Membranous nephropathy (MN) is an autoimmune kidney disease and a major cause of nephrotic syndrome in adults. Although autoantibodies against phospholipase A2 receptor 1 (PLA2R) and complement activation are central to disease pathogenesis, the mechanisms by which anti-PLA2R antibodies activate complement at the podocyte surface remain incompletely defined. Here, we cloned 14 patient-derived anti-PLA2R monoclonal antibodies (mAbs) and found that they predominantly recognized the N-terminal cysteine-rich (CysR) and C-type lectin domain 1 (CTLD1) regions of PLA2R. Individual anti-PLA2R mAbs induced little or no complement-dependent cytotoxicity (CDC) of PLA2R-expressing podocytes in vitro . In contrast, paired mAbs targeting distinct epitopes, particularly CysR and CTLD1, markedly enhanced CDC. This effect was strongest for IgG1 and IgG3 antibodies, whereas IgG4 alone did not activate complement but modulated CDC in combination with IgG1. Purified IgG from patients with PLA2R-associated MN similarly induced CDC, which was augmented by addition of anti-PLA2R IgG1 and reduced by anti-PLA2R IgG4 or Fab fragments targeting CysR or CTLD1. In human PLA2R-expressing mice, paired anti-PLA2R antibodies increased glomerular complement deposition and induced albuminuria. These findings identify epitope pairing as a key determinant of complement activation in PLA2R-associated MN and support epitope-specific targeting strategies as a promising avenue for therapeutic intervention.
Pain is a common and disabling feature of myotonic disorders, yet its biological basis remains poorly understood and no targeted analgesic therapies currently exist. Here, we demonstrate that skeletal muscle hyperexcitability is sufficient to initiate a persistent pain state independent of inflammation, nerve injury, or overt tissue damage. Using complementary pharmacological and genetic models of myotonia resulting from loss of the voltage-gated skeletal muscle chloride channel ClC-1 function, we show that transient and chronic myotonia produce robust mechanical, thermal, and cold hypersensitivity, as well as spontaneous pain-like behavior. Notably, pain-like behaviors induced by transient myotonia persist long after overt motor symptoms have resolved, suggesting that a transient episode of muscle hyperexcitability is sufficient to trigger prolonged alterations in nociceptive processing. Physiological recordings revealed altered excitability of dorsal root ganglion and superficial dorsal horn neurons and enhanced sensory-evoked activity in the parabrachial nucleus, indicating altered nociceptive processing across multiple levels of the pain neuraxis. Transient myotonia increased total sodium current density in sensory neurons, with a shift toward a greater tetrodotoxin-resistant current fraction. Pharmacological inhibition with the NaV1.8-directed analgesic Suzetrigine markedly attenuated pain-like behaviors in both models of myotonia. Together, these findings establish a link between myotonia and persistent alterations in nociceptive processing and identify NaV1.8-directed analgesia as a promising therapeutic strategy for myotonia-associated pain.
Transport of nucleoside chemotherapeutic drugs into tumor cells is primarily accomplished through Equilibrative Nucleoside Transporter 1 (ENT1), considered to be constitutively-active, redistributing drugs across lipid bilayers via facilitated diffusion. Here we discover that ENT1 is not constitutively-active but rather requires activation of acid sphingomyelinase (ASMase) by gemcitabine, generating ceramide-rich platforms (CRPs) on external plasma membranes of endothelial and tumor cells into which ENT1 inserts, dimerizing therein to functionalize transmembrane gemcitabine transport. Whereas sarcoma cells synthesize minimal ASMase, they take up gemcitabine poorly in vitro and in murine xenografts. A strategy designed to augment gemcitabine-induced ASMase secretion into the extravascular space by ASMase-rich neo-angiogenic cells, which then targets tumor cell plasma membranes, yields "bystander" CRPs on sarcoma cells and ENT1 insertion therein, conferring markedly-enhanced gemcitabine uptake and xenograft response. Engaging this biology in a prospective Phase II clinical trial in advanced sarcoma yielded robust volumetric changes in evaluated tumors that developed early and were often durable.
Regulatory T (Treg) cells hold great promise as next-generation therapeutics for autoimmune diseases. However, maintaining their functional persistence within inflamed tissues remains a major translational challenge. Using an in vitro system that recapitulates the inflammatory CNS milieu of multiple sclerosis (MS), together with a pooled shRNA screen, we identify necroptotic signaling as a key driver of Treg cell death, thereby compromising Treg functional persistence under inflammatory conditions. We further demonstrate that Treg cells in both a mouse model of MS and patients with MS exhibit a preferential susceptibility to RIPK1 kinase-dependent necroptosis. Mechanistically, a FOXP3-driven low-glucose metabolic program renders Treg cells intrinsically susceptible to necroptosis by limiting O-GlcNAc modification on RIPK1. This vulnerability is not shared by conventional T cells under comparable inflammatory conditions. Finally, in combined with adoptive Treg cell transfer, we show that selective inhibition of necroptosis in Treg cells enhances their survival and suppressive function at sites of active inflammation, thereby reducing autoimmune pathology in mouse models of MS and systemic lupus erythematosus. Together, these findings identify necroptotic cell death as a barrier to Treg persistence within inflamed tissues and highlight the therapeutic potential of necroptosis-resistant Treg cells for the treatment of autoimmune diseases.
Activating mutations in FMS-like tyrosine kinase 3 (FLT3) drive aggressive acute myeloid leukemia (AML) and confer poor prognosis. Although FLT3 inhibitors have improved outcomes, their efficacy is frequently limited by microenvironment-mediated signaling and treatment-emergent resistance. XY0206 is a structurally optimized derivative of sunitinib, an inhibitor approved for multiple solid tumors. Biochemical, multi-omics, and functional analyses showed that XY0206 directly engages FLT3 and suppresses downstream STAT5, AKT, and ERK signaling, resulting in apoptosis in FLT3-ITD AML cells. Across models of FLT3-dependent resistance, XY0206 retained antileukemic activity, including in FLT3-ITD cells harboring the F691L gatekeeper mutation, a recurrent alteration conferring resistance to approved FLT3 inhibitors. In primary AML blasts and xenograft models, XY0206 exhibited enhanced antileukemic activity with favorable tolerability relative to gilteritinib. In a phase I/II trial (NCT04471064) of XY0206 monotherapy in patients with relapsed or refractory (R/R) AML, XY0206 achieved a composite complete remission rate (CRc) of 45.7% overall, with a notable 60.0% CRc rate among patients with FLT3-ITD mutations. Three of eight patients with prior FLT3 inhibitor-exposed R/R AML also achieved CRc. Together, these findings support further clinical evaluation of XY0206 as a FLT3-directed therapeutic in AML, particularly in disease settings with reduced sensitivity to existing FLT3 inhibitors.
Multiple sclerosis (MS) is a complex inflammatory disease of the CNS resulting from an intricate interplay between genetic predisposition and environmental factors. Vitamin D (VD) deficiency is one of the established risk factors for MS. CD46 costimulation of CD4+ T cells induces a switch from Th1 to type I regulatory cells (Tr1), characterized by increased IL-10 production. This switch is impaired in MS T cells but can be restored by VD, which also strongly promotes expression of CD226 on CD46-activated T cells. The rs763361 polymorphism in the CD226 gene, resulting in a non-synonymous Gly307Ser variant, is associated with increased risk for MS. Herein, we show that expression of this CD226 risk allele disrupts the ability of CD46-activated T cells to operate the IFNγ/IL-10 switch upon VD exposure. Mechanistically, the risk variant impairs activation of the integrin LFA-1, which promotes the Tr1 phenotype. LFA-1-mediated Tr1 differentiation is also impaired in MS T cells expressing the CD226 risk allele upon CD46 and VD stimulation. Our study unveils how, in the context of MS susceptibility, a genetic polymorphism and an environmental factor act in concert to control the differentiation of Tr1 cells.
The neutrophil-to-lymphocyte ratio (NLR) is associated with unfavorable prognosis and hemorrhagic transformation (HT) in patients with ischemic stroke, yet the underlying mechanisms remain unclear. Using patient samples and a murine stroke model, we identified CD8⁺ regulatory T cells (CD8 Tregs) key regulators of neutrophil homeostasis after ischemic stroke, thereby limiting endothelial disruption and HT. Loss of CD8 Tregs expanded circulating neutrophils by extending their lifespan rather than altering proliferation, bone marrow release, or direct cytotoxicity. Mechanistically, CD8 Tregs shortened neutrophil lifespan by modulating HIF-1α-dependent glycolytic activity and relieving PD-L1-mediated suppression of bone marrow clearance. Finally, co-culture experiments with human CD8 Tregs and neutrophils revealed similar neutrophil-regulatory effects, accompanied by improved endothelial barrier integrity. These findings reveal a previously unrecognized CD8 Treg-neutrophil axis and suggest potential therapeutic strategies for preventing HT after stroke.
Allergen-specific monoclonal antibodies (mAbs) that block IgE binding to allergens are emerging as new therapeutics for treating allergies to pollen, peanuts, and cats. Alpha-Gal syndrome (AGS) is an allergy to galactose-α-1,3-Galactose (α-Gal), which is present in mammalian meat and tissue-derived products. Initially aiming to identify mAbs targeting α-Gal on malaria parasites, we isolated 42 α-Gal-specific mAbs from B cells of individuals who had been exposed to malaria but found that they bound weakly to the Plasmodium falciparum parasite. These mAbs predominantly used the IGHV3 gene family and had a wide range of mutation frequencies. We then screened these mAbs for their ability to bind α-Gal on AGS allergens and to block the binding of serum IgE of patients with AGS to AGS allergens. Thirteen mAbs bound to the AGS allergens angiotensin-I-converting enzyme (ACE), aminopeptidase-N (AP-N), and cetuximab, and 2 mAbs- AG028 as both IgA2 and IgM, and AG050 IgA1 - blocked the binding of serum IgE from patients with AGS to ACE and AP-N. Additionally, AG028 IgA2 and AG028 IgM suppressed ACE-mediated activation of basophils sensitized with serum of patients with AGS. This study supports the development of α-Gal-specific mAbs as a new intervention to prevent α-Gal allergy.
Regulation of mitochondrial health is critical for maintaining cellular homeostasis in the nervous system. Damaged mitochondria can have detrimental effects on neuronal health and are thought to be key contributors to the progression of neurodegenerative disorders including Parkinson's disease and amyotrophic lateral sclerosis. To mitigate this damage, multiple quality control mechanisms have evolved to eliminate aged or damaged mitochondria. One such quality control process is autophagy, a process that involves turnover of mitochondria at presynaptic sites and the axon terminal under basal conditions. This highly conserved mechanism sequesters mitochondria from the cytosol within autophagosomes followed by degradation upon fusion with a lysosome. Acute mitochondrial damage activates a selective form of autophagy called mitophagy that involves receptor-mediated engulfment and degradation of the damaged organelle. Multiple mechanisms have been shown to drive efficient mitophagy in neurons and glia, including PTEN induced kinase 1 (PINK1)/Parkin-dependent mitophagy and receptor-mediated mitophagy. Genetic, pathological, and experimental evidence all implicate defects in the removal of damaged mitochondria in the onset or progression of neurodegenerative disease. Both the initiation of PINK1/Parkin-dependent mitophagy and deficits in the removal of damaged mitochondria are linked to activation of neuroinflammatory pathways, including NF-κB and cyclic GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) signaling. In this Review, we discuss the molecular pathways governing mitophagy in neurons and glial cells and how deficits in these pathways may lead to neurodegeneration. We also highlight emerging therapeutic strategies aimed at restoring mitophagy to preserve neuronal homeostasis and function.
Fibrosis remains a major driver of organ dysfunction, yet the metabolic programs that sustain extracellular matrix production are incompletely understood. In this issue of the JCI, Takizawa and colleagues identified branched-chain amino acid transaminase 1 (BCAT1) as a crucial metabolic regulator of fibroblast activation and fibrosis in a model of cardiac fibrosis. Their observations were corroborated by analyses of datasets from patients with heart failure with preserved ejection fraction and metabolic dysfunction-associated steatohepatitis. They report that by coupling mechanical and TGF-β signaling to a proline biosynthesis and utilization program, BCAT1 enhanced collagen production in activated cardiac fibroblasts. These findings place branched-chain amino acid metabolism as a pivotal contributor to fibroblast activation and highlight BCAT1 as a promising therapeutic target for fibrotic disease.
Menopause may have important consequences for gut barrier health. The roles of estradiol and progesterone in immune and mucosal barrier homeostasis have been well studied in the female reproductive tract. However, few human studies have described these hormones' corresponding regulation in the gastrointestinal tract or how the menopausal transition affects gut barrier integrity. In this issue of the JCI, Shieh et al. report that markers of gut epithelial barrier dysfunction and microbial translocation-related immune activation increased across the menopause transition in a longitudinal study of healthy women. These findings suggest that ovarian aging may contribute to gut barrier dysfunction in midlife women and highlight new questions about clinical consequences and potential interventions.
Mechanosensitive feedback between tissue stiffness and cellular contractile forces instructs cell identity. To characterize phosphorylation-mediated mechanosensing, we charted the global phosphoproteome dynamics of primary human lung fibroblasts on fibronectin-coated polydimethylsiloxane substrates of defined stiffness. We identified a key signaling threshold at 2-8 kPa, above which cells activated cytoskeletal remodeling, ECM secretion, and transition to a CTHRC1+/ACTA2+ myofibroblast state, accompanied by stiffness-dependent phosphorylation of the transcription factor NFATC4 at S213/S217. In micro-CT staged pulmonary fibrosis tissues, NFATC4 expression increased progressively, colocalizing with CTHRC1 and ACTA2 in myofibroblasts. Transcription factor regulon inference from a multicohort pulmonary fibrosis atlas confirmed elevated NFATC4 activity in disease fibroblasts, revealing a core 119-gene NFATC4-dependent fibrotic program with CTHRC1 as a top target. Phosphomimetic S213D/S217D mutants drove myofibroblast differentiation on soft substrates independently of TGFB, while phospho-dead S213A/S217A mutants blocked differentiation even on stiff matrix with TGFB, establishing the phospho-switch as both necessary and sufficient. Stiff matrix and TGFB converged on this JNK- and calcineurin-dependent switch to amplify the fibrotic response. This positions NFATC4 S213/S217 as a mechanosensitive checkpoint for CTHRC1+ myofibroblast fate and a candidate therapeutic target in multiorgan fibrosis.
γδ T cells are a subset of lymphoid cells that, unlike their αβ lineage counterparts, express a heterodimeric TCR that mostly operates in an MHC-independent manner. γδ T cells are abundant in barrier tissues, where they continuously monitor epithelial cells for signs of stress or damage. Thus, γδ T cells are among the first responders to pathophysiological conditions, including viral infection and oncogenesis. Human γδ T cells can be classified based on TCR γ and δ chain usage into three main subsets: (a) Vγ9+Vδ2+ cells, accounting for most circulating γδ T cells; (b) Vδ1+ cells, which are common in epithelial linings, and (c) Vδ3+ T cells, which are fairly rare but exhibit unique specificities. Moreover, both human and murine γδ T cells can assume a spectrum of states with divergent phenotypic and functional properties. Accumulating evidence demonstrates that γδ T cells can mediate robust anticancer effects or support tumor progression and resistance to therapy, depending on numerous variables, including functional state and tumor type. Here, we critically discuss the context-dependent interaction between γδ T cells and cancer, focusing on recent developments and the challenges facing current efforts to manipulate this versatile lymphocyte subset for therapeutic purposes.
Monocytes and macrophages promote tissue repair following myocardial infarction, but the mechanisms tuning their effector functions remain elusive. While macrophages are essential in clearing debris and resolving inflammation, they can also contribute to uncontrolled inflammation and provoke additional damage. Thus, factors that influence macrophage differentiation trajectories and phenotypes play an important role in cardiac repair outcomes. By combining genetic lineage tracing with cell-specific targeting, the study from Koenig et al. sheds light on key signaling events that shape monocyte fate decisions in the injured myocardium, establishing a differentiation hierarchy among monocyte-macrophage subsets. The findings also reveal that macrophages with an IFN response signature give rise to MHCIIhi macrophages, which, in turn, contribute to regulatory T cell generation and cardioprotection. This work underscores the importance of understanding cardiac macrophage phenotypic plasticity within a broader framework of lineage relationships.
