Biology subjects

Agostini, L.

Publications and source records attributed to Agostini, L..

5 recordsLinked to original sources

bioRxiv2024

Structural insights into SSNA1 self-assembly and its microtubule binding for centriole maintenance

SSNA-1 is a fibrillar protein localized at the area where dynamic microtubule remodeling occurs including centrosomes. Despite the important activities of SSNA1 to microtubules such as nucleation, co-polymerization, and lattice sharing microtubule branching, the underlying molecular mechanism have remained unclear due to a lack of structural information. Here, we determined the cryo-EM structure of C. elegans SSNA-1 at 4.55 [A] resolution and evaluated its role during embryonic development in C. elegans. We found that SSNA1 forms an anti-parallel coiled-coil, and its self-assembly is facilitated by the overhangs of 16 residues at its C-terminus, which dock on the adjacent coiled-coil to form a triple-stranded helical junction. Notably, the microtubule-binding region is within the triple-stranded junction, highlighting that self-assembly of SSNA-1 facilitates effective microtubule interaction by creating hubs along a fibril. Furthermore, our genetical analysis elucidated that deletion of SSNA-1 resulted in a significant reduction in embryonic viability and the formation of multipolar spindles during cell division. Interestingly, when the ability of SSNA-1 self-assembly was impaired, embryonic viability stayed low, comparable to that of the knockout strain. Our study provides molecular insights into the self-assembly mechanisms of SSNA-1, shedding light on its role in controlling microtubule binding and cell division through the regulation of centriole stability.

cell biology↗

bioRxiv2024

The C. elegans homolog of Sjögrens Syndrome Nuclear Antigen 1 is required for the structural integrity of the centriole and bipolar mitotic spindle assembly

Centrioles play central roles in ciliogenesis and mitotic spindle assembly. Once assembled, centrioles exhibit long-term stability, a property essential for maintaining numerical control. How centriole stability is achieved and how it is lost in certain biological contexts are still not completely understood. In this study we show that SSNA-1, the Caenorhabditis elegans ortholog of Sjogrens Syndrome Nuclear Antigen 1, is a centriole constituent that localizes close to the microtubule outer wall, while also exhibiting a developmentally regulated association with centriole satellite-like structures. A complete deletion of the ssna-1 gene results in an embryonic lethal phenotype marked by the appearance of extra centrioles and spindle poles. We show that SSNA-1 genetically interacts with the centriole stability factor SAS-1 and is required post assembly for centriole structural integrity. In SSNA-1s absence, centrioles assemble but fracture leading to extra spindle poles. However, if the efficiency of cartwheel assembly is reduced, the absence of SSNA-1 results in daughter centriole loss and monopolar spindle formation, indicating that the cartwheel and SSNA-1 cooperate to stabilize the centriole during assembly. Our work thus shows that SSNA-1 contributes to centriole stability during and after assembly, thereby ensuring proper centriole number.

cell biology↗

bioRxiv2022

Direct Cryo-ET observation of platelet deformation induced by SARS-CoV-2 Spike protein

SARS-CoV-2 is a novel coronavirus responsible for the COVID-19 pandemic. Its high pathogenicity is due to SARS-CoV-2 spike protein (S protein) contacting host-cell receptors. A critical hallmark of COVID-19 is the occurrence of coagulopathies. Here, we report the direct observation of the interactions between S protein and platelets. Live imaging showed that the S protein triggers platelets to deform dynamically, in some cases, leading to their irreversible activation. Strikingly, cellular cryo-electron tomography revealed dense decorations of S protein on the platelet surface, inducing filopodia formation. Hypothesizing that S protein binds to filopodia-inducing integrin receptors, we tested the binding to RGD motif-recognizing platelet integrins and found that S protein recognizes integrin v{beta}3. Our results infer that the stochastic activation of platelets is due to weak interactions of S protein with integrin, which can attribute to the pathogenesis of COVID-19 and the occurrence of rare but severe coagulopathies.

cell biology↗

bioRxiv2021

Deep-sea plastisphere: long-term colonization by plastic-associated bacterial and archaeal communities in the Southwest Atlantic Ocean

Marine plastic pollution is a global concern because of continuous release into the oceans over the last several decades. Although recent studies have made efforts to characterize the so-called plastisphere, or microbial community inhabiting plastic substrates, it is not clear whether the plastisphere is defined as a core community or as a random attachment of microbial cells. Likewise, little is known about the influence of the deep-sea environment on the plastisphere. In our experimental study, we evaluated the microbial colonization on polypropylene pellets and two types of plastic bags: regular high density polyethylene (HDPE) and HDPE with the oxo-biodegradable additive BDA. Gravel was used as control. Samples were deployed at three sites at 3,300 m depth in the Southwest Atlantic Ocean and left for microbial colonization for 719 days. For microbial communities analysis, DNA was extracted from the biofilm on plastic and gravel substrates, and then the 16S rRNA was sequenced through the Illumina Miseq platform. Cultivation was performed to isolate strains from the plastic and gravel substrates. Substrate type strongly influenced the microbial composition and structure, while no difference between sites was detected. Although several taxa were shared among plastics, we observed some groups specific for each plastic substrate. These communities comprised taxa previously reported from both epipelagic zones and deep-sea benthic ecosystems. The core microbiome (microbial taxa shared by all plastic substrates) was exclusively composed by low abundance taxa, with some members well-described in the plastisphere and with known plastic-degradation capabilities. Additionally, we obtained bacterial strains that have been previously reported inhabiting plastic substrates and/or degrading hydrocarbon compounds, which corroborates our metabarcoding data and suggests the presence of microbial members potentially active and involved with degradation of these plastics in the deep sea.

microbiology↗

bioRxiv2019

In silico design of glyco-D,L-peptide antiviral molecules.

Backgroundmost licensed antiviral drugs are nucleoside analogs. A recent research focuses on blocking a virus from entering the cells in the viral cell adsorption/entry stage. In this entry mechanism the glycans present on the viral surface play a fundamental role. Homochiral L-peptides acting this fusion mechanism have shown some inhibition of viral infection. Peptides with regularly alternating enantiomeric sequence (L,D-peptides) can assume structures, which are not accessible to the corresponding homochiral molecules. Further, L,D-peptides are less sensitive to the enzymatic digestion.\n\nAimin silico design a L,D-peptide with a high affinity for the viral surface glycans, and consequently able to interfere with its fusion mechanism.\n\nMethodsa 3,6-Mannopentaose (3-6MP) molecule was used to simulate a viral surface glycan. Molecular Dynamics (MD) simulations of 3-6MP and D,L-peptide in water are performed using the force field AMBER12-GLYCAM06i. The binding constant was evaluated from trajectories. The D,L-peptide molecule was modified over the sequence, the length, the terminals and finally glycosylated to attain a very high binding constant value for 3-6MP.\n\nIn addition, the specific interaction between T lymphocyte CD4 glycoprotein and HIV envelope gp120 glycoprotein was studied through MD simulations between a D,L-peptide, bounded to a typical CD4 glycan, and a highly conserved HIV gp120 glycan.\n\nResultsin the case of interaction with 3-6MP molecule, the very effective molecule obtained was H-D-Trp-L-Pro-D-Asn-L-Pro-D-Trp-L-Pro-D-Asn-L-Pro-OH where the Asn residues in position 3 and 7 are glycosylated with alpha-D-Mannopyranosyl-(1->3)-[alpha-D-mannopyranosyl-(1->6)]-alpha-D-mannopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-1-OH.\n\nIn the case of interaction with HIV envelope, the very effective molecule obtained, able to antagonize the CD4 glycoprotein, was H-D-Trp-L-Pro-D-Asn-L-Pro-D-Trp-L-Pro-D-Asn-L-Pro-OH where the Asn residue in position 3 is glycosylated with alpha-D-galactopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-(1->2)-alpha-D-Mannopyranosyl-(1->3)-[alpha-D-galactopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-(1->2)-alpha-D-Mannopyranosyl-(1->6)]-beta-D-mannopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-(1->4)-N-acetyl-beta-D-glucopyranosyl-1-OH\n\nConclusionthese glycosylated D,L-peptide molecules are very promising representatives of a new class of antiviral agents.

bioinformatics↗