Metastasis-associated protein 1 (MTA1) regulates the catecholamine production homeostasis via transcriptional repression of aromatic l-amino acid decarboxylase (Aadc) in the interstitial cells of Cajal of mouse prostate.

Based on the lately identified role for the interstitial cells of Cajal (ICCs) of mouse prostate in catecholamine production, as well as the well-established role for the master coregulator metastasis-associated protein 1 (MTA1) in inflammation, we probed into the functional link between aberrant MTA1 expression and pathogenesis of chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS) using both a MTA1-/- mouse model of experimental autoimmune prostatitis (EAP) and an in vitro chronic prostatitis model in cultured murine ICCs. EAP-induced MTA1 expression was enriched in ICCs of mouse prostate. EAP resulted in a higher increase in the pelvic pain response in MTA1-/- mice compared to WT mice. Consistently, the ICCs from MTA1-/- mice produced higher levels of catecholamines upon induction of in vitro chronic prostatitis. Mechanistically, MTA1 could directly suppress the transcription of Aadc, a rate-limiting enzyme during catecholamine synthesis, in a HDAC2-depdendent manner. Importantly, treatment with AADC inhibitor NSD-1015 significantly ameliorated EAP-elicited pain response and catecholamine overactivity in MTA1-/- mice. Taken together, our findings reveal an inherent regulatory role of the MTA1/AADC pathway in the maintenance of catecholamine production homeostasis in prostate ICCs, and also point to a potential use of HDAC inhibitors and/or AADC inhibitors to treat CP/CPPS.

A biochemical and functional protein complex involving dopamine synthesis and transport into synaptic vesicles.

Synaptic transmission depends on neurotransmitter pools stored within vesicles that undergo regulated exocytosis. In the brain, the vesicular monoamine transporter-2 (VMAT(2)) is responsible for the loading of dopamine (DA) and other monoamines into synaptic vesicles. Prior to storage within vesicles, DA synthesis occurs at the synaptic terminal in a two-step enzymatic process. First, the rate-limiting enzyme tyrosine hydroxylase (TH) converts tyrosine to di-OH-phenylalanine. Aromatic amino acid decarboxylase (AADC) then converts di-OH-phenylalanine into DA. Here, we provide evidence that VMAT(2) physically and functionally interacts with the enzymes responsible for DA synthesis. In rat striata, TH and AADC co-immunoprecipitate with VMAT(2), whereas in PC 12 cells, TH co-immunoprecipitates with the closely related VMAT(1) and with overexpressed VMAT(2). GST pull-down assays further identified three cytosolic domains of VMAT(2) involved in the interaction with TH and AADC. Furthermore, in vitro binding assays demonstrated that TH directly interacts with VMAT(2). Additionally, using fractionation and immunoisolation approaches, we demonstrate that TH and AADC associate with VMAT(2)-containing synaptic vesicles from rat brain. These vesicles exhibited specific TH activity. Finally, the coupling between synthesis and transport of DA into vesicles was impaired in the presence of fragments involved in the VMAT(2)/TH/AADC interaction. Taken together, our results indicate that DA synthesis can occur at the synaptic vesicle membrane, where it is physically and functionally coupled to VMAT(2)-mediated transport into vesicles.

Median eminence dopaminergic nerve terminals: a novel target in autoimmune polyendocrine syndrome?

CONTEXT: Autoantibodies to adenohypophyseal endocrine cells or to vasopressin neurohypophyseal neurons have long been known. Conversely, autoimmune targeting of further hypothalamic-hypophyseal structures, such as the blood-brain barrier-deprived median eminence, has been little studied. OBJECTIVE AND METHODS: We studied a case of autoimmune polyendocrine syndrome type I with GH secretory deficiency, a distinctly rare event in autoimmune polyendocrine syndrome type I. We used rat and bovine tissue substrates to study autoantibodies against hypothalamic-hypophyseal nerve structures and endocrine cells. RESULTS: In the study case, circulating autoantibodies selectively decorated median eminence dopaminergic nerve terminals, as well as pituitary gonadotropes, but not GHRH nerve terminals or pituitary somatotropes. Such autoantibodies appeared de novo in parallel with the onset of GH secretory deficiency, whereas no median eminence labeling was found in patients suffering of idiopathic GH deficiency (n = 7) or in healthy controls (n = 23). CONCLUSIONS: The pathophysiological significance of our patient's autoantibodies remains to be confirmed. Nonetheless, the heterogeneous neuroendocrine structures of the median eminence are pointed out as potential immune targets, relevant to autoimmune polyendocrinopathy, as well as to a wide range of other conditions.

Analysis of antibody reactivity against cysteine sulfinic acid decarboxylase, a pyridoxal phosphate-dependent enzyme, in endocrine autoimmune disease.

The structurally related group II pyridoxal phosphate (PLP)-dependent amino acid decarboxylases glutamic acid decarboxylase (GAD), aromatic L-amino acid decarboxylase (AADC), and histidine decarboxylase (HDC) are known autoantigens in endocrine disorders. We report, for the first time, the prevalence of serum autoantibody reactivity against cysteine sulfinic acid decarboxylase (CSAD), an enzyme that shares 50% amino acid identity with the 65- and 67-kDa isoforms of GAD (GAD-65 and GAD-67), in endocrine autoimmune disease. Three of 83 patients (3.6%) with autoimmune polyendocrine syndrome type 1 (APS1) were anti-CSAD positive in a radioimmunoprecipitation assay. Anti-CSAD antibodies cross-reacted with GAD-65, and the anti-CSAD-positive sera were also reactive with AADC and HDC. The low frequency of anti-CSAD reactivity is in striking contrast to the prevalence of antibodies against GAD-65, AADC, and HDC in APS1 patients, suggesting that different mechanisms control the immunological tolerance toward CSAD and the other group II decarboxylases. Moreover, CSAD may be a useful mold for the construction of recombinant chimerical antigens in attempts to map conformational epitopes on other group II PLP-dependent amino acid decarboxylases.

Immunocytochemical colocalizations of serotonin, aromatic L-amino acid decarboxylase and polypeptide hormones in A- and PP-cells of the chicken endocrine pancreas.

The colocalization of serotonin and aromatic L-amino acid decarboxylase (AADC) in the avian pancreatic polypeptide-containing PP-cells and glucagon-storing A-cells of the chicken endocrine pancreas was investigated using combined pre-embedding immuno-peroxidase and post-embedding immunogold electron microscopic immunocytochemistry. The avian pancreatic polypeptide-immunoreactive cells manifested by the labeling of immunogold particles on secretory granules were also immunoreactive with antisera directed against serotonin and AADC, an enzyme involved in the synthesis of serotonin. In PP-cells immunoreactivity against the anti-serotonin serum was stronger in secretory granules than in the cytoplasmic matrix, whereas immunoreaction with the anti-AADC serum was observed to be more intense in the cytoplasmic matrix. Immunoreactions with the serotonin and AADC antisera were also found in secretory granules of glucagon-storing A-cells. These results indicate that serotonin is co-stored within secretory granules of both A- and PP-cells, and that AADC is localized within secretory granules of A-cells, and may be present in the cytoplasmic matrix of PP-cells. It is probable that serotonin is synthesized and released simultaneously with secretory granules from both A- and PP-cells of the chicken endocrine pancreas.