Biology subjects

Martel, N.

Publications and source records attributed to Martel, N..

11 recordsLinked to original sources

bioRxiv2025

A Standardized Protocol to Investigate Trans-Endothelial Trafficking in Zebrafish: Nano-bio Interactions of PEG-based Nanoparticles in Live Vasculature

Trans-endothelial transport of nanoparticles remains poorly characterized in live organisms. The zebrafish is a well-established model for direct in vivo imaging; however, standardized controls are not consistently applied across studies. Here, we developed a standardized protocol to assess nanoparticle trans-endothelial trafficking in live zebrafish. We tested a range of tracers and identified 2000 kDa dextran as an optimal control for standardizing microinjections and quantifying nanoparticle transport in a systematic unbiased manner. As validation, we identified the early physiological trans-endothelial transport pathways in zebrafish embryos using 40 kDa dextran as a nanoparticle surrogate. Using our workflow, we assessed the extravasation of 3, 7, 32 and 47 nm polyethylene glycol (PEG)-based nanoparticles. Using cAMP stimulation to restrict paracellular routes, and inhibitors to impede dynamin-dependent endocytosis, we demonstrated that PEG-based hyperbranched polymer (HBP) nanoparticles of 3 to 7 nm traverse the endothelial barrier via paracellular routes and 32 and 47 nm PEG micelles adopt dynamin- dependent endocytic trafficking over paracellular transport. We characterized the emergence of caveolae in the vasculature up to 17 days post-fertilization (dpf) using a cavin1b knock-in zebrafish line. Using cavin1a/cavin1b double knockout (DKO) zebrafish, and tumor-bearing Cavin-1 null mice, we showed that caveolae do not contribute to the transvascular transport of these PEG-based nanoparticles. This work highlights the rigour of the standardized protocol for assessing nanoparticle trans-endothelial transport in the live zebrafish, providing a systematic approach for quantification using a standardized control.

cell biology↗

bioRxiv2024

Unsaturated lipids as key control points for caveola formation and disassembly

Caveolae are specialized plasma membrane domains with a unique lipid composition. Recent work has implicated lipid peroxidation in triggering caveola disassembly, releasing caveolar proteins to regulate the cellular response to oxidative stress. Here we investigated the role of specific lipid species in caveola formation and response to oxidative stress. Systematic screening of lipid enzymes identified ACSL4, a critical enzyme in the synthesis of polyunsaturated fatty acid-containing lipids, and enzymes involved in the biosynthesis of pro-ferroptotic ether lipids, as key regulators of caveola formation. Omega-6 fatty acids promoted efficient caveola formation, while their oxidation or displacement by omega-3 or monounsaturated fatty acids disrupted this process. Moreover, we found that omega-6 fatty acid-containing membrane lipids were required for oxidative stress-induced caveola disassembly. These findings unveil a new model for caveola formation, highlighting specific unsaturated lipids as essential caveolar components and key control points for caveola disassembly in response to an oxidizing environment.

cell biology↗

bioRxiv2024

A modular encapsulation system for precision delivery of proteins, nucleic acids and therapeutics

Targeted nanoparticles have the potential to revolutionize therapeutics for medical applications. Here, we demonstrate the utility of a flexible precision nanovesicle delivery system for functional delivery of DNA, RNA, proteins and drugs into target cells. Nanovesicles generated by the membrane sculpting protein caveolin, termed caveospheres, can be loaded with RNA, DNA, proteins or drugs post-synthesis or incorporate genetically-encoded cargo proteins during production without the need for protein purification. Functionalized fluorescently-labeled caveospheres form a modular system that shows high stability in biological fluids, specific uptake by target-positive cells, and can deliver proteins, drugs, DNA, and mRNA directly to the cytoplasm and nuclei of only the target cells. The negligible level of off-target transduction and uniform levels of targeted expression demonstrates advantages of the system over lipid-mediated gene delivery. Caveospheres can also be engineered to mimic viral particles by displaying the SARS-CoV-2-RBD protein, enabling targeted delivery to human bronchial epithelial cells. We demonstrate their application as a targeted transfection system for cells in culture, and critically, their efficacy in precision tumor killing in vivo.

bioengineering↗

bioRxiv2023

Flexing fish: cell surface plasticity in response to shape change in the whole organism

Plasma membrane rupture can result in catastrophic cell death. The skeletal muscle fibre plasma membrane, the sarcolemma, provides an extreme example of a membrane subject to mechanical stress since these cells specifically evolved to generate contraction and movement. A quantitative model correlating ultrastructural remodelling of surface architecture with tissue changes in vivo is required to understand how membrane domains contribute to the shape changes associated with tissue deformation in whole animals. We and others have shown that loss of caveolae, small invaginations of the plasma membrane particularly prevalent in the muscle sarcolemma, renders the plasma membrane more susceptible to rupture during stretch1-3. While it is thought that caveolae are able to flatten and be absorbed into the bulk membrane to buffer local membrane expansion, a direct demonstration of this model in vivo has been unachievable since it would require measurement of caveolae at the nanoscale combined with detailed whole animal morphometrics under conditions of perturbation. Here, we describe the development and application of the "active trapping model" where embryonic zebrafish are immobilised in a curved state that mimics natural body axis curvature during an escape response. The model is amenable to multiscale, multimodal imaging including high-resolution whole animal three-dimensional quantitative electron microscopy. Using the active trapping model, we demonstrate the essential role of caveolae in maintaining sarcolemmal integrity and quantify the specific contribution of caveolar-derived membrane to surface expansion. We show that caveolae directly contribute to an increase in plasma membrane surface area under physiologically relevant membrane deformation conditions.

cell biology↗

bioRxiv2022

A role for caveolar proteins in regulation of the circadian clock

Caveolae are specialized invaginations of the plasma membrane that are formed by the co-assembly of caveolin integral membrane proteins and a cytoplasmic cavin coat complex. Previous work has proposed an interaction of the cavin coat protein, CAVIN3, with the key circadian clock protein, PER2. Here we show that cavin proteins can play a role in the regulation of the circadian clock by external stimuli. Loss of Cavin1 in mice caused a shortening of the free-running period of locomotor activity. CAVIN1 and CAVIN3 were found to play a central role in core clock dynamics with either cavin protein directly interacting with PER2 and their perturbation leading to significant disruption in core clock mRNA expression and CRY1 protein oscillation. In cells, association of cavins and PER2 was increased upon caveola disassembly caused by oxidative stress or by calcium influx, stimuli linked to circadian clock regulation. We thus propose that the caveola system can play a modulatory role in circadian regulation through the cavin proteins.

cell biology↗

bioRxiv2021

Caveolae, CAVIN1, and lipid peroxidation mediate the oxidative stress response

Caveolae have been linked to many biological functions, but their precise roles are unclear. Using quantitative whole cell proteomics of genome-edited cells, we show that the oxidative stress response is the major pathway dysregulated in cells lacking the key caveola structural protein, CAVIN1. CAVIN1 deletion compromised sensitivity to oxidative stress in cultured cells and in animals. Wound-induced accumulation of reactive oxygen species and apoptosis were suppressed in Cavin1-null zebrafish, negatively affecting regeneration. Oxidative stress triggered lipid peroxidation and induced caveolar disassembly. The resulting release of CAVIN1 from caveolae allowed direct interaction between CAVIN1 and NRF2, a key regulator of the antioxidant response, facilitating NRF2 degradation. CAVIN1-null cells with impaired negative regulation of NRF2 showed resistance to lipid peroxidation-induced ferroptosis. Thus, caveolae, via lipid peroxidation and CAVIN1 release, maintain cellular susceptibility to oxidative stress-induced cell death demonstrating a crucial role for this enigmatic organelle in cellular homeostasis and wound response.

cell biology↗

bioRxiv2021

Muscle-specific Cavin4 interacts with Bin1 to promote T-tubule formation and stability in developing skeletal muscle

The cavin proteins are essential for caveola biogenesis and function. Here, we identify a role for the muscle-specific component, Cavin4, in skeletal muscle T-tubule development by analyzing two vertebrate systems: mouse and zebrafish. In both models Cavin4 localized to T-tubules and loss of Cavin4 resulted in aberrant T-tubule maturation. In zebrafish, which possess duplicated cavin4 paralogs, Cavin4b was shown to directly interact with the T-tubule-associated BAR domain protein, Bin1. Loss of both Cavin4a and Cavin4b caused aberrant accumulation of interconnected caveolae within the T-tubules, a fragmented T-tubule network enriched in Caveolin-3, and an impaired Ca2+ response upon mechanical stimulation. We propose a role for Cavin4 in remodeling the T-tubule membrane early in development by recycling caveolar components from the T-tubule to the sarcolemma. This generates a stable T-tubule domain lacking caveolae that is essential for T-tubule function.

cell biology↗

bioRxiv2020

In vivo proteomic mapping through GFP-directed proximity dependent biotin labelling in zebrafish

Protein interaction networks are crucial for complex cellular processes. However, the elucidation of protein interactions occurring within highly specialised cells and tissues is challenging. Here we describe the development, and application, of a new method for proximity-dependent biotin labelling in whole zebrafish. Using a conditionally stabilised GFP-binding nanobody to target a biotin ligase to GFP-labelled proteins of interest, we show tissue-specific proteomic profiling using existing GFP-tagged transgenic zebrafish lines. We demonstrate the applicability of this approach, termed BLITZ (Biotin Labelling In Tagged Zebrafish), in diverse cell types such as neurons and vascular endothelial cells. We applied this methodology to identify interactors of caveolar coat protein, cavins, in skeletal muscle. Using this system, we defined specific interaction networks within in vivo muscle cells for the closely related but functionally distinct Cavin4 and Cavin1 proteins.

cell biology↗

bioRxiv2020

APEX-Gold: A genetically-encoded particulate marker for robust 3D electron microscopy

Genetic tags allow rapid localization of tagged proteins in cells and tissues. APEX, an ascorbate peroxidase, has proven to be one of the most versatile and robust genetic tags for ultrastructural localization by electron microscopy. Here we describe a simple method, APEX-Gold, which converts the diffuse oxidized diaminobenzidine reaction product of APEX into a silver/gold particle akin to that used for immunogold labelling. The method increases the signal to noise ratio for EM detection, providing unambiguous detection of the tagged protein, and creates a readily quantifiable particulate signal. We demonstrate the wide applicability of this method for detection of membrane proteins, cytoplasmic proteins and cytoskeletal proteins. The method can be combined with different electron microscopic techniques including fast freezing and freeze substitution, focussed ion beam scanning electron microscopy, and electron tomography. The method allows detection of endogenously expressed proteins in genome-edited cells. We make use of a cell-free expression system to generate membrane particles with a defined quantum of an APEX-fusion protein. These particles can be added to cells to provide an internal standard for estimating absolute density of expressed APEX-fusion proteins.

cell biology↗

bioRxiv2020

Cavin3 released from caveolae interacts with BRCA1to regulate the cellular stress response

Caveolae-associated protein 3 (cavin3), a putative tumor suppressor protein, is inactivated in most cancers. We characterized how cavin3 affects the cellular proteome using genome-edited cells together with label-free quantitative proteomics. These studies revealed a prominent role for cavin3 in DNA repair with BRCA1 and BRCA1 A-complex components being downregulated on cavin3 deletion. Cellular and cell-free expression assays, we show a direct interaction between BRCA1 and cavin3. Association of BRCA1 and cavin3 occurs when cavin3 is released from caveolae that are disassembled in response to UV and mechanical stress. Supporting a role in DNA repair, cavin3-deficient cells were sensitized to the effects of PARP inhibition, which compromises DNA repair, and showed reduced recruitment of the BRCA1 A-complex to UV DNA damage foci. Overexpression and RNAi-depletion revealed that cavin3 sensitized various cancer cells to UV-induced apoptosis. We conclude that cavin3 functions together with BRCA1 in multiple pathways that contribute to tumorigenesis.

cancer biology↗

bioRxiv2020

An Endocytic Capture Model for Skeletal Muscle T-tubule Formation

The skeletal muscle T-tubule is a specialized membrane domain essential for coordinated muscle contraction that shows dysmorphology in a number of genetically inherited muscle diseases. However, in the absence of genetically tractable systems the mechanisms involved in T-tubule formation are unknown. Here, we have used the optically transparent and genetically tractable zebrafish system to probe T-tubule development in vivo. By combining live imaging with three-dimensional electron microscopy we derived a four-dimensional quantitative model for T-tubule formation. To elucidate the mechanisms involved in T-tubule formation in vivo we developed a quantitative screen for proteins that associate with and modulate early T-tubule formation including an overexpression screen of the entire zebrafish Rab protein family. We propose a new endocytic capture model involving i) formation of dynamic endocytic tubules at transient nucleation sites on the sarcolemma ii) stabilization by myofibrils/sarcoplasmic reticulum and iii) delivery of membrane from the recycling endosome and Golgi complex.

cell biology↗