Centrosome polarization delivers secretory granules to the immunological synapse

Genome-wide association analysis study on host resistance against the Aeromonas veronii of largemouth bass Micropterus salmoides

Largemouth bass (Micropterus salmoides) has become one of the most important freshwater economic fish farmed almost all over China in recent years. At the same time, the increasing outbreaks of diseases in its aquaculture process have caused substantial economic losses to this industry. However, at present, the genetic basis of disease resistance, including resistance against Aeromonas veronii infection, in largemouth bass is very limited. Therefore, a genome-wide association study (GWAS) on host resistance against the A. veronii of largemouth bass was conducted in the present study. A total of 627 largemouth bass were artificially challenged by A. veronii, among which 160 of the earliest deaths and 173 of the final survivals were genotyped. A total of 3076 high-quality SNPs were used for further analysis employing two analysis models, of which six shared SNPs were finally identified as significant molecular markers with the explaining phenotypic variance ranging from 2.28 % to 8.95 %. Furthermore, seven candidate genes were identified, including one gene, T-cell surface antigen CD2, which is directly involved in T cell activation and the cellular immune response. Additionally, the other identified genes play roles in critical processes such as cell survival, inflammatory responses, and signal transduction. This study lays a genetic foundation for research on largemouth bass disease resistance and studies related to A. veronii. It also contributes significantly to the future development of the commercial production of largemouth bass.

Bystanders or active players: the role of extra centrosomes as signaling hubs

Centrosomes serve as microtubule-organizing organelles that function in spindle pole organization, cell cycle progression, and cilia formation. A non-canonical role of centrosomes that has gained traction in recent years is the ability to act as signal transduction centers. Centrosome amplification, which includes numerical and structural aberrations of centrosomes, is a candidate hallmark of cancer. The function of centrosomes as signaling centers in cancer cells with centrosome amplification is poorly understood. Establishing a model of how cancer cells utilize centrosomes as signaling platforms will help elucidate the role of extra centrosomes in cancer cell survival and tumorigenesis. Centrosomes act in a diverse array of cellular processes, including cell migration, cell cycle progression, and proteasomal degradation. Given that cancer cells with amplified centrosomes exhibit an increased number and larger area of these signaling platforms, extra centrosomes may be acting to promote tumor development by enhancing signaling kinetics in pathways that are essential for the formation and growth of cancer. In this review, we identify the processes centrosomes are involved in as signal transduction platforms and highlight ways in which cancer cells with centrosome amplification may be taking advantage of these mechanisms.

Comparative Analysis of Extracellular Vesicles from Cytotoxic CD8+ αβ T Cells and γδ T Cells

BACKGROUND

Although belonging to different branches of the immune system, cytotoxic CD8+ αβ T cells and γδ T cells utilize common cytolytic effectors including FasL, granzymes, perforin and granulysin. The effector proteins are stored in different subsets of lysosome-related effector vesicles (LREVs) and released to the immunological synapse upon target cell encounter. Notably, in activated cells, LREVs and potentially other vesicles are continuously produced and released as extracellular vesicles (EVs). Presumably, EVs serve as mediators of intercellular communication in the local microenvironment or at distant sites.

METHODS

EVs of activated and expanded cytotoxic CD8+ αβ T cells or γδ T cells were enriched from culture supernatants by differential and ultracentrifugation and characterized by nanoparticle tracking analyses and Western blotting. For a comparative proteomic profiling, EV preparations from both cell types were isobaric labeled with tandem mass tags (TMT10plex) and subjected to mass spectrometry analysis.

RESULTS

686 proteins were quantified in EV preparations of cytotoxic CD8+ αβ T cells and γδ T cells. Both populations shared a major set of similarly abundant proteins, while much fewer proteins presented higher abundance levels in either CD8+ αβ T cells or γδ T cells. To our knowledge, we provide the first comparative analysis of EVs from cytotoxic CD8+ αβ T cells and γδ T cells.

Imaging-Based Efficacy Evaluation of Cancer Immunotherapy in Engineered Tumor Platforms and Tumor Organoids

Cancer immunotherapy is used to treat tumors by modulating the immune system. Although the anticancer efficacy of cancer immunotherapy has been evaluated prior to clinical trials, conventional in vivo animal and endpoint models inadequately replicate the intricate process of tumor elimination and reflect human-specific immune systems. Therefore, more sophisticated models that mimic the complex tumor-immune microenvironment must be employed to assess the effectiveness of immunotherapy. Additionally, using real-time imaging technology, a step-by-step evaluation can be applied, allowing for a more precise assessment of treatment efficacy. Here, an overview of the various imaging-based evaluation platforms recently developed for cancer immunotherapeutic applications is presented. Specifically, a fundamental technique is discussed for stably observing immune cell-based tumor cell killing using direct imaging, a microwell that reproduces a confined space for spatial observation, a droplet assay that facilitates cell-cell interactions, and a 3D microphysiological system that reconstructs the vascular environment. Furthermore, it is suggested that future evaluation platforms pursue more human-like immune systems.

Is the tumor cell side of the immunological synapse a polarized secretory domain?

The formation of a lytic immunological synapse (IS) is crucial for cytotoxic lymphocytes to accurately target and effectively eliminate malignant cells. While significant attention has been focused on the lymphocyte side of the IS, particularly its role as a secretory domain for lytic granules, the cancer cell side of the IS has remained relatively underexplored. Recent findings have revealed that cancer cells can rapidly polarize their actin cytoskeleton toward the IS upon interaction with natural killer (NK) cells, thereby evading NK cell-mediated cytotoxicity. In this Brief Research Report, we present preliminary findings suggesting that actin cytoskeleton remodeling at the cancer cell side of the IS is associated with the targeted secretion of small extracellular vesicles towards the interacting NK cell. We observed that multivesicular bodies (MVBs) preferentially accumulate in the synaptic region in cancer cells exhibiting synaptic accumulation of F-actin, compared to those lacking actin cytoskeleton remodeling. Extracellular immunofluorescence staining revealed increased surface exposure of CD63 at the cancer cell side of the IS, suggestive of the fusion of MVBs with the plasma membrane. This hypothesis was supported by a pH-sensitive probe demonstrating dynamic trafficking of CD63 to the extracellular region of the IS. Collectively, our data support the notion that cancer cells can engage in targeted secretion of extracellular vesicles in response to NK cell attack, underscoring the need for further research into the potential role of this process in facilitating cancer cell immune evasion.

The physical landscape of CAR-T synapse

Chimeric antigen receptor (CAR)-T cells form dynamic immunological synapses with their cancer cell targets. After a CAR-antigen engagement, the CAR-T synapse forms, matures, and finally disassembles, accompanied by substantial remodeling of cell surface proteins, lipids, and glycans. In this review, we provide perspectives for understanding protein distribution, membrane topology, and force transmission across the CAR-T synapse. We highlight the features of CAR-T synapses that differ from T cell receptor synapses, including the disorganized protein pattern, adjustable synapse width, diverse mechano-responding properties, and resulting signaling consequences. Through a range of examples, we illustrate how revealing the biophysical nature of the CAR-T synapse could guide the design of CAR-Ts with improved anti-tumor function.

Cytosolic protein translation regulates cell asymmetry and function in early TCR activation of human CD8+ T lymphocytes

Introduction

CD8+ cytotoxic T lymphocytes (CTLs) are highly effective in defending against viral infections and tumours. They are activated through the recognition of peptide-MHC-I complex by the T-cell receptor (TCR) and co-stimulation. This cognate interaction promotes the organisation of intimate cell-cell connections that involve cytoskeleton rearrangement to enable effector function and clearance of the target cell. This is key for the asymmetric transport and mobilisation of lytic granules to the cell-cell contact, promoting directed secretion of lytic mediators such as granzymes and perforin. Mitochondria play a role in regulating CTL function by controlling processes such as calcium flux, providing the necessary energy through oxidative phosphorylation, and its own protein translation on 70S ribosomes. However, the effect of acute inhibition of cytosolic translation in the rapid response after TCR has not been studied in mature CTLs.

Methods

Here, we investigated the importance of cytosolic protein synthesis in human CTLs after early TCR activation and CD28 co-stimulation for the dynamic reorganisation of the cytoskeleton, mitochondria, and lytic granules through short-term chemical inhibition of 80S ribosomes by cycloheximide and 80S and 70S by puromycin.

Results

We observed that eukaryotic ribosome function is required to allow proper asymmetric reorganisation of the tubulin cytoskeleton and mitochondria and mTOR pathway activation early upon TCR activation in human primary CTLs.

Discussion

Cytosolic protein translation is required to increase glucose metabolism and degranulation capacity upon TCR activation and thus to regulate the full effector function of human CTLs.

Lipid switches in the immunological synapse

Adaptive immune responses comprise the activation of T cells by peptide antigens that are presented by proteins of the Major Histocompatibility Complex (MHC) on the surface of an antigen-presenting cell. As a consequence of the T cell receptor interacting productively with a certain peptide-MHC complex, a specialized cell-cell junction known as the immunological synapse forms and is accompanied by changes in the spatiotemporal patterning and function of intracellular signaling molecules. Key modifications occurring at the cytoplasmic leaflet of the plasma and internal membranes in activated T cells comprise lipid switches that affect the binding and distribution of proteins within or near the lipid bilayer. Here, we describe two major classes of lipid switches that act at this critical water/membrane interface. Phosphoinositides are derived from phosphatidylinositol, an amphiphilic molecule that contains two fatty acid chains and a phosphate group that bridges the glycerol backbone to the carbohydrate inositol. The inositol ring can be variably (de-)phosphorylated by dedicated kinases and phosphatases, thereby creating phosphoinositide signatures that define the composition and properties of signaling molecules, molecular complexes, or whole organelles. Palmitoylation refers to the reversible attachment of the fatty acid palmitate to a substrate protein's cysteine residue. DHHC enzymes, named after the four conserved amino acids in their active site, catalyze this post-translational modification and thereby change the distribution of proteins at, between, and within membranes. T cells utilize these two types of molecular switches to adjust their properties to an activation process that requires changes in motility, transport, secretion, and gene expression.

Developmental and tissue-specific roles of mammalian centrosomes

Centrosomes are dominant microtubule organizing centers in animal cells with a pair of centrioles at their core. They template cilia during interphase and help organize the mitotic spindle for a more efficient cell division. Here, we review the roles of centrosomes in the early developing mouse and during organ formation. Mammalian cells respond to centrosome loss-of-function by activating the mitotic surveillance pathway, a timing mechanism that, when a defined mitotic duration is exceeded, leads to p53-dependent cell death in the descendants. Mouse embryos without centrioles are highly susceptible to this pathway and undergo embryonic arrest at mid-gestation. The complete loss of the centriolar core results in earlier and more severe phenotypes than that of other centrosomal proteins. Finally, different developing tissues possess varying thresholds and mount graded responses to the loss of centrioles that go beyond the germ layer of origin.

The bispecific B7H3xCD3 antibody CC-3 induces T cell immunity against bone and soft tissue sarcomas

Sarcomas are rare and heterogeneous malignancies that are difficult to treat. Approximately 50% of patients diagnosed with sarcoma develop metastatic disease with so far very limited treatment options. The transmembrane protein B7-H3 reportedly is expressed in various malignancies, including different sarcoma subtypes. In several cancer entities B7-H3 expression is associated with poor prognosis. In turn, B7-H3 is considered a promising target for immunotherapeutic approaches. We here report on the preclinical characterization of a B7-H3xCD3 bispecific antibody in an IgG-based format, termed CC-3, for treatment of different sarcoma subtypes. We found B7-H3 to be expressed on all sarcoma cells tested and expression on sarcoma patients correlated with decreased progression-free and overall survival. CC-3 was found to elicit robust T cell responses against multiple sarcoma subtypes, resulting in significant activation, release of cytokines and effector molecules. In addition, CC-3 promoted T cell proliferation and differentiation, resulting in the generation of memory T cell subsets. Finally, CC-3 induced potent target cell lysis in a target cell restricted manner. Based on these results, a clinical trial evaluating CC-3 in soft tissue sarcoma is currently in preparation.

Principles of organelle positioning in motile and non-motile cells

Cells are equipped with asymmetrically localised and functionally specialised components, including cytoskeletal structures and organelles. Positioning these components to specific intracellular locations in an asymmetric manner is critical for their functionality and affects processes like immune responses, tissue maintenance, muscle functionality, and neurobiology. Here, we provide an overview of strategies to actively move, position, and anchor organelles to specific locations. By conceptualizing the cytoskeletal forces and the organelle-to-cytoskeleton connectivity, we present a framework of active positioning of both membrane-enclosed and membrane-less organelles. Using this framework, we discuss how different principles of force generation and organelle anchorage are utilised by different cells, such as mesenchymal and amoeboid cells, and how the microenvironment influences the plasticity of organelle positioning. Given that motile cells face the challenge of coordinating the positioning of their content with cellular motion, we particularly focus on principles of organelle positioning during migration. In this context, we discuss novel findings on organelle positioning by anchorage-independent mechanisms and their advantages and disadvantages in motile as well as stationary cells.

Unconventional human CD61 pairing with CD103 promotes TCR signaling and antigen-specific T cell cytotoxicity

Cancer remains one of the leading causes of mortality worldwide, leading to increased interest in utilizing immunotherapy strategies for better cancer treatments. In the past decade, CD103+ T cells have been associated with better clinical prognosis in patients with cancer. However, the specific immune mechanisms contributing toward CD103-mediated protective immunity remain unclear. Here, we show an unexpected and transient CD61 expression, which is paired with CD103 at the synaptic microclusters of T cells. CD61 colocalization with the T cell antigen receptor further modulates downstream T cell antigen receptor signaling, improving antitumor cytotoxicity and promoting physiological control of tumor growth. Clinically, the presence of CD61+ tumor-infiltrating T lymphocytes is associated with improved clinical outcomes, mediated through enhanced effector functions and phenotype with limited evidence of cellular exhaustion. In conclusion, this study identified an unconventional and transient CD61 expression and pairing with CD103 on human immune cells, which potentiates a new target for immune-based cellular therapies.

Positioning centrioles and centrosomes

Centrosomes are the primary microtubule organizer in eukaryotic cells. In addition to shaping the intracellular microtubule network and the mitotic spindle, centrosomes are responsible for positioning cilia and flagella. To fulfill these diverse functions, centrosomes must be properly located within cells, which requires that they undergo intracellular transport. Importantly, centrosome mispositioning has been linked to ciliopathies, cancer, and infertility. The mechanisms by which centrosomes migrate are diverse and context dependent. In many cells, centrosomes move via indirect motor transport, whereby centrosomal microtubules engage anchored motor proteins that exert forces on those microtubules, resulting in centrosome movement. However, in some cases, centrosomes move via direct motor transport, whereby the centrosome or centriole functions as cargo that directly binds molecular motors which then walk on stationary microtubules. In this review, we summarize the mechanisms of centrosome motility and the consequences of centrosome mispositioning and identify key questions that remain to be addressed.

Extracellular vesicles and microvilli in the immune synapse

T cell receptor (TCR) binding to cognate antigen on the plasma membrane of an antigen-presenting cell (APC) triggers the immune synapse (IS) formation. The IS constitutes a dedicated contact region between different cells that comprises a signaling platform where several cues evoked by TCR and accessory molecules are integrated, ultimately leading to an effective TCR signal transmission that guarantees intercellular message communication. This eventually leads to T lymphocyte activation and the efficient execution of different T lymphocyte effector tasks, including cytotoxicity and subsequent target cell death. Recent evidence demonstrates that the transmission of information between immune cells forming synapses is produced, to a significant extent, by the generation and secretion of distinct extracellular vesicles (EV) from both the effector T lymphocyte and the APC. These EV carry biologically active molecules that transfer cues among immune cells leading to a broad range of biological responses in the recipient cells. Included among these bioactive molecules are regulatory miRNAs, pro-apoptotic molecules implicated in target cell apoptosis, or molecules triggering cell activation. In this study we deal with the different EV classes detected at the IS, placing emphasis on the most recent findings on microvilli/lamellipodium-produced EV. The signals leading to polarized secretion of EV at the synaptic cleft will be discussed, showing that the IS architecture fulfills a fundamental task during this route.

Partial loss of Sorting Nexin 27 resembles age- and Down syndrome-associated T cell dysfunctions

BACKGROUND

Sorting Nexin 27 (SNX27)-retromer complex facilitates cargo recycling from endosomes to the plasma membrane. SNX27 downregulation in neurons, as the result of Trisomy 21 (T21), has been linked with cognitive deficits due to impairment of AMPA and NMDA receptor recycling. Studies in human T cell lines likewise demonstrated that SNX27 regulates the correct delivery of cargoes to the immune synapse limiting the activation of pro-inflammatory pathways. Nevertheless, the physiological consequences of partial SNX27 loss in T cell homeostasis are still unclear.

RESULTS

In this study, we have explored the consequences of T cell specific partial SNX27 downregulation in mice. T cells with partial SNX27 deficiency show a marked deficit in the CD4+ T cell pool, a hallmark of aging in mice and humans, and a well-characterized comorbidity of individuals with Down syndrome (DS). When analyzed ex vivo, CD4+ T cells with partial SNX27 deletion demonstrate enhanced proliferation but diminished IL-2 production. In contrast, the CD8+ population show enhanced expression of pro-inflammatory cytokines and lytic enzymes.

CONCLUSIONS

This mouse model supports the relevance of SNX27 in the organization of the immune synapse, previously described in cell lines, as well as in the control of T cell homeostasis. Individuals with DS experiment an acceleration of the aging process, which particularly affects the immune and central nervous systems. Thus, we hypothesize that reduced SNX27 expression in DS could contribute to the dysregulation of these systems and further research in SNX27 will shed light on the molecular factors underlying the phenotypes observed in people with DS and its contribution to aging.

Self-supervised noise modeling and sparsity guided electron tomography volumetric image denoising

Cryo-Electron Tomography (cryo-ET) is a revolutionary technique for visualizing macromolecular structures in near-native states. However, the physical limitations of imaging instruments lead to cryo-ET volumetric images with very low Signal-to-Noise Ratio (SNR) with complex noise, which has a side effect on the downstream analysis of the characteristics of observed macromolecules. Additionally, existing methods for image denoising are difficult to be well generalized to the complex noise in cryo-ET volumes. In this work, we propose a self-supervised deep learning model for cryo-ET volumetric image denoising based on noise modeling and sparsity guidance (NMSG), achieved by learning the noise distribution in noisy cryo-ET volumes and introducing sparsity guidance to ensure smoothness. Firstly, a Generative Adversarial Network (GAN) is utilized to learn noise distribution in cryo-ET volumes and generate noisy volumes pair from single volume. Then, a new loss function is devised to both ensure the recovery of ultrastructure and local smoothness. Experiments are done on five real cryo-ET datasets and three simulated cryo-ET datasets. The comprehensive experimental results demonstrate that our method can perform reliable denoising by training on single noisy volume, achieving better results than state-of-the-art single volume-based methods and competitive with methods trained on large-scale datasets.

Extended-Synaptotagmin-1 and -2 control T cell signaling and function

Upon T-cell activation, the levels of the secondary messenger diacylglycerol (DAG) at the plasma membrane need to be controlled to ensure appropriate T-cell receptor signaling and T-cell functions. Extended-Synaptotagmins (E-Syts) are a family of inter-organelle lipid transport proteins that bridge the endoplasmic reticulum and the plasma membrane. In this study, we identify a novel regulatory mechanism of DAG-mediated signaling for T-cell effector functions based on E-Syt proteins. We demonstrate that E-Syts downmodulate T-cell receptor signaling, T-cell-mediated cytotoxicity, degranulation, and cytokine production by reducing plasma membrane levels of DAG. Mechanistically, E-Syt2 predominantly modulates DAG levels at the plasma membrane in resting-state T cells, while E-Syt1 and E-Syt2 negatively control T-cell receptor signaling upon stimulation. These results reveal a previously underappreciated role of E-Syts in regulating DAG dynamics in T-cell signaling.

The centrosomal protein 131 participates in the regulation of mitochondrial apoptosis

Centriolar satellites are multiprotein aggregates that orbit the centrosome and govern centrosome homeostasis and primary cilia formation. In contrast to the scaffold PCM1, which nucleates centriolar satellites and has been linked to microtubule dynamics, autophagy, and intracellular trafficking, the functions of its interactant CEP131 beyond ciliogenesis remain unclear. Using a knockout strategy in a non-ciliary T-cell line, we report that, although dispensable for centriolar satellite assembly, CEP131 participates in optimal tubulin glycylation and polyglutamylation, and microtubule regrowth. Our unsupervised label-free proteomic analysis by quantitative mass spectrometry further uncovered mitochondrial and apoptotic signatures. CEP131-deficient cells showed an elongated mitochondrial network. Upon cell death inducers targeting mitochondria, knockout cells displayed delayed cytochrome c release from mitochondria, subsequent caspase activation, and apoptosis. This mitochondrial permeabilization defect was intrinsic, and replicable in vitro with isolated organelles. These findings extend CEP131 functions to life-and-death decisions and propose ways to interfere with mitochondrial apoptosis.

Cellular and molecular imaging of CAR-T cell-based immunotherapy

Chimeric Antigen Receptor T cell (CAR-T) therapy has emerged as a transformative therapeutic strategy for hematological malignancies. However, its efficacy in treating solid tumors remains limited. An in-depth and comprehensive understanding of CAR-T cell signaling pathways and the ability to track CAR-T cell biodistribution and activation in real-time within the tumor microenvironment will be instrumental in designing the next generation of CAR-T cells for solid tumor therapy. This review summarizes the signaling network and the cellular and molecular imaging tools and platforms that are utilized in CAR-T cell-based immune therapies, covering both in vitro and in vivo studies. Firstly, we provide an overview of the existing understanding of the activation and cytotoxic mechanisms of CAR-T cells, compared to the mechanism of T cell receptor (TCR) signaling pathways. We further describe the commonly employed tools for live cell imaging, coupled with recent research progress, with a focus on genetically encoded fluorescent proteins (FPs) and biosensors. We then discuss the utility of diverse in vivo imaging modalities, including fluorescence and bioluminescence imaging, Magnetic Resonance Imaging (MRI), Positron Emission Tomography (PET), and photoacoustic (PA) imaging, for noninvasive monitoring of CAR-T cell dynamics within tumor tissues, thereby providing critical insights into therapy's strengths and weaknesses. Lastly, we discuss the current challenges and future directions of CAR-T cell therapy from the imaging perspective. We foresee that a comprehensive and integrative approach to CAR-T cell imaging will enable the development of more effective treatments for solid tumors in the future.

PD-1 inhibits T cell actin remodeling at the immunological synapse independently of its signaling motifs

Engagement of the receptor programmed cell death molecule 1 (PD-1) by its ligands PD-L1 and PD-L2 inhibits T cell-mediated immune responses. Blocking such signaling provides the clinical effects of PD-1-targeted immunotherapy. Here, we investigated the mechanisms underlying PD-1-mediated inhibition. Because dynamic actin remodeling is crucial for T cell functions, we characterized the effects of PD-1 engagement on actin remodeling at the immunological synapse, the interface between a T cell and an antigen-presenting cell (APC) or target cell. We used microscopy to analyze the formation of immunological synapses between PD-1+ Jurkat cells or primary human CD8+ cytotoxic T cells and APCs that presented T cell-activating antibodies and were either positive or negative for PD-L1. PD-1 binding to PD-L1 inhibited T cell spreading induced by antibody-mediated activation, which was characterized by the absence of the F-actin-dense distal lamellipodial network at the immunological synapse and the Arp2/3 complex, which mediates branched actin formation. PD-1-induced inhibition of actin remodeling also prevented the characteristic deformation of T cells that contact APCs and the release of cytotoxic granules. We showed that the effects of PD-1 on actin remodeling did not require its tyrosine-based signaling motifs, which are thought to mediate the co-inhibitory effects of PD-1. Our study highlights a previously unappreciated mechanism of PD-1-mediated suppression of T cell activity, which depends on the regulation of actin cytoskeleton dynamics in a signaling motif-independent manner.

Actin cytoskeleton remodeling at the cancer cell side of the immunological synapse: good, bad, or both?

Cytotoxic lymphocytes (CLs), specifically cytotoxic T lymphocytes and natural killer cells, are indispensable guardians of the immune system and orchestrate the recognition and elimination of cancer cells. Upon encountering a cancer cell, CLs establish a specialized cellular junction, known as the immunological synapse that stands as a pivotal determinant for effective cell killing. Extensive research has focused on the presynaptic side of the immunological synapse and elucidated the multiple functions of the CL actin cytoskeleton in synapse formation, organization, regulatory signaling, and lytic activity. In contrast, the postsynaptic (cancer cell) counterpart has remained relatively unexplored. Nevertheless, both indirect and direct evidence has begun to illuminate the significant and profound consequences of cytoskeletal changes within cancer cells on the outcome of the lytic immunological synapse. Here, we explore the understudied role of the cancer cell actin cytoskeleton in modulating the immune response within the immunological synapse. We shed light on the intricate interplay between actin dynamics and the evasion mechanisms employed by cancer cells, thus providing potential routes for future research and envisioning therapeutic interventions targeting the postsynaptic side of the immunological synapse in the realm of cancer immunotherapy. This review article highlights the importance of actin dynamics within the immunological synapse between cytotoxic lymphocytes and cancer cells focusing on the less-explored postsynaptic side of the synapse. It presents emerging evidence that actin dynamics in cancer cells can critically influence the outcome of cytotoxic lymphocyte interactions with cancer cells.

Who wins the combat, CAR or TCR?

Chimeric antigen receptor T (CAR-T) cell therapy has drawn increasing attention over the last few decades given its remarkable effectiveness and breakthroughs in treating B cell hematological malignancies. Even though CAR-T cell therapy has outstanding clinical successes, most treated patients still relapse after infusion. CARs are derived from the T cell receptor (TCR) complex and co-stimulatory molecules associated with T cell activation; however, the similarities and differences between CARs and endogenous TCRs regarding their sensitivity, signaling pathway, killing mechanisms, and performance are still not fully understood. In this review, we discuss the parallel comparisons between CARs and TCRs from various aspects and how these current findings might provide novel insights and contribute to improvement of CAR-T cell therapy efficacy.

Factors contributing to the potency of CD8+ T cells

CD8+ cytotoxic T lymphocytes (CTLs) play a crucial role in targeting virus-infected and cancer cells. Although other cytotoxic lymphocytes such as CD4+ T and natural killer (NK) cells, as well as chimeric antigen receptor (CAR)-T cells, can also identify and destroy aberrant cells, they seem to be significantly less potent based on available experimental data. Here, I contemplate the molecular mechanisms controlling the sensitivity and kinetics of granule-mediated CD8+ T cell cytolytic responses. I posit that the clustering of MHC-I molecules and T cell receptors (TCRs) on the cell surface, as well as the contribution of the CD8 co-receptor, are major factors driving exceptionally potent cytolytic responses. I also contend that CD8+ T cells with known specificity and engineered TCR-T cells might be among the most efficient cytolytic effectors for treating patients suffering from viral infections or cancer.

Regulation of CD8 T-cell signaling, metabolism, and cytotoxic activity by extracellular lysophosphatidic acid

Lysophosphatidic acid (LPA) is an endogenous bioactive lipid that is produced extracellularly and signals to cells via cognate LPA receptors, which are G-protein coupled receptors (GPCRs). Mature lymphocytes in mice and humans express three LPA receptors, LPA2 , LPA5, and LPA6 , and work from our group has determined that LPA5 signaling by T lymphocytes inhibits specific antigen-receptor signaling pathways that ultimately impair lymphocyte activation, proliferation, and function. In this review, we discuss previous and ongoing work characterizing the ability of an LPA-LPA5 axis to serve as a peripheral immunological tolerance mechanism that restrains adaptive immunity but is subverted during settings of chronic inflammation. Specifically, LPA-LPA5 signaling is found to regulate effector cytotoxic CD8 T cells by (at least) two mechanisms: (i) regulating the actin-microtubule cytoskeleton in a manner that impairs immunological synapse formation between an effector CD8 T cell and antigen-specific target cell, thus directly impairing cytotoxic activity, and (ii) shifting T-cell metabolism to depend on fatty-acid oxidation for mitochondrial respiration and reducing metabolic efficiency. The in vivo outcome of LPA5 inhibitory activity impairs CD8 T-cell killing and tumor immunity in mouse models providing impetus to consider LPA5 antagonism for the treatment of malignancies and chronic infections.

Development of CD30 CAR-T cells in refractory or relapsed Hodgkin's lymphoma

INTRODUCTION

After therapy, approximately 15% of individuals with Hodgkin's lymphoma (HL) develop relapsed or drug-resistant Hodgkin's lymphoma (r/rHL). r/rHL has a high fatality rate and poor therapeutic prognosis. CD30 CAR-T-cell therapy has emerged as a new way to treat r/rHL in recent years. However, CD30CAR-T cells are still being explored in clinical trials. To help more patients, this review focuses on current CD30CAR-T-cell advancements as well as clinical breakthroughs in treatment of r/rHL.

AREAS COVERED

This research examines the mechanism of action of CD30 CAR-T cells, their function in the real-world therapy of r/rHL, and the influence of different treatment regimens on treatment results.

EXPERT OPINION

There has been much research into CD30 CAR-T cells as a result of their successful use in treatment of r/rHL. This research has helped us to understand CD30 CAR-T-cell safety as well as the management options available before and after its administration to increase patient survival and reduce side effects.

NUAK1 governs centrosome replication in pancreatic cancer via MYPT1/PP1β and GSK3β-dependent regulation of PLK4

The AMP-activated protein kinase (AMPK)-related kinase NUAK1 (NUAK family SNF1-like kinase 1) has emerged as a potential vulnerability in MYC-dependent cancer but the biological roles of NUAK1 in different settings are poorly characterised, and the spectrum of cancer types that exhibit a requirement for NUAK1 is unknown. Unlike canonical oncogenes, NUAK1 is rarely mutated in cancer and appears to function as an obligate facilitator rather than a cancer driver per se. Although numerous groups have developed small-molecule NUAK inhibitors, the circumstances that would trigger their use and the unwanted toxicities that may arise as a consequence of on-target activity are thus undetermined. Reasoning that MYC is a key effector of RAS pathway signalling and the GTPase KRAS is almost uniformly mutated in pancreatic ductal adenocarcinoma (PDAC), we investigated whether this cancer type exhibits a functional requirement for NUAK1. Here, we show that high NUAK1 expression is associated with reduced overall survival in PDAC and that inhibition or depletion of NUAK1 suppresses growth of PDAC cells in culture. We identify a previously unknown role for NUAK1 in regulating accurate centrosome duplication and show that loss of NUAK1 triggers genomic instability. The latter activity is conserved in primary fibroblasts, raising the possibility of undesirable genotoxic effects of NUAK1 inhibition.

Control of centrosome distal appendages assembly and disassembly

Centrosomes are microtubule organizing centers involved in chromosome segregation, spindle orientation, cell motility and cilia formation. In recent years, they have also emerged as key modulators of asymmetric cell division. Centrosomes are composed of two centrioles that initiate duplication in S phase. The conservative nature of centriole duplication means that the two centrioles of a G1 cell are of different ages. They are also structurally different as only the older centriole carry appendages, an assembly of a subset of proteins primarily required for cilia formation. In a growing tissue, the non-motile, primary cilium acts as a mechano- and sensory organelle that influences cell behavior via modulation of signaling pathways. Here, we discuss the most recent findings about distal appendage composition and function, as well as cell cycle-specific regulation and their implications in various diseases.

Tumors evade immune cytotoxicity by altering the surface topology of NK cells

The highly variable response rates to immunotherapies underscore our limited knowledge about how tumors can manipulate immune cells. Here the membrane topology of natural killer (NK) cells from patients with liver cancer showed that intratumoral NK cells have fewer membrane protrusions compared with liver NK cells outside tumors and with peripheral NK cells. Dysregulation of these protrusions prevented intratumoral NK cells from recognizing tumor cells, from forming lytic immunological synapses and from killing tumor cells. The membranes of intratumoral NK cells have altered sphingomyelin (SM) content and dysregulated serine metabolism in tumors contributed to the decrease in SM levels of intratumoral NK cells. Inhibition of SM biosynthesis in peripheral NK cells phenocopied the disrupted membrane topology and cytotoxicity of the intratumoral NK cells. Targeting sphingomyelinase confers powerful antitumor efficacy, both as a monotherapy and as a combination therapy with checkpoint blockade.

Analysis of centrosomal area actin reorganization and centrosome polarization upon lymphocyte activation at the immunological synapse

T cell receptor (TCR) and B cell receptor (BCR) stimulation of T and B lymphocytes, by antigen presented on an antigen-presenting cell (APC) induces the formation of the immunological synapse (IS). IS formation is associated with an initial increase in cortical filamentous actin (F-actin) at the IS, followed by a decrease in F-actin density at the central region of the IS, which contains the secretory domain. This is followed by the convergence of secretion vesicles towards the centrosome, and the polarization of the centrosome to the IS. These reversible, cortical actin cytoskeleton reorganization processes occur during lytic granule secretion in cytotoxic T lymphocytes (CTL) and natural killer (NK) cells, proteolytic granules secretion in B lymphocytes and during cytokine-containing vesicle secretion in T-helper (Th) lymphocytes. In addition, several findings obtained in T and B lymphocytes forming IS show that actin cytoskeleton reorganization also occurs at the centrosomal area. F-actin reduction at the centrosomal area appears to be associated with centrosome polarization. In this chapter we deal with the analysis of centrosomal area F-actin reorganization, as well as the centrosome polarization analysis toward the IS.

Quantification of interaction frequency between antigen-presenting cells and T cells by conjugation assay

Interaction between an antigen-presenting cell and a T cell, and their subsequent conjugation are a prerequisite for the formation of the immunological synapse and productive, antigen-dependent activation of T cells. This initial interaction is accompanied by recognition of the presented antigen by the T cell receptor, and by changes in the morphology of the interacting cells and in actin cytoskeleton structure in the site of interaction. The experimental protocol below describes a simple assay for quantitative assessment of antigen-presenting cells-T cell conjugation using confocal microscopy or flow cytometry.

Imaging polarized granule release at the cytotoxic T cell immunological synapse using TIRF microscopy: Control by polarity regulators

Immunological synapse formation results from a profound T cell polarization process that involves the coordinated action of the actin and microtubule cytoskeleton, and the intracellular traffic of several vesicular organelles. T cell polarization is key for both T cell activation leading to T cell proliferation and differentiation, and for T cell effector functions such as polarized secretion of cytokines by helper T cells, or polarized delivery of lytic granules by cytotoxic T cells. Efficient targeting of lytic granules by cytotoxic T cells is a crucial event for the control and elimination of infected or tumor cells. Understanding how lytic granule delivery is regulated and quantifying its efficiency under physiological and pathological conditions may help to improve immune responses against infection and cancer.

Contribution of natural killer cells in innate immunity against colorectal cancer

Natural killer cells are members of the innate immune system and promote cytotoxic activity against tumor or infected cells independently from MHC recognition. NK cells are modulated by the expression of activator/inhibitory receptors. The ratio of this activator/inhibitory receptors is responsible for the cytotoxic activity of NK cells toward the target cells. Owing to the potent anti-tumor properties of NK cells, they are considered as interesting approach in tumor treatment. Colorectal cancer (CRC) is the second most common cause of death in the world and the incidence is about 2 million new cases per year. Metastatic CRC is accompanied by a poor prognosis with less than three years of overall survival. Chemotherapy and surgery are the most adopted treatments. Besides, targeted therapy and immune checkpoint blockade are novel approach to CRC treatment. In these patients, circulating NK cells are a prognostic marker. The main target of CRC immune cell therapy is to improve the tumor cell's recognition and elimination by immune cells. Adaptive NK cell therapy is the milestone to achieve the purpose. Allogeneic NK cell therapy has been widely investigated within clinical trials. In this review, we focus on the NK related approaches including CAR NK cells, cell-based vaccines, monoclonal antibodies and immunomodulatory drugs against CRC tumoral cells.

Identification of a novel mechanism for LFA-1 organization during NK cytolytic response

The elimination of transformed and viral infected cells by natural killer (NK) cells requires a specialized junction between NK and target cells, denominated immunological synapse (IS). After initial recognition, the IS enables the directed secretion of lytic granules content into the susceptible target cell. The lymphocyte function-associated antigen (LFA)-1 regulates NK effector function by enabling NK-IS assembly and maturation. The pathways underlying LFA-1 accumulation at the IS in NK cells remained uncharacterized. A kinase anchoring protein 350 (AKAP350) is a centrosome/Golgi-associated protein, which, in T cells, participates in LFA-1 activation by mechanisms that have not been elucidated. We first evaluated AKAP350 participation in NK cytolytic activity. Our results showed that the decrease in AKAP350 levels by RNA interference (AKAP350KD) inhibited NK-YTS cytolytic activity, without affecting conjugate formation. The impairment of NK effector function in AKAP350KD cells correlated with decreased LFA-1 clustering and defective IS maturation. AKAP350KD cells that were exclusively activated via LFA-1 showed impaired LFA-1 organization and deficient lytic granule translocation as well. In NK AKAP350KD cells, activation signaling through Vav1 was preserved up to 10 min of interaction with target cells, but significantly decreased afterwards. Experiments in YTS and in ex vivo NK cells identified an intracellular pool of LFA-1, which partially associated with the Golgi apparatus and, upon NK activation, redistributed to the IS in an AKAP350-dependent manner. The analysis of Golgi organization indicated that the decrease in AKAP350 expression led to the disruption of the Golgi integrity in NK cells. Alteration of Golgi function by BFA treatment or AKAP350 delocalization from this organelle also led to impaired LFA-1 localization at the IS. Therefore, this study characterizes AKAP350 participation in the modulation of NK effector function, revealing the existence of a Golgi-dependent trafficking pathway for LFA-1, which is relevant for LFA-1 organization at NK-lytic IS.

Polarity in immune cells

Immune cells are responsible for pathogen detection and elimination, as well as for signaling to other cells the presence of potential danger. In order to mount an efficient immune response, they need to move and search for a pathogen, interact with other cells, and diversify the population by asymmetric cell division. All these actions are regulated by cell polarity: cell polarity controls cell motility, which is crucial for scanning peripheral tissues to detect pathogens, and recruiting immune cells to sites of infection; immune cells, in particular lymphocytes, communicate with each other by a direct contact called immunological synapse, which entails a global polarization of the cell and plays a role in activating lymphocyte response; finally, immune cells divide asymmetrically from a precursor, generating a diversity of phenotypes and cell types among daughter cells, such as memory and effector cells. This review aims at providing an overview from both biology and physics perspectives of how cell polarity shapes the main immune cell functions.

Exploiting the RUSH System to Study Lytic Granule Biogenesis in Cytotoxic T Lymphocytes

The Retention Using Selective Hooks (RUSH) system allows for the synchronized release of one or more proteins of interest from a donor endomembrane compartment, usually the endoplasmic reticulum, and the subsequent monitoring of their traffic toward acceptor compartments. Here we describe the RUSH system applied to cytotoxic T cells to characterize the biogenesis of lytic granules, using as a proof-of-concept granzyme B trafficking to this specialized compartment.

Analyzing Single Cell Secretions by "Shadow Imaging"

Here, we describe a method, which we term "shadow imaging," to analyze the secretions of individual cells at immune synapses or other cell contacts. Following immune synapse formation and cellular activation on ligand-rich slides, the position of each cell is recorded using a pulsed immunofluorescence stain against the proteins on the ligand-rich slide surface. The pulsed stain does not penetrate the synaptic cleft, resulting in an unlabeled region or "shadow" beneath cells that is retained following cellular detachment. The secreted components, such as perforin, exosomes, or other types of extracellular vesicles, are retained on the slide and can be analyzed on a single-cell basis using immunofluorescence. The ability to identify single cells secreting different combinations of particles, proteins, and vesicles enables us to better understand the heterogeneity in immune cell secretions and can be used as a novel approach for phenotyping cell populations.

ALFA-PRF: a novel approach to detect murine perforin release from CTLs into the immune synapse

When killing through the granule exocytosis pathway, cytotoxic lymphocytes release key effector molecules into the immune synapse, perforin and granzymes, to initiate target cell killing. The pore-forming perforin is essential for the function of cytotoxic lymphocytes, as its pores disrupt the target cell membrane and allow diffusion of pro-apoptotic serine proteases, granzyme, into the target cell, where they initiate various cell death cascades. Unlike human perforin, the detection of its murine counterpart in a live cell system has been problematic due its relatively low expression level and the lack of sensitive antibodies. The lack of a suitable methodology to visualise murine perforin secretion into the synapse hinders the study of the cytotoxic lymphocyte secretory machinery in murine models of human disease. Here, we describe a novel recombinant technology, whereby a short ALFA-tag sequence has been fused with the amino-terminus of a mature murine perforin, and this allowed its detection by the highly specific FluoTag^®-X2 anti-ALFA nanobodies using both Total Internal Reflection Fluorescence (TIRF) microscopy of an artificial synapse, and confocal microscopy of the physiological immune synapse with a target cell. This methodology can have broad application in the field of cytotoxic lymphocyte biology and for the many models of human disease.

Inflammatory-driven NK cell maturation and its impact on pathology

NK cells are innate lymphocytes involved in a large variety of contexts and are crucial in the immunity to intracellular pathogens as well as cancer due to their ability to kill infected or malignant cells. Thus, they harbor a strong potential for clinical and therapeutic use. NK cells do not require antigen exposure to get activated; their functional response is rather based on a balance between inhibitory/activating signals and on the diversity of germline-encoded receptors they express. In order to reach optimal functional status, NK cells go through a step-wise development in the bone marrow before their egress, and dissemination into peripheral organs via the circulation. In this review, we summarize bone marrow NK cell developmental stages and list key factors involved in their differentiation before presenting newly discovered and emerging factors that regulate NK cell central and peripheral maturation. Lastly, we focus on the impact inflammatory contexts themselves can have on NK cell development and functional maturation.

Multiple centrosomes enhance migration and immune cell effector functions of mature dendritic cells

Centrosomes play a crucial role during immune cell interactions and initiation of the immune response. In proliferating cells, centrosome numbers are tightly controlled and generally limited to one in G1 and two prior to mitosis. Defects in regulating centrosome numbers have been associated with cell transformation and tumorigenesis. Here, we report the emergence of extra centrosomes in leukocytes during immune activation. Upon antigen encounter, dendritic cells pass through incomplete mitosis and arrest in the subsequent G1 phase leading to tetraploid cells with accumulated centrosomes. In addition, cell stimulation increases expression of polo-like kinase 2, resulting in diploid cells with two centrosomes in G1-arrested cells. During cell migration, centrosomes tightly cluster and act as functional microtubule-organizing centers allowing for increased persistent locomotion along gradients of chemotactic cues. Moreover, dendritic cells with extra centrosomes display enhanced secretion of inflammatory cytokines and optimized T cell responses. Together, these results demonstrate a previously unappreciated role of extra centrosomes for regular cell and tissue homeostasis.

Modern Advances in CARs Therapy and Creating a New Approach to Future Treatment

Genetically engineered T and NK cells expressing a chimeric antigen receptor (CAR) are promising cytotoxic cells for the treatment of hematological malignancies and solid tumors. Despite the successful therapies using CAR-T cells, they have some disadvantages, such as cytokine release syndrome (CRS), neurotoxicity, or graft-versus-host-disease (GVHD). CAR-NK cells have lack or minimal cytokine release syndrome and neurotoxicity, but also multiple mechanisms of cytotoxic activity. NK cells are suitable for developing an "off the shelf" therapeutic product that causes little or no graft versus host disease (GvHD), but they are more sensitive to apoptosis and have low levels of gene expression compared to CAR-T cells. To avoid these adverse effects, further developments need to be considered to enhance the effectiveness of adoptive cellular immunotherapy. A promising approach to enhance the effectiveness of adoptive cellular immunotherapy is overcoming terminal differentiation or senescence and exhaustion of T cells. In this case, EVs derived from immune cells in combination therapy with drugs may be considered in the treatment of cancer patients, especially effector T and NK cells-derived exosomes with the cytotoxic activity of their original cells.

Joining Forces for Cancer Treatment: From "TCR versus CAR" to "TCR and CAR"

T cell-based immunotherapy has demonstrated great therapeutic potential in recent decades, on the one hand, by using tumor-infiltrating lymphocytes (TILs) and, on the other hand, by engineering T cells to obtain anti-tumor specificities through the introduction of either engineered T cell receptors (TCRs) or chimeric antigen receptors (CARs). Given the distinct design of both receptors and the type of antigen that is encountered, the requirements for proper antigen engagement and downstream signal transduction by TCRs and CARs differ. Synapse formation and signal transduction of CAR T cells, despite further refinement of CAR T cell designs, still do not fully recapitulate that of TCR T cells and might limit CAR T cell persistence and functionality. Thus, deep knowledge about the molecular differences in CAR and TCR T cell signaling would greatly advance the further optimization of CAR designs and elucidate under which circumstances a combination of both receptors would improve the functionality of T cells for cancer treatment. Herein, we provide a comprehensive review about similarities and differences by directly comparing the architecture, synapse formation and signaling of TCRs and CARs, highlighting the knowns and unknowns. In the second part of the review, we discuss the current status of combining CAR and TCR technologies, encouraging a change in perspective from "TCR versus CAR" to "TCR and CAR".

Overlapping Machinery in Lysosome-Related Organelle Trafficking: A Lesson from Rare Multisystem Disorders

Lysosome-related organelles (LROs) are a group of functionally diverse, cell type-specific compartments. LROs include melanosomes, alpha and dense granules, lytic granules, lamellar bodies and other compartments with distinct morphologies and functions allowing specialised and unique functions of their host cells. The formation, maturation and secretion of specific LROs are compromised in a number of hereditary rare multisystem disorders, including Hermansky-Pudlak syndromes, Griscelli syndrome and the Arthrogryposis, Renal dysfunction and Cholestasis syndrome. Each of these disorders impacts the function of several LROs, resulting in a variety of clinical features affecting systems such as immunity, neurophysiology and pigmentation. This has demonstrated the close relationship between LROs and led to the identification of conserved components required for LRO biogenesis and function. Here, we discuss aspects of this conserved machinery among LROs in relation to the heritable multisystem disorders they associate with, and present our current understanding of how dysfunctions in the proteins affected in the disease impact the formation, motility and ultimate secretion of LROs. Moreover, we have analysed the expression of the members of the CHEVI complex affected in Arthrogryposis, Renal dysfunction and Cholestasis syndrome, in different cell types, by collecting single cell RNA expression data from the human protein atlas. We propose a hypothesis describing how transcriptional regulation could constitute a mechanism that regulates the pleiotropic functions of proteins and their interacting partners in different LROs.

T cell cytoskeletal forces shape synapse topography for targeted lysis via membrane curvature bias of perforin

Cytotoxic T lymphocytes (CTLs) lyse target cells by delivering lytic granules that contain the pore former perforin to the cytotoxic immunological synapse. Here, we establish that opposing cytoskeletal forces drive lytic granule polarization and simultaneously shape T cell synapse topography to enhance target perforation. At the cell rear, actomyosin contractility drives the anterograde movement of lytic granules toward the nucleus. At the synapse, dynein-derived forces induce negatively curved membrane pockets to which granules are transported around the nucleus. These highly concave degranulation pockets are located directly opposite positively curved bulges on the target cell membrane. We identify a curvature bias in the action of perforin, which preferentially perforates positively curved tumor cell membrane. Together, these findings demonstrate murine and human T cell-mediated cytotoxicity to be a highly tuned mechano-biochemical system, in which the forces that polarize lytic granules locally bend the synaptic membrane to favor the unidirectional perforation of the target cell.

Understanding CAR T cell-tumor interactions: Paving the way for successful clinical outcomes

Since their approval 5 years ago, chimeric antigen receptor (CAR) T cells have gained great importance in the daily clinical practice and treatment of hematological malignancies, although many challenges to their use remain, such as limited long-term CAR T cell efficacy due to disease resistance or recurrence. After a brief overview of CAR T cells, their approval, therapeutic successes, and ongoing limitations, this review discusses what is known about CAR T cell activation, their expansion and persistence, their mechanisms of cytotoxicity, and how the CAR design and/or tumor-intrinsic factors influence these functions. This review also examines the role of cytokines in CAR T cell-associated toxicity and their effects on CAR T cell function. Furthermore, we discuss several resistance mechanisms, including obstacles associated with CAR treatment of solid tumors. Finally, we provide a future outlook on next-generation strategies to further optimize CARs and improve clinical outcomes.

Centrosome function is critical during terminal erythroid differentiation

Red blood cells are produced by terminal erythroid differentiation, which involves the dramatic morphological transformation of erythroblasts into enucleated reticulocytes. Microtubules are important for enucleation, but it is not known if the centrosome, a key microtubule-organizing center, is required as well. Mice lacking the conserved centrosome component, CDK5RAP2, are likely to have defective erythroid differentiation because they develop macrocytic anemia. Here, we show that fetal liver-derived, CDK5RAP2-deficient erythroid progenitors generate fewer and larger reticulocytes, hence recapitulating features of macrocytic anemia. In erythroblasts, but not in embryonic fibroblasts, loss of CDK5RAP2 or pharmacological depletion of centrosomes leads to highly aberrant spindle morphologies. Consistent with such cells exiting mitosis without chromosome segregation, tetraploidy is frequent in late-stage erythroblasts, thereby giving rise to fewer but larger reticulocytes than normal. Our results define a critical role for CDK5RAP2 and centrosomes in spindle formation specifically during blood production. We propose that disruption of centrosome and spindle function could contribute to the emergence of macrocytic anemias, for instance, due to nutritional deficiency or exposure to chemotherapy.

Cell-autonomous Hedgehog signaling controls Th17 polarization and pathogenicity

Th17 cells are key drivers of autoimmune disease. However, the signaling pathways regulating Th17 polarization are poorly understood. Hedgehog signaling regulates cell fate decisions during embryogenesis and adult tissue patterning. Here we find that cell-autonomous Hedgehog signaling, independent of exogenous ligands, selectively drives the polarization of Th17 cells but not other T helper cell subsets. We show that endogenous Hedgehog ligand, Ihh, signals to activate both canonical and non-canonical Hedgehog pathways through Gli3 and AMPK. We demonstrate that Hedgehog pathway inhibition with either the clinically-approved small molecule inhibitor vismodegib or genetic ablation of Ihh in CD4+ T cells greatly diminishes disease severity in two mouse models of intestinal inflammation. We confirm that Hedgehog pathway expression is upregulated in tissue from human ulcerative colitis patients and correlates with Th17 marker expression. This work implicates Hedgehog signaling in Th17 polarization and intestinal immunopathology and indicates the potential therapeutic use of Hedgehog inhibitors in the treatment of inflammatory bowel disease.

Cell-based drug delivery systems and their in vivo fate

Cell-based drug delivery systems (DDSs) have received attention recently because of their unique biological properties and self-powered functions, such as excellent biocompatibility, low immunogenicity, long circulation time, tissue-homingcharacteristics, and ability to cross biological barriers. A variety of cells, including erythrocytes, stem cells, and lymphocytes, have been explored as functional vectors for the loading and delivery of various therapeutic payloads (e.g., small-molecule and nucleic acid drugs) for subsequent disease treatment. These cell-based DDSs have their own unique in vivo fates, which are attributed to various factors, including their biological properties and functions, the loaded drugs and loading process, physiological and pathological circumstances, and the body's response to these carrier cells, which result in differences in drug delivery efficiency and therapeutic effect. In this review, we summarize the main cell-based DDSs and their biological properties and functions, applications in drug delivery and disease treatment, and in vivo fate and influencing factors. We envision that the unique biological properties, combined with continuing research, will enable development of cell-based DDSs as friendly drug vectors for the safe, effective, and even personalized treatment of diseases.

Mechanically active integrins target lytic secretion at the immune synapse to facilitate cellular cytotoxicity

Cytotoxic lymphocytes fight pathogens and cancer by forming immune synapses with infected or transformed target cells and then secreting cytotoxic perforin and granzyme into the synaptic space, with potent and specific killing achieved by this focused delivery. The mechanisms that establish the precise location of secretory events, however, remain poorly understood. Here we use single cell biophysical measurements, micropatterning, and functional assays to demonstrate that localized mechanotransduction helps define the position of secretory events within the synapse. Ligand-bound integrins, predominantly the αLβ2 isoform LFA-1, function as spatial cues to attract lytic granules containing perforin and granzyme and induce their fusion with the plasma membrane for content release. LFA-1 is subjected to pulling forces within secretory domains, and disruption of these forces via depletion of the adaptor molecule talin abrogates cytotoxicity. We thus conclude that lymphocytes employ an integrin-dependent mechanical checkpoint to enhance their cytotoxic power and fidelity.

Podocalyxin Expressed in Antigen Presenting Cells Promotes Interaction With T Cells and Alters Centrosome Translocation to the Contact Site

Podocalyxin (PODXL), a cell surface sialomucin expressed in diverse types of normal and malignant cells, mediates cellular adhesion to extracellular matrix and cell-to-cell interaction. A previous study reported the expression of PODXL protein on monocytes undergoing macrophage differentiation, yet the expression of this molecule in other antigen presenting cells (APCs) and its function in the immune system still remain undetermined. In this study, we report that PODXL is expressed in human monocyte-derived immature dendritic cells at both the mRNA and protein levels. Following dendritric cells maturation using pro-inflammatory stimuli, PODXL expression level decreased substantially. Furthermore, we found that PODXL expression is positively regulated by IL-4 through MEK/ERK and JAK3/STAT6 signaling pathways. Our results revealed a polarized distribution of PODXL during the interaction of APCs with CD4⁺ T cells, partially colocalizing with F-actin. Notably, PODXL overexpression in APCs promoted their interaction with CD4⁺ T cells and CD8⁺ T cells and decreased the expression of MHC-I, MHC-II, and the costimulatory molecule CD86. In addition, PODXL reduced the translocation of CD4⁺ T-cell centrosome toward the APC-contact site. These findings suggest a regulatory role for PODXL expressed by APCs in immune responses, thus representing a potential target for therapeutic blockade in infection and cancer.