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C. Liu

Monoamine biosynthesis via a noncanonical calcium-activatable aromatic amino acid decarboxylase in psilocybin mushroom

November 28, 2018 / Mushrooms / Psilocybin, Papers, Pharmacology & Chemistry, Publications / By / , , , ,

Abstract

Aromatic l-amino acid decarboxylases (AAADs) are a phylogenetically diverse group of enzymes responsible for the decarboxylation of aromatic amino acid substrates into their corresponding aromatic arylalkylamines. AAADs have been extensively studied in mammals and plants as they catalyze the first step in the production of neurotransmitters and bioactive phytochemicals, respectively. Unlike mammals and plants, the hallucinogenic psilocybin mushroom Psilocybe cubensis reportedly employs an unrelated phosphatidylserine-decarboxylase-like enzyme to catalyze l-tryptophan decarboxylation, the first step in psilocybin biosynthesis. To explore the origin of this chemistry in psilocybin mushroom, we generated the first de novo transcriptomes of P. cubensis and investigated several putative l-tryptophan-decarboxylase-like enzymes. We report the biochemical characterization of a noncanonical AAAD from P. cubensis (PcncAAAD) that exhibits substrate permissiveness toward l-phenylalanine, l-tyrosine, and l-tryptophan, as well as chloro-tryptophan derivatives. The crystal structure of PcncAAAD revealed the presence of a unique C-terminal appendage domain featuring a novel double-β-barrel fold. This domain is required for PcncAAAD activity and regulates catalytic rate and thermal stability through calcium binding. PcncAAAD likely plays a role in psilocybin production in P. cubensis and offers a new tool for metabolic engineering of aromatic-amino-acid-derived natural products.

Torrens-Spence, M. P., Liu, C. T., Pluskal, T., Chung, Y. K., & Weng, J. K. (2018). Monoamine Biosynthesis via a Noncanonical Calcium-Activatable Aromatic Amino Acid Decarboxylase in Psilocybin Mushroom. ACS chemical biology, 13(12), 3343-3353., 10.1021/acschembio.8b00821
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Activation of 5-HT2A/2C receptors reduces the excitability of cultured cortical neurons

October 6, 2016 / Neuroscience, Papers, Publications / By / , , , , ,

Abstract

The abundant forebrain serotonergic projections are believed to modulate the activities of cortical neurons. 5-HT2 receptor among multiple subtypes of serotonin receptors contributes to the modulation of excitability, synaptic transmissions and plasticity. In the present study, whole-cell patch-clamp recording was adopted to examine whether activation of 5-HT2A/2C receptors would have any impact on the excitability of cultured cortical neurons. We found that 2,5-Dimethoxy-4-iodoamphetamine (DOI), a selective 5-HT2A/2C receptor agonist, rapidly and reversibly depressed spontaneous action potentials mimicking the effect of serotonin. The decreased excitability was also observed for current-evoked firing. Additionally DOI increased neuronal input resistance. Hyperpolarization-activated cyclic nucleotide-gated cationic channels (HCN) did not account for the inhibition of spontaneous firing. The synaptic contribution was ruled out in that DOI augmented excitation and attenuated inhibition to actually favor an increase in the excitability. Our findings revealed that activation of 5-HT2A/2C receptors reduces neuronal excitability, which would deepen our understanding of serotonergic modulation of cortical activities.
Hu, L., Liu, C., Dang, M., Luo, B., Guo, Y., & Wang, H. (2016). Activation of 5-HT 2A/2C receptors reduces the excitability of cultured cortical neurons. Neuroscience letters, 632, 124-129. 10.1016/j.neulet.2016.08.052
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