The starting point of the review is familiar but consequential: as the electron transport chain loses efficiency with age, proton pumping across the inner mitochondrial membrane falters, the membrane potential falls and ATP output declines. At the same time, electrons leak preferentially at respiratory complexes I and III, feeding the production of reactive oxygen species. These oxidants then attack mitochondrial DNA, respiratory-chain proteins and membrane lipids, further degrading oxidative phosphorylation and locking the organelle into a self-amplifying spiral of bioenergetic failure and oxidative stress. The result, the authors emphasise, is not a sudden energetic crash but a gradual decline in mitochondrial performance that predisposes tissues to dysfunction, disturbs calcium handling and stress signalling, and progressively erodes cellular homeostasis.

A central technical theme of the review is the peculiar genetics of mitochondrial DNA. Most pathogenic mitochondrial mutations are functionally recessive at the cellular level because mutant and wild-type genomes coexist within the same cell, a state known as heteroplasmy. As long as enough wild-type copies remain to sustain mitochondrial transcription, translation and respiratory-chain assembly, intracellular complementation preserves oxidative phosphorylation. Only when mutant genomes exceed a critical, tissue- and mutation-specific threshold does respiratory competence fail. That threshold is not fixed: it depends on the severity of the variant, the energy demand of the tissue and the absolute number of mitochondrial genomes per cell, which can buffer a given mutational burden. Ageing, in this framing, is not simply the accumulation of mutations but the growth in the number of cells in which clonally expanded mutant genomes have crossed the threshold that converts silent heteroplasmy into overt bioenergetic pathology.

Human tissue data support this threshold model. In a study of colorectal biopsies from 207 people aged 17 to 78, ageing was linked to a higher frequency of clonally expanded mitochondrial DNA mutations and of respiratory-chain-deficient crypts, suggesting that expansion of early-life mutations over decades drives focal respiratory failure in the ageing colon. The authors are careful, however, to note the limits of such evidence: cross-sectional designs cannot track mutation expansion within individuals or prove that these changes cause systemic inflammaging. Nor should respiratory deficiency be read as a guarantee that reactive oxygen species, senescence and inflammatory activation all follow in the same cells. What the threshold effect provides is a mechanistic bridge between stochastic mutagenesis and phenotypic decline, with mutant loads remaining functionally silent for years before tipping into membrane depolarisation, falling ATP synthesis and rising oxidant production.

Whether such damage is contained or propagated depends on mitochondrial quality control. Fusion and fission remodel the network and segregate damaged components, chaperones and proteases maintain protein homeostasis, and mitophagy, including the well-characterised PINK1-Parkin pathway, delivers damaged mitochondria to lysosomes for degradation. But clearance is only complete when lysosomal degradation actually finishes; impaired acidification or proteolysis can stall turnover even when upstream mitophagy markers accumulate, a warning that autophagy markers should not be equated with degradative flux. Mitochondrial-derived vesicles add another disposal route and can influence the export of inflammatory cargo. In experimental macrophages, mitophagic removal of damaged mitochondria restrains activation of the NLRP3 inflammasome, so failure of these protective systems favours persistent stress and inflammatory amplification, though their relative importance varies with tissue and context.

The review then reframes mitochondria as platforms for regulated cell death, distinguishing programmes that differ in their terminal effectors and inflammatory consequences. Intrinsic apoptosis, the most mitochondria-centred pathway, proceeds through mitochondrial outer membrane permeabilisation, cytochrome c release and caspase activation, and is generally cleared quietly when efferocytosis is efficient. Yet apoptosis is not binary. Work in senescent human fibroblasts identified minority MOMP, in which only a subset of mitochondria permeabilise, allowing BAX/BAK-dependent release of mitochondrial DNA into the cytosol and activation of the cGAS-STING pathway, which shapes the senescence-associated secretory phenotype without killing the cell. Genetic and pharmacological interventions support a contribution of this mechanism to inflammatory phenotypes in aged mice, although its quantitative role in human ageing remains unknown.

Other death programmes add inflammatory layers. Necroptosis, executed through RIPK3-dependent activation of MLKL, can proceed without mitochondria, but mitochondrial reactive oxygen species, permeability transition and defective mitophagy lower the threshold for necroptotic injury, and impaired apoptotic execution can divert stressed cells toward necroptotic rupture and stronger inflammatory output. In pyroptosis, mitochondria act almost as supramolecular organising centres: NLRP3 and caspase-1 assemble on cardiolipin-rich mitochondrial membranes, and gasdermin D, the pore-forming effector that drives release of IL-1β and IL-18, can itself attack mitochondrial membranes in a cardiolipin-dependent manner, promoting depolarisation and further damage-associated molecular pattern release. Ferroptosis, driven by iron-dependent phospholipid peroxidation, is modulated by tricarboxylic acid cycle activity, electron transport and antioxidant buffering, with aged mitochondria showing precisely the redox imbalance and iron dysregulation that sensitise cells to it. The authors stress that mitochondria are pathway-specific participants, not universal regulators.

The molecular interface between mitochondrial injury and innate immunity is the release of mitochondrial damage-associated molecular patterns, whose danger-signalling power derives from the organelle’s bacterial ancestry. Circular, CpG-rich mitochondrial DNA, poorly protected once displaced from the matrix, is sensed by endosomal TLR9 and, in the cytosol, by the cGAS-STING pathway, which triggers TBK1-IRF3 and NF-kB signalling and type I interferon programmes. Mitochondrial RNA, including double-stranded species, can engage antiviral-like sensors, meaning damaged mitochondria mimic microbial signatures even without infection. Cardiolipin exposure recruits inflammasome components, N-formyl peptides activate formyl peptide receptors like bacterial chemotactic factors, and mitochondrial reactive oxygen species lower the activation thresholds of these interconnected circuits. These signals can escape uncontrolled during cell lysis or be actively packaged into extracellular vesicles, extending inflammatory signalling beyond the injured cell.

The pivotal concept tying the review together is mitochondrial dysfunction-associated senescence, or MiDAS. Direct impairment of mitochondrial function is sufficient to drive stable growth arrest in proliferating human cells, marked by a reduced NAD+/NADH ratio, AMPK-dependent p53 activation and a distinctive secretory phenotype. Crucially, the metabolic shift is not a passive by-product: the AMPK-p53 axis that enforces arrest also blunts the IL-1-dependent, self-amplifying arm of the canonical SASP, so MiDAS carries a rewired, non-canonical secretome rather than a uniformly stronger inflammatory output. Restoring mitochondrial redox balance, for instance with pyruvate in experimental systems, can partially rescue the IL-1 arm and shift MiDAS toward a more canonical secretory programme. This specificity matters because it places mitochondrial failure upstream of tissue degeneration and explains why the inflammatory output of senescent cells is heterogeneous. Comparing this with minority MOMP, where cGAS-STING inhibition attenuates the SASP without reversing the arrest, the authors argue that growth arrest and inflammatory amplification are controlled by related but separable mechanisms, and warn against reading them as sequential stages of one established pathway.

On translation, the review is deliberately sober. In a randomised trial of 66 older adults, the mitophagy-inducing supplement urolithin A improved muscle endurance at two months and shifted some plasma biomarkers, but showed no significant benefit in the primary outcomes of six-minute walk distance and maximal ATP production. Senolytic therapy with dasatinib plus quercetin produced feasibility and tolerability data in a five-participant phase I trial in early Alzheimer’s disease, with only dasatinib detected in cerebrospinal fluid, yet a randomised phase II trial in 60 postmenopausal women found no significant difference in its primary bone resorption endpoint. An open-label trial of the NLRP3 inhibitor dapansutrile in acute gout offers only preliminary, uncontrolled evidence, and favourable cGAS-STING results in aged mice remain preclinical. The authors argue that progress requires validated tissue-specific biomarkers of mitophagy, senescence burden and mitochondrial danger signalling, better-defined responder populations, and longer trials with robust ageing-relevant endpoints, while guarding against the risk that chronic suppression of innate immune sensors could compromise host defence. Their synthesis positions mitochondria not as one hallmark among many but as an organising hub through which bioenergetic failure, senescence and sterile inflammation converge, and through which future interventions to slow age-related decline may ultimately be designed.

Subject of Research: Mechanisms linking mitochondrial dysfunction, cellular senescence and inflammaging in ageing

Article Title: Mitochondrial dysfunction and inflammaging: a mechanistic bridge between bioenergetic failure and senescence

Article References: Nesci, S., & Algieri, C. (2026). Mitochondrial dysfunction and inflammaging: a mechanistic bridge between bioenergetic failure and senescence. GeroScience. https://doi.org/10.1007/s11357-026-02588-y

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02588-y

Keywords: mitochondria, inflammaging, cellular senescence, MiDAS, mitochondrial DNA, SASP, cGAS-STING, NLRP3 inflammasome, mitophagy, regulated cell death, reactive oxygen species, ageing

Integrins are heterodimeric adhesion receptors composed of an alpha and a beta chain, and they sit embedded in cell membranes across virtually all metazoan life. Their job is deceptively simple but biologically profound: they anchor cells to the extracellular matrix, transmit mechanical forces, and relay chemical signals from outside the cell to the interior. In humans, integrins are implicated in everything from wound healing to cancer metastasis, and they have become prized pharmaceutical targets. In parasitic helminths, however, integrin homologues have been identified at the sequence level for years, yet their three-dimensional organization and ligand-binding behavior remained largely uncharted territory. The new study set out to close that gap using an integrative computational pipeline rather than laboratory experiments alone.

The researchers began with comparative sequence analysis across medically important Schistosoma species, searching for conserved integrin genes in the genomes of the parasites. Their screen revealed a striking asymmetry. On the beta side, a single highly conserved orthologue, which they named Smβ1, was present and well preserved across species, suggesting that it performs an essential function that evolution has been reluctant to alter. On the alpha side, the picture was more complicated: four divergent alpha-integrin subunits were identified, each carrying distinctive sequence features that hinted at different evolutionary histories and potentially different binding partners. This combination of one conserved beta chain and several variable alpha chains mirrors the architecture of integrin systems in other organisms, where the beta subunit provides the core ligand-binding machinery and the alpha subunit tunes its specificity.

To move from sequences to structures, the team deployed three independent protein-structure prediction engines: AlphaFold3, RoseTTAFold and trRosetta. Convergent predictions from these tools showed that the betaI-containing region of Smβ1 retains the characteristic integrin fold that has been described in exquisite detail for human receptors. Critically, the model preserved the three canonical metal-coordination sites that define integrin ligand recognition: the metal-ion-dependent adhesion site, known as MIDAS, which directly coordinates the acidic residue of incoming ligands; the adjacent ADMIDAS site, which allosterically regulates the receptor’s activation state; and the synergistic metal-binding site, or SyMBS, which helps stabilize the ligand-bound conformation. The retention of these features in a parasite receptor is significant because it suggests that the fundamental chemistry of integrin-ligand engagement, dependent on metal ions bridging receptor and ligand, has been conserved across hundreds of millions of years of evolution separating flatworms from vertebrates.

With individual subunit structures in hand, the next challenge was determining which alpha chain pairs with Smβ1. Integrin function depends entirely on the correct heterodimer assembly, and predicting which of the four candidate alpha subunits forms a stable, functional complex with the beta chain is a problem that sequence similarity alone cannot solve. The researchers therefore constructed an integrated structural benchmarking framework that scored each candidate assembly across multiple independent dimensions: conservation of the overall fold, stereochemical and backbone quality of the predicted model, VoroMQA-based assessment of Voronoi packing density, the architecture of the alpha-beta interface itself, the buried surface area at the interface, and separate interface-context analyses designed to catch artifacts that single metrics might miss.

When the scores were tallied, one pairing stood out. Smα1 in combination with Smβ1 was ranked as the leading heterodimer candidate, while Smα3 paired with Smβ1 remained a structurally plausible alternative that could not be excluded. This ranking mattered because the identity of the alpha subunit shapes the geometry of the ligand-binding pocket that forms at the interface between the two chains. The team then subjected both candidate assemblies to ligand-challenge modelling, docking RGD-containing peptides into the predicted binding sites and comparing the resulting interaction geometries against a human α5β1 integrin benchmark whose RGD-bound structure is experimentally established.

The results were revealing. Smα1/Smβ1 more readily reproduced the coupled interaction pattern seen in the human benchmark, in which the arginine residue of the RGD motif anchors to a defined pocket on the alpha subunit while the aspartate residue coordinates the MIDAS metal ion on the beta subunit. Smα3/Smβ1, by contrast, was less consistent in reproducing this canonical geometry. Across expanded ensembles of ligand structures, canonical and cyclic RGD-containing peptides preferentially adopted RGD-like interaction geometries with the receptor, whereas an RGE mutant peptide, in which the aspartate is replaced by glutamate, and various non-RGD control peptides showed reduced or absent canonical interaction features. This specificity pattern is exactly what one would expect from a genuine RGD-recognizing integrin, since the RGE substitution is a classic experimental control that abolishes integrin binding in well-characterized systems.

Molecular dynamics simulations provided the temporal dimension that static docking cannot capture. In trajectories running 100 and 200 nanoseconds, the canonical RGD peptide remained within a comparatively restricted conformational regime associated with the receptor, suggesting a stable engagement, while the RGE mutant underwent greater displacement and induced more structural mobility in the contact site. Complementary MM/GBSA energetic analysis computed over the 200-nanosecond trajectory frames further supported more favourable energetic compatibility for RGD than for RGE. Together, these dynamic and energetic measures reinforce the picture painted by the docking experiments: the Smα1/Smβ1 complex behaves, under modelled conditions, like a receptor that genuinely prefers RGD ligands over near-identical decoys.

Beyond ligand binding, the study ventured into signaling territory with an exploratory network analysis using the STRING database. This placed Smβ1 within a predicted adhesome-like network that includes the integrin-linked kinase, or ILK, together with its PINCH and Parvin partners and kinase-associated components. In animal cells, the ILK-PINCH-Parvin complex is a central scaffold of the integrin adhesion complex, coupling receptors at the membrane to the actin cytoskeleton and to signaling pathways. Finding a predicted network of this composition around a schistosome beta integrin raises the possibility that the parasite uses signaling machinery broadly analogous to that of its host, which carries implications for how the worm adheres to and navigates host tissues during its complex life cycle.

The authors are careful to frame their conclusions as hypothesis-generating rather than definitive. Every result in the study derives from computational prediction and simulation, and the models, however sophisticated, remain subject to experimental validation. The paper explicitly presents its findings as experimentally testable hypotheses concerning alpha-beta pairing, metal-dependent ligand recognition and integrin-associated signaling in schistosomes. Still, the implications are considerable. If Smα1/Smβ1 is confirmed as a functional RGD-recognizing receptor, it would open a new window on how S. mansoni interacts with host extracellular matrix during infection, and it would offer a structurally characterized parasite-specific target whose human counterparts are already druggable, potentially accelerating the search for much-needed new therapies against a disease for which treatment still relies almost entirely on a single drug, praziquantel.

Subject of Research: Structural and ligand-binding characterization of Schistosoma mansoni integrin receptors

Article Title: Computational structural analysis of Schistosoma integrins supports Smα1/Smβ1 as an RGD-compatible receptor candidate

Article References: Adu, E. A., Owoloye, A., Shakela, N., Aziz, R. N., Boakye, A. O., Acheampong, E., Nyarko, E. N. Y., Adu-Amoah, L., Afum-Adjei Awuah, A., Amuasi, J. H., & Obirikorang, C. (2026). Computational structural analysis of Schistosoma integrins supports Smα1/Smβ1 as an RGD-compatible receptor candidate. BMC Genomics. https://doi.org/10.1186/s12864-026-13429-9

Image Credits: AI Generated

DOI: 10.1186/s12864-026-13429-9

Keywords: Schistosoma mansoni, schistosomiasis, integrins, Smβ1, Smα1, RGD motif, AlphaFold3, molecular dynamics, MIDAS, protein-ligand interactions, host-parasite interactions, structural genomics

The core logic of MIDAS is disarmingly simple. Instead of building plasmids, researchers design overlapping PCR fragments that together encode a complete transcription unit, including a promoter, the variant coding sequence, and a polyadenylation signal. Mutations are introduced through primers at defined target regions, and a secondary overlap-extension PCR stitches the fragments into full-length genes. Each PCR product encodes one defined variant and is transfected into one well of a multiwell plate, so the association between sequence and measured function is preserved by well position alone. Because no ligation, transformation, bacterial culture, plasmid purification, or sequence verification is required, generating 384 variants takes roughly four hours of hands-on time and about 2,000 dollars in reagents, compared with an estimated 192 hours and 20,000 dollars for conventional cloning of the same number of constructs.

The platform comes in several flavors that expand its reach beyond single-site substitutions. Polytemplated monofocal MIDAS, or MIDAS-PM, uses multiple plasmid templates to generate arrays of mutants at one location. Polytemplated polyfocal MIDAS, or MIDAS-PP, extends this to combinations of changes at multiple sites by mixing primary PCR products combinatorially. Most notably, the team developed monotemplated protocols, MIDAS-MM and MIDAS-MP, which work from a single plasmid template. The trick lies in adding unique DNA tags to the 5-prime ends of the outermost primers, so that secondary PCR primers recognize only the assembled primary products and never re-amplify the parental plasmid. Sequencing confirmed that this nested-primer design eliminates template contamination, meaning researchers can begin mutagenizing a protein of interest immediately without first subcloning it into multiple backbone plasmids.

To demonstrate the method, the team took on an ambitious target: a bioluminescent indicator for acetylcholine, a neurotransmitter central to arousal, attention, learning, and memory, and one whose signaling declines early in Alzheimer’s, Parkinson’s, and Lewy body dementias. Fluorescent acetylcholine sensors exist, but they require implanted optical elements to deliver excitation light, which is impractical for moving organs outside the brain. A bioluminescent sensor, by contrast, generates its own light and could report cholinergic activity noninvasively anywhere in the body. The researchers built their prototype, ACh-NeuBI0.1, by inserting split NanoLuc luciferase fragments into OpuBC, a bacterial periplasmic binding protein previously engineered to bind acetylcholine over choline. The initial construct responded to acetylcholine with a modest 22 percent luminescence increase, a starting point that would demand extensive optimization.

MIDAS delivered that optimization in rapid iterative rounds. First, MIDAS-MP screened all 36 combinations of glycine linker lengths connecting the binding protein to the luciferase fragments, identifying a configuration that boosted responsiveness by roughly 50 percent. Next, MIDAS-MM tested all 20 amino acids at a single linker position, revealing that phenylalanine improved the response to about 80 percent. A third round tuned the energetics of luciferase fragment assembly by screening SmBiT variants, finding that a three-residue C-terminal truncation raised the response to approximately 2.5-fold. The team then fused the orange fluorescent protein mScarlet-I to the sensor, enabling resonance energy transfer that shifts a portion of the emission above 610 nanometers, wavelengths that penetrate tissue far more effectively than NanoLuc’s native blue light. At each step, plasmid-based validation confirmed that the PCR-transfected results were reliable.

The deepest round of engineering showcased MIDAS’s capacity for true combinatorial saturation mutagenesis. Guided by computational structure predictions from Chai-1, the researchers selected 16 sites around the acetylcholine-binding pocket and screened every possible amino acid at each, uncovering beneficial mutations at three second-shell positions. Because positions 560 and 610 sit close together in space, the team then used MIDAS-MP to test all 400 combinations of side chains at those two residues. Two winners emerged: variant QAE, named ACh-NeuBI1b, which achieved the highest affinity at 188 micromolar, and variant QED, named ACh-NeuBI1c, which suppressed baseline luminescence to deliver maximum contrast. Strikingly, ACh-NeuBI1c responded to 100 micromolar acetylcholine with a 640 percent signal increase, a 29-fold improvement over the original prototype.

The mathematics of why this matters are sobering. Seven of the nine beneficial amino acid changes discovered in the study required two or three nucleotide substitutions. Under error-prone PCR, a functional clone carrying two specific mutations appears roughly once in every 71 million clones, and some combinations once in 140 million, numbers far beyond what multiwell screening can reach. Deterministic PCR assembly sidesteps this barrier by constructing exactly the variants of interest, one per well, whether that means 20 samples for one site or 400 for two. The approach also outperforms degenerate oligonucleotide libraries, which require oversampling that balloons combinatorially: two sites of saturation mutagenesis would demand more than 10,000 screened samples, roughly 25 times what MIDAS requires.

The team applied the same logic to NanoLuc luciferase itself, performing saturation mutagenesis at all 25 residues lining or influencing the substrate-binding pocket, generating 500 variants in a single MIDAS-MM campaign. A D108N mutation improved photon production across three different substrates, while D108S, which requires two adjacent nucleotide changes and would be vanishingly rare in random libraries, selectively enhanced activity on the aqueous substrate FFz. Beyond engineering, the complete activity matrix enabled sequence-fitness analysis, mapping which active-site positions tolerate substitution and which are intolerable, and revealing substrate-specificity determinants whose locations often defied structural prediction. Because NanoLuc produces too few photons for fluorescence-activated cell sorting, the multiwell format proved essential, connecting MIDAS to the gold-standard analytical assays, from luminescence to absorbance to chromatography, that apply to most enzymes.

The biological payoff extended from cell culture into living animals. In primary cortical neurons, ACh-NeuBI1b and ACh-NeuBI1c achieved acetylcholine responses of up to 200-fold while maintaining selectivity over choline and other neurotransmitters. When expressed in mouse liver by hydrodynamic transfection, the optimized indicators detected intraperitoneally administered acetylcholine with signal increases of up to 173-fold, far exceeding the 30-fold response of the pre-optimization sensor, while an unregulated control reporter showed no response. The developers emphasize that improvements measured in mammalian cells, including affinity gains that did not reproduce when proteins were screened as bacterial periplasmic constructs, translated directly into in vivo performance, underscoring the value of screening in the environment where a protein must actually work.

Looking forward, the authors position MIDAS as a data engine for the machine-learning era of protein design. Computational models excel at proposing candidate sequences but cannot reliably identify the single best one, and they remain poorly trained on the dynamic conformational changes underlying enzyme catalysis and biosensor activation. By generating hundreds of precisely defined variants with high-quality functional measurements in mammalian cells within a day, MIDAS can supply exactly the kind of dense sequence-fitness datasets that such models need. The method blurs the traditional boundary between screening and analysis, unifying them in a single workflow that is roughly 48 times faster and ten times cheaper than cloning-based approaches. For laboratories optimizing biosensors, enzymes, or therapeutic proteins in mammalian systems, the bacterial incubator may no longer be the obligatory first stop.

Subject of Research: A cloning-free PCR-based platform for rapid protein engineering and sequence-fitness analysis in mammalian cells

Article Title: Fast analysis and engineering of protein function by microbe-independent deep assembly and screening

Article References: Wu, Y., Wang, P., Liu, L. X., Song, D., Qin, Q., Gao, C., Hageman, M., Kirkland, T. A., Su, Y., & Lin, M. Z. (2026). Fast analysis and engineering of protein function by microbe-independent deep assembly and screening. Molecular Systems Biology, 22(6), 1003-1034. https://doi.org/10.1038/s44320-026-00210-z

Image Credits: AI Generated

DOI: 10.1038/s44320-026-00210-z

Keywords: protein engineering, MIDAS, PCR assembly, mammalian cells, directed evolution, bioluminescent indicator, acetylcholine, NanoLuc, saturation mutagenesis, sequence-fitness analysis, biosensors, Molecular Systems Biology