Adhesion G protein-coupled receptors (aGPCRs) are a unique GPCR family defined by large, modular extracellular regions (ECRs) and a conserved seven-transmembrane (7TM) domain. These domains enable aGPCRs to mediate cell-cell and cell-matrix communication, integrate mechanical and chemical signals, and regulate diverse biological processes including neurodevelopment, angiogenesis, and immune response. Traditionally, models of aGPCR activation have focused on the canonical tethered agonist (TA) mechanism, in which autoproteolytic cleavage reveals an intrinsic peptide (TA) that activates the 7TM domain. However, mounting structural, functional, and biophysical evidence indicates that this TA-dependent mechanism is insufficient to explain all aGPCR functions, especially in cleavage-deficient receptors or under physiological forces. A distinct ECR-dependent mechanism has emerged in which allosteric regulation or structural changes in the ECR directly modulate receptor signaling independent of TA exposure. This ECR-dependent model offers reversible, tunable signaling that can accommodate both pulling and compressive forces, expanding traditional views of aGPCR activation. Here, we critically examine current evidence for TA- and ECR-dependent mechanisms, discuss their structural underpinnings, and propose a unified, biological context-dependent framework integrating all known activation modes. This Review advances understanding of aGPCR signaling and provides a basis for therapeutic approaches targeting aGPCRs.
Neurovascular coupling ensures that active neuronal circuits receive the blood supply needed to sustain brain function. In this issue of Science Signaling, Lavanderos et al. identify STIM1-ORAI-mediated Ca2+ entry as a mechanism that reinforces capillary-to-arteriole communication, sustaining functional hyperemia during repetitive neuronal stimulation.
Neurovascular coupling (NVC), which is initiated by the brain's dense capillary network, matches blood flow to neuronal activity. We found that ORAI1 channels and their regulator STIM1, the main drivers of store-operated Ca2+ entry, were essential for communication from capillaries, which detect neuronal metabolic need, to upstream arterioles, which dilate to increase regional flow. Endothelial cell-specific knockout of either Stim1 or Orai1 disrupted capillary Ca2+ signals, impaired sustained capillary-driven arteriole dilation, and reduced increases in blood flow in the somatosensory cortex evoked by whisker stimulation, indicating that ORAI1 and STIM1 sustain cerebral blood flow during prolonged neuronal stimulation. Moreover, mice with endothelial cell-specific deficiency of Stim1 or Orai1 showed cognitive impairment, whereas mice with endothelial cell-specific deficiency of Orai3 showed anxiety-like behaviors. These in vivo results link impaired capillary-to-arteriole signaling to isoform-specific behavioral aberrations. These findings demonstrate that intravascular communication mediated by ORAI channels and STIM1 is fundamental for NVC and brain health.
Although reperfusion therapy effectively restores blood flow to occluded brain arteries after ischemic stroke, many patients develop persistent white matter injury, a major contributor to long-term neurological disability. Currently, there are few approved clinical therapies that specifically target white matter repair to enhance functional recovery after stroke. We demonstrated that microglial adenosine 2A receptor (A2AR) is essential for spontaneous white matter regeneration after ischemic injury in mice. Deletion of A2AR in microglia specifically impaired chronic-phase repair without altering the severity of acute ischemic injury. Pharmacological activation of A2AR signaling with blood-brain barrier-permeable agonistic micelles during the early reperfusion phase enhanced white matter structural repair and led to sustained improvements in cognitive and sensorimotor function in mice. Mechanistically, A2AR activation promoted microglial efferocytosis of apoptotic cells and myelin debris in the lesioned white matter, thereby limiting secondary necrosis-induced inflammation, enhancing neurotrophic factor release, and establishing a reparative microenvironment conducive to oligodendrocyte precursor cell differentiation and remyelination. Moreover, A2AR signaling engaged HIF1α-dependent metabolic reprogramming to increase glycolysis, thereby providing the energetic support required for efficient and sustained efferocytosis. Together, these findings identify A2AR as a critical regulator of microglia-mediated white matter repair and a promising therapeutic target for enhancing regeneration after stroke.
The way by which cells sense and interpret their microenvironment is fundamental to the regulation of their behaviour. Mechanosignalling is an essential aspect of microenvironmental sensing by cells, particularly within complex three-dimensional tissues, but it remains unclear how this signalling interacts with and modulates organelles such as mitochondria. Mitochondria form a dynamic network throughout the cytoplasm, intricately intertwined with the cytoskeleton and other organelles such as the endoplasmic reticulum. The complex coregulation of these networks controls how cells respond to dynamic changes in metabolic demand. Recent studies have shown that mitochondrial networks are acutely sensitive to mechanosignalling, but it remains in question whether they respond directly to contractile forces from the cytoskeleton or if their reorganisation occurs downstream of broader metabolic reprogramming. Here we discuss recent work highlighting the complexity in understanding this.
Dopamine neurons in the ventral tegmental area (VTA) have roles in motivation, learning, and psychiatric disorders. We found that genetically defined VTA dopamine neuron subtypes had distinct electrophysiological properties, neuronal signaling dynamics in response to reward- and aversion-related stimuli, and roles in somatic optogenetically induced reward dependent on the neurotransmitters they released. Nonglutamate-dopamine neurons increased activity after reward-related stimuli and decreased activity after the omission of an expected reward (negative reward prediction error) and aversion-related stimuli. Glutamate-dopamine and glutamate-only (nonGABAergic and nondopaminergic) neurons were activated by both rewarding and aversive events, but only glutamate-dopamine neurons had sustained cue-induced reward signaling. Recordings of all dopamine neurons without considering glutamate cotransmission showed mixed population responses during prediction error and aversive stimuli that obscured the distinct signaling patterns of its constituent subpopulations. Although the examined cell types largely differ in mediolateral location, cell-type identity better accounted for functional differences than mediolateral location. Glutamate-dopamine neurons were more excitable than nonglutamate-dopamine neurons. Glutamate-dopamine and nonglutamate-dopamine axons had similar but not identical dopamine release dynamics in the nucleus accumbens. Only nonglutamate-dopamine neurons supported somatic optogenetically induced reward and reinforcement. In glutamate-dopamine neurons, the dopamine synthetic enzyme TH contributed to associative learning of aversive or less-beneficial outcomes, whereas the vesicular glutamate transporter VGLUT2 contributed to reward- and exploration-related vigor. Our results suggest that glutamate cotransmission is a distinguishing feature of VTA dopamine neuron signaling patterns and roles in natural reward- or aversion-motivated behavior.
Type I interferons (IFNs) are induced by pattern recognition receptors (PRRs) of the innate immune system to protect against foreign pathogens and malignant transformation, and their production must be tightly regulated to balance antiviral defense with tissue homeostasis. To define the genetic network that governs IFN regulation, we conducted genome-wide CRISPR screens for genes that positively or negatively regulated IFNB1 gene expression induced by the PRR cGAS and its downstream effector STING, in both unprimed THP-1 cells and cells primed with IFN-α to mimic an ongoing inflammatory response. Distinct subsets of genes affected IFNB1 induction in the unprimed and primed states, and many regulators had not previously been associated with IFN responses, thereby linking IFNB1 regulation to various cellular pathways. For example, we found that the NCoR/SMRT corepressor complex components TBL1XR1 and HDAC3 cooperated to support IFNB1 expression, with HDAC3 promoting activation of the kinase TBK1, an essential driver of type I IFN responses. These datasets are a resource for identifying genes associated with type I IFN-related inborn errors of immunity and cancer and for developing therapies to modulate STING signaling in interferonopathies and other conditions of dysregulated type I IFN.
Polyunsaturated fatty acids (PUFAs) play a crucial role in tumor development by influencing not only tumor cells but also immune cells within the tumor microenvironment. Here, we explored the mechanisms by which PUFAs are transported and function within immune cells to regulate tumor growth. We found that PUFA transport through LDL receptor-related protein 5 (LRP5) into natural killer (NK) cells played an essential role in modulating the cells' antitumor function. LRP5 deficiency or expression of LRP5 lacking the LDLa domain enhanced the cytotoxicity and antitumor activity of NK cells both in vivo and in culture. However, wild-type NK cells cultured in the absence of PUFAs and NK cells from mice fed a PUFA-free diet also exhibited enhanced cytotoxicity, eliminating the functional difference between wild-type and NK cells expressing LDLa domain-deficient LRP5. Mechanistically, LRP5-mediated PUFA transport suppressed mTORC1 signaling and glycolysis in NK cells, a metabolic pathway essential for NK cell cytotoxicity. Thus, our study identified LRP5 as an immune checkpoint that restrains NK cell activity through PUFA transport-dependent suppression of mTORC1 signaling.
Mapping mutations to cellular outcomes reveals the molecular mechanisms underlying STING activity.
Astrocytes, oligodendrocyte lineage cells, and microglia dynamically shape the neural extracellular matrix (ECM) across brain development and aging. Recent findings highlight the potential of glial regulation of the ECM as a framework for understanding circuit formation and identify previously unrecognized targets in neurological diseases.
Cilia and flagella exhibit widely conserved structures and functions across species. In humans, defects in these organelles are responsible for diseases called ciliopathies and many model organisms are used to study them. In this review, we will discuss one of them, the parasite Trypanosoma brucei, which is particularly well-suited to investigate general aspects of cilia and flagella, such as construction or protein localisation. Its flagellum remains present throughout the cell cycle, offering the opportunity to monitor flagellum maintenance and assembly within the same cell. This model organism is very convenient for flagellum live imaging as well as expansion microscopy and ultrastructural studies, including focused ion beam - scanning electron microscopy (FIB-SEM). Efficient tools exist to manipulate the genome, including endogenous tagging, inducible expression system, RNA interference and CRISPR-Cas9 approaches. Here, we review original contributions from studies in trypanosome to our understanding of flagellum construction and intraflagellar transport, as well as the impact of gene mutations in some ciliopathies.
Gastrulation is the morphogenetic process by which the single-layered pluripotent epiblast is reorganised into the three germ layers and the basic body plan is established. While the metabolic state of pluripotent stem cells is well characterised, the metabolic remodelling that coincides with germ layer specification is less well understood. Emerging evidence suggests that metabolism functions as more than a passive housekeeping process and instead acts as a dynamic regulator of cell state during these developmental transitions. Here, we review recent work that implicates a role for metabolic pathways in regulating cell fate and morphogenesis during gastrulation. In particular, glucose metabolism appears to serve as a critical regulatory layer, modulating morphogen signalling to promote the emergence and function of mesodermal and endodermal populations. We also discuss the role of the tricarboxylic acid cycle and one-carbon metabolism in epigenetic remodelling and highlight the role of lipid metabolism in coupling the biophysical properties of membranes to cellular identity and morphogenetic movements. A current challenge is to distinguish in which situations metabolic shifts act as instructive drivers or permissive gatekeepers of development. Technological advances in spatial metabolomics, biosensors, and optogenetics are now facilitating the visualisation and manipulation of metabolic activity, paving the way for a mechanistic understanding of how metabolism shapes cell fate and behaviour during gastrulation.
Nutrient-sensing pathways, including mTOR, AMPK, Sirtuins, and insulin/IGF-1 signaling, are central regulators orchestrating adult stem cell (ASC) fate by dynamically modulating cellular metabolism. This review proposes a framework that integrates these pathways into a cohesive network that dictates the metabolic transitions between quiescence, activation, and differentiation in ASCs. Age-related dysregulation of this network leads to metabolic imbalance and stem cell exhaustion, underpinning tissue degeneration. Interventions such as mTOR inhibitors, AMPK activators, NAD+ precursors, and dietary strategies can rejuvenate ASC function by restoring metabolic balance, underscoring their therapeutic potential for mitigating aging and associated diseases.
Biological systems maintain structure and function through hierarchical control, redundancy and surveillance across scales. These same features create leverage points for agents that establish a persistent presence in host systems, including foreign agents such as pathogens, parasites, trophoblasts and gall-inducing insects, and self-defecting agents such as cancer. This review synthesises evidence across immunology, developmental biology, neuroscience, oncology and ecology to treat manipulation as a staged control problem in which local access is converted into distributed effects through shared signalling and feedback loops across scales. We outline a six-step framework in which manipulators establish access, interfere with boundary and identity checks, exploit transient plasticity to reset homeostatic constraints, redirect immune, endocrine and neural communication, remodel host structure through developmental programmes, and stabilise altered states through niche construction and epigenetic remodelling. The framework separates mechanisms required for initiation from those required for maintenance and long-term persistence. We illustrate this framework through four case studies: trophoblast invasion in pregnancy, tumour progression, parasitoid manipulation by Cotesia congregata, and plant galls. The synthesis highlights recurrent vulnerabilities in boundaries, shared signalling and plasticity windows, and motivates stage-specific experiments that test whether candidate mechanisms drive entry, sustain the manipulated state, or increase resistance to reversal. The same logic can help organise thinking about complex pathology in which altered states are maintained by distributed feedback.
The regulation of epithelial cell shape is fundamental to development, homeostasis and disease, and is intricately linked to tissue function. Epithelial morphology emerges from integration of biochemical and mechanical cues across multiple scales, from intrinsic cellular factors to tissue-wide forces. In this review we focus on the mechanical aspects of cell shape control and highlight the multi-scale regulation of epithelial cell shape that links (i) cell-intrinsic factors, such as cytoskeletal organization, contractility and growth, (ii) the local mechanical environment, including cell-matrix interactions and (iii) tissue-scale mechanics governing global morphogenesis. At the cellular level, contractility and growth generate stresses that interact with the surrounding microenvironment, shaped by the extracellular matrix. At the tissue level, large-scale stresses and boundary constraints from neighbouring tissues, bones or cuticles further shape epithelial morphology. Feedback across scales ensures robustness and adaptability of epithelial architecture. In this review, we synthesis recent insights into the mechanical control of epithelial cell-shape transitions and how intrinsic and extrinsic stresses integrate to drive morphogenesis. We also highlight how theoretical modelling frameworks are increasingly essential for disentangling the multiscale interplay of forces that govern epithelial architecture. This review aims to provide perspectives on how epithelial mechanics are coordinated by multiscale regulation and how they contribute to development, homeostasis and disease.
Adult neural stem cells (NSCs) persist throughout life in discrete neurogenic niches of the mammalian brain, most prominently the subventricular zone (SVZ), the subgranular zone (SGZ) of the hippocampal dentate gyrus, and the hypothalamic ventricular zone (HVZ). These niches harbor regionally specialized NSC populations that support neural plasticity, cognitive and emotional regulation, and, in the hypothalamus, systemic metabolic and neuroendocrine homeostasis. While adult neurogenesis in the SGZ and SVZ has been extensively characterized, the HVZ has emerged as a functional adult NSC niche linking stem cell regulation to whole-body physiology. Here, we review recent advances across the SGZ, SVZ, and HVZ to define shared organizational principles and region-specific regulatory mechanisms governing adult NSC identity, homeostasis, and lineage output. We also highlight how intrinsic transcriptional programs, metabolic states, and niche-derived signals shape NSC behavior in each region, and how aging, inflammation, and metabolic stress differentially disrupt these processes. By integrating insights from both classical and hypothalamic neurogenic niches, this review provides a unified framework for understanding adult NSC diversity and disease susceptibility, and discusses strategies to modulate endogenous stem cell niches to preserve homeostasis and minimize disease risk.
Tissue development and regeneration are governed by a dynamic interplay between biochemical signaling programs and biophysical forces that act across molecular, cellular, and tissue scales. Mechanical cues including cytoskeletal tension, extracellular matrix (ECM) stiffness and viscoelasticity, fluid shear, and hydrostatic pressure serve not merely as passive by-products of growth but as active regulators of cell fate, polarity, and morphogenesis. Through integrin- and cadherin-mediated adhesions, RhoA-ROCK contractility, and mechanosensitive pathways such as YAP/TAZ and β-catenin, cells sense and generate forces that coordinate collective migration, apical constriction, convergent extension, branching morphogenesis, and self-organization of organ primordia. Emerging evidence highlights the importance of ECM remodeling, nuclear mechanotransduction, and tissue-scale macromolecular flows as critical determinants of tissue patterning, organ architecture, and stem cell differentiation. This review synthesizes current insights into how mechanical forces shape development and regeneration, emphasizing the regulation of cell, tissue, and organ behavior through mechanochemical feedback loops and the ECM niche. Understanding how physical forces interface with gene regulatory networks will be essential for decoding developmental design principles and engineering functional tissues and organoids.
Recognition of the bacterial product lipopolysaccharide (LPS) by Toll-like receptor 4 (TLR4) initiates inflammatory responses. The unfolded protein response (UPR) elicited by endoplasmic reticulum (ER) stress can strengthen TLR4-dependent inflammatory responses. Here, we report that the ER-localized E3 ubiquitin ligase TRIM13 restrained LPS-induced inflammatory responses in macrophages and in mice by protecting the cells from ER stress. TRIM13 mediated Lys33-linked polyubiquitylation of the ER-localized Ca2+ sensor STIM1, promoting its degradation. TRIM13 deficiency caused STIM1 accumulation and activated store-operated Ca2+ entry (SOCE) and the inositol-requiring enzyme 1 α (IRE1α) branch of the UPR. Suppressing SOCE, chelating extracellular Ca2+, relieving ER stress, or blocking IRE1α activation inhibited the amplification of inflammatory responses caused by the loss of TRIM13 in macrophages. Pharmacological inhibition of IRE1α ameliorated chemically induced colitis in TRIM13-deficient mice. Our study suggests that TRIM13 restrains inflammation by limiting LPS-induced activation of SOCE and the IRE1α branch of the UPR.
