WASP and Mst1 coregulate B-cell development and B-cell receptor signaling

Pan-Cancer Proteomics Analysis Reveals Wiskott-Aldrich Syndrome Protein as a Potential Regulator of Programmed Death-Ligand 1

The programmed death-ligand 1 (PD-L1) is a key mediator of immunosuppression in the tumor microenvironment. The expression of PD-L1 in cancer cells is useful for the clinical determination of an immune checkpoint blockade (ICB). However, the regulatory mechanism of the PD-L1 abundance remains incompletely understood. Here, we integrated the proteomics of 52 patients with solid tumors and examined immune cell infiltration to reveal PD-L1-related regulatory modules. Wiskott-Aldrich syndrome protein (WASP) was identified as a potential regulator of PD-L1 transcription. In two independent cohorts containing 164 cancer patients, WASP expression was significantly associated with PD-L1. High WASP expression contributed to immunosuppressive cell composition, including cells positive for immune checkpoints (PD1, CTLA4, TIGIT, and TIM3), FoxP3+ Treg cells, and CD163+ tumor-associated macrophages. Overexpression of WASP increased, whereas knockdown of WASP decreased the protein level of PD-L1 in cancer cells without alteration of PD-L1 protein stability. The WASP-mediated cell migration and invasion were markedly attenuated by the silence of PD-L1. Collectively, our data suggest that WASP is a potential regulator of PD-L1 and the WASP/PD-L1 axis is responsible for cell migration and an immunosuppressive microenvironment.

MST1/2: Important regulators of Hippo pathway in immune system associated diseases

The Hippo signaling pathway is first found in Drosophila and is highly conserved in evolution. Previous studies on this pathway in mammals have revealed its key role in cell proliferation and differentiation, organ size control, and carcinogenesis. Apart from these, recent findings indicate that mammalian Ste20-like kinases 1 and 2 (MST1/2) have significant effects on immune regulation. In this review, we summarize the updated understanding of how MST1/2 affect the regulation of the immune system and the specific mechanism. The effect of MST1/2 on immune cells and its role in the tumor immune microenvironment can alter the body's response to tumor cells. The relationship between MST1/2 and the immune system suggests new directions in the manipulation of immune responses for clinical immunotherapy, especially for tumor treatment.

Expression of USP25 associates with fibrosis, inflammation and metabolism changes in IgG4-related disease

IgG4-related disease (IgG4-RD) has complex clinical manifestations ranging from fibrosis and inflammation to deregulated metabolism. The molecular mechanisms underpinning these phenotypes are unclear. In this study, by using IgG4-RD patient peripheral blood mononuclear cells (PBMCs), IgG4-RD cell lines and Usp25 knockout mice, we show that ubiquitin-specific protease 25 (USP25) engages in multiple pathways to regulate fibrotic and inflammatory pathways that are characteristic to IgG4-RD. Reduced USP25 expression in IgG4-RD leads to increased SMAD3 activation, which contributes to fibrosis and induces inflammation through the IL-1β inflammatory axis. Mechanistically, USP25 prevents ubiquitination of RAC1, thus, downregulation of USP25 leads to ubiquitination and degradation of RAC1. Decreased RAC1 levels result in reduced aldolase A release from the actin cytoskeleton, which then lowers glycolysis. The expression of LYN, a component of the B cell receptor signalosome is also reduced in USP25-deficient B cells, which might result in B cell activation deficiency. Altogether, our results indicate a potential anti-inflammatory and anti-fibrotic role for USP25 and make USP25 a promising diagnostic marker and potential therapeutic target in IgG4-RD.

MST1/2 in inflammation and immunity

The mammalian Sterile 20-like kinase 1/2 (MST1/2) belongs to the serine/threonine (GC) protein kinase superfamily. Collective studies confirm the vital role MST1/2 in inflammation and immunity. MST1/2 is closely related to the progress of inflammation. Generally, MST1/2 aggravates the inflammatory injury through MST1-JNK, MST1-mROS, MST1-Foxo3, and NF-κB pathways, as well as several regulatory factors such as tumor necrosis factor-α (TNF-α), mitochondrial extension factor 1 (MIEF1), and lipopolysaccharide (LPS). Moreover, MST1/2 is also involved in the regulation of immunity to balance immune activation and tolerance by regulating MST1/2-Rac, MST1-Akt1/c-myc, MST1-Foxos, MST1-STAT, Btk pathways, and lymphocyte function-related antigen 1 (LFA-1), which subsequently prevents immunodeficiency syndrome and autoimmune diseases. This article reviews the effects of MST1/2 on inflammation and immunity.

Ultra-high static magnetic fields cause immunosuppression through disrupting B-cell peripheral differentiation and negatively regulating BCR signaling

To increase the imaging resolution and detection capability, the field strength of static magnetic fields (SMFs) in magnetic resonance imaging (MRI) has significantly increased in the past few decades. However, research on the side effects of high magnetic field is still very inadequate and the effects of SMF above 1 T (Tesla) on B cells have never been reported. Here, we show that 33.0 T ultra-high SMF exposure causes immunosuppression and disrupts B cell differentiation and signaling. 33.0 T SMF treatment resulted in disturbance of B cell peripheral differentiation and antibody secretion and reduced the expression of IgM on B cell membrane, and these might be intensity dependent. In addition, mice exposed to 33.0 T SMF showed inhibition on early activation of B cells, including B cell spreading, B cell receptor clustering and signalosome recruitment, and depression of both positive and negative molecules in the proximal BCR signaling, as well as impaired actin reorganization. Sequencing and gene enrichment analysis showed that SMF stimulation also affects splenic B cells' transcriptome and metabolic pathways. Therefore, in the clinical application of MRI, we should consider the influence of SMF on the immune system and choose the optimal intensity for treatment.

Regulation of the tumor immune microenvironment by the Hippo Pathway: Implications for cancer immunotherapy

The tumor immune microenvironment (TIME) is a dynamic and complex ecosystem consisting of immune cells, stromal cells, and tumor cells. It plays a crucial role in shaping cancer progression and treatment outcomes. Notably, tumor-associated immune cells are key regulators within the TIME, influencing immune responses and therapeutic efficacy. The Hippo pathway is a critical signaling pathway involved in the TIME and cancer progression. In this review, we provide an overview of the Hippo pathway's role in the TIME, focusing on its interactions with immune cells and their implications in cancer biology and therapy. Specifically, we discuss the involvement of the Hippo pathway in regulating T-cell function, macrophage polarization, B-cell differentiation, MDSC activity, and dendritic cell-mediated immune responses. Furthermore, we explore its influence on PD-L1 expression in lymphocytes and its potential as a therapeutic target. While recent progress has been made in understanding the Hippo pathway's molecular mechanisms, challenges remain in deciphering its context-dependent effects in different cancers and identifying predictive biomarkers for targeted therapies. By elucidating the intricate crosstalk between the Hippo pathway and the TME, we aim to contribute to the development of innovative strategies for cancer treatment.

The inositol 5-phosphatase INPP5B regulates B cell receptor clustering and signaling

Upon antigen binding, the B cell receptor (BCR) undergoes clustering to form a signalosome that propagates downstream signaling required for normal B cell development and physiology. BCR clustering is dependent on remodeling of the cortical actin network, but the mechanisms that regulate actin remodeling in this context remain poorly defined. In this study, we identify the inositol 5-phosphatase INPP5B as a key regulator of actin remodeling, BCR clustering, and downstream signaling in antigen-stimulated B cells. INPP5B acts via dephosphorylation of the inositol lipid PI(4,5)P2 that in turn is necessary for actin disassembly, BCR mobilization, and cell spreading on immobilized surface antigen. These effects can be explained by increased actin severing by cofilin and loss of actin linking to the plasma membrane by ezrin, both of which are sensitive to INPP5B-dependent PI(4,5)P2 hydrolysis. INPP5B is therefore a new player in BCR signaling and may represent an attractive target for treatment of B cell malignancies caused by aberrant BCR signaling.

Involvement of MST1/mTORC1/STAT1 activity in the regulation of B-cell receptor signalling by chemokine receptor 2

BACKGROUND

CCR2 is involved in maintaining immune homeostasis and regulating immune function. This study aims to elucidate the mechanism by which CCR2 regulates B-cell signalling.

METHODS

In Ccr2-knockout mice, the development and differentiation of B cells, BCR proximal signals, actin movement and B-cell immune response were determined. Besides, the level of CCR2 in PBMC of SLE patients was analysed by bioinformatics.

RESULTS

CCR2 deficiency reduces the proportion and number of follicular B cells, upregulates BCR proximal signalling and enhances the oxidative phosphorylation of B cells. Meanwhile, increased actin filaments aggregation and its associated early-activation events of B cells are also induced by CCR2 deficiency. The MST1/mTORC1/STAT1 axis in B cells is responsible for the regulation of actin remodelling, metabolic activities and transcriptional signalling, specific MST1, mTORC1 or STAT1 inhibitor can rescue the upregulated BCR signalling. Glomerular IgG deposition is obvious in CCR2-deficient mice, accompanied by increased anti-dsDNA IgG level. Additionally, the CCR2 expression in peripheral B cells of SLE patients is decreased than that of healthy controls.

CONCLUSIONS

CCR2 can utilise MST1/mTORC1/STAT1 axis to regulate BCR signalling. The interaction between CCR2 and BCR may contribute to exploring the mechanism of autoimmune diseases.

The Actin Regulators Involved in the Function and Related Diseases of Lymphocytes

Actin is an important cytoskeletal protein involved in signal transduction, cell structure and motility. Actin regulators include actin-monomer-binding proteins, Wiskott-Aldrich syndrome (WAS) family of proteins, nucleation proteins, actin filament polymerases and severing proteins. This group of proteins regulate the dynamic changes in actin assembly/disassembly, thus playing an important role in cell motility, intracellular transport, cell division and other basic cellular activities. Lymphocytes are important components of the human immune system, consisting of T-lymphocytes (T cells), B-lymphocytes (B cells) and natural killer cells (NK cells). Lymphocytes are indispensable for both innate and adaptive immunity and cannot function normally without various actin regulators. In this review, we first briefly introduce the structure and fundamental functions of a variety of well-known and newly discovered actin regulators, then we highlight the role of actin regulators in T cell, B cell and NK cell, and finally provide a landscape of various diseases associated with them. This review provides new directions in exploring actin regulators and promotes more precise and effective treatments for related diseases.

Actin Remodeling Defects Leading to Autoinflammation and Immune Dysregulation

A growing number of monogenic immune-mediated diseases have been related to genes involved in pathways of actin cytoskeleton remodeling. Increasing evidences associate cytoskeleton defects to autoinflammatory diseases and primary immunodeficiencies. We reviewed the pathways of actin cytoskeleton remodeling in order to identify inflammatory and immunological manifestations associated to pathological variants. We list more than twenty monogenic diseases, ranging from pure autoinflammatory conditions as familial Mediterranean fever, mevalonate kinase deficiency and PAPA syndrome, to classic and novel primary immunodeficiencies as Wiskott-Aldrich syndrome and DOCK8 deficiency, characterized by the presence of concomitant inflammatory and autoimmune manifestations, such as vasculitis and cytopenia, to severe and recurrent infections. We classify these disorders according to the role of the mutant gene in actin cytoskeleton remodeling, and in particular as disorders of transcription, elongation, branching and activation of actin. This expanding field of rare immune disorders offers a new perspective to all immunologists to better understand the physiological and pathological role of actin cytoskeleton in cells of innate and adaptive immunity.

Actin Remodeling Defects Leading to Autoinflammation and Immune Dysregulation

A growing number of monogenic immune-mediated diseases have been related to genes involved in pathways of actin cytoskeleton remodeling. Increasing evidences associate cytoskeleton defects to autoinflammatory diseases and primary immunodeficiencies. We reviewed the pathways of actin cytoskeleton remodeling in order to identify inflammatory and immunological manifestations associated to pathological variants. We list more than twenty monogenic diseases, ranging from pure autoinflammatory conditions as familial Mediterranean fever, mevalonate kinase deficiency and PAPA syndrome, to classic and novel primary immunodeficiencies as Wiskott-Aldrich syndrome and DOCK8 deficiency, characterized by the presence of concomitant inflammatory and autoimmune manifestations, such as vasculitis and cytopenia, to severe and recurrent infections. We classify these disorders according to the role of the mutant gene in actin cytoskeleton remodeling, and in particular as disorders of transcription, elongation, branching and activation of actin. This expanding field of rare immune disorders offers a new perspective to all immunologists to better understand the physiological and pathological role of actin cytoskeleton in cells of innate and adaptive immunity.