Biology subjects

Desbois, C.

Publications and source records attributed to Desbois, C..

3 recordsLinked to original sources

bioRxiv2025

CryoEM of ATP-driven dynamics and itraconazole binding in a fungal ABC pump

Azole resistance in Candida species is often caused by the overexpression of Cdr1. Despite its clinical relevance, the structural basis for its ATP-driven efflux pump function remains elusive. We present four high-resolution cryo-EM structures for Candida glabrata Cdr1 under active turnover conditions in the absence and presence of ATP-Mg{superscript 2}, itraconazole, and vanadate. Additional transient cryo-EM structures were unveiled by 3D variability analysis offering a detailed view of the step-by-step transitions triggered by ATP-hydrolysis. The motion cascade starts with a 4 [A] piston-like retraction of the C-helix from the {gamma}-phosphate/vanadate of the hydrolyzed ATP. This causes the nearby transmembrane helix-1 (TMH-1) to open the drug-binding site via lateral displacement and unwinding of the inner-leaflet region of TMH-2. A reverse squeeze-and-push motion of TMH-2 possibly drives substrate extrusion. High resolution structures also reveal how itraconazole adapts its shape to fit into the drug-binding site. Our findings provide a dynamic structural framework for Cdr1-mediated azole resistance and the conserved chemo-mechanical cycle of ABC proteins, including non-membranous members.

biochemistry↗

bioRxiv2021

Horizontal connectivity in V1 : Prediction of coherence in contour and motion integration

This study demonstrates the functional importance of the Surround context relayed laterally in V1 by the horizontal connectivity, in controlling the latency and the gain of the cortical response to the feedforward visual drive. We report here four main findings : 1) a centripetal apparent motion sequence results in a shortening of the spiking latency of V1 cells, when the orientation of the local inducer and the global motion axis are both co-aligned with the RF orientation preference; 2) this contextual effects grows with visual flow speed, peaking at 150-250{degrees}/s when it matches the propagation speed of horizontal connectivity (0.15-0.25 mm/ms); 3) For this speed range, the axial sensitivity of V1 cells is tilted by 90{degrees} to become co-aligned with the orientation preference axis; 4) the strength of modulation by the surround context correlates with the spatiotemporal coherence of the apparent motion flow. Our results suggest an internally-generated binding process, linking local (orientation /position) and global (motion/direction) features as early as V1. This long-range diffusion process constitutes a plausible substrate in V1 of the human psychophysical bias in speed estimation for collinear motion. Since it is demonstrated in the anesthetized cat, this novel form of contextual control of the cortical gain and phase is a built-in property in V1, whose expression does not require behavioral attention and top-down control from higher cortical areas. We propose that horizontal connectivity participates in the propagation of an internal "prediction" wave, shaped by visual experience, which links contour co-alignment and global axial motion at an apparent speed in the range of saccade-like eye-movements.

neuroscience↗

bioRxiv2018

Transparency reduces predator detection in chemically protected clearwing butterflies

1. Predation is an important selective pressure and some prey have evolved warning colour signals advertising unpalatability (i.e. aposematism) as an antipredator strategy. Unexpectedly, some butterfly species from the unpalatable tribe Ithomiini possess transparent wings, an adaptation rare on land but common in water where it helps avoiding predator detection.\n\n2. We tested if transparency of butterfly wings was associated with decreased detectability by predators, by comparing four butterfly species exhibiting different degrees of transparency, ranging from fully opaque to largely transparent. We tested our prediction using using both wild birds and humans in behavioural experiments. Vision modelling predicted detectability to be similar for these two predator types.\n\n3. In concordance with predictions, more transparent species were almost never the first detected items and were detected less often than the opaque species by both birds and humans, suggesting that transparency enhances crypsis. However, humans could learn to better detect the most transparent species over time. Our study demonstrates for the first time that transparency on land likely decreases detectability by visual predators.

evolutionary biology↗