Biology subjects

Morland, C.

Publications and source records attributed to Morland, C..

3 recordsLinked to original sources

bioRxiv2026

Functional Differentiation of GH172 Arabinofuranosidases Through Divergent Quaternary Structures

Mycobacteria synthesise the unusual glycan [x1D05]-arabinan as a major component of the cell wall glycoconjugates arabinogalactan (AG) and lipoarabinomannan (LAM). We previously identified Dysgonomonas gadei, a member of the Bacteroidota, as capable of complete [x1D05]-arabinan degradation through the concerted action of endo- and exo-acting enzymes. Among these are three glycoside hydrolase family 172 (GH172) enzymes with exo--[x1D05]-arabinofuranosidase activity against AG and LAM, although their linkage specificities were unknown. Here, using defined synthetic substrates, we show that the three enzymes possess distinct linkage preferences. We also develop -[x1D05]-arabinofuranosyl cyclophellitol aziridines as covalent inhibitors and activity-based probes for GH172 enzymes. X-ray crystallography and cryo-EM to reveal strikingly different quaternary assemblies across the three homologues, while a 1.5 [A] cryo-EM structure of dodecameric Dg67 covalently modified by an aziridine inhibitor identifies the catalytic nucleophile and provides direct structural support for a retaining mechanism. A BODIPY-tagged aziridine probe selectively labelled the three GH172 enzymes in D. gadei cell lysates. Together, these findings define functional and structural diversity within GH172 and establish chemical probes for profiling -[x1D05]-arabinofuranosidase activity in complex biological samples.

biochemistry↗

bioRxiv2026

Disruption of glutamine carrier Slc38a1 causes cognitive impairment, anxiety and depressive-like behavior

GABAergic deficit is associated with key neuropsychiatric disorders, such as major depressive disorder (MDD), anxiety, schizophrenia, and autism spectrum disorder (ASD). However, it is not known whether these disorders are causal to or a result of GABAergic dysfunction. We previously showed that the Solute carrier 38 member 1 (Slc38a1) accumulates glutamine in subpopulations of GABAergic neurons and sustains neurotransmitter GABA synthesis. Genetic inactivation of Slc38a1 in mice caused lowered GABA levels, altered synaptic vesicle morphology, slowed {gamma}-oscillations, and reduced cortical processing and plasticity, selectively at GABAergic synapses. We now demonstrate a significant reduction in learning and memory performance in the Morris water maze and increased signs of despair in the forced swim test in Slc38a1-/- mice compared to Slc38a1+/+ mice, implicating cognitive impairments and depressive-like behavior. Examination in the open field maze also indicates anxiety and/or reduced interest in exploration. There are no signs of impaired sociability or recognition of social novelty in the three-chambered test, speaking against involvement in schizophrenia- or ASD-like disorders. Metabolic phenotyping and measurement of the locomotion do not segregate the Slc38a1 genotypes, suggesting that the cognitive impairments, depressive-like behavior and anxiety are brain-dependent. Our data is further supported by a pathologic variant of Slc38a1 in a family with depression and suicidal behavior. Altogether, we demonstrate that dysfunction of Slc38a1-dependent GABA synthesis and the ensuing impaired {gamma}-oscillations underpin the pathogenesis of neurocognitive deficits, anxiety and depression.

animal behavior and cognition↗

bioRxiv2020

Insights into glycan import by a prominent gut symbiont

In Bacteroidetes, one of the dominant phyla of the mammalian gut, active uptake of large nutrients across the outer membrane is mediated by SusCD protein complexes via a "pedal bin" transport mechanism. However, many features of SusCD function in glycan uptake remain unclear, including ligand binding, the role of the SusD lid and the size limit for substrate transport. Here we characterise the {beta}2,6 fructo-oligosaccharide (FOS) importing SusCD from Bacteroides thetaiotaomicron (Bt1762-Bt1763) to shed light on SusCD function. Co-crystal structures reveal residues involved in glycan recognition and suggest that the large binding cavity can accommodate several substrate molecules, each up to [~]2.5 kDa in size, a finding supported by native mass spectrometry and isothermal titration calorimetry. Mutational studies in vivo provide functional insights into the key structural features of the SusCD apparatus and cryo-EM of the intact dimeric SusCD complex reveals several distinct states of the transporter, directly visualising the dynamics of the pedal bin transport mechanism.

microbiology↗