Biology subjects

Poujol, C.

Publications and source records attributed to Poujol, C..

3 recordsLinked to original sources

bioRxiv2023

ER-to-Golgi trafficking via a dynamic intermediate cis-Golgi tubular network in Arabidopsis

Endoplasmic Reticulum (ER)-to-Golgi trafficking is a central process of the secretory system of eukaryotic cells that ensures proper spatiotemporal sorting of proteins and lipids1-5. However, the nature of the ER-Golgi Intermediate Compartments (ERGIC) and the molecular mechanisms mediating the transition between the ERGIC and the Golgi, as well as the universality of these processes amongst Eukaryotes, remain undiscovered. Here, we took advantage of the plant cell system in which the Golgi is highly dynamic and in close vicinity to the ER6-9. We discovered that the ERGIC is composed from at least two distinct subpopulations of cis-Golgi. A subpopulation is a reticulated tubulo-vesicular network mostly independent from the Golgi, highly dynamic at the ER-Golgi interface and crossed by ER-induced release of luminal cargos at early stage. Another subpopulation is more stable, cisterna-like and mostly associated to the Golgi. Our results identified that the generation and dynamics of the ER-Golgi intermediate tubulo-vesicular network is regulated by the acyl-chain length of sphingolipids as well as the contacts it establishes with existing Golgi cisternae. Our study is a major twist in the understanding of the Golgi by identifying that the ERGIC in plants is a Golgi-independent highly dynamic tubular network from which arise more stable cisternae-like Golgi structures. This novel model presents a mechanism for early secretory trafficking adapted to respond to developmental and environmental stimuli, including susceptibility or resistance to diseases, autophagy or cell-reprograming.

cell biology↗

bioRxiv2021

mir124-dependent tagging of glutamatergic synapses by synaptopodin controls non-uniform and input-specific homeostatic synaptic plasticity

Homeostatic synaptic plasticity (HSP) is a process by which neurons adjust synaptic strengths to compensate for various perturbations and which allows to stabilize neuronal activity. Yet, whether the highly diverse synapses harboring a neuron respond uniformly to a same perturbation is unclear and the underlying molecular determinants remain to be identified. Here, using patch-clamp recordings, immunolabeling and imaging approaches, we report that the ability of individual synapses to undergo HSP in response to activity-deprivation paradigms depends on the local expression of the spine apparatus related protein synaptopodin (SP) acting as a synaptic tag to promote AMPA receptor synaptic accumulation and spine growth. Gain and loss-of-function experiments indicate that this process relies on the local de-repression of SP translation by miR124 which supports both non-uniform and synapse-autonomous HSP induced by global or inputspecific activity deprivation, respectively. Our findings uncover an unexpected synaptic-tagging mechanism for HSP, whose molecular actors are intriguingly shared with Hebbian plasticity and linked to multiple neurological diseases.

neuroscience↗

bioRxiv2021

Engineering paralog-specific PSD-95 synthetic binders as potent and minimally invasive imaging probes

Despite the constant advances in fluorescence imaging techniques, monitoring endogenous proteins still constitutes a major challenge in particular when considering dynamics studies or super-resolution imaging. We have recently evolved specific protein-based binders for PSD-95, the main postsynaptic scaffold proteins at excitatory synapses. Since the synthetic binders recognize epitopes not directly involved in the target protein activity, we consider them here as tools to develop endogenous PSD-95 imaging probes. After confirming their lack of impact on PSD-95 function, we validated their use as intrabody fluorescent probes. We further engineered the probes and demonstrated their usefulness in different super-resolution imaging modalities (STED, PALM and DNA-PAINT) in both live and fixed neurons. Finally, we exploited the binders to enrich at the synapse genetically encoded calcium reporters. Overall, we demonstrate that these evolved binders constitute a robust and efficient platform to selectively target and monitor endogenous PSD-95 using various fluorescence imaging techniques.

neuroscience↗