Increased CSF DOPA Decarboxylase Correlates with Lower DaT-SPECT Binding: Analyses in Biopark and PPMI Cohorts.

BACKGROUND: Recent studies identified increased cerebrospinal fluid (CSF) DOPA decarboxylase (DDC) as a promising biomarker for parkinsonian disorders, suggesting a compensation to dying dopaminergic neurons. A correlation with 123I-FP-CIT-SPECT (DaT-SPECT) imaging could shed light on this link. OBJECTIVE: The objective is to assess the relationship between CSF DDC levels and DaT-SPECT binding values. METHODS: A total of 51 and 72 Parkinson's disease (PD) subjects with available DaT-SPECT and CSF DDC levels were selected from the PPMI and Biopark cohorts, respectively. DDC levels were analyzed using proximity extension assay and correlated with DaT-SPECT striatal binding ratios (SBR). All analyses were corrected for age and sex. RESULTS: CSF DDC levels in PD patients correlated negatively with DaT-SPECT SBR in both putamen and caudate nucleus. Additionally, SBR decreased with increased DDC levels over time in PD patients. CONCLUSION: CSF DDC levels negatively correlate with DaT-SPECT SBR in levodopa-treated PD. © 2024 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Systematic-Narrative Hybrid Literature Review: Crosstalk between Gastrointestinal Renin-Angiotensin and Dopaminergic Systems in the Regulation of Intestinal Permeability by Tight Junctions.

In the first part of this article, the role of intestinal epithelial tight junctions (TJs), together with gastrointestinal dopaminergic and renin-angiotensin systems, are narratively reviewed to provide sufficient background. In the second part, the current experimental data on the interplay between gastrointestinal (GI) dopaminergic and renin-angiotensin systems in the regulation of intestinal epithelial permeability are reviewed in a systematic manner using the PRISMA methodology. Experimental data confirmed the copresence of DOPA decarboxylase (DDC) and angiotensin converting enzyme 2 (ACE2) in human and rodent enterocytes. The intestinal barrier structure and integrity can be altered by angiotensin (1-7) and dopamine (DA). Both renin-angiotensin and dopaminergic systems influence intestinal Na+/K+-ATPase activity, thus maintaining electrolyte and nutritional homeostasis. The colocalization of B0AT1 and ACE2 indicates the direct role of the renin-angiotensin system in amino acid absorption. Yet, more studies are needed to thoroughly define the structural and functional interaction between TJ-associated proteins and GI renin-angiotensin and dopaminergic systems.

Expression of Human L-Dopa Decarboxylase (DDC) under Conditions of Oxidative Stress.

Oxidative stress is known to influence mRNA levels, translation, and proteolysis. The importance of oxidative stress has been demonstrated in several human diseases, including neurodegenerative disorders. L-Dopa decarboxylase (DDC) is the enzyme that converts L-Dopa to dopamine (DA). In spite of a large number of studies, little is known about the biological significance of the enzyme under physiological and pathological conditions. Here, we investigated the relationship between DDC expression and oxidative stress in human neural and non-neural cells. Oxidative stress was induced by treatment with H2O2. Our data indicated that mRNA and protein expression of DDC was enhanced or remained stable under conditions of ROS induction, despite degradation of total RNA and increased cytotoxicity and apoptosis. Moreover, DDC silencing caused an increase in the H2O2-induced cytotoxicity. The current study suggests that DDC is involved in the mechanisms of oxidative stress.

DDC-Promoter-Driven Chemogenetic Activation of SNpc Dopaminergic Neurons Alleviates Parkinsonian Motor Symptoms.

Parkinson's disease (PD) is a neurodegenerative disorder with typical motor symptoms. Recent studies have suggested that excessive GABA from reactive astrocytes tonically inhibits dopaminergic neurons and reduces the expression of tyrosine hydroxylase (TH), the key dopamine-synthesizing enzyme, in the substantia nigra pars compacta (SNpc). However, the expression of DOPA decarboxylase (DDC), another dopamine-synthesizing enzyme, is relatively spared, raising a possibility that the live but non-functional TH-negative/DDC-positive neurons could be the therapeutic target for rescuing PD motor symptoms. However, due to the absence of a validated DDC-specific promoter, manipulating DDC-positive neuronal activity has not been tested as a therapeutic strategy for PD. Here, we developed an AAV vector expressing mCherry under rat DDC promoter (AAV-rDDC-mCherry) and validated the specificity in the rat SNpc. Modifying this vector, we expressed hM3Dq (Gq-DREADD) under DDC promoter in the SNpc and ex vivo electrophysiologically validated the functionality. In the A53T-mutated alpha-synuclein overexpression model of PD, the chemogenetic activation of DDC-positive neurons in the SNpc significantly alleviated the parkinsonian motor symptoms and rescued the nigrostriatal TH expression. Altogether, our DDC-promoter will allow dopaminergic neuron-specific gene delivery in rodents. Furthermore, we propose that the activation of dormant dopaminergic neurons could be a potential therapeutic strategy for PD.

Brief sensory deprivation triggers plasticity of dopamine-synthesising enzyme expression in genetically labelled olfactory bulb dopaminergic neurons.

In the glomerular layer of the olfactory bulb, local dopaminergic interneurons play a key role in regulating the flow of sensory information from nose to cortex. These dual dopamine- and GABA-releasing cells are capable of marked experience-dependent changes in the expression of neurotransmitter-synthesising enzymes, including tyrosine hydroxylase (TH). However, such plasticity has most commonly been studied in cell populations identified by their expression of the enzyme being studied and after long periods of sensory deprivation. Here, instead, we used brief 1- or 3-day manipulations of olfactory experience in juvenile mice, coupled with a conditional genetic approach that labelled neurons contingent upon their expression of the dopamine transporter (DAT-tdTomato). This enabled us to evaluate the potential for rapid changes in neurotransmitter-synthesising enzyme expression in an independently identified neuronal population. Our labelling strategy showed good specificity for olfactory bulb dopaminergic neurons, while revealing a minority sub-population of non-dopaminergic DAT-tdTomato cells that expressed the calcium-binding protein calretinin. Crucially, the proportions of these neuronal subtypes were not affected by brief alterations in sensory experience. Short-term olfactory manipulations also produced no significant changes in immunofluorescence or whole-bulb mRNA for the GABA-synthesising enzyme GAD67/Gad1. However, in bulbar DAT-tdTomato neurons, brief sensory deprivation was accompanied by a transient, small drop in immunofluorescence for the dopamine-synthesising enzyme dopa decarboxylase (DDC) and a sustained decrease for TH. Deprivation also produced a sustained decrease in whole-bulb Th mRNA. Careful characterisation of an independently identified, genetically labelled neuronal population therefore enabled us to uncover rapid experience-dependent changes in dopamine-synthesising enzyme expression.

Spectrum of DDC variants causing aromatic l-amino acid decarboxylase (AADC) deficiency and pathogenicity interpretation using ACMG-AMP/ACGS recommendations.

Pathogenic variants in dopa decarboxylase (DDC), the gene encoding the aromatic l-amino acid decarboxylase (AADC) enzyme, lead to a severe deficiency of neurotransmitters, resulting in neurological, neuromuscular, and behavioral manifestations clinically characterized by developmental delays, oculogyric crises, dystonia, and severe neurologic dysfunction in infancy. Historically, therapy has been aimed at compensating for neurotransmitter abnormalities, but response to pharmacologic therapy varies, and in most cases, the therapy shows little or no benefit. A novel human DDC gene therapy was recently approved in the European Union that targets the underlying genetic cause of the disorder, providing a new treatment option for patients with AADC deficiency. However, the applicability of human DDC gene therapy depends on the ability of laboratories and clinicians to interpret the results of genetic testing accurately enough to diagnose the patient. An accurate interpretation of genetic variants depends in turn on expert-guided curation of locus-specific databases. The purpose of this research was to identify previously uncharacterized DDC variants that are of pathologic significance in AADC deficiency as well as characterize and curate variants of unknown significance (VUSs) to further advance the diagnostic accuracy of genetic testing for this condition. DDC variants were identified using existing databases and the literature. The pathogenicity of the variants was classified using modified American College of Medical Genetics and Genomics/Association for Molecular Pathology/Association for Clinical Genomic Science (ACMG-AMP/ACGS) criteria. To improve the current variant interpretation recommendations, in silico variant interpretation tools were combined with structural 3D modeling of protein variants and applied comparative analysis to predict the impact of the variant on protein function. A total of 422 variants were identified (http://biopku.org/home/pnddb.asp). Variants were identified on nearly all introns and exons of the DDC gene, as well as the 3' and 5' untranslated regions. The largest percentage of the identified variants (48%) were classified as missense variants. The molecular effects of these missense variants were then predicted, and the pathogenicity of each was classified using a number of variant effect predictors. Using ACMG-AMP/ACGS criteria, 7% of variants were classified as pathogenic, 32% as likely pathogenic, 58% as VUSs of varying subclassifications, 1% as likely benign, and 1% as benign. For 101 out of 108 reported genotypes, at least one allele was classified as pathogenic or likely pathogenic. In silico variant pathogenicity interpretation tools, combined with structural 3D modeling of variant proteins and applied comparative analysis, have improved the current DDC variant interpretation recommendations, particularly of VUSs.

Is sleep bruxism related to the levels of enzymes involved in the serotonin synthesis pathway?

OBJECTIVES: This exploratory research aimed to evaluate the levels of tryptophan hydroxylase 1 (TPH1) and aromatic l-amino acid decarboxylase (DDC), which play an important role in the serotonin synthesis pathway, in individuals with sleep bruxism (SB) diagnosed using audio-video polysomnography (vPSG) and compare them with that of individuals not presenting with SB. MATERIALS AND METHODS: The study included adult patients hospitalized in the Department and Clinic of Internal Medicine, Occupational Diseases, Hypertension and Clinical Oncology at the Wroclaw Medical University. The participants underwent a single-night vPSG for the evaluation of the SB parameters. Peripheral blood samples were also collected from them for estimating the serum levels of TPH1 and DDC. RESULTS: A total of 105 patients (80 women and 25 men) were included in the study. All the patients were Caucasians and aged 18-63 years (mean age: 33.43 ± 10.8 years). Seventy-five patients (71.43%) presented with SB, of which 50 (47.62%) had severe SB, while the remaining 30 patients (28.57%) did not. No statistically significant differences in TPH1 and DDC levels were observed between the individuals with SB and without SB. A significant negative correlation was found between tonic SB episodes and DDC levels (p = 0.0012). Other correlations between the SB parameters and the levels of the studied enzymes were statistically insignificant (p > 0.05 for all comparisons). CONCLUSIONS: The levels of the enzymes that are crucial for serotonin synthesis (TPH1 and DDC) did not seem to influence SB. CLINICAL RELEVANCE: This study provides important insights for further research on the relationship between the serotonin pathway and SB, which should take into account not only the process of serotonin synthesis but also the effect of serotonin-dependent neurotransmission on SB.

Melanin Synthesis Pathway Interruption: CRISPR/Cas9-mediated Knockout of dopa decarboxylase (DDC) in Harmonia axyridis (Coleoptera: Coccinellidae).

CRISPR/Cas9 technology is a very powerful genome editing tool and has been used in many insect species for functional genomics studies through targeted gene mutagenesis. Here, we successfully established CRISPR/Cas9 research platform in Asian multi-colored ladybird beetle, Harmonia axyridis, an important natural enemy in biological control. In this study, one pivotal gene dopa decarboxylase (DDC) in melanin synthesis was targeted by CRISPR/Cas9 to generate mutants in H. axyridis by CRISPR/Cas9 technology. Our results showed that injection of single guide RNA of the DDC and Cas9 protein into preblastoderm eggs induced one insertion and four deletion (indels) mutant H. axyridis. Mutations of HaDDC gene generated 25% mutant rate with melanin missing phenotype in larva, pupa,l and adult stage. The predation ability of the fourth instar larvae has no significant difference between wild (control) and mutant H. axyridis (G0), while these mutant fourth instar larvae had longer developmental period than that of the wild type. Consequently, the total predation of the fourth instar larvae was significantly increased in H. axyridis mutants comparing with the wild type. These results indicated that the success of CRISPR/Cas9 gene editing in H. axyridis. The gene editing platform in H. axyridis would facilitate the gene function research and promote special strain of predatory ladybird beetle generation.

Elucidating the Interaction between Pyridoxine 5'-Phosphate Oxidase and Dopa Decarboxylase: Activation of B6-Dependent Enzyme.

Pyridoxal 5'-phosphate (PLP), the active form of vitamin B6, serves as a cofactor for scores of B6-dependent (PLP-dependent) enzymes involved in many cellular processes. One such B6 enzyme is dopa decarboxylase (DDC), which is required for the biosynthesis of key neurotransmitters, e.g., dopamine and serotonin. PLP-dependent enzymes are biosynthesized as apo-B6 enzymes and then converted to the catalytically active holo-B6 enzymes by Schiff base formation between the aldehyde of PLP and an active site lysine of the protein. In eukaryotes, PLP is made available to the B6 enzymes through the activity of the B6-salvage enzymes, pyridoxine 5'-phosphate oxidase (PNPO) and pyridoxal kinase (PLK). To minimize toxicity, the cell keeps the content of free PLP (unbound) very low through dephosphorylation and PLP feedback inhibition of PNPO and PLK. This has led to a proposed mechanism of complex formation between the B6-salvage enzymes and apo-B6 enzymes prior to the transfer of PLP, although such complexes are yet to be characterized at the atomic level, presumably due to their transient nature. A computational study, for the first time, was used to predict a likely PNPO and DDC complex, which suggested contact between the allosteric PLP tight-binding site on PNPO and the active site of DDC. Using isothermal calorimetry and/or surface plasmon resonance, we also show that PNPO binds both apoDDC and holoDDC with dissociation constants of 0.93 ± 0.07 µM and 2.59 ± 0.11 µM, respectively. Finally, in the presence of apoDDC, the tightly bound PLP on PNPO is transferred to apoDDC, resulting in the formation of about 35% holoDDC.

Integrating genetic and clinical data to predict impulse control disorders in Parkinson's disease.

BACKGROUND AND PURPOSE: Impulse control disorders (ICDs) are frequent in Parkinson's disease (PD), with associated clinical and genetic risk factors. This study was aimed at analyzing the clinical features and the genetic background that underlie ICDs in PD. METHODS: We included 353 patients with PD in this study (58.9% men, mean age 62.4 ± 10.58 years, mean age at disease onset 52.71 ± 11.94 years). We used the validated Questionnaire for Impulsive-Compulsive Disorders in Parkinson's Disease for ICDs screening. Motor, nonmotor, and treatment-related features were evaluated according to the presence of ICDs. Twenty-one variants related to dopaminergic, serotonergic, glutamatergic, and opioid neurotransmitter systems were assessed. Association studies between polymorphisms and ICDs were performed. The combination of clinical and genetic variables was analyzed with receiver operating characteristic curves to assess the predictability of experiencing ICDs. RESULTS: Impulse control disorders appeared in 25.1% of the cases. Patients with ICDs were younger and presented a higher rate of anxiety. Treatment with dopamine agonists increased the risk of ICDs and it was dose dependent (P < 0.05). Genetic association studies showed that the DOPA decarboxylase gene (DDC), rs1451375, might modulate the risk of ICDs. Plotting the clinical-genetic model, the predictability of ICDs increased 11% (area under curve = 0.80; z = 3.22, P = 0.001) when adding the genotype data for single nucleotide polymorphisms. CONCLUSIONS: Polymorphisms in DDC might act as risk markers for ICDs in PD. The predictability of experiencing ICDs increased by adding genetic factors to clinical features. It is therefore important to assess the patient's genetic background to identify individuals at risk for ICDs.

Aromatic Amino Acid Decarboxylase Deficiency: The Added Value of Biochemistry.

Aromatic amino acid decarboxylase (AADC) deficiency is a rare, autosomal recessive neurometabolic disorder caused by mutations in the DDC gene, leading to a deficit of AADC, a pyridoxal 5'-phosphate requiring enzyme that catalyzes the decarboxylation of L-Dopa and L-5-hydroxytryptophan in dopamine and serotonin, respectively. Although clinical and genetic studies have given the major contribution to the diagnosis and therapy of AADC deficiency, biochemical investigations have also helped the comprehension of this disorder at a molecular level. Here, we reported the steps leading to the elucidation of the functional and structural features of the enzyme that were useful to identify the different molecular defects caused by the mutations, either in homozygosis or in heterozygosis, associated with AADC deficiency. By revisiting the biochemical data available on the characterization of the pathogenic variants in the purified recombinant form, and interpreting them on the basis of the structure-function relationship of AADC, it was possible: (i) to define the enzymatic phenotype of patients harboring pathogenic mutations and at the same time to propose specific therapeutic managements, and (ii) to identify residues and/or regions of the enzyme relevant for catalysis and/or folding of AADC.

L-Dopa-Decarboxylase (DDC) Is a Positive Prognosticator for Breast Cancer Patients and Epinephrine Regulates Breast Cancer Cell (MCF7 and T47D) Growth In Vitro According to Their Different Expression of Gi- Protein- Coupled Receptors.

A coherence between thyroid dysfunction and breast cancer incidence exists. Thyroid hormone metabolites bind to TAAR1 (trace amine-associated receptor 1) and through that modulate the serotonergic and dopaminergic system. Catecholamines themselves are synthesized by the L-dopa decarboxylase (DDC). The aim of our study was to analyze the influence of catecholamines on the DDC expression in primary breast cancer patients and the role of DDC concerning overall survival (OS). DDC expression was analyzed by immunohistochemistry. The effect of epinephrine on the expression of DDC and the Gi- protein was analyzed on the protein level via Western blot. A viability assay was performed to test the metabolic cell viability. The overexpression of DDC in the primary tumor was associated with longer OS (p = 0.03). Stimulation with epinephrine induced the downregulation of DDC (p = 0.038) and significantly increased viability in T47D cells (p = 0.028). In contrast, epinephrine induced an upregulation of DDC and decreased the proliferation of MCF7 cells (p = 0.028). Epinephrine led to an upregulation of Gi protein expression in MCF7 cells (p = 0.008). DDC is a positive prognostic factor for OS in breast cancer patients, and it is regulated through epinephrine differently in MCF7 and T47D. DDC may represent a novel target for the treatment of breast cancer, especially concerning its interaction with epinephrine.

Molecular and Potential Regulatory Mechanisms of Melanin Synthesis in Harmonia axyridis.

Melanization is a common phenomenon in insects, and melanin synthesis is a conserved physiological process that occurs in epidermal cells. Moreover, a comprehensive understanding of the mechanisms of melanin synthesis influencing insect pigmentation are well-suited for investigating phenotype variation. The Asian multi-colored (Harlequin) ladybird beetle, Harmonia axyridis, exhibits intraspecific polymorphism based on relative levels of melanization. However, the specific characteristics of melanin synthesis in H. axyridis remains elusive. In this study, we performed gene-silencing analysis of the pivotal inverting enzyme, tyrosine hydroxylase (TH), and DOPA decarboxylase (DDC) in the tyrosine metabolism pathway to investigate the molecular and regulatory mechanism of melanin synthesis in H. axyridis. Using RNAi of TH and DDC genes in fourth instar larvae, we demonstrated that dopamine melanin was the primary contributor to the overall body melanization of H. axyridis. Furthermore, our study provides the first conclusive evidence that dopamine serves as a melanin precursor for synthesis in the early pupal stage. According to transcription factor Pannier, which is essential for the formation of melanic color on the elytra in H. axyridis, we further demonstrated that suppression of HaPnr can significantly decrease expression levels of HaTH and HaDDC. These results in their entirety lead to the conclusion that transcription factor Pannier can regulate dopamine melanin synthesis in the dorsal elytral epidermis of H. axyridis.

A novel compound heterozygous genotype associated with aromatic amino acid decarboxylase deficiency: Clinical aspects and biochemical studies.

Aromatic amino acid decarboxylase (AADC) deficiency is a rare autosomal neurometabolic disorder caused by a deficit of AADC, a pyridoxal 5'-phosphate (PLP)-dependent enzyme, which catalyzes the synthesis of dopamine and serotonin. While many studies have highlighted the molecular defects of the homozygous pathogenic variants, so far only a study investigated heterozygous variants at protein level. Here, we report a clinical case of one AADC deficiency compound heterozygous patient bearing the A91V mutation and the novel C410G mutation. To elucidate its enzymatic phenotype, the A91V and C410G homodimers were first expressed in Escherichia coli, purified and characterized. Although both apo variants display an unaltered overall tertiary structure, they show a Ì´ 20-fold decreased PLP binding affinity. The C410G mutation only causes a Ì´ 4-fold decrease of the catalytic efficiency, while the A91V mutation causes a 1300-fold decrease of the kcat/Km, and changes in the holoAADC consisting in a marked alteration of the tertiary structure and the coenzyme microenvironment. Structural analyses of these mutations are in agreement with these data. Unfortunately, the C410G/A91V heterodimer was constructed, expressed and purified in rather modest amount. Anyway, measurements of decarboxylase activity indicate that its putative kcat value is lower than that predicted by averaging the kcat values of the two parental enzymes. This indicates a negative interallelic complementation between the C410G and A91V monomers. Overall, this study allowed to relate the clinical to the enzymatic phenotype of the patient and to extend knowledge in the clinical and molecular pathogenesis of AADC deficiency.

Molecular characterization and expression analysis of dopa decarboxylase involved in the antibacterial innate immunity of the freshwater crayfish, Procambarus clarkii.

Dopa decarboxylase (DDC) is responsible for the synthesis of dopamine, which acts as an important modulator in the nervous systems of vertebrates and invertebrates. Recent studies have indicated that DDC also plays crucial roles in the insect innate immune system. However, the functions of DDC in immunomodulation in crustaceans have not been thoroughly elucidated to date. In this study, a new full-length cDNA of the DDC protein was identified from red swamp crayfish, Procambarus clarkii (named Pc-ddc). The ORF of Pc-ddc encoded 474 amino acids, which possessed a 377-amino-acid domain. Pc-ddc was expressed at a relatively high level in the hemocytes and gills of crayfish. This protein was expressed at a relatively low level in the hepatopancreas and intestine. The expression level of Pc-ddc was clearly upregulated in hemocytes, hepatopancreas, gills, and intestine tissues after challenge with S. aureus or E. ictaluri. The results of the enzyme catalysis assay showed that the enzyme catalysis activity of rPc-DDC was 35 ±â€¯2.8 ng h-1 mg-1 (n = 3). In addition, the results of the mimetic crayfish hemocytes encapsulation assay showed that the encapsulation rate of beads coated with rPc-DDC was clearly increased. The results of the bacterial binding assay showed that rPc-DDC strongly binds to S. aureus and E. ictaluri. Finally, when Pc-ddc was knocked down, the number of surviving crayfish clearly decreased after S. aureus or E. ictaluri was injected. All of these results indicate that Pc-DDC is an important immunomodulating enzyme in the neuroendocrine-immune (NEI) system of crayfish.

Fast enzymatic synthesis of n.c.a. 6-[18 F]fluorodopamine (FDA) from n.c.a. 6-[18 F]FDOPA and the fate of 6-FDOPA and 6-FDA in neuroblastoma and Caki-1 cells after their uptake.

The catecholamine analogue [123 I]mIBG has been used for scintigraphic imaging of neuroblastoma since 1984. It is taken up by the noradrenaline transporter (NAT), which is present in most neuroblastoma cells. An alternative imaging method could be PET with 6-[18 F]fluorodopamine, which is also taken up by NAT, but-in contrast to mIBG-also by dopamine transporter (DAT), present in neuroblastoma cells (NAT > DAT). An enzymatic method was established allowing a rapid, quantitative transformation of FDOPA to FDA by DOPA decarboxylase within 25 minutes. This strategy was applied to [18 F]FDOPA, which was produced via nucleophilic synthesis (RCY 15%, 10 GBq, 50 GBq/µmol) and subsequently converted to [18 F]FDA (RCY 35%-50%, n = 5). Uptake and metabolism of FDOPA and FDA were analyzed in human Kelly and SK-N-SH neuroblastoma cell lines and in human Caki-1 kidney cells that can take up catecholamines and mIBG via an organic cation transporter (OCT). FDOPA and FDA were taken up by all three cells, but FDOPA could only be converted to FDA in neuroblastoma cells. As today, [18 F]FDOPA is well available in high yields, efficient enzymatic conversion to [18 F]FDA to be used for NAT/DAT PET imaging in neuroendocrine tumors is an attractive, alternative synthesis route.

Antisense oligonucleotides modulate dopa decarboxylase function in aromatic l-amino acid decarboxylase deficiency.

Aromatic l-amino acid decarboxylase deficiency (AADCD), attributed to mutations in the dopa decarboxylase (DDC) gene, is a rare neurometabolic disease resulting from a defect in the biosynthesis of dopamine and serotonin. The DDC c.714+4A>T mutation is the most prevalent mutation among patients with AADCD, and is also a founder mutation among Taiwanese patients. In this study, the molecular consequences and function of this mutation were examined in AADCD patient-derived lymphoblastoid cells. We identified novel DDC mRNA isoforms spliced with a new exon (exon 6a) in normal and c.714+4A>T lymphoblastoid cells. In addition, we identified the SR proteins (SRSF9 and SRSF6), as well as cis-elements involved in modulating the splicing of this mutated transcript. Notably, we demonstrated that antisense oligonucleotides (ASOs) were able to restore the normal mRNA splicing and increase the level of DDC protein, as well as its downstream product serotonin, in lymphoblastoid cells derived from the patient with AADCD, suggesting that these ASOs might represent a feasible alternative strategy for gene therapy of AADCD in patients with the common c.714+4A>T mutation.

Heterozygosis in aromatic amino acid decarboxylase deficiency: Evidence for a positive interallelic complementation between R347Q and R358H mutations.

Aromatic amino acid or Dopa decarboxylase (AADC or DDC) is a homodimeric pyridoxal 5'-phosphate (PLP) enzyme responsible for the generation of the neurotransmitters dopamine and serotonin. AADC deficiency is a rare inborn disease caused by mutations of the AADC gene leading to a defect of AADC enzyme and resulting in impaired dopamine and serotonin synthesis. Until now, only the molecular effects of homozygous mutations were analyzed. However, although heterozygous carriers of AADC deficiency were identified, the molecular aspects of their enzymatic phenotypes are not yet investigated. Here, we focus our attention on the R347Q/R358H and R347Q/R160W heterozygous mutations, and report for the first time the isolation and characterization, in the purified recombinant form, of the R347Q/R358H heterodimer and of the R358H homodimer. The results, integrated with those already known of the R347Q homodimeric variant, provide evidence that (i) the R358H mutation strongly reduces the PLP-binding affinity and the catalytic activity, and (ii) a positive interallelic complementation exists between the R347Q and the R358H mutations. Bioinformatics analyses provide the structural basis for these data. Unfortunately, the R347Q/R160W heterodimer was not obtained in a sufficient amount to allow its purification and characterization. Nevertheless, the biochemical features of the R160W homodimer give a contribution to the enzymatic phenotype of the heterozygous R347Q/R160W and suggest the possible relevance of Arg160 in the proper folding of human DDC. © 2018 IUBMB Life, 70(3):215-223, 2018.

Cloning and expression analysis of a novel tissue-specific dopa decarboxylase mRNA splicing variant in Bombyx mori.

Dopa decarboxylase (DDC) protein is involved in the synthesis of dopamine and serotonin. Here, we show that in the silkworm Bombyx mori, a novel DDC splicing variant is selectively expressed in the brain and subesophageal ganglia. In Drosophila melanogaster, a neuron-specific isoform of DDC is known to be alternatively spliced in a similar manner.

Synthesis of dopamine in E. coli using plasmid-based expression system and its marked effect on host growth profiles.

L-Dopa and dopamine are important pathway intermediates toward the synthesis of catecholamine such as epinephrine and norepinephrine from amino acid L-tyrosine. Dopamine, secreted from dopaminergic nerve cells, serves as an important neurotransmitter. We report the synthesis of dopamine by extending the aromatic amino acid pathway of Escherichia coli DH5α by the expression of 4-hydroxyphenylacetate-3-hydrolase (HpaBC) from E. coli and an engineered dopa decarboxylase (DDC) from pig kidney cell. The activity of HpaBC and DDC require 200 µM iron supplementation and 50 µM vitamin B6, respectively as additives to the growth media. The maximum concentration of L-dopa and dopamine obtained from the broth was around 26 and 27 mg/L after 24 hr of separate shake flask studies. We observed that in the presence of dopamine synthesized in vivo host growth was remarkably enhanced. These observations lead us to an interesting finding about the role of these catecholamines on bacterial growth. It is clear that synthesis of dopamine in vivo actually promotes growth much efficiently as compared to when dopamine is added to the system from outside. From HPLC and GC-MS data it was further observed that L-dopa was stable within the observable time of experiments whereas dopamine actually was subjected to degradation via oxidation and host consumption.