Regulation of Clathrin-Mediated Endocytosis

LINC08148 promotes the caveola-mediated endocytosis of Zika virus through upregulating transcription of Src

Long non-coding RNAs (lncRNAs) represent a new group of host factors involved in viral infection. Current study identified an intergenic lncRNA, LINC08148, as a proviral factor of Zika virus (ZIKV) and Dengue virus 2 (DENV2). Knockout (KO) or silencing of LINC08148 decreases the replication of ZIKV and DENV2. LINC08148 mainly acts at the endocytosis step of ZIKV but at a later stage of DENV2. RNA-seq analysis reveals that LINC08148 knockout downregulates the transcription levels of five endocytosis-related genes including AP2B1, CHMP4C, DNM1, FCHO1, and Src. Among them, loss of Src significantly decreases the uptake of ZIKV. Trans-complementation of Src in the LINC08148KO cells largely restores the caveola-mediated endocytosis of ZIKV, indicating that the proviral effect of LINC08148 is exerted through Src. Finally, LINC08148 upregulates the Src transcription through associating with its transcription factor SP1. This work establishes an essential role of LINC08148 in the ZIKV entry, underscoring a significance of lncRNAs in the viral infection.

IMPORTANCE

Long non-coding RNAs (lncRNAs), like proteins, participate in viral infection. However, functions of most lncRNAs remain unknown. In this study, we performed a functional screen based on microarray data and identified a new proviral lncRNA, LINC08148. Then, we uncovered that LINC08148 is involved in the caveola-mediated endocytosis of ZIKV, rather than the classical clathrin-mediated endocytosis. Mechanistically, LINC08148 upregulates the transcription of Src, an initiator of caveola-mediated endocytosis, through binding to its transcription factor SP1. This study identifies a new lncRNA involved in the ZIKV infection, suggesting lncRNAs and cellular proteins are closely linked and cooperate to regulate viral infection.

Clathrin mediates membrane fission and budding by constricting membrane pores

Membrane budding, which underlies fundamental processes like endocytosis, intracellular trafficking, and viral infection, is thought to involve membrane coat-forming proteins, including the most observed clathrin, to form Ω-shape profiles and helix-forming proteins like dynamin to constrict Ω-profiles' pores and thus mediate fission. Challenging this fundamental concept, we report that polymerized clathrin is required for Ω-profiles' pore closure and that clathrin around Ω-profiles' base/pore region mediates pore constriction/closure in neuroendocrine chromaffin cells. Mathematical modeling suggests that clathrin polymerization at Ω-profiles' base/pore region generates forces from its intrinsically curved shape to constrict/close the pore. This new fission function may exert broader impacts than clathrin's well-known coat-forming function during clathrin (coat)-dependent endocytosis, because it underlies not only clathrin (coat)-dependent endocytosis, but also diverse endocytic modes, including ultrafast, fast, slow, bulk, and overshoot endocytosis previously considered clathrin (coat)-independent in chromaffin cells. It mediates kiss-and-run fusion (fusion pore closure) previously considered bona fide clathrin-independent, and limits the vesicular content release rate. Furthermore, analogous to results in chromaffin cells, we found that clathrin is essential for fast and slow endocytosis at hippocampal synapses where clathrin was previously considered dispensable, suggesting clathrin in mediating synaptic vesicle endocytosis and fission. These results suggest that clathrin and likely other intrinsically curved coat proteins are a new class of fission proteins underlying vesicle budding and fusion. The half-a-century concept and studies that attribute vesicle-coat contents' function to Ω-profile formation and classify budding as coat-protein (e.g., clathrin)-dependent or -independent may need to be re-defined and re-examined by considering clathrin's pivotal role in pore constriction/closure.

Phosphatidylinositol 3,4-bisphosphate: Out of the shadows and into the spotlight

Phosphoinositide 3-kinases regulate many cellular functions, including migration, growth, proliferation, and cell survival. Early studies equated the inhibition of Class I PI3Ks with loss of; phosphatidylinositol 3,4,5-trisphosphate (PIP3), but over time, it was realised that these; treatments also depleted phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2). In recent years, the; use of better tools and an improved understanding of its metabolism have allowed for the; identification of specific roles of PI(3,4)P2. This includes the production of PI(3,4)P2 and the; activation of its effector Akt2 in response to growth factor signalling. In contrast, a lysosomal pool of PI(3,4)P2 is a negative regulator of mTORC1 during growth factor deprivation. A growing body of literature also demonstrates that PI(3,4)P2 controls many dynamic plasmalemmal processes. The significance of PI(3,4)P2 in cell biology is increasingly evident.

Antidepressant-induced membrane trafficking regulates blood-brain barrier permeability

As the most prescribed psychotropic drugs in current medical practice, antidepressant drugs (ADs) of the selective serotonin reuptake inhibitor (SSRI) class represent prime candidates for drug repurposing. The mechanisms underlying their mode of action, however, remain unclear. Here, we show that common SSRIs and selected representatives of other AD classes bidirectionally regulate fluid-phase uptake at therapeutic concentrations and below. We further characterize membrane trafficking induced by a canonical SSRI fluvoxamine to show that it involves enhancement of clathrin-mediated endocytosis, endosomal system, and exocytosis. RNA sequencing analysis showed few fluvoxamine-associated differences, consistent with the effect being independent of gene expression. Fluvoxamine-induced increase in membrane trafficking boosted transcytosis in cell-based blood-brain barrier models, while a single injection of fluvoxamine was sufficient to enable brain accumulation of a fluid-phase fluorescent tracer in vivo. These findings reveal modulation of membrane trafficking by ADs as a possible cellular mechanism of action and indicate their clinical repositioning potential for regulating drug delivery to the brain.

Influences of bacterial extracellular vesicles on macrophage immune functions

Bacterial extracellular vesicles (EVs) are crucial mediators of information transfer between bacteria and host cells. Macrophages, as key effector cells in the innate immune system, have garnered widespread attention for their interactions with bacterial EVs. Increasing evidence indicates that bacterial EVs can be internalized by macrophages through multiple pathways, thereby influencing their immune functions. These functions include inflammatory responses, antimicrobial activity, antigen presentation, and programmed cell death. Therefore, this review summarizes current research on the interactions between bacterial EVs and macrophages. This will aid in the deeper understanding of immune modulation mediated by pathogenic microorganisms and provide a basis for developing novel antibacterial therapeutic strategies.

Chilling stress response in tobacco seedlings: insights from transcriptome, proteome, and phosphoproteome analyses

Tobacco (Nicotiana tabacum L.) is an important industrial crop, which is sensitive to chilling stress. Tobacco seedlings that have been subjected to chilling stress readily flower early, which seriously affects the yield and quality of their leaves. Currently, there has been progress in elucidating the molecular mechanisms by which tobacco responds to chilling stress. However, little is known about the phosphorylation that is mediated by chilling. In this study, the transcriptome, proteome and phosphoproteome were analyzed to elucidate the mechanisms of the responses of tobacco shoot and root to chilling stress (4 °C for 24 h). A total of 6,113 differentially expressed genes (DEGs), 153 differentially expressed proteins (DEPs) and 345 differential phosphopeptides were identified in the shoot, and the corresponding numbers in the root were 6,394, 212 and 404, respectively. This study showed that the tobacco seedlings to 24 h of chilling stress primarily responded to this phenomenon by altering their levels of phosphopeptide abundance. Kyoto Encyclopedia of Genes and Genomes analyses revealed that starch and sucrose metabolism and endocytosis were the common pathways in the shoot and root at these levels. In addition, the differential phosphopeptide corresponding proteins were also significantly enriched in the pathways of photosynthesis-antenna proteins and carbon fixation in photosynthetic organisms in the shoot and arginine and proline metabolism, peroxisome and RNA transport in the root. These results suggest that phosphoproteins in these pathways play important roles in the response to chilling stress. Moreover, kinases and transcription factors (TFs) that respond to chilling at the levels of phosphorylation are also crucial for resistance to chilling in tobacco seedlings. The phosphorylation or dephosphorylation of kinases, such as CDPKs and RLKs; and TFs, including VIP1-like, ABI5-like protein 2, TCP7-like, WRKY 6-like, MYC2-like and CAMTA7 among others, may play essential roles in the transduction of tobacco chilling signal and the transcriptional regulation of the genes that respond to chilling stress. Taken together, these findings provide new insights into the molecular mechanisms and regulatory networks of the responses of tobacco to chilling stress.

Fluorescent Chiral Quantum Dots to Unveil Origin-Dependent Exosome Uptake and Cargo Release

Exosomes are promising nanocarriers for drug delivery. Yet, it is challenging to apply exosomes in clinical use due to the limited understanding of their physiological functions. While cellular uptake of exosomes is generally known through endocytosis and/or membrane fusion, the mechanisms of origin-dependent cellular uptake and subsequent cargo release of exosomes into recipient cells are still unclear. Herein, we investigated the intricate mechanisms of exosome entry into recipient cells and intracellular cargo release. In this study, we utilized chiral graphene quantum dots (GQDs) as representatives of exosomal cargo, taking advantage of the superior permeability of chiral GQDs into lipid membranes as well as their excellent optical properties for tracking analysis. We observed that the preferential cellular uptake of exosomes derived from the same cell-of-origin (intraspecies exosomes) is higher than that of exosomes derived from different cell-of-origin (cross-species exosomes). This uptake enhancement was attributed to receptor-ligand interaction-mediated endocytosis, as we identified the expression of specific ligands on exosomes that favorably interact with their parental cells and confirmed the higher lysosomal entrapment of intraspecies exosomes (intraspecies endocytic uptake). On the other hand, we found that the uptake of cross-species exosomes primarily occurred through membrane fusion, followed by direct cargo release into the cytosol (cross-species direct fusion uptake). We revealed the underlying mechanisms involved in the cellular uptake and subsequent cargo release of exosomes depending on their cell-of-origin and recipient cell types. Overall, this study envisions valuable insights into further advancements in effective drug delivery using exosomes, as well as a comprehensive understanding of cellular communication, including disease pathogenesis.

Ubiquitin-driven protein condensation initiates clathrin-mediated endocytosis

Clathrin-mediated endocytosis is an essential cellular pathway that enables signaling and recycling of transmembrane proteins and lipids. During endocytosis, dozens of cytosolic proteins come together at the plasma membrane, assembling into a highly interconnected network that drives endocytic vesicle biogenesis. Recently, multiple groups have reported that early endocytic proteins form flexible condensates, which provide a platform for efficient assembly of endocytic vesicles. Given the importance of this network in the dynamics of endocytosis, how might cells regulate its stability? Many receptors and endocytic proteins are ubiquitylated, while early endocytic proteins such as Eps15 contain ubiquitin-interacting motifs. Therefore, we examined the influence of ubiquitin on the stability of the early endocytic protein network. In vitro, we found that recruitment of small amounts of polyubiquitin dramatically increased the stability of Eps15 condensates, suggesting that ubiquitylation could nucleate endocytic assemblies. In live cell imaging experiments, a version of Eps15 that lacked the ubiquitin-interacting motif failed to rescue defects in endocytic initiation created by Eps15 knockout. Furthermore, fusion of Eps15 to a deubiquitylase enzyme destabilized nascent endocytic sites within minutes. In both in vitro and live cell settings, dynamic exchange of Eps15 proteins, a hallmark of liquidlike systems, was modulated by Eps15-Ub interactions. These results collectively suggest that ubiquitylation drives assembly of the flexible protein network responsible for catalyzing endocytic events. More broadly, this work illustrates a biophysical mechanism by which ubiquitylated transmembrane proteins at the plasma membrane could regulate the efficiency of endocytic recycling.

Dynamin1 long- and short-tail isoforms exploit distinct recruitment and spatial patterns to form endocytic nanoclusters

Endocytosis requires a coordinated framework of molecular interactions that ultimately lead to the fission of nascent endocytic structures. How cytosolic proteins such as dynamin concentrate at discrete sites that are sparsely distributed across the plasma membrane remains poorly understood. Two dynamin-1 major splice variants differ by the length of their C-terminal proline-rich region (short-tail and long-tail). Using sptPALM in PC12 cells, neurons and MEF cells, we demonstrate that short-tail dynamin-1 isoforms ab and bb display an activity-dependent recruitment to the membrane, promptly followed by their concentration into nanoclusters. These nanoclusters are sensitive to both Calcineurin and dynamin GTPase inhibitors, and are larger, denser, and more numerous than that of long-tail isoform aa. Spatiotemporal modelling confirms that dynamin-1 isoforms perform distinct search patterns and undergo dimensional reduction to generate endocytic nanoclusters, with short-tail isoforms more robustly exploiting lateral trapping in the generation of nanoclusters compared to the long-tail isoform.

LS, Saftics A, Shodubi O, Raghunandan S, Xu J, Tsai SJ, Dong Y, Li R, Jovanovic-Talisman T, Gould SJ. Endocytosis blocks the vesicular secretion of exosome marker proteins

Exosomes are secreted vesicles of ~30 to 150 nm diameter that play important roles in human health and disease. To better understand how cells release these vesicles, we examined the biogenesis of the most highly enriched human exosome marker proteins, the exosomal tetraspanins CD81, CD9, and CD63. We show here that endocytosis inhibits their vesicular secretion and, in the case of CD9 and CD81, triggers their destruction. Furthermore, we show that syntenin, a previously described exosome biogenesis factor, drives the vesicular secretion of CD63 by blocking CD63 endocytosis and that other endocytosis inhibitors also induce the plasma membrane accumulation and vesicular secretion of CD63. Finally, we show that CD63 is an expression-dependent inhibitor of endocytosis that triggers the vesicular secretion of lysosomal proteins and the clathrin adaptor AP-2 mu2. These results suggest that the vesicular secretion of exosome marker proteins in exosome-sized vesicles occurs primarily by an endocytosis-independent pathway.

The mechanism of mitochondrial autophagy regulating Clathrin-mediated endocytosis in epilepsy

OBJECTIVE

The objective of this study is to determine whether inhibition of mitophagy affects seizures through Clathrin-mediated endocytosis (CME).

METHODS

Pentylenetetrazol (PTZ) was intraperitoneally injected daily to establish a chronic PTZ-kindled seizure. The Western blot (WB) was used to compare the differences in Parkin protein expression between the epilepsy group and the control group. Immunofluorescence was used to detect the expression of MitoTracker and LysoTracker. Transferrin-Alexa488 (Tf-A488) was injected into the hippocampus of mice. We evaluated the effect of 3-methyladenine (3-MA) on epilepsy behavior through observation in PTZ-kindled models.

RESULTS

The methylated derivative of adenine, known as 3-MA, has been extensively utilized in the field of autophagy research. The transferrin protein is internalized from the extracellular environment into the intracellular space via the CME pathway. Tf-A488 uses a fluorescent marker to track CME. Western blot showed that the expression of Parkin was significantly increased in the PTZ-kindled model (p < 0.05), while 3-MA could reduce the expression (p < 0.05). The fluorescence uptake of MitoTracker and LysoTracker was increased in the primary cultured neurons induced by magnesium-free extracellular fluid (p < 0.05); the fluorescence uptake of Tf-A488 was significantly decreased in the 3-MA group compared with the control group (p < 0.05). Following hippocampal injection of Tf-A488, both the epilepsy group and the 3-MA group exhibited decreased fluorescence uptake, with a more pronounced effect observed in the 3-MA group. Inhibition of mitophagy by 3-MA from day 3 to day 9 progressively exacerbated seizure severity and shortened latency.

SIGNIFICANCE

It is speculated that the aggravation of seizures by 3-MA may be related to the failure to remove damaged mitochondria in time and effectively after inhibiting mitochondrial autophagy, affecting the vesicle endocytosis function of CME and increasing the susceptibility to epilepsy.

SUMMARY

Abnormal mitophagy was observed in a chronic pentylenetetrazol-induced seizure model and a Mg2+-free-induced spontaneous recurrent epileptiform discharge model. A fluorescent transferrin marker was utilized to track clathrin-mediated endocytosis. Using an autophagy inhibitor (3-methyladenine) on primary cultured neurons, we discovered that inhibition of autophagy led to a reduction in fluorescent transferrin uptake, while impairing clathrin-mediated endocytosis function mediated by mitophagy. Finally, we examined the effects of 3-methyladenine in an animal model of seizures showing that it exacerbated seizure severity. Ultimately, this study provides insights into potential mechanisms through which mitophagy regulates clathrin-mediated endocytosis in epilepsy.

Loss of tumor suppressor TMEM127 drives RET-mediated transformation through disrupted membrane dynamics

Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTKs) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumor pheochromocytoma (PCC) can be caused by activating mutations of the rearranged during transfection (RET) receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumor suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin-coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation.

Cytotoxicity of Quantum Dots in Receptor-Mediated Endocytic and Pinocytic Pathways in Yeast

Despite the promising applications of the use of quantum dots (QDs) in the biomedical field, the long-lasting effects of QDs on the cell remain poorly understood. To comprehend the mechanisms underlying the toxic effects of QDs in yeast, we characterized defects associated with receptor-mediated endocytosis (RME) as well as pinocytosis using Saccharomyces cerevisiae as a model in the presence of cadmium selenide/zinc sulfide (CdSe/ZnS) QDs. Our findings revealed that QDs led to an inefficient RME at the early, intermediate, and late stages of endocytic patch maturation at the endocytic site, with the prolonged lifespan of GFP fused yeast fimbrin (Sac6-GFP), a late marker of endocytosis. The transit of FM1-43, a lipophilic dye from the plasma membrane to the vacuole, was severely retarded in the presence of QDs. Finally, QDs caused an accumulation of monomeric red fluorescent protein fused carbamoyl phosphate synthetase 1 (mRFP-Cps1), a vacuolar lumen marker in the vacuole. In summary, the present study provides novel insights into the possible impact of CdSe/ZnS QDs on the endocytic machinery, enabling a deeper comprehension of QD toxicity.

Intersectin1 promotes clathrin-mediated endocytosis by organizing and stabilizing endocytic protein interaction networks

During clathrin-mediated endocytosis (CME), dozens of proteins are recruited to nascent CME sites on the plasma membrane. Coordination of endocytic protein recruitment in time and space is important for efficient CME. Here, we show that the multivalent scaffold protein intersectin1 (ITSN1) promotes CME by organizing and stabilizing endocytic protein interaction networks. By live-cell imaging of genome-edited cells, we observed that endogenously labeled ITSN1 is recruited to CME sites shortly after they begin to assemble. Knocking down ITSN1 impaired endocytic protein recruitment during the stabilization stage of CME site assembly. Artificially locating ITSN1 to the mitochondria surface was sufficient to assemble puncta consisting of CME initiation proteins, including EPS15, FCHO, adaptor proteins, the AP2 complex and epsin1 (EPN1), and the vesicle scission GTPase dynamin2 (DNM2). ITSN1 can form puncta and recruit DNM2 independently of EPS15/FCHO or EPN1. Our work redefines ITSN1's primary endocytic role as organizing and stabilizing the CME protein interaction networks rather than a previously suggested role in initiation and provides new insights into the multi-step and multi-zone organization of CME site assembly.

Requirements for efficient endosomal escape by designed mini-proteins

ZF5.3 is a compact, rationally designed mini-protein that escapes efficiently from the endosomes of multiple cell types. Despite its small size (27 amino acids), ZF5.3 can be isolated intact from the cytosol of treated cells and guides multiple classes of proteins into the cytosol and/or nucleus. In the best cases, delivery efficiencies reach or exceed 50% to establish nuclear or cytosolic concentrations of 500 nM or higher. But other than the requirement for unfoldable cargo and an intact HOPS complex, there is little known about how ZF5.3 traverses the limiting endocytic membrane. Here we delineate the attributes of ZF5.3 that enable efficient endosomal escape. We confirm that ZF5.3 is stable at pH values between 5.5 and 7.5, with no evidence of unfolding even at temperatures as high as 95 °C. The high-resolution NMR structure of ZF5.3 at pH 5.5, also reported here, shows a canonical p zinc-finger fold with the penta-arg motif integrated seamlessly into the C-terminal α-helix. At lower pH, ZF5.3 unfolds cooperatively as judged by both circular dichroism and high-resolution NMR. Unfolding occurs upon protonation of a single Zn(II)-binding His side chain whose pKa corresponds almost exactly to that of the late endosomal lumen. pH-induced unfolding is essential for endosomal escape, as a ZF5.3 analog that remains folded at pH 4.5 fails to efficiently reach the cytosol, despite high overall uptake. Finally, using reconstituted liposomes, we identify a high-affinity interaction of ZF5.3 with a specific lipid-BMP-that is selectively enriched in the inner leaflet of late endosomal membranes. This interaction is 10-fold stronger at low pH than neutral pH, providing a molecular picture for why escape occurs preferentially and in a HOPS-dependent manner from late endosomal compartments. The requirements for programmed endosomal escape identified here should aid and inform the design of proteins, peptidomimetics, and other macromolecules that reach cytosolic or nuclear targets intact and at therapeutically relevant concentrations.

Loss of Tumour Suppressor TMEM127 Drives RET-mediated Transformation Through Disrupted Membrane Dynamics

Internalization from the cell membrane and endosomal trafficking of receptor tyrosine kinases (RTK) are important regulators of signaling in normal cells that can frequently be disrupted in cancer. The adrenal tumour pheochromocytoma (PCC) can be caused by activating mutations of the RET receptor tyrosine kinase, or inactivation of TMEM127, a transmembrane tumour suppressor implicated in trafficking of endosomal cargos. However, the role of aberrant receptor trafficking in PCC is not well understood. Here, we show that loss of TMEM127 causes wildtype RET protein accumulation on the cell surface, where increased receptor density facilitates constitutive ligand-independent activity and downstream signaling, driving cell proliferation. Loss of TMEM127 altered normal cell membrane organization and recruitment and stabilization of membrane protein complexes, impaired assembly, and maturation of clathrin coated pits, and reduced internalization and degradation of cell surface RET. In addition to RTKs, TMEM127 depletion also promoted surface accumulation of several other transmembrane proteins, suggesting it may cause global defects in surface protein activity and function. Together, our data identify TMEM127 as an important determinant of membrane organization including membrane protein diffusability, and protein complex assembly and provide a novel paradigm for oncogenesis in PCC where altered membrane dynamics promotes cell surface accumulation and constitutive activity of growth factor receptors to drive aberrant signaling and promote transformation.

Methods, Mechanisms, and Application Prospects for Enhancing Extracellular Vesicle Uptake

Extracellular vesicles (EVs) are considered to be a new generation of bioinspired nanoscale drug delivery systems due to their low immunogenicity, natural functionality, and excellent biocompatibility. However, limitations such as low uptake efficiency, insufficient production, and inhomogeneous performance undermine their potential. To address these issues, numerous researchers have put forward various methods and applications for enhancing EV uptake in recent decades. In this review, we introduce various methods for the cellular uptake of EVs and summarize recent advances on the methods and mechanisms for enhancing EV uptake. In addition, we provide further understanding regarding enhancing EV uptake and put forward prospects and challenges for the development of EV-based therapy in the future.

Design, synthesis and biological evaluation of novel 1,2,4a,5-tetrahydro-4H-benzo[b][1,4]oxazino[4,3-d][1,4]oxazine-based AAK1 inhibitors with anti-viral property against SARS-CoV-2

Coronavirus entry into host cells hinges on the interaction between the spike glycoprotein of the virus and the cell-surface receptor angiotensin-converting enzyme 2 (ACE2), initiating the subsequent clathrin-mediated endocytosis (CME) pathway. AP-2-associated protein kinase 1 (AAK1) holds a pivotal role in this pathway, regulating CME by modulating the phosphorylation of the μ subunit of adaptor protein 2 (AP2M1). Herein, we report a series of novel AAK1 inhibitors based on previously reported 1,2,4a,5-tetrahydro-4H-benzo[b] [1,4]oxazino[4,3-d] [1,4]oxazine scaffold. Among 23 synthesized compounds, compound 12e is the most potent one with an IC50 value of 9.38 ± 0.34 nM against AAK1. The in vitro antiviral activity of 12e against SARS-CoV-2 was evaluated using a model involving SARS-CoV-2 pseudovirus infecting hACE2-HEK293 host cells. The results revealed that 12e was superior in vitro antiviral activity against SARS-CoV-2 entry into host cells when compared to SGC-AAK1-1 and LX9211, and its activity was comparable to that of a related and reference compound 8. Mechanistically, all AAK1 inhibitors attenuated AAK1-induced phosphorylation of AP2M1 threonine 156 and disrupted the direct interaction between AP2M1 and ACE2, ultimately inhibiting SARS-CoV-2 infection. Notably, compounds 8 and 12e exhibited a more potent effect in suppressing the phosphorylation of AP2M1 T156 and the interaction between AP2M1 and ACE2. In conclusion, novel AAK1 inhibitor 12e demonstrates significant efficacy in suppressing SARS-CoV-2 infection, and holds promise as a potential candidate for developing novel antiviral drugs against SARS-CoV-2 and other coronavirus infections.

Alveolar-capillary endocytosis and trafficking in acute lung injury and acute respiratory distress syndrome

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.

Glia trigger endocytic clearance of axonal proteins to promote rodent myelination

Axons undergo striking changes in their content and distribution of cell adhesion molecules (CAMs) and ion channels during myelination that underlies the switch from continuous to saltatory conduction. These changes include the removal of a large cohort of uniformly distributed CAMs that mediate initial axon-Schwann cell interactions and their replacement by a subset of CAMs that mediate domain-specific interactions of myelinated fibers. Here, using rodent models, we examine the mechanisms and significance of this removal of axonal CAMs. We show that Schwann cells just prior to myelination locally activate clathrin-mediated endocytosis (CME) in axons, thereby driving clearance of a broad array of axonal CAMs. CAMs engineered to resist endocytosis are persistently expressed along the axon and delay both PNS and CNS myelination. Thus, glia non-autonomously activate CME in axons to downregulate axonal CAMs and presumptively axo-glial adhesion. This promotes the transition from ensheathment to myelination while simultaneously sculpting the formation of axonal domains.

ALIX and TSG101 are essential for cellular entry and replication of two porcine alphacoronaviruses

Alphacoronaviruses are the primary coronaviruses responsible for causing severe economic losses in the pig industry with the potential to cause human outbreaks. Currently, extensive studies have reported the essential role of endosomal sorting and transport complexes (ESCRT) in the life cycle of enveloped viruses. However, very little information is available about which ESCRT components are crucial for alphacoronaviruses infection. By using RNA interference in combination with Co-immunoprecipitation, as well as fluorescence and electron microscopy approaches, we have dissected the role of ALIX and TSG101 for two porcine alphacoronavirus cellular entry and replication. Results show that infection by two porcine alphacoronaviruses, including porcine epidemic diarrhea virus (PEDV) and porcine enteric alphacoronavirus (PEAV), is dramatically decreased in ALIX- or TSG101-depleted cells. Furthermore, PEDV entry significantly increases the interaction of ALIX with caveolin-1 (CAV1) and RAB7, which are crucial for viral endocytosis and lysosomal transport, however, does not require TSG101. Interestingly, PEAV not only relies on ALIX to regulate viral endocytosis and lysosomal transport, but also requires TSG101 to regulate macropinocytosis. Besides, ALIX and TSG101 are recruited to the replication sites of PEDV and PEAV where they become localized within the endoplasmic reticulum and virus-induced double-membrane vesicles. PEDV and PEAV replication were significantly inhibited by depletion of ALIX and TSG101 in Vero cells or primary jejunal epithelial cells, indicating that ALIX and TSG101 are crucial for PEDV and PEAV replication. Collectively, these data highlight the dual role of ALIX and TSG101 in the entry and replication of two porcine alphacoronaviruses. Thus, ESCRT proteins could serve as therapeutic targets against two porcine alphacoronaviruses infection.

Insights into the role of derailed endocytic trafficking pathway in cancer: From the perspective of cancer hallmarks

The endocytic trafficking pathway is a highly organized cellular program responsible for the regulation of membrane components and uptake of extracellular substances. Molecules internalized into the cell through endocytosis will be sorted for degradation or recycled back to membrane, which is determined by a series of sorting events. Many receptors, enzymes, and transporters on the membrane are strictly regulated by endocytic trafficking process, and thus the endocytic pathway has a profound effect on cellular homeostasis. However, the endocytic trafficking process is typically dysregulated in cancers, which leads to the aberrant retention of receptor tyrosine kinases and immunosuppressive molecules on cell membrane, the loss of adhesion protein, as well as excessive uptake of nutrients. Therefore, hijacking endocytic trafficking pathway is an important approach for tumor cells to obtain advantages of proliferation and invasion, and to evade immune attack. Here, we summarize how dysregulated endocytic trafficking process triggers tumorigenesis and progression from the perspective of several typical cancer hallmarks. The impact of endocytic trafficking pathway to cancer therapy efficacy is also discussed.

An extract of phase II and III trials on recent developments in managing neuropathic pain syndromes: diabetic peripheral neuropathy, trigeminal neuralgia, and postherpetic neuralgia

INTRODUCTION

Neuropathic pain (NP) conditions involve lesions to the somatosensory nervous system leading to chronic and debilitating pain. Many patients suffering from NP utilize pharmacological treatments with various drugs that seek to reduce pathologic neuronal states. However, many of these drugs show poor efficacy as well as cause significant adverse effects. Because of this, there is a major need for the development of safer and more efficacious drugs to treat NP.

AREAS COVERED

In this review, we analyzed current treatments being developed for a variety of NP conditions. Specifically, we sought drugs in phase II/III clinical trials with indications for NP conditions. Various databases were searched including Google Scholar, PubMed, and clinicaltrials.gov.

EXPERT OPINION

All the mentioned targets for treatments of NP seem to be promising alternatives for existing treatments that often possess poor side effect profiles for patients. However, gene therapy potentially offers the unique ability to inject a plasmid containing growth factors leading to nerve growth and repair. Because of this, gene therapy appears to be the most intriguing new treatment for NP.

Tension-induced adhesion mode switching: the interplay between focal adhesions and clathrin-containing adhesion complexes

Integrin-based adhesion complexes are crucial in various cellular processes, including proliferation, differentiation, and motility. While the dynamics of canonical focal adhesion complexes (FAs) have been extensively studied, the regulation and physiological implications of the recently identified clathrin-containing adhesion complexes (CCACs) are still not well understood. In this study, we investigated the spatiotemporal mechanoregulations of FAs and CCACs in a breast cancer model. Employing single-molecule force spectroscopy coupled with live-cell fluorescence microscopy, we discovered that FAs and CCACs are mutually exclusive and inversely regulated complexes. This regulation is orchestrated through the modulation of plasma membrane tension, in combination with distinct modes of actomyosin contractility that can either synergize with or counteract this modulation. Our findings indicate that increased membrane tension promotes the association of CCACs at integrin αVβ5 adhesion sites, leading to decreased cancer cell proliferation, spreading, and migration. Conversely, lower membrane tension promotes the formation of FAs, which correlates with the softer membranes observed in cancer cells, thus potentially facilitating cancer progression. Our research provides novel insights into the biomechanical regulation of CCACs and FAs, revealing their critical and contrasting roles in modulating cancer cell progression.

Pseudorabies virus uses clathrin mediated endocytosis to enter PK15 swine cell line

Pseudorabies virus (PRV), a herpesvirus responsible for Aujeszky's disease, causes high mortality in swine populations. To develop effective and novel antiviral strategies, it is essential to understand the mechanism of entry used by PRV to infect its host. Viruses have different ways of entering host cells. Among others, they can use endocytosis, a fundamental cellular process by which substances from the external environment are internalized into the cell. This process is classified into clathrin-mediated endocytosis (CME) and clathrin-independent endocytosis (CIE), depending on the role of clathrin. Although the involvement of cholesterol-rich lipid rafts in the entry of PRV has already been described, the importance of other endocytic pathways involving clathrin remains unexplored to date. Here, we characterize the role of CME in PRV entry into the PK15 swine cell line. By using CME inhibitory drugs, we report a decrease in PRV infection when the CME pathway is blocked. We also perform the shRNA knockdown of the μ-subunit of the adaptor protein AP-2 (AP2M1), which plays an important role in the maturation of clathrin-coated vesicles, and the infection is greatly reduced when this subunit is knocked down. Furthermore, transmission electron microscopy images report PRV virions inside clathrin-coated vesicles. Overall, this study suggests for the first time that CME is a mechanism used by PRV to enter PK15 cells and provides valuable insights into its possible routes of entry.

Spontaneous transfer of small peripheral peptides between supported lipid bilayer and giant unilamellar vesicles

Vesicular trafficking facilitates material transport between membrane-bound organelles. Membrane protein cargos are trafficked for relocation, recycling, and degradation during various physiological processes. In vitro fusion studies utilized synthetic lipid membranes to study the molecular mechanisms of vesicular trafficking and to develop synthetic materials mimicking the biological membrane trafficking. Various fusogenic conditions which can induce vesicular fusion have been used to establish synthetic systems that can mimic biological systems. Despite these efforts, the mechanisms underlying vesicular trafficking of membrane proteins remain limited and robust in vitro methods that can construct synthetic trafficking systems for membrane proteins between large membranes (>1 μm2) are unavailable. Here, we provide data to show the spontaneous transfer of small membrane-bound peptides (∼4 kD) between a supported lipid bilayer (SLB) and giant unilamellar vesicles (GUVs). We found that the contact between the SLB and GUVs led to the occasional but notable transfer of membrane-bound peptides in a physiological saline buffer condition (pH 7.4, 150 mM NaCl). Quantitative and dynamic time-lapse analyses suggested that the observed exchange occurred through the formation of hemi-fusion stalks between the SLB and GUVs. Larger protein cargos with a size of ∼77 kD could not be transferred between the SLB and GUVs, suggesting that the larger-sized cargos limited diffusion across the hemi-fusion stalk, which was predicted to have a highly curved structure. Compositional study showed Ni-chelated lipid head group was the essential component catalyzing the process. Our system serves as an example synthetic platform that enables the investigation of small-peptide trafficking between synthetic membranes and reveals hemi-fused lipid bridge formation as a mechanism of peptide transfer.

A defined clathrin-mediated trafficking pathway regulates sFLT1/VEGFR1 secretion from endothelial cells

FLT1/VEGFR1 negatively regulates VEGF-A signaling and is required for proper vessel morphogenesis during vascular development and vessel homeostasis. Although a soluble isoform, sFLT1, is often mis-regulated in disease and aging, how sFLT1 is trafficked and secreted from endothelial cells is not well understood. Here we define requirements for constitutive sFLT1 trafficking and secretion in endothelial cells from the Golgi to the plasma membrane, and we show that sFLT1 secretion requires clathrin at or near the Golgi. Perturbations that affect sFLT1 trafficking blunted endothelial cell secretion and promoted intracellular mis-localization in cells and zebrafish embryos. siRNA-mediated depletion of specific trafficking components revealed requirements for RAB27A, VAMP3, and STX3 for post-Golgi vesicle trafficking and sFLT1 secretion, while STX6, ARF1, and AP1 were required at the Golgi. Live-imaging of temporally controlled sFLT1 release from the endoplasmic reticulum showed clathrin-dependent sFLT1 trafficking at the Golgi into secretory vesicles that then trafficked to the plasma membrane. Depletion of STX6 altered vessel sprouting in 3D, suggesting that endothelial cell sFLT1 secretion influences proper vessel sprouting. Thus, specific trafficking components provide a secretory path from the Golgi to the plasma membrane for sFLT1 in endothelial cells that utilizes a specialized clathrin-dependent intermediate, suggesting novel therapeutic targets.

Curvature sensing of curvature-inducing proteins with internal structure

Many types of peripheral and transmembrane proteins can sense and generate membrane curvature. Laterally isotropic proteins and crescent proteins with twofold rotational symmetry, such as Bin/Amphiphysin/Rvs superfamily proteins, have been studied theoretically. However, proteins often have an asymmetric structure or a higher rotational symmetry. We studied theoretically the curvature sensing of proteins with asymmetric structures and structural deformations. First, we examined proteins consisting of two rodlike segments. When proteins have mirror symmetry, their sensing ability is similar to that of single-rod proteins; hence, with increasing protein density on a cylindrical membrane tube, a second- or first-order transition occurs at a middle or small tube radius, respectively. As asymmetry is introduced, this transition becomes a continuous change and metastable states appear at high protein densities. Protein with threefold, fivefold, or higher rotational symmetry has laterally isotropic bending energy. However, when a structural deformation is allowed, the protein can have a preferred orientation and stronger curvature sensing.

ACKR3 Proximity Labeling Identifies Novel G protein- and β-arrestin-independent GPCR Interacting Proteins

The canonical paradigm of GPCR signaling recognizes G proteins and β-arrestins as the two primary transducers that promote GPCR signaling. Recent evidence suggests the atypical chemokine receptor 3 (ACKR3) does not couple to G proteins, and β-arrestins are dispensable for some of its functions. Here, we employed proximity labeling to identify proteins that interact with ACKR3 in cells devoid of β-arrestin. We identified proteins involved in the endocytic machinery and evaluated a subset of proteins conserved across several GPCR-based proximity labeling experiments. We discovered that the bone morphogenic protein 2-inducible kinase (BMP2K) interacts with many different GPCRs with varying dependency on β-arrestin. Together, our work highlights the existence of modulators that can act independently of G proteins and β-arrestins to regulate GPCR signaling and provides important evidence for other targets that may regulate GPCR signaling.

The pathogenesis of influenza in intact alveoli: virion endocytosis and its effects on the lung's air-blood barrier

Lung infection by influenza A virus (IAV) is a major cause of global mortality from lung injury, a disease defined by widespread dysfunction of the lung's air-blood barrier. Endocytosis of IAV virions by the alveolar epithelium - the cells that determine barrier function - is central to barrier loss mechanisms. Here, we address the current understanding of the mechanistic steps that lead to endocytosis in the alveolar epithelium, with an eye to how the unique structure of lung alveoli shapes endocytic mechanisms. We highlight where future studies of alveolar interactions with IAV virions may lead to new therapeutic approaches for IAV-induced lung injury.

Inferring biophysical properties of membranes during endocytosis using machine learning

Endocytosis is a fundamental cellular process in eukaryotic cells that facilitates the transport of molecules into the cell. With the help of fluorescence microscopy and electron tomography, researchers have accumulated extensive geometric data of membrane shapes during endocytosis. These data contain rich information about the mechanical properties of membranes, which are hard to access via experiments due to the small dimensions of the endocytic patch. In this study, we propose an approach that combines machine learning with the Helfrich theory of membranes to infer the mechanical properties of membranes during endocytosis from a dataset of membrane shapes extracted from electron tomography. Our results demonstrate that machine learning can output solutions that both match the experimental profile and satisfy the membrane shape equations derived from Helfrich theory. The learning results show that during the early stage of endocytosis, the inferred membrane tension is negative, indicating the presence of strong compressive forces at the boundary of the endocytic invagination. Our method presents a generic framework for extracting membrane information from super-resolution imaging.

Drug-loaded erythrocytes: Modern approaches for advanced drug delivery for clinical use

Scientific organizations worldwide are striving to create drug delivery systems that provide a high local concentration of a drug in pathological tissue without side effects on healthy organs in the body. Important physiological properties of red blood cells (RBCs), such as frequent renewal ability, good oxygen carrying ability, unique shape and membrane flexibility, allow them to be used as natural carriers of drugs in the body. Erythrocyte carriers derived from autologous blood are even more promising drug delivery systems due to their immunogenic compatibility, safety, natural uniqueness, simple preparation, biodegradability and convenience of use in clinical practice. This review is focused on the achievements in the clinical application of targeted drug delivery systems based on osmotic methods of loading RBCs, with an emphasis on advancements in their industrial production. This article describes the basic methods used for encapsulating drugs into erythrocytes, key strategic approaches to the clinical use of drug-loaded erythrocytes obtained by hypotonic hemolysis. Moreover, clinical trials of erythrocyte carriers for the targeted delivery are discussed. This article explores the recent advancements and engineering approaches employed in the encapsulation of erythrocytes through hypotonic hemolysis methods, as well as the most promising inventions in this field. There is currently a shortage of reviews focused on the automation of drug loading into RBCs; therefore, our work fills this gap. Finally, further prospects for the development of engineering and technological solutions for the automatic production of drug-loaded RBCs were studied. Automated devices have the potential to provide the widespread production of RBC-encapsulated therapeutic drugs and optimize the process of targeted drug delivery in the body. Furthermore, they can expedite the widespread introduction of this innovative treatment method into clinical practice, thereby significantly expanding the effectiveness of treatment in both surgery and all areas of medicine.

Biogenesis and delivery of extracellular vesicles: harnessing the power of EVs for diagnostics and therapeutics

Extracellular vesicles (EVs) are membrane-enclosed particles secreted by a variety of cell types. These vesicles encapsulate a diverse range of molecules, including proteins, nucleic acids, lipids, metabolites, and even organelles derived from their parental cells. While EVs have emerged as crucial mediators of intercellular communication, they also hold immense potential as both biomarkers and therapeutic agents for numerous diseases. A thorough understanding of EV biogenesis is crucial for the development of EV-based diagnostic developments since the composition of EVs can reflect the health and disease status of the donor cell. Moreover, when EVs are taken up by target cells, they can exert profound effects on gene expression, signaling pathways, and cellular behavior, which makes these biomolecules enticing targets for therapeutic interventions. Yet, despite decades of research, the intricate processes underlying EV biogenesis by donor cells and subsequent uptake by recipient cells remain poorly understood. In this review, we aim to summarize current insights and advancements in the biogenesis and uptake mechanisms of EVs. By shedding light on the fundamental mechanisms governing EV biogenesis and delivery, this review underscores the potential of basic mechanistic research to pave the way for developing novel diagnostic strategies and therapeutic applications.

Recent Advances in Delivery of Peptide and Protein Therapeutics to the Brain

The classes of neuropharmaceuticals known as proteins and peptides serve as diagnostic tools and are involved in specific communication in the peripheral and central nervous systems. However, due to tight junctions resembling epithelial cells found in the blood-brain barrier (BBB) in vivo, they are typically excluded from transport from the blood to the brain. The drugs having molecular weight of less than 400 Dalton are able to cross the BBB via lipid-mediated free diffusion. However, large molecule therapeutics are devoid of these characteristics. As an alternative, these substances may be carried via chimeric peptide drug delivery systems, and assist in transcytosis through BBB with the aid of linker strategies. With their recent developments, several forms of nanoparticles, including poly (ethylene glycol)-poly(ε-caprolactone) copolymers, nanogels, liposomes, nanostructured lipid carriers, poly (D, L-lactide-co-glycolide) nanoparticles, chitosan, and solid lipid nanoparticles, have also been considered for their therapeutic applications. Moreover, the necessity for physiologic optimization of current drug delivery methods and their carriers to deliver therapeutic doses of medication into the brain for the treatment of various neurologic illnesses has also been emphasized. Therapeutic use of proteins and peptides has no neuroprotective impact in the absence of all these methods. Each tactic, however, has unique drawbacks and considerations. In this review, we discuss different drug delivery methods for therapeutic distribution of pharmaceuticals, primarily neuroproteins and neuropeptides, through endothelial capillaries via blood-brain barrier. Finally, we have also discussed the challenges and future perspective of protein and peptide therapeutics delivery to the brain. SIGNIFICANCE STATEMENT: Very few reports on the delivery of therapeutic protein and peptide nanoformulations are available in the literature. Herein, we attempted to discuss these nanoformulations of protein and peptide therapeutics used to treat brain diseases.

Membrane transformations of fusion and budding

Membrane fusion and budding mediate fundamental processes like intracellular trafficking, exocytosis, and endocytosis. Fusion is thought to open a nanometer-range pore that may subsequently close or dilate irreversibly, whereas budding transforms flat membranes into vesicles. Reviewing recent breakthroughs in real-time visualization of membrane transformations well exceeding this classical view, we synthesize a new model and describe its underlying mechanistic principles and functions. Fusion involves hemi-to-full fusion, pore expansion, constriction and/or closure while fusing vesicles may shrink, enlarge, or receive another vesicle fusion; endocytosis follows exocytosis primarily by closing Ω-shaped profiles pre-formed through the flat-to-Λ-to-Ω-shape transition or formed via fusion. Calcium/SNARE-dependent fusion machinery, cytoskeleton-dependent membrane tension, osmotic pressure, calcium/dynamin-dependent fission machinery, and actin/dynamin-dependent force machinery work together to generate fusion and budding modes differing in pore status, vesicle size, speed and quantity, controls release probability, synchronization and content release rates/amounts, and underlies exo-endocytosis coupling to maintain membrane homeostasis. These transformations, underlying mechanisms, and functions may be conserved for fusion and budding in general.

Interactions between macrophage membrane and lipid mediators during cardiovascular diseases with the implications of scavenger receptors

The onset and progression of cardiovascular diseases with the major underlying cause being atherosclerosis, occur during chronic inflammatory persistence in the vascular system, especially within the arterial wall. Such prolonged maladaptive inflammation is driven by macrophages and their key mediators are generally attributed to a disparity in lipid metabolism. Macrophages are the primary cells of innate immunity, endowed with expansive membrane domains involved in immune responses with their signalling systems. During atherosclerosis, the membrane domains and receptors control various active organisations of macrophages. Their scavenger/endocytic receptors regulate the trafficking of intracellular and extracellular cargo. Corresponding influence on lipid metabolism is mediated by their dynamic interaction with scavenger membrane receptors and their integrated mechanisms such as pinocytosis, phagocytosis, cholesterol export/import, etc. This interaction not only results in the functional differentiation of macrophages but also modifies their structural configurations. Here, we reviewed the association of macrophage membrane biomechanics and their scavenger receptor families with lipid metabolites during the event of atherogenesis. In addition, the membrane structure of macrophages and the signalling pathways involved in endocytosis integrated with lipid metabolism are detailed. This article establishes future insights into the scavenger receptors as potential targets for cardiovascular disease prevention and treatment.

Cellular Uptake of Engineered Extracellular Vesicles: Biomechanisms, Engineered Strategies, and Disease Treatment

Extracellular vesicles (EVs), lipid-enclosed nanosized membrane vesicles, are regarded as new vehicles and therapeutic agents in intercellular communication. During internal circulation, if EVs are not effectively taken up by recipient cells, they will be cleared as "cellular waste" and unable to deliver therapeutic components. It can be seen that cells uptake EVs are the prerequisite premise for sharing intercellular biological information. However, natural EVs have a low rate of absorption by their recipient cells, off-target delivery, and rapid clearance from circulation, which seriously reduces the utilization rate. Affecting the uptake rate of EVs through engineering technologies is essential for therapeutic applications. Engineering strategies for customizing EV uptake can potentially overcome these limitations and enable desirable therapeutic uses of EVs. In this review, the mechanism and influencing factors of natural EV uptake will be described in detail. Targeting each EV uptake mechanism, the strategies of engineered EVs and their application in diseases will be emphatically discussed. Finally, the future challenges and perspectives of engineered EVs are presented multidimensionally.

Co-delivery of oxaliplatin prodrug liposomes with Bacillus Calmette-Guérin for chemo-immunotherapy of orthotopic bladder cancer

To reduce recurrence rate after transurethral resection of bladder tumor, long-term intravesical instillations of Bacillus Calmette-Guérin (BCG) and/or chemotherapeutic drugs is the standard treatment for non-muscle invasive bladder carcinoma. However, the main challenges of intravesical therapy, such as short retention time and poor permeability of drugs in the bladder, often require frequent and high-dose administrations, leading to significant adverse effects and financial burden for patients. Aiming at addressing these challenges, we developed a novel approach, in which the cell-penetrating peptide modified oxaliplatin prodrug liposomes and a low-dose BCG were co-delivered via a viscous chitosan solution (LRO-BCG/CS). LRO-BCG/CS addressed these challenges by significantly improving the retention capability and permeability of chemotherapy agents across the bladder wall. Then, oxaliplatin triggered the immunogenic cell death, and the combination of BCG simultaneously further activated the systemic anti-tumor immune response in the MB49 orthotopic bladder tumor model. As a result, LRO-BCG/CS demonstrated superior anti-tumor efficacy and prolonged the survival time of tumor-bearing mice significantly, even at relatively low doses of oxaliplatin and BCG. Importantly, this combinational chemo-immunotherapy showed negligible side effects, offering a promising and well-tolerated therapeutic strategy for bladder cancer patients.

Small RNA-big impact: exosomal miRNAs in mitochondrial dysfunction in various diseases

Mitochondria are multitasking organelles involved in maintaining the cell homoeostasis. Beyond its well-established role in cellular bioenergetics, mitochondria also function as signal organelles to propagate various cellular outcomes. However, mitochondria have a self-destructive arsenal of factors driving the development of diseases caused by mitochondrial dysfunction. Extracellular vesicles (EVs), a heterogeneous group of membranous nano-sized vesicles, are present in a variety of bodily fluids. EVs serve as mediators for intercellular interaction. Exosomes are a class of small EVs (30-100 nm) released by most cells. Exosomes carry various cargo including microRNAs (miRNAs), a class of short noncoding RNAs. Recent studies have closely associated exosomal miRNAs with various human diseases, including diseases caused by mitochondrial dysfunction, which are a group of complex multifactorial diseases and have not been comprehensively described. In this review, we first briefly introduce the characteristics of EVs. Then, we focus on possible mechanisms regarding exosome-mitochondria interaction through integrating signalling networks. Moreover, we summarize recent advances in the knowledge of the role of exosomal miRNAs in various diseases, describing how mitochondria are changed in disease status. Finally, we propose future research directions to provide a novel therapeutic strategy that could slow the disease progress mediated by mitochondrial dysfunction.

Enhancement of Oral Bioavailability of Protein and Peptide by Polysaccharide-based Nanoparticles

Oral drug delivery is a prevalent and cost-effective method due to its advantages, such as increased drug absorption surface area and improved patient compliance. However, delivering proteins and peptides orally remains a challenge due to their vulnerability to degradation by digestive enzymes, stomach acids, and limited intestinal membrane permeability, resulting in poor bioavailability. The use of nanotechnology has emerged as a promising solution to enhance the bioavailability of these vital therapeutic agents. Polymeric NPs, made from natural or synthetic polymers, are commonly used. Natural polysaccharides, such as alginate, chitosan, dextran, starch, pectin, etc., have gained preference due to their biodegradability, biocompatibility, and versatility in encapsulating various drug types. Their hydrophobic-hydrophilic properties can be tailored to suit different drug molecules.

The Regulation of Exosome Generation and Function in Physiological and Pathological Processes

Exosomes, a type of extracellular vesicle with a diameter of approximately 100 nm that is secreted by all cells, regulate the phenotype and function of recipient cells by carrying molecules such as proteins, nucleic acids, and lipids and are important mediators of intercellular communication. Exosomes are involved in various physiological and pathological processes such as immunomodulation, angiogenesis, tumorigenesis, metastasis, and chemoresistance. Due to their excellent properties, exosomes have shown their potential application in the clinical diagnosis and treatment of disease. The functions of exosomes depend on their biogenesis, uptake, and composition. Thus, a deeper understanding of these processes and regulatory mechanisms can help to find new targets for disease diagnosis and therapy. Therefore, this review summarizes and integrates the recent advances in the regulatory mechanisms of the entire biological process of exosomes, starting from the formation of early-sorting endosomes (ESCs) by plasma membrane invagination to the release of exosomes by fusion of multivesicular bodies (MVBs) with the plasma membrane, as well as the regulatory process of the interactions between exosomes and recipient cells. We also describe and discuss the regulatory mechanisms of exosome production in tumor cells and the potential of exosomes used in cancer diagnosis and therapy.

Plant elicitor peptide induces endocytosis of plasma membrane proteins in Arabidopsis

In plants, the regulation of plasma membrane (PM) dynamics through endocytosis plays a crucial role in responding to external environmental cues and defending against pathogens. The Arabidopsis plant elicitor peptides (Peps), originating from precursor proteins called PROPEPs, have been implicated in various aspects of plant immunity. This study delves into the signaling pathway of Peps, particularly Pep1, and its effect on PM protein internalization. Using PIN2 and BRI1 as PM markers, we demonstrated that Pep1 stimulates the endocytosis of these PM-localized proteins through clathrin-mediated endocytosis (CME). CLC2 and CLC3, two light chains of clathrin, are vital for Pep1-induced PIN2-GFP and BRI1-GFP internalization.The internalized PIN2 and BRI1 are subsequently transported to the vacuole via the trans-Golgi network/early endosome (TGN/EE) and prevacuolar compartment (PVC) pathways. Intriguingly, salicylic acid (SA) negatively regulates the effect of Pep1 on PM endocytosis. This study sheds light on a previously unknown signaling pathway by which danger peptides like Pep1 influence PM dynamics, contributing to a deeper understanding of the function of plant elicitor peptide.

Fluorescent Chiral Quantum Dots to Unveil Origin-Dependent Exosome Uptake and Cargo Release

Exosomes are promising nanocarriers for drug delivery. Yet, it is challenging to apply exosomes in clinical use due to the limited understanding of their physiological functions. While cellular uptake of exosomes is generally known through endocytosis and/or membrane fusion, the mechanisms of origin-dependent cellular uptake and subsequent cargo release of exosomes into recipient cells are still unclear. Herein, we investigated the intricate mechanisms of exosome entry into recipient cells and the intracellular cargo release. In this study, we utilized chiral graphene quantum dots (GQDs) as representatives of exosomal cargo, taking advantage of the superior permeability of chiral GQDs into lipid membranes, as well as their excellent optical properties for tracking analysis. We observed a higher uptake rate of exosomes in their parental recipient cells. However, these exosomes were predominantly entrapped in lysosomes through endocytosis (intraspecies endocytic uptake). On the other hand, in non-parental recipient cells, exosomes exhibited a greater inclination for cellular uptake through membrane fusion, followed by direct cargo release into the cytosol (cross-species direct fusion uptake). We revealed the underlying mechanisms involved in the cellular uptake and the subsequent cargo release of exosomes depending on their cell-of-origin and recipient cell types. This study envisions valuable insights into further advancements in the effective drug delivery using exosomes, as well as a comprehensive understanding of cellular communication, including disease pathogenesis.

The Molecular Aspects of Functional Activity of Macrophage-Activating Factor GcMAF

Group-specific component macrophage-activating factor (GcMAF) is the vitamin D3-binding protein (DBP) deglycosylated at Thr420. The protein is believed to exhibit a wide range of therapeutic properties associated with the activation of macrophagal immunity. An original method for GcMAF production, DBP conversion to GcMAF, and the analysis of the activating potency of GcMAF was developed in this study. Data unveiling the molecular causes of macrophage activation were obtained. GcMAF was found to interact with three CLEC10A derivatives having molecular weights of 29 kDa, 63 kDa, and 65 kDa. GcMAF interacts with high-molecular-weight derivatives via Ca2+-dependent receptor engagement. Binding to the 65 kDa or 63 kDa derivative determines the pro- and anti-inflammatory direction of cytokine mRNA expression: 65 kDa-pro-inflammatory (TNF-α, IL-1β) and 63 kDa-anti-inflammatory (TGF-β, IL-10). No Ca2+ ions are required for the interaction with the canonical 29 kDa CLEC10A. Both forms, DBP protein and GcMAF, bind to the 29 kDa CLEC10A. This interaction is characterized by the stochastic mRNA synthesis of the analyzed cytokines. Ex vivo experiments have demonstrated that when there is an excess of GcMAF ligand, CLEC10A forms aggregate, and the mRNA synthesis of analyzed cytokines is inhibited. A schematic diagram of the presumable mechanism of interaction between the CLEC10A derivatives and GcMAF is provided. The principles and elements of standardizing the GcMAF preparation are elaborated.

Nutrient deprivation alters the rate of COPII subunit recruitment at ER subdomains to tune secretory protein transport

Co-assembly of the multilayered coat protein complex II (COPII) with the Sar1 GTPase at subdomains of the endoplasmic reticulum (ER) enables secretory cargoes to be concentrated efficiently within nascent transport intermediates, which subsequently deliver their contents to ER-Golgi intermediate compartments. Here, we define the spatiotemporal accumulation of native COPII subunits and secretory cargoes at ER subdomains under differing nutrient availability conditions using a combination of CRISPR/Cas9-mediated genome editing and live cell imaging. Our findings demonstrate that the rate of inner COPII coat recruitment serves as a determinant for the pace of cargo export, irrespective of COPII subunit expression levels. Moreover, increasing inner COPII coat recruitment kinetics is sufficient to rescue cargo trafficking deficits caused by acute nutrient limitation. Our findings are consistent with a model in which the rate of inner COPII coat addition acts as an important control point to regulate cargo export from the ER.

The Salmonella Typhimurium Effector SpvB Subverts Host Membrane Trafficking by Targeting Clathrin and AP-1

Salmonella enterica, the etiological agent of gastrointestinal and systemic diseases, translocates a plethora of virulence factors through its type III secretion systems to host cells during infection. Among them, SpvB has been reported to harbor an ADP-ribosyltransferase domain in its C terminus, which destabilizes host cytoskeleton by modifying actin. However, whether this effector targets other host factors as well as the function of its N terminus still remains to be determined. Here, we found that SpvB targets clathrin and its adaptor AP-1 (adaptor protein 1) via interactions with its N-terminal domain. Notably, our data suggest that SpvB-clathrin/AP-1 associations disrupt clathrin-mediated endocytosis and protein secretion pathway as well. In addition, knocking down of AP-1 promotes Salmonella intracellular survival and proliferation in host cells.

MHC cross-dressing in antigen presentation

Dendritic cells (DCs) orchestrate T cell responses by presenting antigenic peptides on major histocompatibility complex (MHC) and providing costimulation and other instructive signals. Professional antigen presenting cells (APCs), including DCs, are uniquely capable of generating and presenting peptide antigens derived from exogenous proteins. In addition to these canonical cross-presentation and MHC-II presentation pathways, APCs can also display exogenous peptide/MHC (p/MHC) acquired from neighboring cells and extracellular vesicles (EVs). This process, known as MHC cross-dressing, has been implicated in the regulation of T cell responses in a variety of in vivo contexts, including allogeneic solid organ transplantation, tumors, and viral infection. Although the occurrence of MHC cross-dressing has been clearly demonstrated, the importance of this antigen presentation mechanism continues to be elucidated. The contribution of MHC cross-dressing to overall antigen presentation has been obfuscated by the fact that DCs express the same MHC alleles as all other cells in the host, making it difficult to distinguish p/MHC generated within the DC from p/MHC acquired from another cell. As a result, much of what is known about MHC cross-dressing comes from studies using allogeneic organ transplantation and bone marrow chimeric mice, though recent development of mice bearing conditional knockout MHC and β2-microglobulin alleles should facilitate substantial progress in the coming years. In this review, we highlight recent advances in our understanding of MHC cross-dressing and its role in activating T cell responses in various contexts, as well as the experimental insights into the mechanism by which it occurs.

Invasion by exogenous RNA: cellular defense strategies and implications for RNA inference

Exogenous RNA poses a continuous threat to genome stability and integrity across various organisms. Accumulating evidence reveals complex mechanisms underlying the cellular response to exogenous RNA, including endo-lysosomal degradation, RNA-dependent repression and innate immune clearance. Across a variety of mechanisms, the natural anti-sense RNA-dependent defensive strategy has been utilized both as a powerful gene manipulation tool and gene therapy strategy named RNA-interference (RNAi). To optimize the efficiency of RNAi silencing, a comprehensive understanding of the whole life cycle of exogenous RNA, from cellular entry to its decay, is vital. In this paper, we review recent progress in comprehending the recognition and elimination of foreign RNA by cells, focusing on cellular entrance, intracellular transportation, and immune-inflammatory responses. By leveraging these insights, we highlight the potential implications of these insights for advancing RNA interference efficiency, underscore the need for future studies to elucidate the pathways and fates of various exogenous RNA forms, and provide foundational information for more efficient RNA delivery methods in both genetic manipulation and therapy in different organisms.

Surface modification strategies in translocating nano-vesicles across different barriers and the role of bio-vesicles in improving anticancer therapy

Nanovesicles and bio-vesicles (BVs) have emerged as promising tools to achieve targeted cancer therapy due to their ability to overcome many of the key challenges currently being faced with conventional chemotherapy. These challenges include the diverse and often complex pathophysiology involving the progression of cancer, as well as the various biological barriers that circumvent therapeutic molecules reaching their target site in optimum concentration. The scientific evidence suggests that surface-functionalized nanovesicles and BVs camouflaged nano-carriers (NCs) both can bypass the established biological barriers and facilitate fourth-generation targeting for the improved regimen of treatment. In this review, we intend to emphasize the role of surface-functionalized nanovesicles and BVs camouflaged NCs through various approaches that lead to an improved internalization to achieve improved and targeted oncotherapy. We have explored various strategies that have been employed to surface-functionalize and biologically modify these vesicles, including the use of biomolecule functionalized target ligands such as peptides, antibodies, and aptamers, as well as the targeting of specific receptors on cancer cells. Further, the utility of BVs, which are made from the membranes of cells such as mesenchymal stem cells (MSCs), white blood cells (WBCs), red blood cells (RBCs), platelets (PLTs) as well as cancer cells also been investigated. Lastly, we have discussed the translational challenges and limitations that these NCs can encounter and still need to be overcome in order to fully realize the potential of nanovesicles and BVs for targeted cancer therapy. The fundamental challenges that currently prevent successful cancer therapy and the necessity of novel delivery systems are in the offing.

Triacylglycerol uptake and handling by macrophages: From fatty acids to lipoproteins

Macrophages are essential innate immune cells and form our first line of immune defense. Also known as professional phagocytes, macrophages interact and take up various particles, including lipids. Defective lipid handling can drive excessive lipid accumulation leading to foam cell formation, a key feature of various cardiometabolic conditions such as atherosclerosis, non-alcoholic fatty liver disease, and obesity. At the same time, intracellular lipid storage and foam cell formation can also be viewed as a protective and anti-lipotoxic mechanism against a lipid-rich environment and associated elevated lipid uptake. Traditionally, foam cell formation has primarily been linked to cholesterol uptake via native and modified low-density lipoproteins. However, other lipids, including non-esterified fatty acids and triacylglycerol (TAG)-rich lipoproteins (very low-density lipoproteins and chylomicrons), can also interact with macrophages. Recent studies have identified multiple pathways mediating TAG uptake and processing by macrophages, including endocytosis and receptor/transporter-mediated internalization and transport. This review will present the current knowledge of how macrophages take up different lipids and lipoprotein particles and address how TAG-rich lipoproteins are processed intracellularly. Understanding how macrophages take up and process different lipid species such as TAG is necessary to design future therapeutic interventions to correct excessive lipid accumulation and associated co-morbidities.