The team began by searching for cellular partners of vIRF3 in lymphatic endothelial cells using immunoprecipitation followed by mass spectrometry. Among the proteins that specifically co-purified with the viral factor was a polypeptide of roughly sixty kilodaltons corresponding to pyruvate kinase M. Although vIRF3 could bind both the PKM1 and PKM2 isoforms in pull-down assays, only PKM2 was expressed in lymphatic endothelial cells, so the investigators focused their attention on the vIRF3–PKM2 axis. Detailed binding experiments mapped the interaction to a short region of vIRF3 spanning amino acids 250 to 280. Deleting this segment produced a mutant viral protein, vIRF3-MT, that lost the ability to bind PKM2 while retaining its interactions with other known partners, including IRF7, HIF1α and HDAC5, making it a clean genetic tool for isolating the metabolic consequences of the interaction.

The biological significance of the binding became apparent when the researchers examined the oligomeric state of PKM2. This enzyme exists in two functionally distinct forms: a tetramer that acts as an active pyruvate kinase, channeling carbon from phosphoenolpyruvate into pyruvate and onward into the tricarboxylic acid cycle, and a nuclear dimer that functions as a transcriptional co-factor supporting aerobic glycolysis. When wild-type vIRF3 was expressed in lymphatic endothelial cells, cross-linking experiments showed a striking increase in PKM2 tetramerization, accompanied by elevated pyruvate kinase activity, higher intracellular acetyl coenzyme A levels and reduced lactate concentrations. The mutant viral protein, lacking the PKM2-binding region, produced none of these effects. Seahorse metabolic flux analysis reinforced the picture: cells expressing wild-type vIRF3 showed significantly increased oxygen consumption rates, including higher basal respiration, ATP production and maximal respiratory capacity, while their extracellular acidification rate, a proxy for glycolysis, declined.

To trace where the newly abundant acetyl-CoA came from, the team performed liquid chromatography–mass spectrometry metabolomics and isotope tracing with uniformly labeled carbon-13 glucose. In cells expressing wild-type vIRF3, pyruvate accumulated predominantly in the M+3 isotopologue form, a signature of enhanced PKM2 activity, and the labeled carbon flowed into M+1 and M+2 acetyl-CoA, which then fed the biosynthesis of citrate, α-ketoglutarate, succinate, fumarate and malate. Glutamate labeling patterns indicated that the cells were not relying on glutaminolysis to replenish the cycle, and measurements of fatty acid oxidation intermediates showed that this pathway was actually suppressed: carnitine accumulated while expression of carnitine palmitoyltransferase 1A and downstream β-oxidation intermediates fell. The evidence therefore pointed to enhanced pyruvate catabolism, rather than fatty acid oxidation or glutamine metabolism, as the principal source of the expanded acetyl-CoA pool.

Acetyl-CoA is not merely a fuel; it donates acetyl groups for the lysine acetylation of thousands of proteins, including transcription factors. Consistent with this, wild-type vIRF3 expression raised the global acetylation level of cellular proteins, and this increase depended on citrate exported from mitochondria and processed by ATP citrate lyase, since the ACLY inhibitor BMS-303141 abolished the effect. A human protein acetylation microarray then identified twenty-four proteins whose acetylation rose specifically in the presence of the vIRF3–PKM2 interaction. Among them, the investigators prioritized SMAD5, a transcriptional effector of TGFβ–BMP signaling with established roles in endothelial-to-mesenchymal transition, the process by which endothelial cells lose their identity and acquire invasive, mesenchymal characteristics.

Immunoprecipitation confirmed that SMAD5 acetylation was markedly increased in cells expressing wild-type vIRF3 but not the binding-defective mutant, and co-immunoprecipitation identified the acetyltransferase p300 as the enzyme responsible, since the p300 inhibitor A-485 reduced SMAD5 acetylation. The functional consequences were dramatic. Cells expressing wild-type vIRF3 adopted a spindle-shaped, mesenchymal morphology, downregulated the endothelial markers LYVE-1 and VE-cadherin, and upregulated mesenchymal markers including vimentin, fibronectin, N-cadherin and α-smooth muscle actin. Three-dimensional spheroid invasion assays in Matrigel and Boyden chamber migration assays demonstrated that these behaviors depended on SMAD5: silencing SMAD5 with short hairpin RNAs abolished both the invasive growth and the migration induced by vIRF3.

Critical controls established that this metabolic hijacking is separable from the viral life cycle itself. Using bacterial artificial chromosome-based recombination, the team constructed recombinant KSHV clones carrying either wild-type vIRF3, the Δ250-280 deletion mutant, or a revertant restoring the wild-type sequence. The mutant virus replicated normally, produced comparable infectious virions and expressed latent and lytic genes at levels indistinguishable from wild type. Yet when lymphatic endothelial cells were infected with these viruses, only wild-type and revertant infections raised pyruvate kinase activity and acetyl-CoA levels, drove spheroid invasion, and enabled colony formation in soft agar. The phenotypes were reproduced in primary human lymphatic endothelial cells, confirming that the metabolic reprogramming is a genuine consequence of KSHV infection rather than an artifact of immortalized cell lines.

The in vivo consequences were equally striking. In xenograft experiments with immunodeficient NCr-nu/nu mice, cells infected with wild-type or revertant KSHV formed tumors efficiently, whereas cells infected with the vIRF3-MT virus did not. Moreover, mice bearing wild-type-derived tumors developed secondary lesions in the stomach, spleen and liver that displayed hallmark histopathological features of Kaposi’s sarcoma, including extravasated erythrocytes, hemosiderin deposits and spindle-shaped cells positive for the viral latency antigen LANA, vIRF3, the endothelial marker CD31 and the lymphatic lineage factor PROX1. Human vimentin-positive cells at these sites traced back to the implanted infected endothelial cells. No secondary tumors appeared in mice injected with the PKM2-binding-defective virus, directly implicating the vIRF3–PKM2 interaction in disseminated visceral disease.

The study also delivers a potential therapeutic lead. Because amino acids 250 to 260 of vIRF3 were sufficient for PKM2 binding, the researchers designed a short vIRF3-derived peptide, termed VDP, fused to the HIV TAT transduction domain for intracellular delivery. VDP competed with vIRF3 for PKM2 binding, blocked vIRF3-induced PKM2 tetramerization and enzymatic activity, and lowered acetyl-CoA and ATP levels, while a binding-defective mutant peptide, mVDP, did none of these things. Structural modeling with AlphaFold-Multimer and molecular dynamics simulations showed VDP occupying the intersubunit interface of PKM2, and biolayer interferometry measured a dissociation constant of 1.28 micromolar, roughly twenty-nine-fold tighter than the mutant peptide. In chick embryo chorioallantoic membrane assays, TAT-VDP suppressed vIRF3-driven invasion into the endoderm layer, and in xenograft mice the peptide markedly inhibited tumor formation and regressed established tumors without substantial toxicity.

The authors caution that the vIRF3–PKM2–acetyl-CoA–SMAD5 axis still requires validation in patient-derived Kaposi’s sarcoma tissues, which have been difficult to obtain in adequately preserved form, and that their xenograft model does not distinguish true metastatic dissemination from other routes of systemic distribution. Even so, the work provides the most complete mechanistic account to date of how an oncogenic herpesvirus converts a host metabolic enzyme into an engine of tumor progression, linking acetyl-CoA flux through the TCA cycle to epigenetic modification of a developmental transcription factor. By demonstrating that a rationally designed viral peptide can reverse this process in living animals, the study positions PKM2 not merely as a metabolic marker but as an actionable target for treating disseminated Kaposi’s sarcoma.

Subject of Research: KSHV vIRF3–PKM2 interaction, acetyl-CoA metabolic reprogramming and SMAD5 acetylation in Kaposi's sarcoma progression

Article Title: KSHV vIRF3–PKM2 interaction induces SMAD5 acetylation, promoting Kaposi’s sarcoma progression

Article References: Kim, Y. J., Lim, J., Lee, J. J., Kumar, A., Kannappan, S., Zhang, J., Kim, S., Kim, H.-J., Kim, K. K., Toth, Z., Eoh, H., Choi, K.-C., & Lee, H.-R. (2026). KSHV vIRF3–PKM2 interaction induces SMAD5 acetylation, promoting Kaposi’s sarcoma progression. Experimental & Molecular Medicine. https://doi.org/10.1038/s12276-026-01849-2

Image Credits: AI Generated

DOI: 10.1038/s12276-026-01849-2

Keywords: KSHV, Kaposi's sarcoma, vIRF3, PKM2, acetyl-CoA, SMAD5 acetylation, lymphatic endothelial cells, endothelial-to-mesenchymal transition, metabolic reprogramming, p300, TCA cycle, therapeutic peptide

Atherosclerosis, characterized by the accumulation of lipid-laden plaques within arterial walls, remains a leading cause of morbidity and mortality worldwide. The stability of these plaques is a critical determinant of clinical outcomes. Rupture of unstable plaques often precipitates myocardial infarctions and strokes, yet the precise molecular events governing plaque stabilization have remained elusive. This latest study, published in Nature Communications, meticulously delineates how TWIST1 modulates the transformation of endothelial cells, which line the vessel lumen, into mesenchymal-like cells, thereby fortifying the structural integrity of plaques.

Endothelial cells traditionally serve as a barrier between the bloodstream and tissues, maintaining vascular homeostasis. However, under pathological conditions, these cells can undergo EndMT, losing their endothelial characteristics and acquiring mesenchymal features such as increased migratory capacity and extracellular matrix production. TWIST1 emerges as a master regulator of this phenotypic shift, activating gene expression programs that enable endothelial cells to contribute to the fibrotic scaffold within plaques, enhancing their durability.

The researchers employed an array of sophisticated techniques, including lineage tracing, single-cell RNA sequencing, and in vivo plaque modeling, to elucidate the role of TWIST1. Their data compellingly demonstrate that endothelial cells expressing TWIST1 adopt a mesenchymal phenotype and secrete collagen and other matrix components critical for plaque reinforcement. Moreover, modulation of TWIST1 expression directly influenced plaque composition, with enhanced TWIST1 activity correlating with increased plaque stability.

Mechanistically, TWIST1 orchestrates a complex network of downstream targets implicated in cellular adhesion, migration, and extracellular matrix remodeling. The study highlights the upregulation of fibronectin, alpha-smooth muscle actin, and other mesenchymal markers concomitant with TWIST1 activation. Importantly, these molecular changes translate into histological alterations within the plaque microenvironment, solidifying the plaque cap and reducing the likelihood of rupture.

Beyond cellular and molecular analyses, the investigation extended to examining the hemodynamic influences on TWIST1 expression. Shear stress, a mechanical force acting on endothelial cells, was found to modulate TWIST1 levels, suggesting that biomechanical signals integrate with transcriptional programs to regulate EndMT and plaque stabilization. This insight underscores the multifactorial nature of atherosclerosis progression and highlights TWIST1 as a nodal point at the convergence of molecular biology and vascular biomechanics.

The translational implications of these findings are profound. Therapeutic strategies aimed at selectively enhancing TWIST1-mediated EndMT within atherosclerotic plaques could bolster their resistance to rupture, presenting a novel paradigm in cardiovascular disease management. Conversely, aberrant or excessive EndMT also bears the potential for adverse fibrosis and vascular dysfunction, necessitating precise modulation of this pathway.

In the broader context of vascular biology, this research enriches the conceptual framework regarding cellular plasticity and phenotypic transitions within diseased tissue. It reinforces the notion that endothelial cells are dynamic participants in vascular remodeling, capable of adopting diverse phenotypes in response to pathological cues. TWIST1’s role as a regulatory switch in this process provides a compelling target for further exploration.

Future studies are warranted to decipher the upstream regulators of TWIST1 in endothelial cells and to delineate the signaling cascades that integrate environmental stimuli with transcriptional control. Additionally, in vivo validation across diverse models of atherosclerosis and assessment of long-term outcomes following modulation of TWIST1-driven EndMT will be critical.

The integration of advanced imaging modalities with molecular analyses promises to yield spatial and temporal resolution of EndMT dynamics within plaques, offering unprecedented insights into disease heterogeneity. Such endeavors will be instrumental in tailoring personalized interventions for patients at risk of atherosclerotic complications.

Furthermore, this study invites a re-examination of existing therapeutic agents and their potential to influence TWIST1 expression or function. Pharmacological modulation of EndMT represents an exciting frontier, with possibilities for repurposing drugs or developing novel compounds targeting this pathway.

The convergence of vascular biology, molecular genetics, and bioengineering heralds a new era in understanding and manipulating the cellular constituents of atherosclerotic plaques. TWIST1 stands at the crossroads of these disciplines, emblematic of the intricate interplay between gene regulation and tissue architecture in health and disease.

As cardiovascular disease continues to impose a heavy global burden, research such as this propels the scientific community closer to achieving durable, mechanism-based therapies. The identification of TWIST1 as a stabilizing factor in atherosclerosis exemplifies the potential of fundamental science to inform clinical innovation and improve patient outcomes.

This landmark publication not only expands the molecular lexicon of atherosclerosis but also exemplifies the power of integrative research approaches in unraveling the complexities of vascular pathology. As the field advances, TWIST1-focused investigations are poised to yield transformative insights and therapeutic breakthroughs.

The authors, Tardajos Ayllon, Diagbouga, Das, and colleagues, have presented a compelling narrative underscoring the significance of cellular plasticity in atherosclerotic disease progression and plaque stability. Their meticulous work provides a robust platform for clinical translation and inspires renewed optimism in combating cardiovascular disease.

In sum, TWIST1-driven EndMT represents a crucial mechanism reinforcing the fibrous cap of atherosclerotic plaques, thus serving as a biological safeguard against plaque rupture. Unlocking the therapeutic potential of this pathway could transform future cardiovascular interventions, marking a critical leap forward in the prevention of myocardial infarction and stroke.

Subject of Research:

The molecular mechanisms by which TWIST1 regulates endothelial-to-mesenchymal transition to stabilize atherosclerotic plaques and the implications for cardiovascular disease.

Article Title:

TWIST1 Drives Endothelial-to-Mesenchymal Transition to Stabilize Atherosclerotic Plaques

Article References:

Tardajos Ayllon, B., Diagbouga, M., Das, A. et al. TWIST1 drives endothelial-to-mesenchymal-transition to stabilize atherosclerotic plaques.
Nat Commun (2026). https://doi.org/10.1038/s41467-026-69808-z

Image Credits: AI Generated

Understanding the biology behind age-related macular degeneration and its implications for treatment necessitates an in-depth look at vascular changes occurring during the disease’s progression. At the cellular level, endothelial cells lining the blood vessels undergo a transformation into mesenchymal-like cells, a process that could be activated by multiple factors associated with cellular aging. The researchers hypothesize that this conversion plays a significant role in the growth of fibrous tissue beneath the retina, potentially hastening the degeneration of vision.

The study meticulously delineates the cellular pathways involved in this endothelial-to-mesenchymal transition. Using advanced techniques such as flow cytometry and gene expression analysis, the team elucidated the specific markers and signaling pathways implicated in this process. They observed that senescent endothelial cells exhibited increased expression of mesenchymal markers, such as vimentin and fibronectin, providing compelling evidence for the transformation induced by senescence.

One of the intriguing aspects of this study is the identification of key factors that may trigger the EMT process in the context of neovascular AMD. The researchers found that oxidative stress, a hallmark of aging, significantly contributes to the activation of signaling pathways that encourage endothelial cells to adopt a mesenchymal phenotype. This observation underscores the interplay between aging and environmental stressors in the pathogenesis of AMD, suggesting new avenues for therapeutic intervention that target cellular stress mechanisms.

Moreover, the team investigated the role of cytokines and growth factors in promoting subretinal fibrosis. Their findings reveal that pro-inflammatory cytokines can exacerbate the EMT process in senescent endothelial cells, further fueling the fibrotic response typical of advanced AMD. This highlights the importance of inflammatory pathways in ocular diseases and opens up possibilities for anti-inflammatory therapies aimed at preventing vision loss in affected patients.

In tandem with these findings, the researchers explored potential therapeutic strategies to counteract senescence-induced EMT. They tested pharmacological agents known to mitigate oxidative stress, observing that such treatments inhibited the expression of mesenchymal markers in endothelial cells. This provides a promising lead for future clinical trials, where antioxidants and anti-inflammatory drugs could be evaluated for their efficacy in preserving vision in patients with neovascular AMD.

The implications of this research extend beyond AMD itself. The mechanisms of endothelial-to-mesenchymal transition are relevant to a wide array of fibrotic diseases, and insights garnered from this study may inform the understanding and treatment of conditions such as cardiac fibrosis and pulmonary fibrosis. As such, this work not only contributes to the understanding of AMD but also broadens the scope of fibrotic disease research.

Furthermore, the innovative methodologies employed in this research exemplify the future direction of regenerative medicine and targeted therapies. By focusing on the cellular and molecular underpinnings of disease, scientists are poised to develop more effective and specific treatments that can halt or even reverse the pathological changes associated with aging and disease.

Collectively, the research team’s findings suggest that therapeutic strategies targeting the endothelial-to-mesenchymal transition and the associated inflammatory responses could significantly influence the clinical landscape of age-related macular degeneration. By potentially slowing the progression of fibrosis in the subretinal space, these strategies might preserve vision in countless individuals facing the challenges of this age-related condition.

In essence, this study serves as a clarion call to the scientific community to further investigate the dual roles of cellular senescence and inflammation in ocular health. As research into the cellular mechanisms underlying age-related diseases continues to evolve, opportunities for breakthrough therapies abound. The pathways illuminated by this groundbreaking work promise to lead to novel approaches that can profoundly improve the quality of life for patients afflicted with neovascular age-related macular degeneration and similar fibrotic diseases.

The urgency of addressing age-related macular degeneration cannot be understated, given the aging global population. As such, ongoing research inspired by these findings is crucial not only for elucidating the disease mechanisms but also for translating this knowledge into tangible and effective treatments. By leveraging the insights garnered from this study, researchers and clinicians alike can strive towards a future where vision loss from AMD becomes increasingly rare, allowing individuals to maintain their quality of life well into their golden years.

Subject of Research: Age-related Macular Degeneration and Endothelial-to-Mesenchymal Transition
Article Title: Senescence-induced endothelial-to-mesenchymal transition accelerates the subretinal fibrosis in neovascular age-related macular degeneration
Article References: Wang, Y., Ma, H., Ge, J. et al. Senescence-induced endothelial-to-mesenchymal transition accelerates the subretinal fibrosis in neovascualr age-related macular degeneration. J Transl Med (2026). https://doi.org/10.1186/s12967-026-07707-z
Image Credits: AI Generated
DOI: 10.1186/s12967-026-07707-z
Keywords: Age-related macular degeneration, endothelial-to-mesenchymal transition, fibrosis, senescence, cellular aging, inflammation, oxidative stress.