Biology subjects

Calvo, E.

Publications and source records attributed to Calvo, E..

At least 19 recordsLinked to original sources

bioRxiv2026

Membrane surface geometry is a determinant of mitochondrial electron transfer and cellular adaptation

Energy conversion in living organisms relies on biological membranes that facilitate electron transfer between oxidoreductases. In mitochondria, this process is mediated by the electron transport chain embedded in the inner mitochondrial membrane (IMM). Under various physiological and genetic conditions, mitochondrial matrix Na+ levels increase, reducing IMM fluidity through the formation of ternary coordination adducts between Na+ and phospholipids. These adducts impair ubiquinone (CoQ) transfer between respiratory complexes, thereby promoting mitochondrial reactive oxygen species (mtROS) production and activating the hypoxic adaptive pathway. Here, we show that modifying solely the ionic subatomic interaction with phospholipids is sufficient to prevent initiation of this pathway. Compound A (CA) outcompetes Na+ for phospholipid binding without impairing CoQ transfer, thereby preventing mtROS production and hypoxic adaptation. This divergence arises from the penta-coordinate complexes formed by CA with phospholipids, in contrast to the trigonal adducts formed by Na+. This structural distinction preserves IMM fluidity because CA:phospholipid assemblies adopt a less angular configuration. These findings establish membrane-surface geometry, modulated by ion:phospholipid interactions, as an unexpected determinant of membrane biology, mitochondrial energy conversion, redox signalling, and cellular adaptation, with profound implications for physiology and disease.

biochemistry↗

bioRxiv2026

Chromosome-Level Nuclear Genome of Simulium vittatum Links Black Fly Cytogenetics to Genome Organization and Evolution

Black flies (Diptera: Simuliidae) are important vectors of pathogens affecting human and animal health, yet the absence of a chromosome-level nuclear reference genome has constrained molecular and evolutionary studies of the family. Here, we present the first chromosome-level nuclear genome and a developmental transcriptomic resource for the long-established IS-7 laboratory lineage of Simulium vittatum. Combining Oxford Nanopore long-read sequencing with Hi-C scaffolding, we assembled a 340.4-Mb genome, with 99.1% of the assembly resolved into three chromosome-length scaffolds (N50=104.8 Mb, BUSCO completeness 93.9%), consistent with the known 2n = 6 karyotype. Using the historically mapped molecular landmarks SVAT and SVEP, we assigned the two arms of chromosome III as IIIS and IIIL, respectively, linking sequence coordinates to the classical polytene chromosome map. Repetitive DNA comprises 46.48% of the assembly, including 29.68% unclassified repeats, and annotation identified 14,732 protein-coding genes and 16,417 transcripts. Integration with larval RNA-seq recovered the previously characterized silk gland proteins SGP-1-SGP-3 and resolved the expressed SGP-2 sequence despite a remaining discrepancy with the genomic sequence. This reference genome connects classical black fly cytogenetics with sequence-level analyses of genome organization, structural variation, and gene content, addressing a major genomic gap within Culicomorpha and providing a foundation for comparative studies of chromosome evolution, hematophagy, and vector biology across Simuliidae.

genomics↗

bioRxiv2026

Prognostic stratification by LGR5 expression identifies surface-accessible, structurally ligandable and condensate-forming targets in colorectal cancer

Background: LGR5 marks colorectal cancer stem cells and is associated with poor outcome, but its expression on normal intestinal stem cells has constrained direct therapeutic targeting, and the molecular landscape of LGR5-high tumors remains incompletely defined. A transcriptional signature is not itself a set of drug targets: its constituent genes differ in whether and how they can be engaged pharmacologically, a distinction rarely applied systematically to a tumor-defined gene set. Methods: We stratified 396 colorectal tumors from The Cancer Genome Atlas by LGR5 expression and compared transcriptional, somatic mutation, and copy number profiles between LGR5-high and LGR5-low groups using non-parametric testing with combined significance and effect-size thresholds. Genome-wide CRISPR knockout data were interrogated to test genetic dependency. Each signature gene was then triaged by pharmacological tractability rather than essentiality, along three axes: surface accessibility, from surfaceome annotation and membrane topology; cavity ligandability, from pocket detection on predicted structures using three independent algorithms; and condensate propensity, from saturation concentration prediction and coarse-grained molecular dynamics simulation. Results: LGR5-high tumors displayed a coordinated program spanning Wnt signaling, stemness, and matrix remodeling, arising on an APC-mutant background with co-occurring IGF2 amplification. No constituent gene scored as a selective dependency. The three axes partitioned the signature with minimal overlap and nominated three candidates engaged by orthogonal modalities: ENPP3, a single-pass ectoenzyme presenting an accessible ectodomain and carrying clinical antibody-drug conjugate precedent; PLCB4, combining a well-defined catalytic pocket with additional predicted ligandable sites; and NKD1, accessible by neither route but undergoing RNA-stabilized homotypic phase separation, unlike SATB1 and MEX3A. Simulations further indicated that NKD1 partitions into DVL2-containing condensates and reduces DVL2-Wnt contacts, suggesting a biophysical basis for its negative-feedback role. Conclusions: LGR5 expression defines a colorectal cancer subset that is pharmacologically tractable despite the absence of genetic dependency. Triaging by modality rather than essentiality converts descriptive tumor signatures into stratified, experimentally testable therapeutic hypotheses, including condensate-directed modulation of NKD1 as a route to targets inaccessible by antibody- or pocket-based approaches.

molecular biology↗

bioRxiv2026

A generalizable normalization framework to decouple protocol and instrument effects: Application to high-sensitivity proteomics multicentric study (PME13)

Multicenter studies are essential for benchmarking analytical workflows, yet their interpretation is often confounded by the combined effects of experimental protocols and instrumentation. To address this challenge, we introduce a simple normalization-based analytical framework, the recovery metric ({rho}), designed to decouple protocol driven effects from instrument dependent variability. We applied this framework to the 13th Proteomics Multicentric Experiment (PME13), a large multicentric proteomics dataset generated across 27 laboratories using high sensitivity workflows and varying sample preparation protocols. By leveraging a common digested reference sample, {rho} enables direct cross-comparison of all datasets on a unified scale, effectively minimizing instrument-related biases. Using this approach, we demonstrate that apparent instrument dependent trends are largely removed when evaluated through {rho}, revealing consistent protocol driven effects across laboratories. Statistical modeling identified key variables influencing {rho}, including sample input amount, reduction and alkylation, and the use of n-dodecyl-{beta}-D-maltoside (DDM). While DDM was associated with improved {rho}, reduction and alkylation and additional handling steps led to reduced performance, particularly at low input levels. We further highlight practical considerations for the application of ratio based normalization, including the occurrence of values exceeding theoretical bounds, which reflect deviations from underlying assumptions and require appropriate filtering. Overall, this work establishes a generalizable analytical strategy for disentangling confounding factors in multicentric datasets and provides practical guidelines for optimizing high sensitivity proteomics (HSP) workflows. The proposed framework is broadly applicable to other analytical fields where cross laboratory comparability is required.

bioinformatics↗

bioRxiv2026

Human SHED-derived extracellular cues activate a specialized neuroprotective and regenerative program in developing retinal ganglion cells

Axonal degeneration and insufficient neuronal survival remain major barriers to central nervous system repair. Stem cells from human exfoliated deciduous teeth (SHED) represent an accessible, developmentally immature, neural crest-derived mesenchymal stem cell population with potential relevance for neuroregenerative medicine. Here, we show that SHED display enhanced proliferative stability, preserved mesenchymal identity, and more sustained expansion capacity than adult dental pulp stem cells, supporting their suitability for scalable regenerative applications. Using embryonic chick retinal explants at neurogenic and post-neurogenic stages, we demonstrate that SHED robustly promote retinal ganglion cell axonogenesis, axonal regeneration, and neuronal survival. At embryonic day 5, SHED enhanced axonal outgrowth in both newly generated EdU/TUJ1 neurons and pre-existing EdU-/TUJ1 retinal ganglion cells. At embryonic day 13, when retinal neurons are post-mitotic and intrinsically less regenerative, SHED still significantly increased regenerative axonal extension and reduced developmental cell death. To investigate the molecular mechanisms underlying the neuroprotective and axogenic effects of SHED, proteomic profiling of SHED-retina co-culture secretomes was performed, revealing a highly enriched extracellular environment containing matrix-associated and neurodevelopmental proteins, including thrombospondin-1 (THBS1), galectin1 and 3, and multiple proteins associated with IGF2 pathway. Proteomic analysis of the SHED secretome, together with prior evidence implicating thrombospondin signaling in neuronal development and synaptogenesis, identified THBS1 as a strong candidate mediator of SHED-induced effects in chick retinal co-culture systems. Neutralization of THBS1, particularly in combination with gabapentin-mediated blockade of 2{delta}-1-dependent thrombospondin signaling, markedly reduced SHED-induced axonal growth and induced neuritic swellings consistent with impaired axonal integrity. In contrast, inhibition of THBS1 signaling did not significantly abolish the neuroprotective effect of SHED on neuronal survival, suggesting that distinct paracrine mechanisms independently regulate axonal regeneration and cell survival. Together, these findings demonstrate that SHED-derived combined secreted factors promote neuronal survival and axonal regeneration through partially divergent extracellular matrix-associated developmental pathways, positioning SHED and their secretome as promising candidates for cell-based and cell-free neuroregenerative strategies.

cell biology↗

bioRxiv2026

Condensate-Driven Transcriptional Reprogramming Defines Core Vulnerabilities in Esophageal and Gastric Cancers

Biomolecular condensates organize key nuclear functions by compartmentalizing biomolecules, yet their contribution to gastrointestinal tumorigenesis remains poorly defined. Integrating multi-omics profiling, functional genomics, and molecular dynamics simulations, we reveal that esophageal and gastric cancers share a condensate-enriched transcriptional program driven by intrinsically disordered proteins involved in transcription, RNA processing, and replication stress. Transcriptomic analyses identify a hyperactive transcriptional state with upregulation of condensate-associated genes, including TOPBP1 and CHERP. Dependency mapping demonstrates that these proteins are essential for tumor cell viability, defining a conserved condensate core across different tumor types. Machine-learned predictions and residue-resolution coarse-grained simulations confirm that TOPBP1 and CHERP undergo phase separation through homotypic interactions mediated by intrinsically disordered regions, with saturation concentrations below 2 {micro}M, consistent with spontaneous condensate formation observed in vitro. Together, these findings establish condensate organization as a fundamental mesoscale principle in upper gastrointestinal cancers and nominate condensate scaffolds as tractable therapeutic vulnerabilities.

bioinformatics↗

bioRxiv2026

Pathological stiffening by crosslinking glycation of titin

Heterogeneous, non-enzymatic glycation chemistry triggered by sugar-derived metabolites is typical of diseases that also entail pathological stiffening of cells, such as diabetes and age-related disorders. However, the mechanisms responsible for cell stiffening and the role of glycated biomolecules remain largely unexplored. Here, we show that glycation of cardiac titin, a giant intracellular protein scaffolding contractile sarcomeres, is increased in diabetes and leads to rigidification of both the protein and cardiomyocytes. Mechanistically, glycation-induced titin stiffening results from decreased contour length and enhanced folding of otherwise structurally intact protein domains following extensive formation of intramolecular crosslinking advanced glycation end products (AGEs). These stiffening effects outweigh softening contributions by competing, non-crosslinking AGEs. In combination, our work overcomes the intrinsic chemical complexity typical of glycation to uncover crosslinking AGEs as a source of pathological stiffening of cells, which we propose contributes to tissue dysfunction in situations of glycative stress.

biophysics↗

bioRxiv2025

Integrative multi-layer workflow for quantitative analysis of post-translational modifications

Novel algorithms based on ultratolerant database searching have paved the way for comprehensive analysis of all possible post-translational modifications (PTM) that can be detected by mass spectrometry-based proteomics, obviating their prior knowledge. These tools together with novel quantitative statistical models allow hypothesis-free approaches to study the role and impact of PTM on biological systems. However, interpretation of this information from a pathophysiological perspective is challenging due to the huge amounts of PTM data, the existence of chemical, structural, and statistical artifacts and the lack of dedicated tools for their analysis. Here we propose a novel integrative workflow that automatically captures several layers of PTM-related information, including variations in trypsin efficiency, zonal changes, specific PTM changes and hypermodified regions, allowing advanced control of artefacts and coherent and comprehensive interpretation of PTM data. We show the performance of the new workflow by reanalyzing proteomics data from animal models of mitochondrial heteroplasmy and ischemia/reperfusion, revealing relevant PTM information not previously detectable, including consistent detection of novel oxidative modifications in Met and Cys residues from raw proteomics data. The workflow is available through the application PTM-compass.

bioinformatics↗

bioRxiv2024

A deep audit of the PeptideAtlas database uncovers evidence for unannotated coding genes and aberrant translation

The human genome has been the subject of intense scrutiny by experimental and manual curation projects for more than two decades. Novel coding genes have been proposed from large-scale RNASeq, ribosome profiling and proteomics experiments. Here we carry out an in-depth analysis of an entire proteomics database. We analysed the proteins, peptides and spectra housed in the human build of the PeptideAtlas proteomics database to identify coding regions that are not yet annotated in the GENCODE reference gene set. We find support for hundreds of missing alternative protein isoforms and unannotated upstream translations, and evidence of cross-contamination from other species. There was reliable peptide evidence for 34 novel unannotated open reading frames (ORFs) in PeptideAtlas. We find that almost half belong to coding genes that are missing from GENCODE and other reference sets. Most of the remaining ORFs were not conserved beyond human, however, and their peptide confirmation was restricted to cancer cell lines. We show that this is strong evidence for aberrant translation, raising important questions about the extent of aberrant translation and how these ORFs should be annotated in reference genomes.

genomics↗

bioRxiv2024

Environmental and anthropic factors influencing Aedes aegypti and Aedes albopictus (Diptera: Culicidae), with emphasis on natural infection and dissemination: Implications for an emerging vector in Colombia.

BackgroundViruses such as dengue virus (DENV), Zika virus (ZIKV), and chikungunya virus (CHIKV) pose major threats to human health, causing endemic, emerging, and reemerging diseases. These arboviruses have complex life cycles involving Aedes mosquitoes, driven by environmental, ecological, socioeconomic, and cultural factors. In Colombia, Aedes aegypti is the primary vector, but Aedes albopictus is expanding across the country. Understanding the unique characteristics of each species is crucial for managing arbovirus spread, particularly in areas where they coexist. Methodology/Principal FindingsWe conducted an entomological survey of A. aegypti and A. albopictus (larvae, pupae, and adults) in urban and rural areas of four municipalities across different elevations (200-2200 meters above sea level) in Colombia. Household conditions and knowledge of DENV were assessed through interviews. Female A. albopictus were tested individually for arbovirus RNA, while A. aegypti were tested in pools. Both species were found up to 2100 masl. A. aegypti comprised 78% of the immature forms collected, while A. albopictus made up 22%. Larvae from both species coexisted in common artificial breeding sites in urban and rural areas, with no evidence of competition. A. albopictus preferred rural areas, lower elevations (<1500 masl), high precipitation (>270 mm), and poor household conditions, while A. aegypti was more abundant in urban areas, intradomicile environments, and areas with moderate precipitation (100-400 mm). Biting risk was higher for A. aegypti (0.02-0.22 females per person), particularly in urban areas, while A. albopictus exhibited lower biting risk (0.001-0.08), with the highest values in rural Patia. Natural infections of DENV (12.4%) and CHIKV (12.4%) were found in A. aegypti, while A. albopictus showed CHIKV (41.2%) and DENV (23%) infections, with virus dissemination to the legs and salivary glands. Conclusions/SignificanceIntegrating household conditions and community knowledge with environmental data can enhance predictive models for vector presence and guide surveillance and educational strategies. Our findings highlight the need to consider A. albopictus as a potentially significant arbovirus vector in Colombia, especially given the presence of arboviruses in its salivary glands, its use of artificial breeding sites, its biting risk inside homes, and its differing ecological preferences and seasonal associations compared to A. aegypti. AUTHOR SUMMARYIn this study, we investigated the ecological and epidemiological dynamics of Aedes aegypti and Aedes albopictus and their natural infection with DENV, ZIKV, and CHIKV in Colombia. An entomological survey conducted across four municipalities revealed distinct environmental and human-related factors influencing the distribution and abundance of these species. A. aegypti was more abundant in urban environments, favoring areas with lowest precipitation and a range of household conditions, while A. albopictus was more common in rural areas with higher precipitation and poorer household conditions. Both species were naturally infected with DENV and CHIKV, with A. albopictus showing the ability to disseminate, as indicated by their presence in the legs and salivary glands. Our findings underscore the importance of understanding species-specific ecological characteristics and incorporating community knowledge into predictive models to improve vector surveillance and control strategies, particularly in regions where both species coexist and contribute to arbovirus transmission.

ecology↗

bioRxiv2024

Time-resolved mitochondrial-focused screening identifies regulatory components of oxidative metabolism

Defects in mitochondrial oxidative metabolism contribute to various genetic inherited disorders, termed mitochondrial diseases, with limited treatment options. Given the lack of functional annotation for numerous mitochondrial proteins, there is a necessity for an extensive gene inventory related to mitochondrial function, with special interest in Oxidative Phosphorylation (OXPHOS). To address this gap, we developed a CRISPR/Cas9 loss-of-function library targeting nuclear-encoded mitochondrial genes and conducted galactose-based screenings at various time points to uncover novel regulators of mitochondrial function. Our study resulted in a gene catalog essential for mitochondrial oxidative metabolism, and constructed a dynamic timeline mapping a broad network of mitochondrial pathways, with a particular focus on the OXPHOS complexes. Computational analysis pinpointed RTN4IP1 and ECHS1 as key genes strongly associated with OXPHOS and whose mutations are associated with mitochondrial diseases in humans. RTN4IP1 was found to be crucial for mitochondrial respiration, with complexome profiling revealing its role as an assembly factor required for the complete assembly of complex I. Furthermore, we discovered that ECHS1 controls oxidative metabolism independently of its canonical function in fatty acid oxidation. Deletion of ECHS1 leads to reduced catabolism of branched-chain amino acids (BCAAs), which impairs the activity of lipoic acid-dependent enzymes such as pyruvate dehydrogenase (PDH). This deleterious phenotype can be rescued by restricting valine intake or catabolism in ECHS1-deficient cells.

molecular biology↗

bioRxiv2024

Dysregulated Skeletal Muscle Myosin Super-relaxation in Type II, but Not Type I, Diabetes Mellitus

Disrupted energy balance is critical for the onset and development of Type II diabetes. The exact underlying metabolic mechanisms remain incomplete but skeletal muscle is thought to play an important pathogenic role. As the super-relaxed state of its most abundant protein, myosin, regulates cellular energetics, here, we aimed to investigate whether it is altered in patients with type II diabetes. For that, we used vastus lateralis biopsy specimens (obtained from patients with type II diabetes and matched controls) and run a combination of structural and functional assays consisting of loaded Mant-ATP chase experiments, X-ray diffraction and LC-MS/MS proteomics in isolated muscle fibres. Our studies revealed a greater muscle myosin super-relaxation and decreased cellular ATP demand in patients than controls. Subsequent proteomic analyses indicated that these (mal)adaptations likely originated from remodeled sarcomeric proteins and greater myosin glycation levels in patients than controls. Overall, our findings emphasize a complex molecular dysregulation of myosin super-relaxed state and energy consumption in type II diabetes. Ultimately, pharmacological targeting of myosin could benefit skeletal muscle and whole-body metabolic health through the enhancement of ATP consumption. Significance StatementMyosin super-relaxation, essential for the regulation of skeletal muscle metabolic rate, is disrupted in type II diabetes due to protein hyper-glycation. As a consequence, myosin ATP demand is significantly lowered. Overall, our findings provide a strong rationale for the use of activators of myosin ATPase to enhance basal energy expenditure in type II diabetes.

cell biology↗

bioRxiv2024

Global genomics of Aedes aegypti unveils widespread and novel persistent infectious viruses capable of triggering a small RNA response

The mosquito Aedes aegypti is a prominent vector for arboviruses, but the breadth of mosquito viruses that infects this specie is not fully understood. In the broadest global survey to date of over 200 Ae. aegypti small RNA samples, we detected viral small interfering RNAs (siRNAs) and Piwi interacting RNAs (piRNAs) arising from mosquito viruses. We confirmed that most academic laboratory colonies of Ae. aegypti lack persisting viruses, yet two commercial strains were infected by a novel tombus-like virus. Ae. aegypti from North to South American locations were also teeming with multiple insect viruses, with Anphevirus and a bunyavirus displaying geographical boundaries from the viral small RNA patterns. Asian Ae. aegypti small RNA patterns indicate infections by similar mosquito viruses from the Americas and reveal the first wild example of dengue virus infection generating viral small RNAs. African Ae. aegypti also contained various viral small RNAs including novel viruses only found in these African substrains. Intriguingly, viral long RNA patterns can differ from small RNA patterns, indicative of viral transcripts evading the mosquitoes RNA interference (RNAi) machinery. To determine whether the viruses we discovered via small RNA sequencing were replicating and transmissible, we infected C6/36 and Aag2 cells with Ae. aegypti homogenates. Through blind passaging, we generated cell lines stably infected by these mosquito viruses which then generated abundant viral siRNAs and piRNAs that resemble the native mosquito viral small RNA patterns. This mosquito small RNA genomics approach augments surveillance approaches for emerging infectious diseases.

genomics↗

bioRxiv2024

ARHGEF17/TEM4 regulates the cell cycle through control of G1 progression

The Ras homolog (Rho) small GTPases, via their role in regulating the actin cytoskeleton, coordinate diverse cellular functions including cell morphology, adhesion and motility, as well as cell cycle progression, survival and apoptosis. The upstream Rho regulators for many of these functions are unknown. ARHGEF17 (also known as TEM4) is a Rho family guanine nucleotide exchange factor (GEF) that been implicated in cell migration, cell-cell junction formation and the mitotic checkpoint. In this study we characterize the regulation of the cell cycle by TEM4. We demonstrate that TEM4 depleted cells exhibit multiple defects in mitotic entry and duration, spindle morphology, and spindle orientation. In addition, we find that TEM4 insufficiency leads to excessive cortical actin polymerization and cell rounding defects. Mechanistically, we demonstrate that TEM4 depleted cells delay in G1 as a consequence of elevated levels of the G1/S inhibitor p21waf1/cip1 and that TEM4 depleted cells that progress through to mitosis, do so with decreased transcription of CCNB1 and thus attenuated levels of cyclin B. Importantly, cyclin B overexpression in TEM4-depleted cells largely rescues mitotic progression and chromosome segregation defects in anaphase. Our study thus illustrates the consequences of Rho signalling imbalance on cell cycle progression and identifies TEM4 as the first GEF governing Rho GTPase-mediated regulation of G1/S.

cell biology↗

bioRxiv2024

Broad therapeutic benefit of myosin inhibition in hypertrophic cardiomyopathy

Myosin inhibitor mavacamten is the only targeted treatment available for hypertrophic cardiomyopathy (HCM), a disease caused by hundreds of genetic variants that affect mainly sarcomeric myosin and its negative regulator cardiac myosin-binding protein C (cMyBP-C, encoded by MYBPC3). Here, we have examined whether the reported limited efficacy of mavacamten in a fraction of HCM patients can result from dissimilar HCM pathomechanisms triggered by different genetic variants, a scenario particularly relevant for MYBPC3-associated HCM. To this aim, we have generated knock-in mice including missense pathogenic variant cMyBP-C p.R502W, which, different from patients who carry truncations in the protein, develop progressive pathogenic myocardial remodeling in the absence of alterations of cMyBP-C levels and localization. Mechanistically, we find that mutation R502W reduces the binding affinity of cMyBP-C for myosin without inducing a shift towards more active myosin conformations as observed when cMyBP-C levels are reduced. Despite these diverging molecular alterations, we show that mavacamten blunts myocardial remodeling both in R502W and cMyBP-C-deficient, knock-out hearts. These beneficial effects are accompanied by improved tolerance to exercise only in R502W animals. Hence, our results indicate that myosin inhibition is effective to treat HCM caused by both truncating and missense variants in MYBPC3 regardless of the primary pathomechanisms they elicit.

physiology↗

bioRxiv2024

In-gel protein digestion using acidic methanol produces a highly selective methylation of glutamic 1 acid residues.

Mass-tolerant open search methods allow the high-throughput analysis of modified peptides by mass spectrometry. These techniques have paved the way to unbiased analysis of post-translational modifications (PTMs) in biological contexts, as well as of chemical modifications produced during the manipulation of protein samples. In this work, we have analyzed in-depth a wide variety of samples of different biological origin, including cells, extracellular vesicles, secretomes, centrosomes and tissue preparations, using Comet-ReCom, a recently improved version of the open search engine Comet-PTM. Our results demonstrate that glutamic acid residues undergo intensive methyl esterification when protein digestion is performed using in-gel techniques, but not using gel-free approaches. This effect was highly specific to Glu and was not found for other methylable residues such as Asp.

systems biology↗

bioRxiv2023

Na+/H+ antiporter activity by respiratory complex I controls mitochondrial membrane potential and is impaired in LHON disease

The mitochondrial electron transport chain (mETC) converts the energy of substrate oxidation into a H+ electrochemical gradient ({Delta}p), which is composed by an inner mitochondrial membrane (IMM) potential ({Delta}{Psi}mt) and a pH gradient ({Delta}pH). So far, {Delta}{Psi}mt has been assumed to be composed exclusively by H+. Mitochondrial Ca2+ and Na+ homeostasis, which are essential for cellular function, are controlled by exchangers and antiporters in the inner mitochondrial membrane (IMM). In the last few years, some of them have been identified, except for the Na+-specific mitochondrial Na+/H+ exchanger (mNHE). Here, using a rainbow of mitochondrial and nuclear genetic models, we have identified the P-module of complex I (CI) as the major mNHE. In turn, its activity creates a Na+ gradient across the IMM, parallel to {Delta}pH, which accounts for half of the {Delta}{Psi}mt in coupled respiring mitochondria. We have also found that a deregulation of this mNHE function in CI, without affecting its enzymatic activity, occurs in Leber hereditary optic neuropathy (LHON), which has profound consequences in {Delta}{Psi}mt and mitochondrial Ca2+ homeostasis and explains the previously unknown molecular pathogenesis of this neurodegenerative disease.

biochemistry↗

bioRxiv2023

Anopheles salivary apyrase regulates blood meal hemostasis and drives malaria parasite transmission

Mosquito salivary proteins play a crucial role in regulating hemostatic responses at the bite site during blood feeding. In this study, we investigate the function of Anopheles gambiae salivary apyrase (AgApyrase) in Plasmodium transmission. Our results demonstrate that salivary apyrase interacts with and activates tissue plasminogen activator, facilitating the conversion of plasminogen to plasmin, a human protein previously shown to be required for Plasmodium transmission. Microscopy imaging shows that mosquitoes ingest a substantial amount of apyrase during blood feeding which reduces coagulation in the blood meal by enhancing fibrin degradation and inhibiting platelet aggregation. Supplementation of Plasmodium infected blood with apyrase significantly enhanced Plasmodium infection in the mosquito midgut. In contrast, AgApyrase immunization inhibited Plasmodium mosquito infection and sporozoite transmission. This study highlights a pivotal role for mosquito salivary apyrase for regulation of hemostasis in the mosquito blood meal and for Plasmodium transmission to mosquitoes and to the mammal host, underscoring the potential for new strategies to prevent malaria transmission.

microbiology↗