field of study in neuroscience. The birth of histochemistry and its ulterior developments allowed in situ localization of the molecular agents related to the functioning of the cholinergic synapse. This report presents historical landmarks in the histochemistry of major cholinergic agents (acetylcholinesterase, nicotinic acetylcholine receptor, choline acetyltransferase, and ACh), a domain which has greatly contributed to the knowledge of the nerve system. It is emphasized that despite extraordinary progresses made in this field, basic problems, such as in situ localization of ACh, still remain to be solved.

The cholinergic gene locus in amphioxus: molecular characterization and developmental expression patterns

The cholinergic gene locus (CGL), consisting of the vesicular acetylcholine transporter (VAChT)/choline acetyltransferase (ChAT) gene, encodes two specific cholinergic neuronal markers used extensively to study cholinergic transmission. In the present work, we isolated the amphioxus homologs of VAChT and ChAT and examined their expression during development. Analysis of the 5' untranslated region of VAChT and ChAT suggests that the splicing of the VAChT/ChAT mRNA has been evolutionarily conserved in amphioxus and mammals. By double whole-mount in situ hybridization, we demonstrate that VAChT and ChAT are coexpressed in the same cells. They are first expressed in four pairs of differentiating cells in the neural plate. Their later expression is primarily in the anterior nerve cord in several types of motoneurons, some of the interneurons and in the receptor cells of the larval ocellus.

ATP and acetylcholine, equal brethren

Acetylcholine was the first neurotransmitter identified and ATP is the hitherto final compound added to the list of small molecule neurotransmitters. Despite the wealth of evidence assigning a signaling role to extracellular ATP and other nucleotides in neural and non-neural tissues, the significance of this signaling pathway was accepted very reluctantly. In view of this, this short commentary contrasts the principal molecular and functional components of the cholinergic signaling pathway with those of ATP and other nucleotides. It highlights pathways of their discovery and analyses tissue distribution, synthesis, uptake, vesicular storage, receptors, release, extracellular hydrolysis as well as pathophysiological significance. There are differences but also striking similarities. Comparable to ACh, ATP is taken up and stored in synaptic vesicles, released in a Ca(2+)-dependent manner, acts on nearby ligand-gated or metabotropic receptors and is hydrolyzed extracellularly. ATP and acetylcholine are also costored and coreleased. In addition, ATP is coreleased from biogenic amine storing nerve terminals as well as from at least subpopulations of glutamatergic and GABAergic terminals. Both ACh and ATP fulfill the criteria postulated for neurotransmitters. More recent evidence reveals that the two messengers are not confined to neural functions, exerting a considerable variety of non-neural functions in non-innervated tissues. While it has long been known that a substantial number of pathologies originate from malfunctions of the cholinergic system there is now ample evidence that numerous pathological conditions have a purinergic component.

Partial cloning and expression of mRNA coding choline acetyltransferase in the spinal cord of the goldfish, Carassius auratus

Choline acetyltransferase (ChAT, EC 2.3.1.6) synthesizes a neurotransmitter, acetylcholine in cholinergic neurons. ChAT is considered to be the most specific marker for cholinergic neurons. To obtain a better marker of the neurons, as the first step, we isolated a partial ChAT cDNA from the goldfish (Carassius auratus) brain by RT-PCR methods. The partial cDNA of the goldfish ChAT was composed of 718 nucleotides. The amino acid sequence of the goldfish ChAT is approximately 70% identical to those of mammalian and chicken ChAT. Northern blot analysis demonstrated that ChAT mRNA was expressed in the brain and the spinal cord of the goldfish, and much abundant in the spinal cord. In the spinal cord of the goldfish, ChAT-positive neurons were detected mainly in the ventral horn by in situ hybridization. In addition, fluorescence in situ hybridization combined with a retrograde labeling by using True Blue demonstrated ChAT mRNA positive neurons were exactly motoneurons. In the cord, putative presynaptic sympathetic neurons were also labeled.

Cloning of chicken choline acetyltransferase and its expression in early embryonic retina

The enzyme choline acetyltransferase [EC 2.3.1.6] (ChAT) synthesizes the neurotransmitter acetylcholine that plays a key morphogenic role in vertebrate retina development. As the embryonic avian retina is particularly useful for morphogenetic studies, we cloned the complete coding region of chicken ChAT cDNA. At the deduced amino acid level, chicken ChAT is approximately 76% identical to mammalian ChAT proteins. We also report here the cloning of the complete 5' end of the complex cholinergic locus. This locus contains both the ChAT gene and the nested intronless gene for the vesicular acetylcholine transporter (VAChT). The genomic organization of the 5' end of the chicken cholinergic locus is similar to that reported in other vertebrate species. A 5.7 kb mRNA corresponding to the ChAT message was detected in both embryonic retina and post-hatch brain. An analysis of the ChAT mRNA in embryonic chick retina shows that the message can be detected by E6 and its level increased during early retinal development. Vertebrate ChAT mRNAs can contain one or more of three non-coding exons, M, N or R and by RT-PCR we demonstrate, at least, a chicken ChAT mRNA containing exon M.

Choline acetyltransferase: regulation and coupling with protein kinase and vesicular acetylcholine transporter on synaptic vesicles

Both the membrane-bound choline acetyltransferase (MChAT) and soluble ChAT (SChAT) were found to be activated by ATP-mediated protein phosphorylation. ATP activation of MChAT but not SChAT was found to depend on the integrity of proton gradient of synaptic vesicles because conditions disrupting the proton gradient also abolished the activation of MChAT by ATP. Among the kinases studied, Ca2+/calmodulin kinase II is most effective in activation of MChAT. Transport of ACh into synaptic vesicles by vesicular acetylcholine transporter (VAChT) is also proton gradient-dependent; therefore we proposed that there is a functional coupling between ACh synthesis and its packaging into synaptic vesicles. This notion is supported by the following findings: first, the newly synthesized [3H]-ACh from [3H]-choline was taken up much more efficiently than the pre-existing ACh; second, ATP-activation of MChAT was abolished when VAChT was inhibited by the specific inhibitor vesamicol; third, the activity of ChAT was found to be markedly increased when neurons are under depolarizing conditions.

A novel untranslated 'exon H' of the human choline acetyltransferase gene in placenta

To investigate the existence of 5'-region(s) of human choline acetyltransferase (hChAT) mRNA in placenta we analyzed the presence or absence of ChAT 5'-untranslated regions (UTR) in human neuronal and non-neuronal cells. Total RNA from human spinal cord, placenta, cultured choriocarcinoma JEG-3 and neuroblastoma CHP126 and MC-IXC cells was reverse transcribed and used for polymerase chain reaction amplification (RT-PCR). We used a sense primer located in the 5'-flanking region, in the previously defined intronic sequence and an anti-sense primer located in the common coding exon 2 of the hChAT gene. An amplified product of 567 bp in size was obtained only in human placenta and in JEG-3 cells whereas it was absent in spinal cord, CHP126 and MC-IXC cells. It was designated 'H-type' of ChAT mRNA. Whereas CHP126 produced the R- and N-type of ChAT mRNAs, no transcript of the N-and R-type was detected in JEG-3 and human placenta. In addition, CHP126 and JEG-3 cells and placenta showed the expression of the M-type of ChAT mRNA. The identity of the amplified 567 bp product (H-type) was confirmed by Southern hybridization and sequencing. The nucleotide sequence of the amplified fragment in placenta revealed the existence of a previously unknown type of ChAT mRNA produced by alternative splicing. Using primer extension we further determined the transcription initiation site of the H-type hChAT mRNA in placenta. These results demonstrate the expression of a novel ChAT mRNA isoform in human placenta in addition to the M-type. These data may be possibly explained by the presence of a placenta specific promoter in the ChAT gene, which might be the proximal promoter P1.

Choline acetyltransferase mutations cause myasthenic syndrome associated with episodic apnea in humans

Choline acetyltransferase (ChAT; EC ) catalyzes the reversible synthesis of acetylcholine (ACh) from acetyl CoA and choline at cholinergic synapses. Mutations in genes encoding ChAT affecting motility exist in Caenorhabditis elegans and Drosophila, but no CHAT mutations have been observed in humans to date. Here we report that mutations in CHAT cause a congenital myasthenic syndrome associated with frequently fatal episodes of apnea (CMS-EA). Studies of the neuromuscular junction in this disease show a stimulation-dependent decrease of the amplitude of the miniature endplate potential and no deficiency of the ACh receptor. These findings point to a defect in ACh resynthesis or vesicular filling and to CHAT as one of the candidate genes. Direct sequencing of CHAT reveals 10 recessive mutations in five patients with CMS-EA. One mutation (523insCC) is a frameshifting null mutation. Three mutations (I305T, R420C, and E441K) markedly reduce ChAT expression in COS cells. Kinetic studies of nine bacterially expressed ChAT mutants demonstrate that one mutant (E441K) lacks catalytic activity, and eight mutants (L210P, P211A, I305T, R420C, R482G, S498L, V506L, and R560H) have significantly impaired catalytic efficiencies.

Nuclear factor kappaB/p49 is a negative regulatory factor in nerve growth factor-induced choline acetyltransferase promoter activity in PC12 cells

Anovel nuclear factor kappaB (NF-kappaB) binding site has been identified within the promoter region of the mouse gene encoding choline acetyltransferase (ChAT), the enzyme that synthesizes acetylcholine and has been implicated in the cognitive deficits associated with aging and Alzheimer's disease. This binding site, which is located within the nerve growth factor (NGF)-responsive enhancer element, was recognized by the NF-kappaB protein p49 but not p65 or p50. p49 from both basal forebrain and PC12 nuclear extracts interacted with this specific sequence in electrophoretic mobility shift assays. Mutation of the NF-kappaB site caused an increase in NGF-induced promoter activation, whereas overexpression of p49 in NGF-differentiated PC12 cells caused a decrease in endogenous ChAT enzyme activity and a decrease in promoter activity that was specifically mediated through this NF-kappaB binding site. Treatment of PC12 cells with NGF resulted in a drastic reduction in nuclear p49 binding to the ChAT NF-kappaB site after 24 h, but nuclear p49 levels were not altered, suggesting that late NGF-mediated events prevent binding of p49 to the ChAT promoter by an unknown mechanism other than nuclear translocation. Decreased ChAT expression and increased NF-kappaB activity in the brain are associated with aging and Alzheimer's disease. These data indicate that p49 is a negative regulator of ChAT expression and suggest a possible mechanism for aging-associated declines in cholinergic function.

Choline acetyltransferase detection in normal and denervated electrocyte from Electrophorus electricus (L.) using a confocal scanning optical microscopy analysis

Acetylcholine is the neurotransmitter responsible for the transmission of impulses from cholinergic neurons to cells of innervated tissues. Its biosynthesis is catalyzed by the enzyme Choline acetyltransferase that is considered to be a phenotypically specific marker for cholinergic system. It is well known that the regulation of Choline acetyltransferase activity under physiological and pathological conditions is important for development and neuronal activities of cholinergic functions. We observed the distribution of Choline acetyltransferase in sections from the normal and denervated main electric organ sections of Electrophorus electricus (L.) by immunofluorescence using a anti-Choline acetyltransferase antibody. The animals were submitted to a surgical procedure to remove about 20 nerves and after 30 and 60 days, they were sacrificed. After 30 days, the results from immunohistochemistry demonstrated an increase on the Choline acetyltransferase distribution at denervated tissue sections when compared with the sections from the normal contralateral organ. A very similar labeling was observed between normal and denervated tissue sections of the animals after 60 days. However, Choline acetyltransferase activity (nmolesACh/ min/ mg of protein) in extracts obtained from electrocyte microsomal preparation, estimated by Fonnun's method (Fonnun 1975), was 70% lower in the denervated extracts.

Identification and characterization of the high-affinity choline transporter

In cholinergic neurons, high-affinity choline uptake in presynaptic terminals is the rate-limiting step in acetylcholine synthesis. Using information provided by the Caenorhabditis elegans Genome Project, we cloned a cDNA encoding the high-affinity choline transporter from C. elegans (cho-1). We subsequently used this clone to isolate the corresponding cDNA from rat (CHT1). CHT1 is not homologous to neurotransmitter transporters, but is homologous to members of the Na+-dependent glucose transporter family. Expression of CHT1 mRNA is restricted to cholinergic neurons. The characteristics of CHT1-mediated choline uptake essentially match those of high-affinity choline uptake in rat brain synaptosomes.

A protein encoded by an alternative splice variant of choline acetyltransferase mRNA is localized preferentially in peripheral nerve cells and fibers

Central cholinergic systems have been visualized by immunohistochemistry using antibodies to choline acetyltransferase (ChAT). Peripheral cholinergic cells and fibers, however, have been hardly detectable with most of these antibodies. This phenomenon suggests that a different form of ChAT may exist in peripheral tissues. Here we report two types of mRNA for ChAT expressed by alternative splicing in rat pterygopalatine ganglion. One is exactly identical with ChAT mRNA reported in the central nervous system (ChAT of a common type; cChAT). The other lacks exons 6, 7, 8 and 9, which was detected only in the pterygopalatine ganglion (ChAT of a peripheral type; pChAT). The peculiarity of pChAT in chemical structure, possessing a splice joint of the exons 5 and 10, led us to produce rabbit antisera against a recombinant peptide of 41 amino acids which spans over the splice joint. On Western blots using a successfully obtained antiserum, an intense band of about 50 kDa, corresponding to the expected molecular weight of pChAT, was detected in the pterygopalatine ganglion but not in the brain. Immunohistochemistry using the antiserum failed to reveal positive staining of known brain cholinergic structures, while it permitted us to observe peripheral, probably cholinergic, nerve cells and fibers including those in the pterygopalatine ganglion and enteric nervous system.

Choline acetyltransferase: the structure, distribution and pathologic changes in the central nervous system

Choline acetyltransferase (ChAT), the enzyme responsible for the biosynthesis of acetylcholine, is presently the most specific indicator for monitoring the functional state of cholinergic neurones in the central and peripheral nervous systems. ChAT is a single-strand globular protein. The enzyme is synthesized in the perikaryon of cholinergic neurones and transported to the nerve terminals probably by both slow and rapid axoplasmic flows. ChAT exists in at least two forms in cholinergic nerve terminals: (i) soluble; and (ii) non-ionically membrane-bound forms. Multiple mRNA species of ChAT (R-, N-and M-types) are transcribed from different promoter regions and produced by different splicing in the mouse, rat, and human. All transcripts encode the same ChAT protein in rodents, while in human M-type mRNA has the capability to generate both large and small forms of ChAT proteins and R-and N-types ChAT mRNA generate a small form, which corresponds to the rodent ChAT. The genomic structure of ChAT is unique compared with other enzymes for neurotransmitters. The first intron of the ChAT gene encompasses the open reading frame encoding another protein, vesicular acetylcholine transporter (VAChT), which is responsible for the transportation of acetylcholine from the cytoplasm into the synaptic vesicles. The expressions of ChAT and VAChT appear to be coordinately regulated by multiple regulatory elements in cholinergic neurones. Immunohistochemical and in situ hybridization studies have revealed the localization of cholinergic neurones in the central nervous system: the medial septal nucleus, the nucleus of the diagonal band of Broca, the basal nucleus of Meynert, the caudate nucleus, the putamen, the nucleus accumbens, the pedunculopontine tegmental nucleus, the laterodorsal tegmental nucleus, the medial habenular nucleus, the parabigeminal nucleus, some cranial nerve nuclei, and the anterior horn of the spinal cord. Focally distributed cholinergic neurones project fibers to many areas in the central nervous system and construct a complicated cholinergic network, playing an important role in neuropsychic activities, such as learning, memory, arousal, sleep and movement. Central cholinergic neurones are involved in several neurodegenerative diseases such as Alzheimer's disease and amyotrophic lateral sclerosis, in which disturbance of the central cholinergic system does not appear to be closely related to the etiology, but rather to the development of clinical symptoms. In addition, abnormalities of ChAT in the brain have been recently demonstrated in schizophrenia and sudden infant death syndrome.

Enzyme activity and protein of multiple forms of choline acetyltransferase: effects of calyculin A and okadaic acid

Choline acetyltransferase (ChAT) appears to exist in multiple forms, three of which can be isolated biochemically as cytosolic (cChAT), ionically-membrane bound (ibChAT) and non-ionic membranous (mChAT). In this study, we first examined whether the quantitative distribution of enzyme protein and enzyme activity was the same. Enzyme activity and ChAT protein distributed similarly: the majority of ChAT activity and protein were found in cChAT followed by mChAT and least activity and amount were in ibChAT. Our second objective was to investigate the effects of calyculin A or okadaic acid on the subcellular distribution of ChAT activity and amount from rat hippocampal formation. Calyculin A and okadaic acid decreased significantly (p < 0.01) cytosolic and membranous ChAT activity; ionically-bound ChAT was not significantly (p > 0.67) different from control. Removal of calyculin A or okadaic acid restored cytosolic ChAT activity (p > 0.9 as compared to control), but not membranous enzyme activity (p < 0.05 as compared to control). The immunoreactive cytosolic ChAT was reduced significantly (p < 0.01) by calyculin A and okadaic acid. Enzyme amount of membranous ChAT was decreased significantly by calyculin A (p < 0.01) and okadaic acid (p < 0.001). Enzyme amount of ionically-bound ChAT was not changed (p > 0.99) by either of these two phosphatase inhibitors. This investigation demonstrates that alterations in ChAT activity of each subfraction parallel changes in enzyme amounts in the same fractions.

Production and functional expression of an epitope-tagged human choline acetyltransferase

cDNA containing the entire coding region of the human choline acetyltransferase gene (hChAT) was fused to the influenza virus hemagglutinin (HA) epitope preceded by a Kozak sequence. The recombinant HA-hChAT was then inserted into an expression vector under the transcriptional control of the cytomegalovirus (CMV) promoter. After transient transfection into COS-1 cells, expression was assayed by Northern and Western blot analysis and immunofluorescence. The chimeric HA-hChAT protein was compared to native hChAT for its ability to synthesize acetylcholine. It behaves identically to unmodified hChAT showing that the HA epitope does not affect ChAT activity. This approach enables one to distinguish the expression of the HA-hChAT from endogenous ChAT. Genetically engineered cells that express a high level of HA-hChAT could be used as a promising experimental tool for gene transfer and neurografting techniques as well as to produce and study transgenic mice.

Influence of anti-androgens on the anterior horn cells of rat spinal cord: morphometric and in-situ hybridization studies

To examine the roles of the androgens for growth and maintenance of anterior horn cells (AHCs) of the spinal cord, one of the two anti-androgen agents, flutamide or cyproterone, was injected into young rats. Morphometric analysis of the spinal cords after the injections showed that the average area occupied by an AHC was significantly smaller in the rats treated with the anti-androgens than in the controls. By contrast, neurons in the posterior horns did not show significant difference in their size. Moreover, an in-situ hybridization of choline acetyltransferase (CAT) messenger RNA revealed a significant reduction in the signal density in AHCs in the treated rats. These results show that androgens play an important role in the growth and maintenance of AHCs, and influence a wide range of protein synthesis, including that of CAT.

Study of subcellular localization of membrane-bound choline acetyltransferase in Drosophila central nervous system and its association with membranes

Choline acetyltransferase (ChAT), the enzyme which catalyses the biosynthesis of the neurotransmitter acetylcholine, exists in a soluble and membrane-bound form in cholinergic nerve terminals of different animal species. This study was performed on the enzyme present in Drosophila central nervous system. We show that the two forms of the enzyme have the same apparent molecular weight (75 kDa) when analysed by immunoblotting using an antibody we raised against the recombinant enzyme. According to different authors, membrane-bound enzyme might be associated with synaptic vesicles or plasma membrane. Subfractionation of Drosophila head homogenates in linear glycerol gradients showed that ChAT does not associate with synaptic vesicles. Analysis of ChAT activity and immunoreactivity showed that two peaks of ChAT were produced. One peak was present in fractions containing soluble components and the other was associated with rapidly sedimenting membranes containing plasma membranes. ChAT in the first peak was mainly hydrophilic. A large proportion of ChAT associated with rapidly sedimenting membranes was amphiphilic. Further fractionation of these membranes by flotation in sucrose gradients showed that membrane-associated ChAT sedimented in fractions containing plasma membrane marker. Membrane-bound ChAT was neither solubilized nor converted to hydrophilic enzyme after membrane treatment with 1 M hydroxylamine, suggesting that the enzyme is not palmitoylated and therefore not anchored to membrane through thioester-linked long chain fatty acid. Partial solubilization of ChAT present on membranes with urea and carbonate suggests that this form of ChAT is a peripheral membrane protein. Carbonate solubilization of membrane-bound ChAT converted the enzyme from hydrophobic to hydrophilic protein.

Transcriptional activation of human choline acetyltransferase by AP2- and NGF-induced factors

ChAT (choline acetyltransferase) is the enzyme responsible for acetylcholine synthesis and is specifically expressed in cholinergic neurons. To further characterize the transcriptional regulation of the hCHAT (human ChAT) gene by NGF, we examined the effects upon ChAT promoter activity of a family of transcription factors which are activated by NGF and several extracellular stimuli and encoded by immediate-early genes. These include NGFI-A (Egr1, zif268), NGFI-C (Egr2), Krox-20 and NGFI-B (Nurr77). Two fragments of the hChAT gene were used for functional analysis carrying 944 bp (P1) and 4000 bp (P1 + P2) of the 5' flanking region in front of the chloramphenicol acetyltransferase (CAT) reporter gene. They were transiently co-transfected with NGFI-A, NGFI-C, Krox-20 and NGFI-B expression vectors in NG108-15, SN6 and COS-1 cells. CAT activity after transfection of the p4000 ChAT-CAT reporter into both neuronal cell lines (NG108-15 and SN6 cells) was increased up to 5-fold in the presence of co-transfected NGFI-A and up to 5- and 12-fold after co-transfection of NGFI-C expression vector in NG108-15 and SN6 cells, respectively. In NG108-15 cells, dbcAMP excerted a strong enhancing activity on the transactivation properties of NGFI-C while this was not observed when cells were transfected with NGFI-A. These trans-activation effects were specific for neuronal cells. When NG108-15 cells were treated with dbcAMP in the presence of H89, a specific PKA inhibitor, the increase of transcriptional activity of NGFI-C was abolished, indicating that a signalling transduction mechanism through PKA plays a role in NGFI-C-induced trans-activation. Electrophoretic mobility-shift assays showed that the sequence GCCCGGGGAG (NGFRE) located 1205 bp upstream of the first coding ATG (E1) can bind NGFI-A but not NGFI-C. Several possibilities explaining the observed results are discussed. Finally, transfections of ChAT-CAT reporters including the P1 + P2 region or a minimal ChAT enhancer present in the P2 region in front of a heterologous promoter indicated the presence of a regulatory element which conferred AP2-dependent trans-activation with homologous as well as with heterologous promoter constructs.

Characterization of monoclonal and polyclonal antibodies to human choline acetyltransferase and epitope analysis

Choline acetyltransferase (ChAT) was partially purified from human placenta and brain. In order to raise monoclonal antibodies, Balb/c mice were immunized with a preparation from placenta or with a mixture of eight synthetic peptides that were deduced from the primary structures of porcine and human ChAT. Polyclonal antibodies were raised in rabbits against five synthetic peptides deduced from the amino acid sequence of human ChAT. The monoclonal and polyclonal antibodies were characterized by their ability to recognize ChAT in various immunoassays: immunoblot, enzyme-linked immunosorbent assay (ELISA), two-side ELISA and immunohistochemistry. With one exception all monoclonal antibodies recognized ChAT on immunoblots, some were particularly sensitive; one bound active ChAT in ELISA when used as capture reagent; most antibodies recognized immobilized ChAT in ELISA. Two monoclonal antibodies out of nine gave particularly excellent results in staining cholinergic neurons and fibers on sections from rat and primate brain. With the help of nine synthetic peptides it was possible to evaluate two major binding sites for the monoclonal antibodies on the ChAT molecule, comprising amino acids 167-189 and 57-76, respectively.

Peroxisomal and mitochondrial carnitine acetyltransferases of the n-alkane-assimilating yeast Candida Tropicalis. Analysis of gene structure and translation products

A genomic DNA clone encoding carnitine acetyltransferases (EC 2.3.1.7), localized in two subcellular organelles, peroxisomes and mitochondria of an n-alkane-assimilating yeast Candida tropicalis, was isolated from the yeast lambda EMBL library using a carnitine acetyltransferase CDNA probe. Nucleotide sequence analysis disclosed that the open reading frame was 1881 bp, corresponding to 627 amino acids with a molecular mass of 70760 Da. Comparison of the predicted amino acid sequence of the C. tropicalis enzyme with that of Saccharomyces cerevisiae mitochondrial matrix carnitine acetyltransferase revealed 46.3% identity. It was noticeable that the C. tropicalis enzymes had amino acid sequences similar to both proposed mitochondrial and peroxisomal targeting signals. When the C. tropicalis gene was expressed in S. cerevisiae using its own 5'-upstream region, a 12-fold increase in activity was observed. Western blot analysis revealed the presence of two major proteins whose sizes corresponded to the peroxisomal and mitochondrial proteins detected in C. tropicalis. This suggested that peroxisomal and mitochondrial carnitine acetyltransferases were encoded by one gene, as suggested for the S. cerevisiae enzyme. Furthermore, we have separated and purified these enzymes from peroxisomes and mitochondria of C. tropicalis, and analyzed the amino-terminal amino acid sequences of each. The amino-terminal sequence of the mitochondrial enzyme suggested that a signal sequence had been cleaved during translocation into mitochondria. Concerning the peroxisomal enzyme, the evidence obtained indicated that in vivo the translation was initiated at the second methionine of the open reading frame.

Identification of an active site arginine in rat choline acetyltransferase by alanine scanning mutagenesis

Kinetic as well as chemical modification studies have implicated the presence of an active site arginine in choline acetyltransferase, whose function is to stabilize coenzyme binding by interacting with the 3'-phosphate of the coenzyme A substrate. In order to identify this residue seven conserved arginines in rat choline acetyltransferase were converted to alanine by site-directed mutagenesis, and the properties of these mutants were compared with the wild type enzyme. Substitution of arginine 452 with alanine resulted in a 7-12-fold increase in the Km for both CoA and acetylcholine as well as kcat, with little change in the Km for dephospho-CoA. Product inhibition studies showed choline to be a competitive inhibitor with respect to acetylcholine, indicating R452A follows the same Theorell-Chance kinetic mechanism as the wild type enzyme. Similar results were obtained with R452Q and R452E, with the latter showing the largest changes in kinetic parameters. These findings are consistent with Arg-452 mutations increasing the rate constant, k5, for dissociation of the coenzyme from the enzyme. Direct evidence that arginine 452 is involved in coenzyme A binding was obtained by showing a 5-10-fold decrease in affinity of the R452A mutant for coenzyme A as determined by the ability to protect against phenylglyoxal inactivation as well as thermal inactivation.

Human choline acetyltransferase gene: localization of alternative first exons

Two overlapping cosmids containing the 5' end of human choline acetyltransferase (ChAT) gene have been cloned. Using heterologous probes, we localized two alternative first exons homologous to rodent ChAT exons R and M (Misawa et al.: J Biol Chem 267:20392-20399, 1992). The sequence of rodent exon N was not conserved in the human gene. Northern blot analysis of mRNA purified from the human neuroepithelioma cell lines LA-N2 and MC-I-XC revealed that both exons R and M were transcribed in mRNA species of 6.0 and 2.5 kb. Only the 6-kb species was detected with both R- and M-specific probes in the neuroepithelioma cell line CHP126. Reverse transcription-polymerase chain reaction (RT-PCR) analysis suggested that the major mRNA species in MC-I-XC and CHP126 cells contained the proximal part of exon M spliced to exon 1, which contains the alternative ACG initiation codon. RT-PCR also allowed the characterization of a mRNA species containing exon R spliced to exon 1, but no species containing both exon R and the distal part of exon M could be detected. RT-PCR was also used to evidence an alternative exon (tentatively numbered exon 8) in the coding sequence.

Positive and negative effects of nuclear receptors on transcription activation by AP-1 of the human choline acetyltransferase proximal promoter

We have examined the 5'-flanking region (944 bp) of the human choline acetyltransferase (hChAT) gene for sequences that modulate its transcriptional activity and identified a sequence 5'-TGACCCA-3' which confers c-Jun/c-Fos (AP-1) inducibility of homologous and heterologous promoters. Using transient transfections in neuroblastoma NE-1-115 and COS-1 cells, we show that ligand-activated estrogen receptor (HEGo) represses the transcriptional activation by c-Fos/c-Jun. Testing HEGo mutants in transfection assays reveals that the ligand-binding domain is crucial for this repression, whereas the N-terminal (A/B) region and the DNA-binding domain are not essential. Gel retardation assays show that the hChAT AP-1 recognition sequence binds in vitro baculovirus-produced c-Jun/c-Fos proteins. This binding is inhibited by addition of baculovirus-produced HEGo. In contrast to HEGo, ligand-activated glucocorticoid, androgen, and retinoic acid receptors (RARs) enhance the transcription activation induced by c-Jun/c-Fos. All three types of RARs--RAR alpha, beta, gamma--and RXR alpha are able to stimulate AP-1 activity on the proximal hChAT promoter. Several mechanism possibilities involving protein-protein interaction are discussed to explain the phenomena.

Choline acetyltransferase: celebrating its fiftieth year

It is well known that the regulation of choline acetyltransferase (ChAT) activity under physiological and pathological conditions is important for the development and neuronal activities of cholinergic systems involved in many fundamental brain functions. This review focuses on recent progress in understanding the regulation of ChAT at the levels of both the protein and the mRNA. A deficiency in ChAT activity has been reported for neurodegenerative conditions such as Alzheimer's disease, amyotrophic lateral sclerosis, and schizophrenia. Although a major feature of ChAT regulation is likely to involve the spatial and temporal control of transcription, regulation of expression can also be at the level of RNA processing, transport/translocation, turnover, or translation. In addition, there is increasing evidence that ChAT might be regulated at the posttranslational level by compartmentation and/or covalent modification, i.e., phosphorylation, as well as noncovalent modification (protein-protein interaction, etc.). Synaptic activity and the state of neuronal transmission may also involve the regulation of ChAT at different levels via both positive and negative feedback loops, as was demonstrated in the characterization of two ChAT mutant Drosophila strains. Clearly, identification of cholinergic-specific elements and the characterization of the trans-acting factors that bind to them represent an important area of future research. Equally important is research on the mechanisms governing ChAT as an enzymatic entity. The future should be an exciting time during which we look forward to the elucidation of the cholinergic signal and its regulation as well as the determination of the three-dimensional structure of the enzyme.

Phosphorylation of rat brain choline acetyltransferase and its relationship to enzyme activity

Choline acetyltransferase catalyzes the formation of acetylcholine from choline and acetyl-CoA in cholinergic neurons. The present study examined conditions for modulation of kinase-mediated phosphorylation of this enzyme. By using a monospecific polyclonal rabbit anti-human choline acetyltransferase antibody to immunoprecipitate cytosolic and membrane-associated subcellular pools of enzyme from rat hippocampal synaptosomes, we determined that only the cytosolic fraction of the enzyme (67,000 +/- 730 daltons) was phosphorylated under basal, unstimulated conditions. The quantity of this endogenous phosphoprotein was dependent, in part, upon the level of intracellular calcium, with 32Pi incorporation into the enzyme in nerve terminals incubated in nominally calcium-free medium only 43 +/- 7% of control. The corresponding enzymatic activity of cytosolic choline acetyltransferase did not appear to be altered by lowered cytosolic calcium, whereas membrane-associated choline acetyltransferase activity was decreased to 58 +/- 11% of control. Depolarization of synaptosomes with 50 microM veratridine neither altered the extent of phosphorylation or specific activity of cytosolic choline acetyltransferase, nor induced detectable phosphorylation of membrane-associated choline acetyltransferase, although the specific activity of the membrane-associated enzyme was increased to 132 +/- 5% of control. In summary, phosphorylation of choline acetyltransferase does not appear to regulate cholinergic neurotransmission by a direct action on catalytic activity of the enzyme.

Expression, purification, and characterization of recombinant Drosophila choline acetyltransferase

A cDNA for Drosophila choline acetyltransferase (EC 2.3.1.6; ChAT) was fused with a polyhistidine sequence and expressed in Escherichia coli. The recombinant enzyme was purified to a specific activity of 500 mumol/min/mg of protein using metal affinity chromatography and ion exchange chromatography. Kinetic properties of the recombinant enzyme did not differ significantly from those previously determined. Circular dichroism (CD) spectra revealed that the secondary structure of the enzyme is largely alpha-helical. Intrinsic fluorescence spectra of the enzyme indicate that its tryptophan residues are buried. Neither CD nor fluorescence spectra changed significantly in the presence of substrates. The cysteine content of the recombinant Drosophila ChAT was determined to be 16 in the absence and 22 in the presence of 6 M guanidine hydrochloride. Finally, crystallization of recombinant Drosophila ChAT was achieved.

Antibodies raised against synthetic peptides react with choline acetyltransferase in various immunoassays and in immunohistochemistry

Antisera were raised in rabbits against five synthetic peptides. These peptides have been identified as potentially antigenic epitopes from the sequence of porcine choline acetyltransferase (ChAT) using primary and secondary structure analysis. All five antisera recognized immunoaffinity-purified antigen from porcine brain in an ELISA and on western blots. Four antisera recognized ChAT on dot blots, and another four antisera reacted with native and degraded enzyme in a sandwich ELISA using monoclonal antibodies as the capture antibody. One peptide antiserum was of similar avidity in this sandwich ELISA as a polyclonal antibody raised against immunoaffinity-purified ChAT. The same antiserum reacted with the enzyme from human placenta in an ELISA and on western and dot blots and recognized ChAT in rat, primate, and human neurons. Thus, a single peptide (amino acids 168-189) provides the means for easy, reliable, and reproducible generation of antibodies against ChAT suitable for replacing conventional polyclonal and monoclonal antibodies.

Comparison of the promoter region of the human and porcine choline acetyltransferase genes: localization of an important enhancer region

Genomic clones of human and porcine choline acetyltransferase were obtained by screening genomic libraries with synthetic oligonucleotides. The human and porcine genes exhibit significant conservation of both their intron/exon structure and the nucleotide sequence in their 5' flanking regions. However, the two genes differ in several respects, including the absence of a "TATA" box in the human gene and differences in the position of the methionine start codon. Analysis of the promoter region of the two genes has led to the localization of an enhancer element that appears necessary for efficient transcription of the gene.

Functional analysis of conserved histidines in choline acetyltransferase by site-directed mutagenesis

The choline acetyltransferase (ChAT) reaction involves the transfer of the acetyl group of acetyl-CoA to choline, in which an active site histidine is believed to act as a general acid/base catalyst. A comparison of the deduced amino acid sequences of the enzyme from Drosophila, pig, rat, and Caernohabditis elegans revealed three conserved histidines: Drosophila His268, His393, and His426. Each of these histidines was replaced by a leucine and a glutamine, and the kinetic properties of each of the recombinant mutant enzymes were determined. The mutations yielded active His268Leu-ChAT, His268Gln-ChAT, and His393Gln-ChAT and inactive His393Leu-ChAT, His426Leu-ChAT, and His426Gln-ChAT. The kinetic constants Km(CoA), Km(acetylcholine), and Vmax were essentially the same for all of the active mutants. When the integrity of the CoASAc binding site was investigated in the inactive mutants, the data suggested that the binding site in His393Leu-ChAT is disrupted but conserved in His426Leu-ChAT and His426Gln-ChAT. These results suggest that His426 is an essential catalytic residue and could serve as an acid/base catalyst.

Molecular genetics of aminoglycoside resistance genes and familial relationships of the aminoglycoside-modifying enzymes

The three classes of enzymes which inactivate aminoglycosides and lead to bacterial resistance are reviewed. DNA hybridization studies have shown that different genes can encode aminoglycoside-modifying enzymes with identical resistance profiles. Comparisons of the amino acid sequences of 49 aminoglycoside-modifying enzymes have revealed new insights into the evolution and relatedness of these proteins. A preliminary assessment of the amino acids which may be important in binding aminoglycosides was obtained from these data and from the results of mutational analysis of several of the genes encoding aminoglycoside-modifying enzymes. Recent studies have demonstrated that aminoglycoside resistance can emerge as a result of alterations in the regulation of normally quiescent cellular genes or as a result of acquiring genes which may have originated from aminoglycoside-producing organisms or from other resistant organisms. Dissemination of these genes is aided by a variety of genetic elements including integrons, transposons, and broad-host-range plasmids. As knowledge of the molecular structure of these enzymes increases, progress can be made in our understanding of how resistance to new aminoglycosides emerges.

Acetylcholine transport, storage, and release

ACh is released from cholinergic nerve terminals under both resting and stimulated conditions. Stimulated release is mediated by exocytosis of synaptic vesicle contents. The structure and function of cholinergic vesicles are becoming known. The concentration of ACh in vesicles is about 100-fold greater than the concentration in the cytoplasm. The AChT exhibits the lowest binding specificity among known ACh-binding proteins. It is driven by efflux of protons pumped into the vesicle by the V-type ATPase. A potent pharmacology of the AChT based on the allosteric VR has been developed. It has promise for clinical applications that include in vivo evaluation of the density of cholinergic innervation in organs based on PET and SPECT. The microscopic kinetics model that has been developed and the very low transport specificity of the vesicular AChT-VR suggest that the transporter has a channel-like or multidrug resistance protein-like structure. The AChT-VR has been shown to be tightly associated with proteoglycan, which is an unexpected macromolecular relationship. Vesamicol and its analogs block evoked release of ACh from cholinergic nerve terminals after a lag period that depends on the rate of release. Recycling quanta of ACh that are sensitive to vesamicol have been identified electrophysiologically, and they constitute a functional correlate of the biochemically identified VP2 synaptic vesicles. The concept of transmitter mobilization, including the observation that the most recently synthesized ACh is the first to be released, has been greatly clarified because of the availability of vesamicol. Differences among different cholinergic nerve terminal types in the sensitivity to vesamicol, the relative amounts of readily and less releasable ACh, and other aspects of the intracellular metabolism of ACh probably are more apparent than real. They easily could arise from differences in the relative rates of competing or sequential steps in the complicated intraterminal metabolism of ACh rather than from fundamental differences among the terminals. Nonquantal release of ACh from motor nerve terminals arises at least in part from the movement of cytoplasmic ACh through the AChT located in the cytoplasmic membrane, and it is blocked by vesamicol. Possibly, the proteoglycan component of the AChT-VR produces long-term residence of the macromolecular complex in the cytoplasmic membrane through interaction with the synaptic matrix. The preponderance of evidence suggests that a significant fraction of what previously, heretofore, had been considered to be nonquantal release from the motor neuron actually is quantal release from the neuron at sites not detected electrophysiologically.(ABSTRACT TRUNCATED AT 400 WORDS)

Enhanced acetylcholine secretion in neuroblastoma x glioma hybrid NG108-15 cells transfected with rat choline acetyltransferase cDNA

Neuroblastoma x glioma hybrid NG108-15 cells and mouse neuroblastoma N18TG-2 and N1E-115 cells were transiently transfected with the sense cDNA coding for rat choline acetyltransferase (ChAT). All transfected cell lines showed a high level of ChAT activity. ACh secretion was monitored by recording miniature end-plate potentials (MEPPs) in striated muscle cells that had been co-cultured with transfected cells. The number of muscle cells with synaptic responses and the MEPP frequency were higher in co-culture with transfected NG108-15 cells than with control or mock cells. No synaptic response was detected in muscle cells co-cultured with transfected N18TG-2 or N1E-115 cells. The results show that ACh secretion into the synaptic cleft was enhanced due to ChAT overexpression in NG108-15 hybrid cells but not in neuroblastoma cells.

Decreased choline acetyltransferase mRNA expression in the nucleus basalis of Meynert in Alzheimer disease: an in situ hybridization study

The subnormal choline acetyltransferase (ChoAcTase) activity in the cerebral cortex of patients with Alzheimer disease (AD) is thought to originate from the loss of cholinergic neurons in the nucleus basalis of Meynert (nbM). To examine possible changes in the functional activity of the remaining cholinergic neurons in the nbM of patients with AD, the level of expression of ChoAcTase mRNA was evaluated. A procedure for double-labeling cholinergic neurons to detect ChoAcTase mRNA and the corresponding protein in the same cell was developed, taking advantage of an anti-ChoAcTase antibody and the recently isolated cDNA complementary to a sequence of the human ChoAcTase mRNA. In the study of three controls and four patients with AD, the presence of both ChoAcTase mRNA and protein was observed in the same large neurons in both nbM and putamen. Specificity of in situ hybridization was further supported by the absence of neuronal staining with a sense probe. In AD patients a subnormal level of expression of ChoAcTase mRNA per cholinergic cell was detected in the nbM but not in the putamen. Our data support the hypothesis that expression of ChoAcTase mRNA might be down-regulated in the surviving cholinergic neurons in the nbM of patients with AD, raising the possibility of functional restoration by stimulating ChoAcTase synthesis.

Two mRNAs are transcribed from the human gene for choline acetyltransferase

The product of the choline acetyltransferase (ChAT) gene is the enzyme that synthesizes the neurotransmitter acetylcholine. A 14.4-kb portion of the human ChAT gene contains 7 exons, which are estimated to comprise approximately one-third of the human protein coding sequence by comparison with porcine ChAT mRNA. Two of the exons were used to identify polyadenylated human ChAT gene transcripts on Northern blots. An exon with 84% identity to the region of porcine ChAT mRNA that codes for the amino terminus of the corresponding protein detected 6,000- and 2,300-nucleotide mRNAs in RNA isolated from human CHP134 neuroblastoma cells. Only the 2,300-nucleotide mRNA was detected by a second probe containing an exon with 96% identity to porcine ChAT mRNA in the domain that encodes amino acids 204-263 of the predicted porcine ChAT protein. Further evidence that two species of human mRNA are produced from the human ChAT gene was obtained from nuclease protection assays using an antisense RNA probe prepared from a human ChAT cDNA clone. Total RNA isolated from either CHP134 cells or adult human nucleus basalis protected 525- and 400-nucleotide fragments of this probe, confirming the presence of two species of RNA that differ by the inclusion of an internal exon. cDNA clones of each of these transcripts have been isolated. Their sequences suggest that the 2,300-nucleotide mRNA encodes enzymatically active human ChAT, while translation of the 6,000-nucleotide mRNA would be terminated prematurely by a shift in the reading frame. These results indicate that a complex pattern of transcription produces two mRNAs with different coding potentials from the human ChAT gene.

Choline acetyltransferase expression studied with an oligonucleotide probe

1. The localization of choline acetyltransferase messenger RNA has been studied using a digoxigenin-tailed complementary oligodeoxynucleotide probe for in situ hybridization. 2. Putative cholinergic cells of the rat and ferret spinal cord and the ferret retina were labeled. 3. This technique affords superior resolution compared to radioactively labeled probes, with apparently equal sensitivity.

Effects of choline and quiescence on Drosophila choline acetyltransferase expression and acetylcholine production by transduced rat fibroblasts

Rat-1 fibroblasts were transduced to express Drosophila choline acetyltransferase. The presence of an active enzyme in these cells (Rat-1/dChAT) was confirmed using various methods. Rat-1/dChAT fibroblasts released acetylcholine (ACh) into the culture medium. Moreover, intra- and extracellular levels of ACh could be increased by adding exogenous choline chloride. In addition, serum starvation or confluence-induced quiescence caused an 80% decrease in recombinant choline acetyltransferase activity (compared with actively growing cells). ACh release was also repressed in quiescent fibroblast cultures. Exogenous choline could mitigate the decrease in ACh release. These results indicate that Rat-1 fibroblasts can be genetically modified to produce ACh and that ACh release can be controlled by introducing choline into the culture medium. Furthermore, these data demonstrate that the expression of the retroviral promoter used in this study decreases with the onset of quiescence; however, exogenous choline can increase the amount of ACh released by quiescent fibroblasts.

Cloning of the rat gene encoding choline acetyltransferase, a cholinergic neuron-specific marker

The neurotransmitter acetylcholine is synthesized by choline acetyltransferase (ChAT; EC 2.3.1.6). Since the expression of ChAT in the nervous system is restricted to cholinergic neurons, it serves as a specific marker for these neurons. In Alzheimer disease, ChAT activity is markedly reduced in the affected brain areas. Nerve growth factor can increase the ChAT activity of brain cholinergic neurons in vitro and in vivo. We have cloned the rat ChAT gene and identified one 5' noncoding exon and 14 exons that account for the entire coding sequence. The exon organization is compared with the protein domains conserved during evolution. These exons are distributed over at least 64 kilobases in the rat genome; the largest intron is at least 14 kilobases long. Within a 0.7-kilobase region immediately upstream of the confirmed sequence of the noncoding exon, TATA-like elements and numerous potential binding sites for transcription factors are found, including AP-1, Sp1, octamer-binding factor(s), CTF/NF-1, and the nuclear oncoprotein Myb.

High-level synthesis and fate of acetylcholine in baculovirus-infected cells: characterization and purification of recombinant rat choline acetyltransferase

Rat choline acetyltransferase (ChAT) has been expressed at a high level in Spodoptera frugiperda Sf9 cells using a baculovirus expression system. A cDNA containing the coding sequence for ChAT was inserted into the transfer vector pAcYM1 to yield the recombinant vector pAcYM1/ChAT. Sf9 cells were then coinfected with pAcYM1/ChAT and the wild-type Autographa californica virus. One recombinant virus particle, containing the cDNA for ChAT, was selected that expressed a protein of 68.5 kDa. Forty hours after infection of cells with the recombinant virus, the specific activity of ChAT in the cytosol was 190 nmol of acetylcholine/min/mg of protein, accounting for approximately 24% of the cell cytosolic proteins as being ChAT. The apparent Km values of the enzyme for choline and acetyl-CoA were 299 and 221 microM, respectively, whereas the respective Vmax values were 10.6 and 11.4 mumol of acetylcholine/min/mg of protein. In addition, analysis of the protein revealed that ChAT is phosphorylated in Sf9 cells. About 0.5 mg of ChAT was obtained from a one-step purification procedure starting with 10(8) infected Sf9 cells. Addition of choline to the incubation medium led to accumulation of high amounts of acetylcholine in the cytosol of the infected cells. The neurotransmitter was not released by Sf9 cells in response to membrane depolarization or on ionophore-mediated calcium entry. Some acetylcholine, which most likely originated from cell death inherent to viral infection, accumulated in the culture medium. The infected insect cells, which synthesize and store neurotransmitter, provide a new and convenient model for analyzing synaptic transmission at the molecular level.

Genomic organization of Drosophila choline acetyltransferase

Choline acetyltransferase (ChAT; acetyl-CoA:choline-O-acetyltransferase; EC 2.3.1.6) is the enzyme responsible for the synthesis of the neurotransmitter acetylcholine and is thus the genetic determinant of neurons with a cholinergic phenotype. We have screened a Drosophila genomic library using a cRNA probe, transcribed from Drosophila ChAT cDNA, and isolated three independent clones representing all the exons of this gene. The gene spans more than 26 kb of DNA and is organized into eight exons containing 594, 80, 192, 759, 408, 147, 201, and 1,612 nucleotides. All inserts that hybridized with a cRNA probe have been subcloned and the sequence of intron/exon boundaries determined. The only part of the ChAT gene not represented in our clones is a part of the first intron. A minimum size for this uncloned DNA has been deduced from Southern analysis of Drosophila genomic DNA. We also have probed the transcripts of the ChAT gene by northern analysis of total Drosophila RNA using two different exon-specific antisense RNA probes. An exon I probe detected two bands of RNA whereas an exon VIII probe hybridized with only the smaller band, previously identified as ChAT mRNA. These results indicate a complex transcription pattern for the ChAT locus in Drosophila.

Recombinant cholinergic differentiation factor (leukemia inhibitory factor) regulates sympathetic neuron phenotype by alterations in the size and amounts of neuropeptide mRNAs

The cholinergic differentiation factor (CDF) in heart cells is identical to leukemia inhibitory factor (LIF). Recombinant CDF/LIF was shown to alter dramatically neurotransmitter production as well as the levels of several neuropeptides in cultured rat sympathetic neurons. Here it is shown that these changes are likely to be caused by alterations in the mRNA for these proteins and peptides. Growth in 1 nM recombinant CDF/LIF induces mRNA for acetyl CoA: choline-O-acetyltransferase [EC 2.3.1.6; choline acetyltransferase (ChAT)], somatostatin (SOM), substance P, and vasoactive intestinal polypeptide while lowering mRNA levels of tyrosine hydroxylase (EC 1.14.16.2) and neuropeptide Y (NPY). In addition, the sizes of the mRNAs for ChAT, SOM, and NPY are larger after recombinant CDF/LIF treatment.

Developmental and regional expression of choline acetyltransferase mRNA in the rat central nervous system

The developmental and regional expression of choline acetyltransferase (ChAT) mRNA was examined in the rat brain and spinal cord by northern blot analysis and in situ hybridization. ChAT mRNA expression in the brain showed a biphasic increase during development, with a first peak at two weeks postnatally, a marked decrease by the third week, and a second increase between the third and fifth week after birth, indicating that emergence of the cholinergic phenotype occurs at different times in different brain regions. In the spinal cord, ChAT mRNA was detected at similar levels from embryonic stage 13 (E13) until birth, increasing thereafter until adulthood. In the adult rat central nervous system, high levels of ChAT mRNA were detected in the spinal cord and brain stem structures. Lower levels were seen in midbrain, septum, striatum, thalamus, and olfactory bulb. ChAT mRNA containing cells were identified by in situ hybridization in the olfactory tubercule, piriform cortex, striatum, several basal forebrain nuclei, and spinal cord. A nearly two-fold increase in adult spinal cord ChAT mRNA levels were seen one week after a bilateral crush lesion of the sciatic nerve, indicating that ChAT mRNA expression is regulated during motoneuron regeneration.