Biology subjects

Silva, J. L.

Publications and source records attributed to Silva, J. L..

7 recordsLinked to original sources

bioRxiv2024

Oncogenic Phase Transitions: How Mutant p53 Drives Amyloid Formation in p63 and p73 Liquid Droplets

Phase separation (PS) of p53 is critical in its path to amyloid aggregation, a process linked to cancer. P63 and p73 exhibit dual roles as tumor suppressors and oncogenes and are often heightened in tumors. Their coaggregation has been proposed in cancer, yet their PS contribution remains unknown. This study investigates the phase behaviors of p53, p63, and p73. P63 and p73 undergo liquid-liquid phase separation (LLPS). Unlike p53, p63 and p73 do not form amyloids under increased temperatures, underscoring an aspect of the processes involved in cancer. Unlike p63 and p73, wild-type and the M237I mutant p53 initially form droplets at 4{degrees}C, but at temperatures up to 37{degrees}C, they begin to aggregate and bind to Congo red, showing amyloidogenesis. Intriguingly, mutant p53 promotes amyloid-like states in p63 and p73 and hijacks p73 into membrane less organelles. Wild-type p53 has a moderate effect on p63 and p73s amyloid aggregation. Additionally, heparin prevents the prion-like aggregation of p63 and p73 induced by p53. Our results shed light on how mutant and wild-type p53 may trigger amyloid aggregation of p63 and p73, revealing the capacity of p53 amyloid droplets within cancer. These insights expand the possibilities for developing cancer therapies targeting the prion-like conversion of p63 and p73 influenced by mutated p53. RelevanceThe prion-like action of mutant p53 on p63 and p73 droplets would be the basis for an oncogenic gain of function of the p53 mutation.

cancer biology↗

bioRxiv2022

SARS-CoV-2 spike protein induces long-term TLR4-mediated synapse and cognitive loss recapitulating Post-COVID syndrome

Cognitive dysfunction is often reported in post-COVID patients, but its underlying mechanisms remain unknown. While some evidence indicate that SARS-CoV-2 can reach and directly impact the brain, others suggest viral neuroinvasion as a rare event. Independently of brain viral infection, the ability of SARS-CoV-2 spike (S) protein to cross the BBB and reach memory-related brain regions has already been shown. Here, we demonstrate that brain infusion of S protein in mice induces late cognitive impairment and increases serum levels of neurofilament light chain (NFL), which recapitulates post-COVID features. Neuroinflammation, hippocampal microgliosis and synapse loss are induced by S protein. Increased engulfment of hippocampal presynaptic terminals late after S protein brain infusion were found to temporally correlate with cognitive deficit in mice. Blockage of TLR4 signaling prevented S-associated detrimental effects on synapse and memory loss. In a cohort of 86 patients recovered from mild COVID-19, genotype GG TLR4 -2604G>A (rs10759931) was associated with poor cognitive outcome. Collectively, these findings indicate that S protein directly impacts the brain and suggest that TLR4 is a potential target to prevent post-COVID cognitive dysfunction. One Sentence SummaryTLR4 mediates long-term cognitive impairment in mice and its genetic variant increases the risk of poor cognitive outcome in post-COVID patients.

neuroscience↗

bioRxiv2022

Uncovering the structural flexibility of SARS-CoV-2 glycoprotein spike variants

The severe acute respiratory syndrome CoV-2 rapidly spread worldwide, causing a pandemic. After a period of evolutionary stasis, a set of SARS-CoV-2 mutations has arisen in the spike, the leading glycoprotein at the viral envelope and the primary antigenic candidate for vaccines against the 2019 CoV disease (COVID-19). Here, we present comparative biochemical data of the glycosylated full-length ancestral and D614G spike together with three other highly transmissible strains classified by the World Health Organization as variants of concern (VOC): beta, gamma, and delta. By showing that only D614G early variant has less hydrophobic surface exposure and trimer persistence at mid-temperatures, we place D614G with features that support a model of temporary fitness advantage for virus spillover worldwide. Further, during the SARS-CoV-2 adaptation, the spike accumulates alterations leading to less structural rigidity. The decreased trimer stability observed for the ancestral and the gamma strain and the presence of D614G uncoupled conformations mean higher ACE-2 affinities when compared to the beta and delta strains. Mapping the energetic landscape and flexibility of spike variants is necessary to improve vaccine development.

biochemistry↗

bioRxiv2020

Rapid local adaptation in both sexual and asexual invasive populations of monkeyflowers (Mimulus spp.)

Background and AimsTraditionally, local adaptation has been seen as the outcome of a long evolutionary history, particularly in sexual lineages. In contrast, phenotypic plasticity has been thought to be most important during the initial stages of population establishment and in asexual species. We evaluated the roles of adaptive evolution and phenotypic plasticity in the invasive success of two closely related species of invasive monkeyflowers (Mimulus) in the United Kingdom (UK) that have contrasting reproductive strategies: M. guttatus combines sexual (seeds) and asexual (clonal growth) reproduction while M. x robertsii is entirely asexual. MethodsWe compared the clonality (number of stolons), floral and vegetative phenotype, and phenotypic plasticity of native (M. guttatus) and invasive (M. guttatus and M. x robertsii) populations grown in controlled environment chambers under the environmental conditions at each latitudinal extreme of the UK. The goal was to discern the roles of temperature and photoperiod on the expression of phenotypic traits. Next, we tested the existence of local adaptation in the two species within the invasive range with a reciprocal transplant experiment at two field sites in the latitudinal extremes of the UK, and analysed which phenotypic traits underlie potential local fitness advantage in each species. Key ResultsPopulations of M. guttatus in the UK showed local adaptation through sexual function (fruit production), while M. x robertsii showed local adaptation via asexual function (stolon production). Phenotypic selection analyses revealed that different traits are associated with fitness in each species. Invasive and native populations of M. guttatus had similar phenotypic plasticity and clonality. M. x robertsii presents greater plasticity and clonality than native M. guttatus, but most populations have restricted clonality under the warm conditions of the south of UK. ConclusionsOur study provides experimental evidence of local adaptation in a strictly asexual invasive species with high clonality and phenotypic plasticity. This indicates that even asexual taxa can rapidly (< 200 years) adapt to novel environmental conditions in which alternative strategies may not ensure the persistence of populations.

evolutionary biology↗

bioRxiv2020

Equine hyperimmune globulin raised against the SARS-CoV-2 spike glycoprotein has extremely high neutralizing titers

We used the trimeric spike (S) glycoprotein (residues 1-1208) in the prefusion conformation to immunize horses for production of hyperimmune globulins against SARS-CoV-2. Serum antibody titers measured by anti-spike ELISA were above 1:1,000,000, and neutralizing antibody titer was 1:14,604 (average PRNT90), which is 140-fold higher than the average neutralizing titer of plasma from three convalescent COVID-19 patients analyzed for comparison. Using the same technology routinely used for industrial production of other horse hyperimmune products, plasma from immunized animals was pepsin digested to remove the Fc portion and purified, yielding a F(ab)2 preparation with PRNT90 titers 150-fold higher than the neutralizing titers in human convalescent plasma. Repeating the hyperimmunization in a second group of horses confirmed the very high neutralizing titers in serum and in a GMP clinical F(ab)2 lot. Virus-neutralizing activity in samples from mice that received the F(ab)2 preparation was detected even three days after injection, indicating an appropriate half-life for therapeutic intervention. These results supported the design of a clinical trial (identifier NCT04573855) to evaluate safety and efficacy of this horse F(ab)2 preparation.

immunology↗

bioRxiv2019

Liquid-liquid phase separation and aggregation of the prion protein globular domain modulated by a high-affinity DNA aptamer

Structural conversion of cellular prion protein (PrPC) into scrapie PrP (PrPSc) and subsequent aggregation are key events for the onset of Transmissible Spongiform Encephalopathies (TSEs). Experimental evidences support the role of nucleic acids (NAs) in assisting the protein conversion process. Here, we used the SELEX methodology to identify two 25-mer DNA aptamers against the globular domain of recombinant murine PrP (rPrP90-231), namely A1 and A2. High-affinity binding of A1 and A2 to rPrP was verified by ITC. Aptamers structure was characterized by theoretical predictions, CD, NMR and SAXS, revealing that A1 adopts a hairpin conformation. Aptamer binding caused dynamic aggregation of rPrP90-231, resulting from the ability of rPrP90-231 to undergo liquid-liquid phase separation (LLPS). While free rPrP90-231 phase separated into large droplets, aptamer binding increased the amount but reduced the size of the condensates. Strikingly, a modified A1 aptamer that does not adopt a hairpin structure induced transition to an ordered state, suggestive of amyloid formation on the surface of the droplets. Our results describe for the first time PrP:NA interaction leading to LLPS and modulation of this effect depending on NA structure and binding stoichiometry, shedding light on the role of NAs in PrP misfolding and TSEs.

biophysics↗

bioRxiv2019

Yellow Fever Vaccine Protects Resistant and Susceptible Mice Against Zika Virus Infection

Zika virus (ZIKV) emerged as an important infectious disease agent in Brazil in 2016. Infection usually leads to mild symptoms but severe congenital neurological disorders and Guillain-Barre syndrome have been reported following ZIKV exposure. The development of an effective vaccine against Zika virus is a public health priority, encouraging the preclinical and clinical studies of different vaccine strategies. Here, we describe the protective effect of an already licensed attenuated yellow fever vaccine (17DD) on type-I interferon receptor knockout mice (A129) and immunocompetent (BALB/c) mice infected with ZIKV. Yellow fever virus vaccination results in robust protection against ZIKV, with decreased mortality in the A129 mice, a reduction in the cerebral viral load in all mice, and weight loss prevention in the BALB/c mice. Despite the limitation of yellow fever (17DD) vaccine to elicit antibody production and neutralizing activity against ZIKV, we found that YF immunization prevented the development of neurological impairment induced by intracerebral virus inoculation in adult. Although we used two vaccine doses in our protocol, a single dose was protective, reducing the cerebral viral load. Different Zika virus vaccine models have been tested; however, our work shows that an efficient and certified vaccine, available for use for several decades, effectively protects mice against Zika virus infection. These findings open the possibility for using an available and inexpensive vaccine to a large-scale immunization in the event of a Zika virus outbreak.

immunology↗