Search Results (817)

The matrix metalloproteinase (MMP) family includes several membrane-bound enzymes. Membrane-type 5 matrix metalloproteinase (MT5-MMP) is unique amongst the MMP family in being primarily expressed in the brain and during development. It is proposed to contribute to synaptic plasticity and is implicated in several pathologies, including multiple cancers and Alzheimer’s disease. In cancer, MT5-MMP expression has been correlated to cancer progression, but a distinct mechanistic role has yet to be uncovered. In Alzheimer’s disease, MT5-MMP exhibits pro-amyloidogenic activity, functioning as an η-secretase that cleaves amyloid precursor protein (APP), ultimately generating two synaptotoxic fragments, Aη-α and Aη-β. Several intracellular binding partners for MT5-MMP have been identified, and of these, N4BP2L1, EIG121, BIN1, or TMX3 binding to MT5-MMP results in a significant increase in MT5-MMP η-secretase activity. Beyond direct effects on APP, MT5-MMP may also facilitate APP trafficking to endosomal/lysosomal compartments and enhance proinflammatory responses. Overall, the substrate profile of MT5-MMP has not been well defined, and selective inhibitors of MT5-MMP have not been described. These advances will be needed for further consideration of MT5-MMP as a therapeutic target in Alzheimer’s disease and other pathologies. Full article

Spurred by the enormous therapeutic success of glucagon-like peptide-1 receptor (GLP-1R) agonists (GLP1-RAs) against diabetes and obesity, glucagon family receptor pharmacology has garnered a tremendous amount of interest. Glucagon family receptors, e.g., the glucagon receptor itself (GCGR), the GLP-1R, and the glucose-dependent insulinotropic peptide receptor (GIPR), belong to the incretin receptor superfamily, i.e., receptors that increase blood glucose-dependent insulin secretion. All incretin receptors are class B1 G protein-coupled receptors (GPCRs), coupling to the G_s type of heterotrimeric G proteins which activates adenylyl cyclase (AC) to produce cyclic adenosine monophosphate (cAMP). Most GPCRs undergo desensitization, i.e., uncouple from G proteins and internalize, thanks to interactions with the βarrestins (arrestin-2 and -3). Since the βarrestins can also mediate their own G protein-independent signaling, any given GPCR can theoretically signal (predominantly) either via G proteins or βarrestins, i.e., be a G protein- or βarrestin-“biased” receptor, depending on the bound ligand. A plethora of experimental evidence suggests that the GLP-1R does not undergo desensitization in physiologically relevant tissues in vivo, but rather, it produces robust and prolonged cAMP signals. A particular property of constant cycling between the cell membrane and caveolae/lipid rafts of the GLP-1R may underlie its lack of desensitization. In contrast, GIPR signaling is extensively mediated by βarrestins and the GIPR undergoes significant desensitization, internalization, and downregulation, which may explain why both agonists and antagonists of the GIPR exert the same physiological effects. Here, we discuss this evidence and make a case for the GLP-1R being a phenotypically or functionally G_s-selective receptor. We also discuss the implications of this for the development of GLP-1R poly-ligands, which are increasingly pursued for the treatment of obesity and other diseases. Full article

Background/Objectives: SARS-CoV-2 vaccine candidates comprising the receptor binding domain (RBD) of the spike protein have been shown to confer protection against infection. Previous research evaluating vaccine candidates with SARS-CoV-2 RBD fused to ferritin (RBD-ferritin) and other scaffolds suggested that multimeric assemblies of RBD can enhance antigen presentation to improve the potency and breadth of immune responses. Though RBDs directly fused to a self-assembling scaffold can be delivered as messenger RNA (mRNA) formulated with lipid nanoparticles (LNPs), reports of SARS-CoV-2 vaccine candidates that combine these approaches remain scarce. Methods: Here, we designed RBD fused to AP205 or TIP60 self-assembling nanoparticles following a search of available structures focused on several scaffold properties. RBD-AP205 and RBD-TIP60 were tested for antigenicity following transfection and for immunogenicity and neutralization potency when delivered as mRNA in mice, with RBD-ferritin as a direct comparator. Results: All scaffolded RBD constructs were readily secreted to transfection supernatant and showed antigenicity in ELISA, though clear heterogeneity in assembly was observed. RBD-AP205 and RBD-TIP60 also exhibited robust antibody binding and neutralization titers in mice that were comparable to those elicited by RBD-ferritin or a full-length membrane-bound spike. Conclusions: These data suggest that AP205 and TIP60 can present RBD as effectively as ferritin and induce similar immune responses. By describing additional scaffolds for multimeric display that accommodate mRNA delivery platforms, this work can provide new tools for future vaccine design efforts. Full article

TREM2 (triggering receptor expressed on myeloid cells 2) is a membrane-bound receptor primarily expressed on microglia in the central nervous system (CNS). TREM2 plays a crucial role in regulating immune responses, phagocytosis, lipid metabolism, and inflammation. Mutations in the TREM2 gene have been linked to various neurodegenerative diseases, including Alzheimer’s disease (AD), frontotemporal dementia (FTD), Parkinson’s disease (PD), and Nasu–Hakola disease (NHD). These mutations are suggested to impair microglial activation and reduce the ability to clear amyloid aggregates, leading to exacerbated neuroinflammatory responses and accelerating disease progression. This review provides an overview of TREM2 structure, functions, and known pathogenic variants—including Arg47His, Arg62His, His157Tyr, Tyr38Cys, and Thr66Met. Furthermore, the molecular and cellular consequences of TREM2 mutations are introduced, such as impaired ligand binding, altered protein folding and trafficking, enhanced TREM2 shedding, and dysregulated inflammatory signaling. We also highlight recent advances in therapeutic strategies aimed at modulating TREM2 signaling. These include monoclonal antibodies (e.g., AL002, CGX101), small molecule agonists, and gene/cell-based therapies that seek to restore microglial homeostasis, enhance phagocytosis, and reduce neuroinflammation. While these approaches show promise in in vivo/in vitro studies, their clinical translation may be challenged by disease heterogeneity and mutation-specific responses. Additionally, determining the appropriate timing and precise dosing will be essential. Full article

Background: Oral squamous cell carcinoma (OSCC) is a common head and neck cancer with low survival rates, especially in advanced stages, despite improved therapies. New developments show that immune checkpoint inhibitors (ICIs) are promising treatment options. A better understanding of immune suppression in OSCC could enable new therapeutic approaches and effective ICI combinations. Methods: The aim of this cross-sectional study was to investigate the significance of the differential expression of cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), CD28 and their ligands CD80 and CD86 for the diagnosis and treatment of OSCC. To this end, mRNA expression was analysed by RT-PCR and compared in 65 healthy oral mucosa samples (NOM) and 104 OSCC samples. Results: The expression of CTLA-4 (a soluble and membrane-bound isoform) was increased in OSCC by 1.72-fold (p = 0.004) and 6.88-fold (p < 0.001), respectively. There was no significant difference for CD28 (p = 0.283), nor for the soluble isoform of CD86 (p = 0.845). The membrane isoform of CD86 was increased in OSCC by a factor of 1.39 (p = 0.009) and CD80 by 6.11-fold (p < 0.001). Conclusions: The results show a significant association between CTLA-4, CD80 and membrane-bound CD86 expression and diagnosis. They could improve diagnostics in multi-marker approaches and serve as therapeutic targets for ICI strategies. In particular, the data indicate a stronger immunosuppressive role of CD80 compared to CD86 in a tumor tissue context, suggesting the exploration of anti-CTLA-4 and anti-CD80 antibody combinations in animal models. Full article

Background/Objectives: Radiotherapy (RT) is a mainstay of clinical cancer therapy that causes broad immune responses. The complement system is a pivotal effector mechanism in the innate immune response, but the impact of RT is less well understood. This study investigates the interaction between RT and the complement system as a possible approach to improve immune responses in cancer treatment. Methods: Human solid cancer (lung, prostate, liver, breast cancer), lymphoma, and leukemia cells were irradiated using X-rays and treated with polyclonal antibodies or anti-CD20 monoclonal antibodies, respectively. Chromium release assay was applied to measure cell lysis after radiation with or without complement-activating antibody treatment. The expression of membrane-bound complement regulatory proteins (mCRPs; CD46, CD55, CD59), which confer resistance against complement activation, CD20 expression, apoptosis, and radiation-induced DNA double-strand breaks (γH2AX), was measured by flow cytometry. The radiosensitivity of tumor cells was assessed by colony-forming assay. Results: We demonstrate that RT profoundly impacts complement function by upregulating the expression of membrane-bound complement regulatory proteins (mCRPs) on tumor cells in a dose- and time-dependent manner. Impaired complement-mediated tumor cell lysis could thus potentially contribute to radiotherapeutic resistance. We also observed RT-induced upregulation of CD20 expression on lymphoma and leukemic cells. Notably, complement activation prior to RT proved more effective in inducing RT-dependent early apoptosis compared to post-irradiation treatment. While complement modulation does not significantly alter RT-induced DNA-damage repair mechanisms or intrinsic radiosensitivity in cancer cells, our results suggest that combining RT with complement-based anti-cancer therapy may enhance complement-dependent cytotoxicity (CDC) and apoptosis in tumor cells. Conclusions: This study sheds light on the complex interplay between RT and the complement system, offering insights into potential novel combinatorial therapeutic strategies and a potential sequential structure for certain tumor types. Full article

The sodium–citrate cotransporter (NaCT) plays a crucial role in citrate transport during amelogenesis. Mutations in the SLC13A5 gene, which encodes the NaCT, cause early infantile epileptic encephalopathy 25 and amelogenesis imperfecta. We analyzed developing pig molars and determined that the citrate concentrations in secretory- and maturation-stage enamel are both 5.3 µmol/g, with about 95% of the citrate being bound to mineral. To better understand how citrate might enter developing enamel, we developed Slc13a5^Flag reporter mice that express NaCT with a C-terminal Flag-tag (DYKDDDDK) that can be specifically and accurately recognized by commercially available anti-Flag antibodies. The 24-base Flag coding sequence was located immediately upstream of the natural translation termination codon (TAG) and was validated by Sanger sequencing. The general development, physical activities, and reproductive outcomes of this mouse strain were comparable to those of the C57BL/6 mice. No differences were detected between the Slc13a5^Flag and wild-type mice. Tooth development was extensively characterized using dissection microscopy, bSEM, light microscopy, in situ hybridization, and immunohistochemistry. Tooth formation was not altered in any detectable way by the introduction of the Flag. The Slc13a5^Flag citrate transporter was observed on all outer membranes of secretory ameloblasts (distal, lateral, and proximal), with the strongest signal on the Tomes process, and was detectable in all but the distal membrane of maturation-stage ameloblasts. The papillary layer also showed positive immunostaining for Flag. The outer membrane of odontoblasts stained stronger than ameloblasts, except for the odontoblastic processes, which did not immunostain. As NaCT is thought to only facilitate citrate entry into the cell, we performed in situ hybridization that showed Ank is not expressed by secretory- or maturation-stage ameloblasts, ruling out that ANK can transport citrate into enamel. In conclusion, we developed Slc13a5^Flag reporter mice that provide specific and sensitive localization of a fully functional NaCT-Flag protein. The localization of the Slc13a5^Flag citrate transporter throughout the ameloblast membrane suggests that either citrate enters enamel by a paracellular route or NaCT can transport citrate bidirectionally (into or out of ameloblasts) depending upon local conditions. Full article

Respiratory syncytial virus (RSV) is a major etiological agent of lower respiratory tract infections, particularly among infants and the elderly. Activation of B cells in the mucosa and the production of specific neutralizing antibodies are essential for protective immunity against pulmonary infection. B-cell activating factor (BAFF) is a critical survival factor for B cells and has been associated with antiviral responses; however, its regulation during RSV infection remains poorly understood. This study examined BAFF regulation in BEAS-2B cells exposed to RSV or IFN-β. The treatments resulted in a progressive increase in gene expression over time, accompanied by higher protein levels. BAFF mRNA peaked at 12 h post-infection and declined by 48 h, coinciding with the release of soluble BAFF protein into the culture supernatant. Pre-treatment with anti-IFN-β antibodies prior to RSV infection reduced both BAFF mRNA and protein levels, indicating that IFN-β plays a regulatory role in BAFF production by airway epithelial cells. Western blot analysis revealed membrane-bound BAFF (~31 kDa) in non-infected cells, with elevated expression at 24 h post-infection. By 48 h, this form was cleaved into a soluble ~17 kDa form, which was detected in the supernatant. Immunostaining further demonstrated reduced surface expression of membrane-bound BAFF in RSV-infected cells compared to uninfected controls, suggesting that RSV infection promotes the cleavage and release of BAFF into the extracellular environment. Additionally, the release of BAFF was not affected by furin convertase inhibition or ER–Golgi transport blockade, indicating a potentially novel cleavage mechanism. Co-culturing BAFF produced by BEAS-2B cells with isolated B cells enhanced B cell viability. Overall, these results indicate that RSV infection stimulates BAFF production in airway epithelial cells through a pathway involving IFN-β, potentially contributing to B cell activation and promoting local antibody-mediated immunity. Understanding this mechanism may offer valuable insights for improving mucosal vaccine strategies and enhancing immunity against respiratory pathogens. Full article

Copper (Cu) is an essential micronutrient for cyanobacteria, where it functions as a cofactor in key proteins involved in photosynthesis and antioxidant defense. However, at elevated concentrations, Cu becomes toxic, exhibiting algicidal effects by disrupting metal homeostasis and competing for metal-binding sites on critical cellular proteins. Due to the considerable morphological and physiological diversity within the phylum Cyanobacteria, the thresholds for Cu deficiency or toxicity vary considerably among strains. Maintaining Cu homeostasis in cyanobacterial cells is a complex process involving multiple layers of regulation. It begins at the extracellular polysaccharide layer, involves specialized membrane-bound proteins (in the outer, plasma, and thylakoid membranes), and results in transcriptional regulation in response to intracellular Cu status. This review summarizes the current understanding of Cu uptake and efflux pathways in cyanobacteria and explores how these mechanisms contribute to maintaining cellular Cu balance. The knowledge gained may contribute to the application of cyanobacteria in bioremediation strategies and/or the targeted use of Cu in the control of harmful cyanobacterial blooms. Full article

Background and Objectives: To evaluate the mRNA vaccine platform for blood-stage Plasmodium parasites, we completed a proof-of-concept study using the P. yoelii mouse model of malaria and two mRNA-based vaccines. Both encoded PyMSP1₁₉ fused to PyMSP8 (PyMSP1/8). One was designed for secretion of the encoded protein (PyMSP1/8-sec); the other encoded membrane-bound antigen (PyMSP1/8-mem). Methods: Secretion of PyMSP1/8-sec and membrane localization of PyMSP1/8-mem were verified in mRNA-transfected cells. As recombinant PyMSP1/8 (rPyMSP1/8) is known to protect mice against lethal P. yoelii 17XL infection, we first compared immunogenicity and efficacy of the PyMSP1/8-sec mRNA vaccine versus the recombinant formulation in outbred mice. Animals were immunized three times followed by challenge with a lethal dose of P. yoelii 17XL-parasitized RBCs (pRBCs). Similar immunization and challenge experiments were conducted to compare PyMSP1/8-sec versus PyMSP1/8-mem mRNA vaccines. Results: Immunogenicity of the PyMSP1/8-sec mRNA vaccine was superior to the recombinant formulation, inducing higher antibody titers against both vaccine components. Following challenge with P. yoelii 17XL pRBCs, all PyMSP1/8-sec-immunized animals survived, with 50% of these showing no detectible pRBCs in circulation (<0.01%). In addition, mean peak parasitemia in PyMSP1/8-sec mRNA-immunized mice was significantly lower than that in the rPyMSP1/8 vaccine group. Both PyMSP1/8-sec and PyMSP1/8-mem were protective against P. yoelii 17XL challenge, with PyMSP1/8-mem immunization providing a significantly higher level of protection than PyMSP1/8-sec immunization considering the number of animals with no detectable pRBCs in circulation and the mean peak parasitemia in animals with detectable parasitemia. Conclusions: mRNA vaccines were highly immunogenic and potently protective against blood-stage malaria, outperforming a similar recombinant-based vaccine. The membrane-bound antigen was more effective at inducing protective antibody responses, highlighting the need to consider antigen localization for mRNA vaccine design. Full article

From a previously performed proteomics screen, GPP130, or Golgi phosphoprotein of 130 kDa, was identified as a potential substrate of the proprotein convertase 7 (PC7; PCSK7). GPP130 is a type-II transmembrane protein with a luminal domain containing endosomal and Golgi-retrieval determinants, enabling a unique trafficking route. Most of the previous work on GPP130 relates to its binding and retrograde trafficking of the Shiga toxin. However, its cellular biology and its biochemical characterization remain understudied. Recently, GPP130 was reported to be implicated in cell cycle progression and cell proliferation in head and neck cancer cells. This led us to analyze the cBioPortal for Cancer Genomics, revealing that the GPP130/GOLIM4 gene is amplified in many cancers, including lung, ovarian, and cervical. This observation led us to use the A549 lung cancer cell line to investigate the growth-regulating roles of endogenous and overexpressed GPP130 and to analyze the impact of its cleavage/shedding by PC7 and/or Furin on cellular growth. Our cell-based assays suggest that GPP130 is a novel pro-protein convertase substrate that increases cell proliferation in A549, SKOV3, and HeLa cells, and that the latter activity is enhanced following its cleavage by PC7 and/or Furin into a membrane-bound N-terminal product and secreted C-terminal fragments. This novel work sheds light on the cell biology of the poorly characterized GPP130, its proliferative activity, and modulation upon its shedding by PC7 and Furin in lung cancer progression. Full article

Recurrent bacterial cystitis in women can lead to interstitial cystitis or bladder pain syndrome (IC/BPS). Activation of Toll-like receptor 4 (TLR4) by LPS can upregulate signaling of the pro-inflammatory receptor p75^NTR. The aim of the presented study was to assess whether p75^NTR antagonist THX-B can modulate LPS-mediated inflammation in bladder cells. In vitro expression and LPS-activation of p75^NTR were confirmed in urothelial (URO) and smooth muscle (SMC) cells. In UROs, p75^NTR antagonism abolished the LPS-elicited rise in membrane-bound and soluble TNF-α. However, it could not prevent LPS-induced rise in phosphorylated ERK nor decrease in phosphorylated p38MAPK, nor the increase in iNOS and nitric oxide (NO) content. On the other hand, in SMCs, LPS increased phosphorylation of JNK, nuclear translocation of NF-κB, and association of TRAF6 to p75^NTR, outcomes prevented by p75^NTR antagonism. In UROs, LPS decreased the expression of tight junction proteins, ZO-1 and occludin, with the latter rescued by p75^NTR antagonism. Intraurethral instillation of LPS increased inflammation in the lamina propria, activation of JNK, and contractile activity of bladder tissue. Alternatively, intraperitoneal THX-B injections prevented LPS-induced inflammation but not enhanced muscle contraction. Our results suggest that inhibition of p75^NTR could help in reducing bladder symptoms during cystitis. Full article

Background/Objectives: Oats and oat bran are rich in dietary fiber, polyphenols and other phytochemicals. Methods: In this study, we evaluated the phytochemical content and established LPS-induced RAW 264.7 macrophage inflammation and DSS-induced Caco-2 cell inflammation models to investigate the anti-inflammatory activities of oat and oat bran polyphenols and their molecular mechanisms. Results: The results showed that oat and oat bran polyphenols (free and bound polyphenols) enhanced phagocytosis, decreased the expression of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), reduced the production of NO and ROS, increased the mitochondrial membrane potential, and reduced the inflammatory cytokines (TNF-α, IL-1β, and IL-6) at the gene level in the RAW 264.7 macrophage inflammation model induced by LPS expression, thus demonstrating strong anti-inflammatory activity. In Caco-2 cells, oat and oat bran polyphenols pretreatment attenuated the DSS-induced decrease in trans-epithelial electron resistance value, increased tight junction protein expression, and reduced cell permeability in Caco-2 cell monolayers, which in turn reduced inflammatory damage in the organism. Conclusions: In summary, the present study not only reveals the mechanism by which oat and oat bran polyphenols inhibit macrophage inflammation and impairment of intestinal barrier function at defined concentration in vitro, but also highlights potential for oat bran as a functional food. Full article

Ricin is a highly potent toxin that causes severe lung injury upon inhalation by initiating a complex cascade of cellular responses that ultimately leads to cell death. The low-density lipoprotein receptor-related protein 1 (LRP1) is a multifunctional receptor involved in various physiological processes, including ricin-mediated toxicity. This study explores the role of LRP1 shedding in the development of ricin-induced lung injury. Analysis of bronchoalveolar lavage fluid (BALF) from ricin-intoxicated mice and swine showed a significant increase in soluble LRP1 (sLRP1) levels, whereas serum LRP1 levels remained largely unchanged, suggesting the lungs are the primary source of sLRP1 release. In vitro assays demonstrated the formation of ricin-sLRP1 complexes, indicating that sLRP1 in BALF retained ricin-binding capability. Flow cytometric analysis of lung cells revealed a reduction in both the percentage and total number of LRP1-expressing cells following ricin exposure. Further investigation of specific lung cell populations showed that alveolar epithelial type II (AT-II) cells, despite experiencing significant injury, exhibited minimal LRP1 shedding. No shedding of LRP1 occurred in neutrophils. In contrast, fibroblasts, which were resistant to ricin-induced cell death, exhibited increased shedding of LRP1 and a corresponding decrease in membrane-bound LRP1 expression. This shedding of the LRP1 ectodomain was mediated by metalloproteinases. Immunohistochemical staining further confirmed decreased LRP1 expression in fibroblasts from ricin-exposed mice. Macrophages also showed substantial LRP1 shedding, despite undergoing significant depletion. These findings highlight the complex cell-specific nature of LRP1 shedding in response to ricin intoxication and suggests the potential role of LRP1 in modulation of cellular susceptibility and resistance to ricin-induced lung injury. Full article

Extracellular vesicles (EVs) are membrane-bound structures released by cells that contain bioactive cargo such as cytokines or non-coding RNA. It is widely known that EVs influence the activity of other cells; they take part in the pathogenesis and compensatory mechanisms of multiple diseases. Frequently, EVs can share the properties of their source cells, thus allowing the use of EVs as non-cellular vectors or therapeutic agents. Importantly, these structures can express the ligand for the programmed cell death protein 1 (PD-L1). It binds to the PD-1 protein present on the immune cells, which suppresses the activity of T cells. The PD-1/PD-L1 axis is widely known in the field of oncology, as PD-L1 present on the surface of cancer cells inhibits cytotoxic activity of T cells, thus promoting cancer growth and treatment resistance. Immunotherapy prevents PD-1/PD-L1 binding and restores anticancer properties of the immune cells. By contrast, the above-mentioned binding is desired in the context of autoimmunity, where abnormal activity of immune cells is a hallmark element in the pathogenesis of these conditions. The aim of this review is to present and discuss the latest findings regarding the role of EVs-PD-L1 in cancer and autoimmunity. Full article