-
Scientific Reports Oct 2023Vesicular transport driven by membrane trafficking systems conserved in eukaryotes is critical to cellular functionality and homeostasis. It is known that homotypic...
Vesicular transport driven by membrane trafficking systems conserved in eukaryotes is critical to cellular functionality and homeostasis. It is known that homotypic fusion and vacuole protein sorting (HOPS) and class C core endosomal vacuole tethering (CORVET) interact with Rab-GTPases and SNARE proteins to regulate vesicle transport, fusion, and maturation in autophagy and endocytosis pathways. In this study, we identified two novel "Hybrid" tethering complexes in mammalian cells in which one of the subunits of HOPS or CORVET is replaced with the subunit from the other. Substrates taken up by receptor-mediated endocytosis or pinocytosis were transported by distinctive pathways, and the newly identified hybrid complexes contributed to pinocytosis in the presence of HOPS, whereas receptor-mediated endocytosis was exclusively dependent on HOPS. Our study provides new insights into the molecular mechanisms of the endocytic pathway and the function of the vacuolar protein sorting-associated (VPS) protein family.
Topics: Animals; Vacuoles; Vesicular Transport Proteins; Endosomes; Endocytosis; SNARE Proteins; Membrane Fusion; Saccharomyces cerevisiae Proteins; Mammals
PubMed: 37907479
DOI: 10.1038/s41598-023-45418-3 -
Frontiers in Immunology 2023Invariant chain (Ii, CD74) is a type II transmembrane glycoprotein that acts as a chaperone and facilitates the folding and transport of MHC II chains. By assisting the...
Invariant chain (Ii, CD74) is a type II transmembrane glycoprotein that acts as a chaperone and facilitates the folding and transport of MHC II chains. By assisting the assembly and subcellular targeting of MHC II complexes, Ii has a wide impact on the functions of antigen-presenting cells such as antigen processing, endocytic maturation, signal transduction, cell migration, and macropinocytosis. Ii is a multifunctional molecule that can alter endocytic traffic and has several interacting molecules. To understand more about Ii's function and to identify further Ii interactors, a yeast two-hybrid screening was performed. Retinoic Acid-Induced 14 (Rai14) was detected as a putative interaction partner, and the interaction was confirmed by co-immunoprecipitation. Rai14 is a poorly characterized protein, which is believed to have a role in actin cytoskeleton and membrane remodeling. In line with this, we found that Rai14 localizes to membrane ruffles, where it forms macropinosomes. Depletion of Rai14 in antigen-presenting cells delays MHC II internalization, affecting macropinocytic activity. Intriguingly, we demonstrated that, similar to Ii, Rai14 is a positive regulator of macropinocytosis and a negative regulator of cell migration, two antagonistic processes in antigen-presenting cells. This antagonism is known to depend on the interaction between myosin II and Ii. Here, we show that Rai14 also binds to myosin II, suggesting that Ii, myosin II, and Rai14 work together to coordinate macropinocytosis and cell motility.
Topics: Tretinoin; Histocompatibility Antigens Class II; Pinocytosis; Cytoskeletal Proteins; Myosin Type II
PubMed: 37545539
DOI: 10.3389/fimmu.2023.1182180 -
Frontiers in Cardiovascular Medicine 2023Endocytosis constitutes a cellular process in which cells selectively encapsulate surface substances into endocytic vesicles, also known as endosomes, thereby modulating... (Review)
Review
Endocytosis constitutes a cellular process in which cells selectively encapsulate surface substances into endocytic vesicles, also known as endosomes, thereby modulating their interaction with the environment. Platelets, as pivotal hematologic elements, play a crucial role not only in regulating coagulation and thrombus formation but also in facilitating tumor invasion and metastasis. Functioning as critical components in the circulatory system, platelets can internalize various endosomal compartments, such as surface receptors, extracellular proteins, small molecules, and pathogens, from the extracellular environment through diverse endocytic pathways, including pinocytosis, phagocytosis, and receptor-mediated endocytosis. We summarize recent advancements in platelet endocytosis, encompassing the catalog of cargoes, regulatory mechanisms, and internal trafficking routes. Furthermore, we describe the influence of endocytosis on platelet regulatory functions and related physiological and pathological processes, aiming to offer foundational insights for future research into platelet endocytosis.
PubMed: 38264257
DOI: 10.3389/fcvm.2023.1308170 -
Frontiers in Immunology 2024Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key... (Review)
Review
Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key role in all phases of acute lung injury (ALI), including the initial insult, development of respiratory failure due to alveolar flooding, as a consequence of altered alveolar-capillary barrier function, as well as in the resolution or deleterious remodeling after injury. In particular, clathrin-, caveolae-, endophilin- and glycosylphosphatidyl inositol-anchored protein-mediated endocytosis, as well as, macropinocytosis and phagocytosis have been implicated in the setting of acute lung damage. This manuscript reviews our current understanding of these endocytic pathways and subsequent intracellular trafficking in various phases of ALI, and also aims to identify potential therapeutic targets for patients with ARDS.
Topics: Humans; Respiratory Distress Syndrome; Endocytosis; Acute Lung Injury; Pinocytosis; Phagocytosis
PubMed: 38533500
DOI: 10.3389/fimmu.2024.1360370 -
Journal of Extracellular Vesicles Apr 2024Besides participating in diverse pathological and physiological processes, extracellular vesicles (EVs) are also excellent drug-delivery vehicles. However, clinical...
Besides participating in diverse pathological and physiological processes, extracellular vesicles (EVs) are also excellent drug-delivery vehicles. However, clinical drugs modulating EV levels are still lacking. Here, we show that proton pump inhibitors (PPIs) reduce EVs by enhancing macropinocytosis-mediated EV uptake. PPIs accelerate intestinal cell endocytosis of autocrine immunosuppressive EVs through macropinocytosis, thereby aggravating inflammatory bowel disease. PPI-induced macropinocytosis facilitates the clearance of immunosuppressive EVs from tumour cells, improving antitumor immunity. PPI-induced macropinocytosis also increases doxorubicin and antisense oligonucleotides of microRNA-155 delivery efficiency by EVs, leading to enhanced therapeutic effects of drug-loaded EVs on tumours and acute liver failure. Mechanistically, PPIs reduce cytosolic pH, promote ATP6V1A (v-ATPase subunit) disassembly from the vacuolar membrane and enhance the assembly of plasma membrane v-ATPases, thereby inducing macropinocytosis. Altogether, our results reveal a mechanism for macropinocytic regulation and PPIs as potential modulators of EV levels, thus regulating their functions.
Topics: Proton Pump Inhibitors; Extracellular Vesicles; Endocytosis; Pinocytosis; Adenosine Triphosphatases
PubMed: 38532609
DOI: 10.1002/jev2.12426 -
Molecular Biology of the Cell Mar 2024Cells rely on a diverse array of engulfment processes to sense, exploit, and adapt to their environments. Among these, macropinocytosis enables indiscriminate and rapid...
Cells rely on a diverse array of engulfment processes to sense, exploit, and adapt to their environments. Among these, macropinocytosis enables indiscriminate and rapid uptake of large volumes of fluid and membrane, rendering it a highly versatile engulfment strategy. Much of the molecular machinery required for macropinocytosis has been well established, yet how this process is regulated in the context of organs and organisms remains poorly understood. Here, we report the discovery of extensive macropinocytosis in the outer epithelium of the cnidarian . Exploiting 's relatively simple body plan, we developed approaches to visualize macropinocytosis over extended periods of time, revealing constitutive engulfment across the entire body axis. We show that the direct application of planar stretch leads to calcium influx and the inhibition of macropinocytosis. Finally, we establish a role for stretch-activated channels in inhibiting this process. Together, our approaches provide a platform for the mechanistic dissection of constitutive macropinocytosis in physiological contexts and highlight a potential role for macropinocytosis in responding to cell surface tension.
Topics: Animals; Hydra; Pinocytosis
PubMed: 38265917
DOI: 10.1091/mbc.E22-02-0065 -
Plants (Basel, Switzerland) Dec 2023M.Bieb is a promising repository of active phytochemicals. These bioactive compounds work synergistically to promote the plant's antioxidant, anticancer, and...
M.Bieb is a promising repository of active phytochemicals. These bioactive compounds work synergistically to promote the plant's antioxidant, anticancer, and immunomodulatory capabilities. The present study aimed to discover the potential immunomodulatory and cytotoxicity of different extracts of roots. Aqueous ethanol (70%), aqueous methanol (90%), ethyl acetate, and n-hexane extracts were tested against five cell lines (T47D, MDA-MB231, Caco-2, EMT6/P, and Vero). Among these extracts, ethyl acetate and n-hexane extracts showed significant activity in inhibiting the proliferation of cancerous cells because of the presence of several phytochemical compounds, including flavonoids, phenolics, and alkaloids. The n-hexane extract was the most potent extract against T47D and Caco-2 cell lines and had IC values of 0.067 mg/mL and 0.067 mg/mL, respectively. In comparison, ethyl acetate extract was active against T47D and MDAMB231, and IC values were 0.0179 mg/mL and 0.03 mg/mL, respectively. Both n-hexane and ethyl acetate extracts reduced tumor size (by 49.981% and 51.028%, respectively). Remarkably, extracts decreased the average weight of the tumor cells in the in vivo model. The plant induced significant apoptotic activity by the activation of caspase-3, immunomodulation of macrophages, and triggering of pinocytosis. The implications of these intriguing findings demand additional research to broaden the scope of the understanding of this field, opening the doors to the possibilities of using M.Bieb as an effective cancer treatment adjuvant in the future.
PubMed: 38202350
DOI: 10.3390/plants13010042 -
Frontiers in Cellular and Infection... 2023is the main causative agent of hospital-acquired diarrhea and the potentially lethal disease, infection. The cornerstone of the current therapy is the use of...
is the main causative agent of hospital-acquired diarrhea and the potentially lethal disease, infection. The cornerstone of the current therapy is the use of antibiotics, which is not fully effective. The molecular mechanisms, inflammatory conditions and host-immune responses that could benefit the persistence or elimination of remain unclear. Macrophages perform different ways of endocytosis as part of their immune surveillance functions and platelets, classically known for their coagulatory role, are also important modulators of the immune system. The aim of this study was to evaluate the endocytosis of vegetative by human macrophages and the involvement of platelets in this process. Our results showed that both macrophages and platelets interact with live and heat-killed . Furthermore, platelets form complexes with human monocytes in healthy donor's fresh blood and the presence of increased these cell-cell interactions. Using flow cytometry and confocal microscopy, we show that macrophages can internalize and that platelets improve this uptake. By using inhibitors of different endocytic pathways, we demonstrate that macropinocytosis is the route of entry of into the cell. Taken together, our findings are the first evidence for the internalization of vegetative non-toxigenic and hypervirulent by human macrophages and highlight the role of platelets in innate immunity during infection. Deciphering the crosstalk of with immune cells could provide new tools for understanding the pathogenesis of infection and for the development of host-directed therapies.
Topics: Humans; Clostridioides difficile; Clostridioides; Blood Platelets; Macrophages; Pinocytosis
PubMed: 38249298
DOI: 10.3389/fcimb.2023.1252509 -
Haematologica Apr 2024Belantamab mafodotin (belantamab) is a first-in-class anti-BCMA antibody-drug conjugate approved for the treatment of triple-class refractory multiple myeloma. It...
Belantamab mafodotin (belantamab) is a first-in-class anti-BCMA antibody-drug conjugate approved for the treatment of triple-class refractory multiple myeloma. It provides a unique therapeutic option for patients ineligible for CAR-T and bispecific antibody therapy, and/or patients progressing on anti-CD38 treatment where CAR-T and bispecifics might be kept in reserve. Wider use of the drug can be challenged by its distinct ocular side effect profile, including corneal microcysts and keratopathy. While dose reduction has been the most effective way to reduce these toxicities, the underlying mechanism of this BCMA off-target effect remains to be characterized. In this study, we provide the first evidence for soluble BCMA (sBCMA) in lacrimal fluid and report on its correlation with tumor burden in myeloma patients. We confirm that corneal cells do not express BCMA, and show that sBCMA-belantamab complexes may rather be internalized by corneal epithelial cells through receptor-ligand independent pinocytosis. Using an hTcEpi corneal cell-line model, we show that the pinocytosis inhibitor EIPA significantly reduces belantamab-specific cell killing. As a proof of concept, we provide detailed patient profiles demonstrating that, after belantamab-induced cell killing, sBCMA is released into circulation, followed by a delayed increase of sBCMA in the tear fluid and subsequent onset of keratopathy. Based on the proposed mechanism, pinocytosis-induced keratopathy can be prevented by lowering the entry of sBCMA into the lacrimal fluid. Future therapeutic concepts may therefore consist of belantamab-free debulking therapy prior to belantamab consolidation and/or concomitant use of gamma-secretase inhibition as currently evaluated for belantamab and nirogacestat in ongoing studies.
PubMed: 38572568
DOI: 10.3324/haematol.2024.285205 -
Biology Open Nov 2023Autotaxin, encoded by the Enpp2 gene, is an exoenzyme that produces lysophosphatidic acid, thereby regulating many biologic functions. We previously reported that Enpp2...
Autotaxin, encoded by the Enpp2 gene, is an exoenzyme that produces lysophosphatidic acid, thereby regulating many biologic functions. We previously reported that Enpp2 mRNA was abundantly expressed in yolk sac visceral endoderm (VE) cells and that Enpp2-/- mice were lethal at embryonic day 9.5 owing to angiogenic defects in the yolk sac. Enpp2-/- mice showed lysosome fragmentation in VE cells and embryonic abnormalities including allantois malformation, neural tube defects, no axial turning, and head cavity formation. However, whether the defects in endocytic vesicle formation affect membrane trafficking in VE cells remained to be directly examined. In this study, we found that pinocytosis, transcytosis, and secretion of angiogenic factors such as vascular endothelial growth factor and transforming growth factor β1 were impaired in Enpp2-/- VE cells. Moreover, pharmacologic inhibition of membrane trafficking phenocopied the defects of Enpp2-/- mice. These findings demonstrate that Enpp2 promotes endocytosis and secretion of angiogenic factors in VE cells, thereby regulating angiogenesis/vasculogenesis and embryonic development.
Topics: Animals; Female; Mice; Pregnancy; Cell Differentiation; Embryonic Development; Endoderm; Vascular Endothelial Growth Factor A; Yolk Sac; Phosphoric Diester Hydrolases
PubMed: 37795611
DOI: 10.1242/bio.060081