Targeting the CBM complex causes Treg cells to prime tumours for immune checkpoint therapy.

Solid tumours are infiltrated by effector T cells with the potential to control or reject them, as well as by regulatory T (Treg) cells that restrict the function of effector T cells and thereby promote tumour growth1. The anti-tumour activity of effector T cells can be therapeutically unleashed, and is now being exploited for the treatment of some forms of human cancer. However, weak tumour-associated inflammatory responses and the immune-suppressive function of Treg cells remain major hurdles to broader effectiveness of tumour immunotherapy2. Here we show that, after disruption of the CARMA1-BCL10-MALT1 (CBM) signalosome complex, most tumour-infiltrating Treg cells produce IFNγ, resulting in stunted tumour growth. Notably, genetic deletion of both or even just one allele of CARMA1 (also known as Card11) in only a fraction of Treg cells-which avoided systemic autoimmunity-was sufficient to produce this anti-tumour effect, showing that it is not the mere loss of suppressive function but the gain of effector activity by Treg cells that initiates tumour control. The production of IFNγ by Treg cells was accompanied by activation of macrophages and upregulation of class I molecules of the major histocompatibility complex on tumour cells. However, tumour cells also upregulated the expression of PD-L1, which indicates activation of adaptive immune resistance3. Consequently, blockade of PD-1 together with CARMA1 deletion caused rejection of tumours that otherwise do not respond to anti-PD-1 monotherapy. This effect was reproduced by pharmacological inhibition of the CBM protein MALT1. Our results demonstrate that partial disruption of the CBM complex and induction of IFNγ secretion in the preferentially self-reactive Treg cell pool does not cause systemic autoimmunity but is sufficient to prime the tumour environment for successful immune checkpoint therapy

Semen amyloids participate in spermatozoa selection and clearance

Unlike other human biological fluids, semen contains multiple types of amyloid fibrils in the absence of disease. These fibrils enhance HIV infection by promoting viral fusion to cellular targets, but their natural function remained unknown. The similarities shared between HIV fusion to host cell and sperm fusion to oocyte led us to examine whether these fibrils promote fertilization. Surprisingly, the fibrils inhibited fertilization by immobilizing sperm. Interestingly, however, this immobilization facilitated uptake and clearance of sperm by macrophages, which are known to infiltrate the female reproductive tract (FRT) following semen exposure. In the presence of semen fibrils, damaged and apoptotic sperm were more rapidly phagocytosed than healthy ones, suggesting that deposition of semen fibrils in the lower FRT facilitates clearance of poor-quality sperm. Our findings suggest that amyloid fibrils in semen may play a role in reproduction by participating in sperm selection and facilitating the rapid removal of sperm antigens

The efficiency of Vpx-mediated SAMHD1 antagonism does not correlate with the potency of viral control in HIV-2-infected individuals

Background: The presence of a vpx gene distinguishes HIV-2 from HIV-1, the main causative agent of AIDS. Vpx degrades the restriction factor SAMHD1 to boost HIV-2 infection of macrophages and dendritic cells and it has been suggested that the activation of antiviral innate immune responses after Vpx-dependent infection of myeloid cells may explain why most HIV-2-infected individuals efficiently control viral replication and become long-term survivors. However, the role of Vpx-mediated SAMHD1 antagonism in the virological and clinical outcome of HIV-2 infection remained to be investigated. Results: Here, we analyzed the anti-SAMHD1 activity of vpx alleles derived from seven viremic and four long-term aviremic HIV-2-infected individuals. We found that effective Vpx-mediated SAMHD1 degradation and enhancement of myeloid cell infection was preserved in most HIV-2-infected individuals including all seven that failed to control the virus and developed AIDS. The only exception were vpx alleles from an aviremic individual that predicted a M68K change in a highly conserved nuclear localization signal which disrupted the ability of Vpx to counteract SAMHD1. We also found that HIV-2 is less effective than HIV-1 in inducing innate immune activation in dendritic cells. Conclusions: Effective immune control of viral replication in HIV-2-infected individuals is not associated with increased Vpx-mediated degradation of SAMHD1

Kalziumsignalmechanismen in Alveolarepithelzellen : Auswirkung physiologischer und pathophysiologischer Bedingungen

The Lung is an important organ of the body which performs the function of gas exchange and maintenance of homeostasis. To do this function lungs are endowed with an extremely large surface which is exposed to the environment and is prone to environmental influences as well as pathogen.Alveoli are the smallest and the most important part of respiratory system, the alveolar epithelium is composed of alveolar epithelial type I and type II (ATII) cells. ATII cells, account for about 95% of the alveolar cell population and perform many of the essential functions in the alveolus such as surfactant exocytosis and maintenance of a thin layer of surfactant on alveolar epithelial surface by endocytosis. Ca2+ signaling plays a crucial role in ATII cell functioning. Therefore, the aim of this work was to characterize the complex Ca2+ signaling mechanisms in ATII cells and to investigate cellular processes which are regulated by specific Ca2+ signaling pathways.In this study, we showed that the Ca2+ channel modulators 2- Aminoethoxydiphenyl-borinate and capsazepine, activated a Ca2+ signaling pathway which, in turn activated clathrin -dependent endocytosis. Further experiments showed that the endocytosis mediated a reversible and synchronized internalization of microvilli from the cell surface. This process was associated with the restructuring of cytoskeletal components.ATP activates purinergic receptors resulting in an increased intracellular calcium ([Ca2+]c) that activates release of surfactant from ATII cells. Unlike the Ca2+ signaling triggered by 2-APB and capsazepine, purinergic stimulation with ATP activated an endocytic process which was independent of both clathrin and caveolin pathways.In addition to the pharmacological activation of intracellular Ca2+ signaling, we also showed that the exotoxin from Streptococcus pyogenes, streptolysin O (SLO), can trigger a complex Ca2+ signaling. SLO is a toxin which forms pores in the cell membranes of target cells by oligomerization. Previously, it was assumed that the formation of toxin pores results in a strong Ca2+ influx into the cell and ultimately causes cell damage. Our results challenge the existing notion, and show that SLO-induced signaling can take place independently of toxin pore; and that intracellular Ca2+ stores play an essential role in SLO-activated Ca2+ signaling. In this study, we showed for the first time that intracellular Ca2+ stores play an important role in SLO-activated Ca2+ signaling and activate STIM1 and Orai1 proteins mediated store operated Ca2+ (SOC) entry. We also showed that SOC entry forms the basis of early host response to SLO and results in inflammatory reaction in the epithelial cells.Among other important observations, this work showed that physiological and patho-physiological outcomes can be distinguished on the basis of underlying Ca2+ signaling. Our results show that physiologically Ca2+ signaling plays an important role in regulating endocytic processes in alveolar epithelial cells through different pathways. On the other hand, bacterial toxin streptolysin O, which at the concentrations used in our study represents an early stage of a streptococcal infection, induced a Ca2+ signaling pathway which resulted in pro-inflammatory response.<br /

2-APB and capsazepine-induced Ca2+ influx stimulates clathrin-dependent endocytosis in alveolar epithelial cells

Calcium as a second messenger influences many cellular and physiological processes. In lung, alveolar type II (ATII) cells sense mechanical stress and respond by Ca2+ dependent release of surfactant, which is essential for respiratory function. Nevertheless, Ca2+ signaling mechanisms in these cells - in particular Ca2+ entry pathways are still poorly understood. Herein, we investigated pharmacological properties of non-voltage-gated Ca2+ channel modulators in ATII and NCI-H441 cells and demonstrate that 2-Aminoethoxydiphenyl-borinate (2-APB) and capsazepine (CPZ) activate Ca2+ entry with pharmacologically distinguishable components. Surprisingly, 2-APB and CPZ activated clathrin dependent endocytosis in ATII and NCI-H441 cells, which was dependent on Ca2+ entry. The internalized material accumulated in non-acidic granules distinct from surfactant containing lamellar bodies (LB). LB exocytosis was not observed under these conditions. Our study demonstrates that 2-APB/CPZ induces Ca2+ entry which unlike ATP- or stretch-induced Ca2+ entry in ATII cells does not activate exocytosis but an opposing endocytotic mechanism

Molecular basis of early epithelial response to streptococcal exotoxin: role of STIM1 and Orai1 proteins: Streptolysin O activates SOC entry

Streptolysin O (SLO) is a cholesterol-dependent cytolysin (CDC) from Streptococcus pyogenes. SLO induces diverse types of Ca2+ signalling in host cells which play a key role in membrane repair and cell fate determination. The mechanisms behind SLO-induced Ca2+ signalling remain poorly understood. Here, we show that in NCI-H441 cells, wild-type SLO as well as non-pore-forming mutant induces long-lasting intracellular Ca2+ oscillations via IP3-mediated depletion of intracellular stores and activation of store-operated Ca2+ (SOC) entry. SLO-induced activation of SOC entry was confirmed by Ca2+ add-back experiments, pharmacologically and by overexpression as well as silencing of STIM1 and Orai1 expression. SLO also activated SOC entry in primary cultivated alveolar type II (ATII) cells but Ca2+ oscillations were comparatively short-lived in nature. Comparison of STIM1 and Orai1 revealed a differential expression pattern in H441 and ATII cells. Overexpression of STIM1 and Orai1 proteins in ATII cells changed the short-lived oscillatory response into a long-lived one. Thus, we conclude that SLO-mediated Ca2+ signalling involves Ca2+ release from intracellular stores and STIM1/Orai1-dependent SOC entry. The phenotype of Ca2+ signalling depends on STIM1 and Orai1 expression levels. Our findings suggest a new role for SOC entry-associated proteins in S. pyogenes-induced lung infection and pneumonia

The efficiency of Vpx-mediated SAMHD1 antagonism does not correlate with the potency of viral control in HIV-2-infected individuals

textabstractBackground: The presence of a vpx gene distinguishes HIV-2 from HIV-1, the main causative agent of AIDS. Vpx degrades the restriction factor SAMHD1 to boost HIV-2 infection of macrophages and dendritic cells and it has been suggested that the activation of antiviral innate immune responses after Vpx-dependent infection of myeloid cells may explain why most HIV-2-infected individuals efficiently control viral replication and become long-term survivors. However, the role of Vpx-mediated SAMHD1 antagonism in the virological and clinical outcome of HIV-2 infection remained to be investigated. Results: Here, we analyzed the anti-SAMHD1 activity of vpx alleles derived from seven viremic and four long-term aviremic HIV-2-infected individuals. We found that effective Vpx-mediated SAMHD1 degradation and enhancement of myeloid cell infection was preserved in most HIV-2-infected individuals including all seven that failed to control the virus and developed AIDS. The only exception were vpx alleles from an aviremic individual that predicted a M68K change in a highly conserved nuclear localization signal which disrupted the ability of Vpx to counteract SAMHD1. We also found that HIV-2 is less effective than HIV-1 in inducing innate immune activation in dendritic cells. Conclusions: Effective immune control of viral replication in HIV-2-infected individuals is not associated with increased Vpx-mediated degradation of SAMHD1

Liquefaction of Semen Generates and Later Degrades a Conserved Semenogelin Peptide That Enhances HIV Infection

UnlabelledSemen enhances HIV infection in vitro, but how long it retains this activity has not been carefully examined. Immediately postejaculation, semen exists as a semisolid coagulum, which then converts to a more liquid form in a process termed liquefaction. We demonstrate that early during liquefaction, semen exhibits maximal HIV-enhancing activity that gradually declines upon further incubation. The decline in HIV-enhancing activity parallels the degradation of peptide fragments derived from the semenogelins (SEMs), the major components of the coagulum that are cleaved in a site-specific and progressive manner upon initiation of liquefaction. Because amyloid fibrils generated from SEM fragments were recently demonstrated to enhance HIV infection, we set out to determine whether any of the liquefaction-generated SEM fragments associate with the presence of HIV-enhancing activity. We identify SEM1 from amino acids 86 to 107 [SEM1(86-107)] to be a short, cationic, amyloidogenic SEM peptide that is generated early in the process of liquefaction but that, conversely, is lost during prolonged liquefaction due to the activity of serine proteases. Synthetic SEM1(86-107) amyloids directly bind HIV-1 virions and are sufficient to enhance HIV infection of permissive cells. Furthermore, endogenous seminal levels of SEM1(86-107) correlate with donor-dependent variations in viral enhancement activity, and antibodies generated against SEM1(86-107) recognize endogenous amyloids in human semen. The amyloidogenic potential of SEM1(86-107) and its virus-enhancing properties are conserved among great apes, suggesting an evolutionarily conserved function. These studies identify SEM1(86-107) to be a key, HIV-enhancing amyloid species in human semen and underscore the dynamic nature of semen's HIV-enhancing activity.ImportanceSemen, the most common vehicle for HIV transmission, enhances HIV infection in vitro, but how long it retains this activity has not been investigated. Semen naturally undergoes physiological changes over time, whereby it converts from a gel-like consistency to a more liquid form. This process, termed liquefaction, is characterized at the molecular level by site-specific and progressive cleavage of SEMs, the major components of the coagulum, by seminal proteases. We demonstrate that the HIV-enhancing activity of semen gradually decreases over the course of extended liquefaction and identify a naturally occurring semenogelin-derived fragment, SEM1(86-107), whose levels correlate with virus-enhancing activity over the course of liquefaction. SEM1(86-107) amyloids are naturally present in semen, and synthetic SEM1(86-107) fibrils bind virions and are sufficient to enhance HIV infection. Therefore, by characterizing dynamic changes in the HIV-enhancing activity of semen during extended liquefaction, we identified SEM1(86-107) to be a key virus-enhancing component of human semen