Dadi, P. | bioRxiv Science

bioRxiv2024

Synthesis of versatile neuromodulatory molecules by a gut microbial glutamate decarboxylase

Dysbiosis of the microbiome correlates with many neurological disorders, yet very little is known about the chemistry that controls the production of neuromodulatory molecules by gut microbes. Here, we found that an enzyme glutamate decarboxylase (BfGAD) of a gut microbe Bacteroides fragilis forms multiple neuromodulatory molecules such as {gamma}-aminobutyric acid (GABA), hypotaurine, taurine, homotaurine, and {beta}-alanine. We evolved BfGAD and doubled its taurine productivity. Additionally, we increased its specificity towards the substrate L-glutamate. Here, we provide a chemical strategy via which the BfGAD activity could be fine-tuned. In future, this strategy could be used to modulate the production of neuromodulatory molecules by gut microbes.

biochemistry↗

bioRxiv2020

A novel mutation in KCNK16 causing a gain-of-function in the TALK-1 potassium channel: a new cause of maturity onset diabetes of the young.

BackgroundMaturity-onset diabetes of the young (MODY) is a heterogeneous group of monogenic disorders of impaired glucose-stimulated insulin secretion (GSIS). Mechanisms include {beta}-cell KATP channel dysfunction (e.g., KCNJ11 (MODY13) or ABCC8 (MODY12) mutations); however, no other {beta}-cell channelopathies have been identified in MODY. MethodsA four-generation family with autosomal dominant non-obese, non-ketotic antibody-negative diabetes, without mutations in known MODY genes, underwent exome sequencing. Whole-cell and single-channel K+ currents, Ca2+ handling, and GSIS were determined in cells expressing either mutated or wild-type (WT) protein. ResultsWe identified a novel non-synonymous genetic mutation in KCNK16 (NM_001135105: c.341T>C, p.Leu114Pro) segregating with MODY. KCNK16 is the most abundant and {beta}-cell-restricted K+ channel transcript and encodes the two-pore-domain K+ channel TALK-1. Whole-cell K+ currents in transfected HEK293 cells demonstrated drastic (312-fold increase) gain-of-function with TALK-1 Leu144Pro vs. WT, due to greater single channel activity. Glucose-stimulated cytosolic Ca2+ influx was inhibited in mouse islets expressing TALK-1 Leu114Pro (area under the curve [AUC] at 20mM glucose: Leu114Pro 60.1 vs. WT 89.1; P=0.030) and less endoplasmic reticulum calcium storage (cyclopiazonic acid-induced release AUC: Leu114Pro 17.5 vs. WT 46.8; P=0.008). TALK-1 Leu114Pro significantly blunted GSIS compared to TALK-1 WT in both mouse (52% decrease, P=0.039) and human (38% decrease, P=0.019) islets. ConclusionsOur data identify a novel MODY-associated gene, KCNK16; with a gain-of-function mutation limiting Ca2+ influx and GSIS. A gain-of-function common polymorphism in KCNK16 is associated with type 2 diabetes (T2DM); thus, our findings have therapeutic implications not only for KCNK16-associated MODY but also for T2DM.

genetics↗