Biology subjects

Zhang, X.

Publications and source records attributed to Zhang, X..

At least 181 records · Page 10Linked to original sources

bioRxiv2026

Extracellular NAD(P) activates systemic acquired resistance through LecRK-VI.2-mediated phosphorylation of NPR1

Systemic acquired resistance (SAR) is a long-lasting, broad-spectrum immune response induced in distal tissues by signals generated at primary infection sites. Although numerous mobile immune signals have been implicated in SAR, how these signals are perceived and mechanistically coupled to transcriptional reprogramming in systemic tissues remains poorly understood. Extracellular NAD(P) [eNAD(P)] functions as a key integrative SAR signal that activates immunity through the plasma membrane-localized lectin receptor kinase LecRK-VI.2 and the master immune coactivator NONEXPRESSOR OF PATHOGENESIS-RELATED GENES1 (NPR1). However, the mechanism linking eNAD(P) perception to activation of NPR1 has remained unknown. Here, we show that LecRK-VI.2 constitutively associates with NPR1 and directly phosphorylates NPR1 at T359 and likely S356 upon eNAD(P) perception. NADP+-induced phosphorylation of NPR1 occurs rapidly in vivo and requires LecRK-VI.2. Nonphosphorylatable NPR1 variants abolish eNADP+-induced local and systemic immunity as well as biologically induced SAR, whereas phosphomimetic variants retain NPR1 function. Mechanistically, LecRK-VI.2-mediated phosphorylation promotes NPR1 interaction with TGACG-binding transcription factors (TGAs) and the Mediator subunit MED15, thereby enhancing assembly of a transcriptional activation complex required for defense gene expression. We further demonstrate that NPR1 facilitates TGA-MED15 association in a phosphorylation-dependent manner. Together, these findings establish a receptor-to-coactivator signaling mechanism that directly links extracellular immune signal perception to transcriptional activation. This work closes a major mechanistic gap in the SAR signaling pathway and reveals receptor-mediated coactivator activation as a mechanism for rapid conversion of extracellular immune cues into coordinated transcriptional outputs during systemic immunity.

plant biology↗

bioRxiv2026

Dual-channel whole-brain imaging reveals distinct dopamine and calcium dynamics in walking Drosophila

Simultaneous recording of intra- and extracellular neuronal signals across the brain during behavior is crucial for unraveling brain information processing. In Drosophila, large-scale recordings have been explored, yet simultaneous dual-channel whole-brain imaging remains a significant challenge. We developed a system combining a Fourier light-field microscope with dual-focal microlens arrays optimized for adult walking flies, extending imaging volume while maintaining resolution requirements. This optical system is further combined with a cross-modal 3D registration and segmentation pipeline to integrate functional and structural data. Using this system, we simultaneously measured brain-wide intracellular calcium activity and extracellular dopamine release during locomotion. We found that functional maps and neural dynamics for dopamine and calcium are distinct across the brain and within specific compartments, particularly in the mushroom body and central complex, aligning with their anatomical bases. Both calcium and dopamine representations of locomotion are distributed, yet they exhibit different patterns. Mushroom body compartments can be functionally categorized into two types based on their responses to specific locomotive actions. Forward walking or acceleration boosts activity in compartments innervated by PAM dopaminergic neurons, while dampening activity in those targeted by PPL1 dopaminergic neurons. Conversely, backward walking or deceleration heightens PPL1 activity while reducing PAM activity, consistent with the functions of these neurons in encoding approach and avoidance choices. Notably, single-compartment activity can reliably decode behavior choices. Our findings, spanning whole-brain, brain-region, and single-compartment, demonstrate the capability of our system to uncover neural dynamics across multiple scales and channels in behaving animals.

neuroscience↗

bioRxiv2026

Rat hepatitis E virus infection has multiphasic viral replication kinetics in vivo

Background and AimsHepatitis E virus (HEV) infections are a growing threat to global public health. To obtain an in-depth understanding of HEV infections in untreated and ribavirin-treated rats, we characterized the early HEV viral kinetics using rat HEV (rHEV) as a surrogate model and using two routes of virus inoculation: intravenous (I.V.) or oral infection. Approach and ResultsWe frequently collected feces, serum, and tissue samples up to 60 days after infection in both infection models to characterize the rHEV viral kinetics. A ~2-week delay in quantifiable RNA levels in feces was observed in the oral versus the I.V. infection model. Early rHEV viral kinetics in feces were found to be multiphasic and showed good concordance with those in the various tissue compartments studied. Comparison of the viral kinetics in these samples also revealed that the liver may serve as the initial site of rHEV replication, followed by replication in the intestine and spleen. While a dosage of 60 mg/kg/day ribavirin was found optimal to maintain rHEV RNA levels at (nearly) undetectable in feces, levels were detectable in the liver and increased both in feces and liver after treatment discontinuation. ConclusionsWe found that the two rHEV infection models share similar multiphasic viral kinetics with the liver as the main site of viral replication. Additionally, the rHEV RNA load in feces could be used as a reliable proxy for that in the liver, spleen, and intestine. We also show that ribavirin at 60 mg/kg/day was partially effective in preventing viral rebound. These findings may aid in exploring the correlation between the infection phases and antiviral efficacy, ultimately guiding therapeutic decisions.

microbiology↗

bioRxiv2026

TBC1D23-AAVR Interaction Drives Endosome-to-TGN Trafficking Required for rAAV Transduction

The adeno-associated virus receptor (AAVR; also known as KIAA0319L) is the proteinaceous receptor required for the transduction of multi-serotype adeno-associated viruses (AAVs). While the extracellular polycystic kidney disease (PKD) domains of AAVR directly bind AAV capsids, the function of its C-terminal cytosolic domain (AAVR-C) in governing AAV internalization and intracellular trafficking remains undefined. Using targeted pulldown of AAVR-interacting host proteins with a glutathione S-Transferase (GST)-fused AAVR-C recombinant protein (GST-AAVR-C) as a bait, we identified that TBC1 domain family member 23 (TBC1D23), a specialized intracellular trafficking adaptor and bridging factor, binds AAVR via the AAVR-C and mediates AAVs endosome-to-trans-Golgi network (TGN) transport. Biolayer interferometry (BLI) demonstrates nanomolar-affinity binding between AAVR-C and the C-terminal scaffold domain of TBC1D23 (TBC1D23-C). CRISPR-mediated knockout of TBC1D23 severely impairs rAAV transduction across multiple human cell types, including polarized human airway epithelium (HAE). Loss of TBC1D23 disrupts convergence of internalized AAV capsids at the TGN, leading to diminished nuclear import of AAV vectors. Mutational analyses of AAVR-C reveal that its acidic residue cluster is required for TBC1D23 binding and AAV retrograde transport from the endosome to the TGN. Together, these findings define TBC1D23 as a receptor-proximal trafficking module that couples AAV-AAVR engagement to vesicle transport, revealing a missing core regulatory step in AAV retrograde transport that is essential for productive rAAV transduction. SignificanceRecombinant adeno-associated viruses (rAAVs) are widely used gene delivery vectors, yet the intracellular trafficking steps that enable productive transduction remain incompletely defined. We identify TBC1D23 as a critical host adaptor that directly binds the cytosolic tail of the AAV receptor (AAVR) and mediates retrograde transport of AAV vectors from endosomes to the trans-Golgi network (TGN). Disruption of the AAVR acidic residue cluster abolishes TBC1D23 binding, blocks TGN trafficking, impairs nuclear import, and severely reduces transduction across multiple serotypes and in polarized human airway epithelium. These findings reveal a receptor-proximal trafficking checkpoint essential for rAAV gene delivery and define a host-vector interface with potential for rational vector engineering and therapeutic modulation.

microbiology↗

bioRxiv2026

Distinct defense strategies against interbacterial antagonism underpin Acinetobacter persistence in polymicrobial environments

Despite intense interbacterial antagonism mediated by mechanisms such as the type VI secretion system (T6SS), pathogenic Acinetobacter frequently persist within highly competitive polymicrobial infections. How these pathogens navigate such hostile environments to achieve co-existence remains poorly understood. Here, we show that pathogenic Acinetobacter employ distinct, multifaceted strategies to resist elimination by both distantly related competitors and closely related kin. T6SS-active strains outcompete heterologous bacteria by deploying a large and diverse repertoire of antibacterial effectors. In contrast, some naturally T6SS-deficient strains resist exogenous T6SS attacks by elaborating a unique, high-density polysaccharide capsule (KL34) that functions as an effective physical shield. Most intriguingly, we uncover a mechanism that prevents lethal competition among kins. A conjugative multidrug-resistant plasmid encoding T6SS repressors is transferred into aggressive strains upon T6SS-mediated attack, leading to suppression of their antibacterial activity. We also found that conjugation is induced by T6SS attack, which effectively suppresses attacking kin and promotes co-infection in vivo. Together, these findings reveal a dynamic and multilayer defense program that enables Acinetobacter to withstand interbacterial warfare while facilitating co-existence. Our study establishes a paradigm in which damage-triggered plasmid transfer enforces targeted suppression, reshaping microbial interactions in polymicrobial communities.

microbiology↗

bioRxiv2026

Inhibition of hexokinase 2 undermines cartilage health and accelerates osteoarthritis

ObjectiveEnhanced glycolysis is a metabolic hallmark of chondrocytes in osteoarthritis (OA); however, the roles of the glycolytic rate-limiting enzyme hexokinase 2 (HK2) in cartilage remain poorly understood. MethodsPharmacological approach (3-bromopyruvate (3-BrPA) treatment) and mice model involving HK2 knockout in Col2a1-expressing chondrocytes are utilized to access the impact of HK2 blockage on cartilage ex vivo and in vivo. The in vivo effects of HK2 inhibition on OA progression were evaluated using a destabilization of the medial meniscus (DMM)-induced OA mouse model, through both intra-articular 3-BrPA administration and chondrocyte HK2 deletion. Additionally, we analyzed published single-cell RNA sequencing (scRNA-seq) datasets from human articular cartilage and integrated these with bulk RNA-seq data from HK2-deficient chondrocytes to characterize HK2 expression features across conditions. ResultsBoth pharmacological inhibition and genetic deletion of HK2 impair cartilage formation ex vivo. Bulk RNA-seq analysis and ex vivo studies demonstrated a promoted ossification-like process due to HK2 ablation in chondrocytes. Through pseudotime analysis of published single-cell RNA sequencing (scRNA-seq) datasets from human articular cartilages, we further identified that HK2 is differentially expressed across conditions, with a feature of a relatively high expression level at terminal stages of chondrocyte differentiation in the context of OA. We next confirmed HK2 deficiency in chondrocytes significantly exacerbated OA progression but having no impact on skeletal development in mice. ConclusionsHK2 plays a critical role in maintaining cartilage health, likely through the regulation of calcification, thereby highlighting the potential risks associated with targeting glycolytic enzymes as a therapeutic strategy for OA.

pathology↗

bioRxiv2026

Human hindbrain organoids with segment-specific 5-HT neurons for motor modulation

The serotonergic system regulates human mood, reward, and motor control, and its impairment contributes to debilitating psychiatric disorders. Serotonergic neurons (SNs) arise predominantly in the hindbrain and acquire segment-specific identities and functions; however, the lack of human models remains a challenge to understanding the human serotonergic system. Here, we generate human serotonergic-enriched rostral and caudal hindbrain organoids (hsrHOs and hscHOs) that produce segment-specific SNs with regional identities corresponding to rhombomeres r2-r3 and r5-r8, respectively. hsrHOs and hscHOs produce SNs that recapitulate their in vivo counterparts in transcriptomic profiles, function, and ascending or descending projection preferences. Assembly with human neuromusculoskeletal organoids enables modeling of serotonergic modulation of motor control. This system further reveals that deficiency of the schizophrenia risk gene DISC1 disrupts human serotonergic development and impairs motor modulation. Together, our study establishes a human organoid platform for modeling development, circuit function and disease-associated dysfunction of the serotonergic modulatory system.

neuroscience↗

bioRxiv2026

Objective curriculum-guided design of multi-property proteins

Designing functional proteins that simultaneously possess multiple bio-chemical properties remains a significant challenge, as key protein properties, such as solubility, stability, binding affinity, and chemical resistance, are often interdependent or even conflicting. Current approaches typically attempt to jointly optimize multiple functional objectives in one shot, followed by extensive screening to identify rare feasible designs. Here, we introduce OCDesign, an objective curriculum-guided framework for multi-property protein design. OCDesign is based on the objective curriculum principle, i.e., the order in which objectives are introduced can shape the accessibility of functional solutions. In each design round of OCDesign, candidate sequences are generated in silico, assessed across multiple properties, selected based on Pareto-optimal trade-offs, and experimentally validated, with each experimental stage testing the role of the newly introduced objective within the curriculum. Using antibody-binding protein A as a model system, we show that one-shot optimization fails to yield functional designs, whereas a staged curriculum--progressing from solubility and structural consistency to binding affinity, and then to alkaline resistance--enables the design of proteins possessing multiple desired properties through substantially fewer wet-lab experiments. These results establish OCDesign as a practical computational-experimental strategy for organizing and integrating multiple objectives in protein design, and suggest that objective ordering is a key determinant of accessibility in high-dimensional design spaces.

bioengineering↗

bioRxiv2026

Neuronal UBE3A loss engages a TNF-driven neuron-to-microglia axis that promotes synapse remodeling

Neuron-microglia communication shapes neuroimmune homeostasis and circuit maturation, yet the neuron-derived cues that tune microglial inflammatory state and phagocytic programs remain incompletely defined. The E3 ubiquitin ligase UBE3A is critical for brain development and synaptic function, and altered UBE3A dosage or activity is linked to neurodevelopmental phenotypes with emerging connections to inflammation. Using Angelman syndrome (AS), where UBE3A loss is largely neuron-selective due to imprinting, as a tractable framework, we investigated how neuronal UBE3A deficiency engages microglial programs. In human iPSC-derived neuron-microglia co-cultures, neuronal UBE3A depletion induced a TNF-associated secretory signature and was accompanied by increased microglial inflammatory markers, including complement components. Neuron-conditioned media was sufficient to elicit microglial cytokine/complement transcripts, supporting a role for soluble neuron-derived cues. In these co-cultures, neuronal UBE3A loss increased synapse engulfment by microglia, which was reduced by TNF receptor pathway inhibition with the TNFR1 antagonist R7050 alongside decreased microglial inflammatory readouts. In vivo, juvenile AS mouse hippocampus showed early microglial dysregulation, and reanalysis of a maternal-deletion AS pig single-nucleus RNA-seq dataset revealed enrichment of microglial activation and phagosome/lysosome pathways. Together, these findings implicate a TNF-linked neuron-to-microglia signaling axis downstream of neuronal UBE3A loss that can be pharmacologically modulated during development.

neuroscience↗

bioRxiv2026

BMSC-Laden PEGDA/HAMA Dual-Crosslinked Hydrogels with Distinct Stiffness Profiles for Osteochondral Defect Repair

This study aimed to develop a BMSC-laden polyethylene glycol diacrylate/methacrylated hyaluronic acid (PEGDA/HAMA) dual-crosslinked hydrogel and evaluate its effects on osteochondral defect repair. Two PEGDA concentrations, 3.75% and 7.5% (w/v), were used to prepare representative soft and stiff hydrogel formulations, respectively. The hydrogels were characterized in terms of morphology, cytocompatibility, and compressive behavior, and their ability to support BMSC-associated matrix deposition was evaluated in vitro. Repair outcomes were further assessed in a rat osteochondral defect model at 4 and 8 weeks. The 7.5% PEGDA/HAMA hydrogel exhibited higher stiffness than the 3.75% formulation and supported BMSC viability and matrix deposition in vitro. In vivo, the stiff hydrogel group showed improved defect filling and subchondral bone remodeling compared with the soft hydrogel and defect groups. However, histological and immunohistochemical analyses revealed predominant collagen type I deposition and limited collagen type II expression in the repair region, indicating fibrocartilaginous rather than hyaline-like cartilage repair. These findings suggest that BMSC-laden PEGDA/HAMA hydrogels may provide a useful platform for osteochondral defect repair, while further optimization of degradation behavior, matrix maturation, and collagen type II deposition is required to improve hyaline cartilage-oriented repair.

bioengineering↗

bioRxiv2026

De novo design of binder proteins targeting Helicobacter pylori adhesin BabA

Helicobacter pylori has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer of the World Health Organization and is one of the most well-established risk factors for gastric cancer. Long-term colonization by H. pylori depends on adhesin-mediated attachment to the gastric mucosa, among which the blood group antigen-binding adhesin BabA is a key surface factor involved in host recognition, tissue tropism, and persistent infection. In this study, we established a structure-guided computational design pipeline to develop compact protein binders targeting functionally relevant epitopes of BabA. First, using experimentally resolved BabA-antibody and BabA-nanobody complex structures as templates, we extracted structural contact residues on BabA through heavy-atom contact analysis, thereby defining antibody-recognition epitopes supported by complex-structure evidence. In addition, sequence-based, structure-based, and evolutionary conservation analyses were integrated to identify candidate functional epitope residues with high antigenicity, strong conservation, and surface-exposed features. On this basis, constrained de novo backbone generation was performed around the prioritized epitope regions, followed by amino acid sequence design and structural back-validation of the candidate binders. Candidate BabA-binder complexes were further evaluated using molecular docking, molecular dynamics simulations, and residue-level interface perturbation analysis to assess interface stability, epitope occupancy, and potential binding hotspots. This workflow enables systematic screening of BabA-targeting binders that may compete with antibody-recognized functional surfaces. Although these candidates still require experimental validation, this study provides a transferable computational framework for designing compact protein binders against pathogen adhesins by integrating experimentally resolved complex-structure resources with computational epitope prioritization based on sequence, conformation, and evolutionary conservation, and establishes a preliminary library of BabA candidate binders for subsequent validation and optimization.

bioengineering↗

bioRxiv2026

Humanized patient-derived xenografts preserve tumour-specific immune microenvironments

Defining the genetic and cellular programs that allow solid tumours to evade immune control requires preclinical models that preserve the complexity of the human tumour immune microenvironment. Most available systems capture only part of this biology. Organoid cultures and ex vivo tumour fragments can retain patient-derived tumour architecture and associated immune cells, but immune populations are typically maintained only for short periods. These models also cannot capture antitumour immune responses in the physiological setting of a living organism. Patient-derived xenografts propagated in humanized mice offer a potential path to overcome these limitations by combining patient-derived tumour tissue with a reconstituted human immune system. However, few studies have systematically tested whether these models reproduce the diverse immune cell phenotypes present in the parental tumours from which they are derived. This has limited their use for studying tumour-intrinsic mechanisms that shape immune composition and promote immune evasion. To address this gap, we profiled tumour-infiltrating, splenic, and bone marrow immune cells from ovarian, head and neck, and renal PDX models propagated in CD34+ hematopoietic stem cell (HSC)-derived huNOG-EXL mice expressing human IL-3 and GM-CSF. By comparing tumours grown across distinct HSC donor backgrounds with their matched primary tumour samples, we found that tumour-intrinsic factors are a dominant determinant of immune composition in humanized PDX tumours. Across models, these immune infiltrates generally resembled those of the corresponding parental tumours. These findings support humanized PDX models as a platform for functionally interrogating tumour-intrinsic drivers of immune composition and immune evasion in solid tumours.

cancer biology↗

bioRxiv2026

Targeting THOC2-Mediated mRNA Export Induces PARP Inhibitor Vulnerability in DNA Repair-Competent Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) remains a lethal malignancy with limited therapeutic options. While Poly (ADP-ribose) polymerase inhibitors (PARPi) exploit synthetic lethality in tumors with DNA repair defects, their clinical utility in HCC is hindered by the low prevalence of canonical repair gene mutations and the enhancing DNA repair capacity. Through proteomic analysis of two independent cohorts (n=260), we identified the THO complex component THOC2 as a master regulator of DNA damage response (DDR) via mRNA nuclear export control. Clinically, THOC2 overexpression predicted poor survival (HR=2.68-6.84, P<0.001) and correlated with enhanced DDR gene expression. Mechanistically, THOC2 chaperones mRNA nuclear export of DDR effectors (MDC1, PRKDC, MSH6) and proliferation drivers (TOP2A), thereby establishing a dual pro-repair/pro-growth program. Targeting this vulnerability, THOC2 knockdown induced synthetic lethality with PARPi, reducing Olaparib IC50 by up to 61% and suppressing tumor growth by 76% (P<0.001). Our study illuminates mRNA transport as a druggable DDR modulator and establishes THOC2 as both a prognostic biomarker and a therapeutic target to overcome PARPi resistance in HCC. This work pioneers a strategy to expand synthetic lethality beyond genetic defects by targeting post-transcriptional regulation.

cancer biology↗

bioRxiv2026

Estimating Daily Taxon-specific Tree Pollen at a 1-km Resolution in Atlanta, GA from 2020 to 2024

While tree pollen is a major trigger of allergic respiratory conditions and different taxa exhibit varying allergenic potentials, the lack of high-resolution, taxon-specific exposure metrics have limited our ability to identify which local pollen taxa are primarily responsible for respiratory illness. Traditional pollen monitoring networks, which have an intermittent sampling schedule, are not ideal for examining the delayed effects of pollen exposure due to the missing days. In this study, we developed a modeling framework integrating atmospheric dispersion effects, taxa-specific phenology, and machine learning to predict daily counts of 13 tree taxa in the five-county Metro Atlanta area, Georgia at a 1-km resolution from 2020 to 2024. Machine learning model performance was validated with daily pollen counts collected by a multi-site monitoring network equipped with automated pollen sensors. Findings showed that Betula and Quercus pollens exhibited higher predictive performance than other taxa, with R2 values ranging from 0.69 to 0.92 and from 0.71 to 0.89, respectively. Our 1-kilometer prediction data provides gapless exposure metrics to understand the spatial and temporal variability in pollen exposure, can facilitate investigation of urban pollen hotspots and support epidemiologic studies of pollen-related respiratory outcomes.

plant biology↗

bioRxiv2026

GABA antagonises ABA perception and signalling in plants

Abscisic acid (ABA) is a central regulator of plant growth and stress responses. However, it also negatively impact germination, growth, and reproductive performance, highlighting the need for mechanisms that fine-tune its signalling. Here, we identify {gamma}-aminobutyric acid (GABA) as an endogenous antagonist of plant ABA receptor. We show that GABA binds the clade A protein phosphatase-ABI1, disrupting its association with the ABA receptor PYL1, blocking ABA binding, thereby attenuating ABA signalling. GABA modulates ABA-control of stomatal aperture and seed germination, demonstrating its broad physiological influence. Notably, GABA accumulation during stress coincides with the subsequent decline in ABA, consistent with a delayed feedback signal of ABA activity. Together, this work identifies GABA as an antagonist of ABA and provides a mechanism balancing plant stress resilience and growth.

plant biology↗

bioRxiv2026

Streptococcal superantigen SpeC induces IL-8 secretion in human epithelial cells

Streptococcal pyrogenic exotoxin C (SpeC) is a prototypical superantigen produced by group A Streptococcus. It potently activates a broad subset of T lymphocytes via a bridging interaction involving TCR{beta}-SpeC-MHC-II. Our recent work demonstrated that SpeC induced profound release of IL-8 from human pharyngeal epithelial cells and this effect was reversible through a specific point mutation in SpeC. This study systematically investigated cellular signaling pathways using integrated transcriptomic profiling and Western blot analysis, with a focus on membrane-associated receptors and downstream intracellular signaling effectors. Our results demonstrate that this biological process is critically associated with the activation of Erk1/2, p38 MAPK and NF-{kappa}B signaling cascade. This study identifies a novel mechanism through which a bacterial superantigen target epithelial cells-the body primary physical barrier and first line of innate immune defense.

microbiology↗

bioRxiv2026

How the Body Shapes the Mind's Eye: Cardiac vagal reactivity predicts visual imagery vividness

Mental imagery is known to be accompanied by autonomic responses, traditionally viewed as merely downstream consequences of imagery. Recent theoretical work has challenged this view, proposing that mental imagery requires the integration of cortical sensory representations with ascending interoceptive signals supplied by the autonomic nervous system. These two views make opposite predictions: if autonomic activity is only a consequence of imagery, then the responsiveness of the autonomic nervous system should not predict imagery vividness. If instead autonomic input shapes the generation of mental images, individuals with greater autonomic responsiveness should experience more vivid imagery. The present study tested these competing predictions by examining whether individual differences in cardiac vagal reactivity predict self-reported visual imagery vividness, with imagery assessed at a separate time point from the paced breathing protocol. Cardiac vagal reactivity significantly predicted VVIQ scores after controlling for factors such as resting HRV, respiratory amplitude, age and negative affect (b = 13.75, p = .022; model R2 = 0.12), whereas neither baseline HRV nor fast-breathing evoked HRV change were linked to imagery, suggesting the effect is specific to the capacity to enter a high parasympathetic state rather than reflecting general autonomic capacity. Self-reported interoceptive noticing (MAIA Noticing) was significantly associated with both delta HRV and VVIQ, suggesting that cardiac vagal reactivity and imagery vividness are linked through a broader individual difference in interoceptive function. These findings indicate that the vividness of mental imagery is not exclusively central in origin but also appears to be shaped by the capacity of the autonomic nervous system to enter a high parasympathetic state. Imagery thus likely involves bidirectional interaction between cortical and autonomic processes, with descending efferent pathways activating autonomic responses while ascending interoceptive signals contributing to the construction of mental images.

physiology↗

bioRxiv2026

Rap1 Activates Endosomal AC9 to Drive the Second cAMP Wave

GsPCR signaling orchestrates cAMP production in three distinct spatial waves originating from the plasma membrane (PM), endosomes, and the nucleus. While the molecular drivers of the PM and nuclear waves are well defined, the regulation of the endosomal cAMP wave remains insufficiently understood. Here, we identify the small GTPase Rap1b as a direct activator of the endosomal adenylyl cyclase 9 (AC9), revealing a novel mechanism for intracellular cAMP synthesis. Like Gs, Rap1b-GTP interacts with the C2 domain of AC9, allosterically enhancing its catalytic activity both in vitro and in cells. Using AC9 mutations that selectively disrupt Rap1b versus Gs binding, we elucidate the role of the Rap1b-AC9 unit in mediating the endosomal cAMP wave, introducing a new layer of spatial regulation to cAMP signaling.

cell biology↗