Mechanisms of clathrin-mediated endocytosis

Micropterus salmoides rhabdovirus enters cells via clathrin-mediated endocytosis pathway in a pH-, dynamin-, microtubule-, rab5-, and rab7-dependent manner

IMPORTANCE

Although Micropterus salmoides rhabdovirus (MSRV) causes serious fish epidemics worldwide, the detailed mechanism of MSRV entry into host cells remains unknown. Here, we comprehensively investigated the mechanism of MSRV entry into epithelioma papulosum cyprinid (EPC) cells. This study demonstrated that MSRV enters EPC cells via a low pH, dynamin-dependent, microtubule-dependent, and clathrin-mediated endocytosis. Subsequently, MSRV transports from early endosomes to late endosomes and further into lysosomes in a microtubule-dependent manner. The characterization of MSRV entry will further advance the understanding of rhabdovirus cellular entry pathways and provide novel targets for antiviral drug against MSRV infection.

Altered Platelet-Megakaryocyte Endocytosis and Trafficking of Albumin and Fibrinogen in RUNX1 Haplodeficiency

Platelet α-granules have numerous proteins, some synthesized by megakaryocytes (MK) and others not synthesized but incorporated by endocytosis, an incompletely understood process in platelets/MK. Germline RUNX1 haplodeficiency, referred to as familial platelet defect with predisposition to myeloid malignancies (FPDMM), is associated with thrombocytopenia, platelet dysfunction and granule deficiencies. In previous studies, we found that platelet albumin, fibrinogen and IgG levels were decreased in a FPDMM patient. We now show that platelet endocytosis of fluorescent-labeled albumin, fibrinogen and IgG is decreased in the patient and his daughter with FPDMM. In megakaryocytic human erythroleukemia (HEL) cells, siRNA RUNX1 knockdown (KD) increased uptake of these proteins over 24 hours compared to control cells, with increases in caveolin-1 and flotillin-1 (two independent regulators of clathrin-independent endocytosis), LAMP2 (a lysosomal marker), RAB11 (a marker of recycling endosomes) and IFITM3. Caveolin-1 downregulation in RUNX1-deficient HEL cells abrogated the increased uptake of albumin, but not fibrinogen. Albumin, but not fibrinogen, partially colocalized with caveolin-1. RUNX1 knockdown increased colocalization of albumin with flotillin and of fibrinogen with RAB11 suggesting altered trafficking of both. The increased albumin and fibrinogen uptake and levels of caveolin-1, flotillin-1, LAMP2 and IFITM3 were recapitulated by shRNA RUNX1 knockdown in CD34 + -derived MK. These studies provide the first evidence that in RUNX1- haplodeficiency platelet endocytosis of albumin and fibrinogen is impaired and that megakaryocytes have enhanced endocytosis with defective trafficking leading to loss of these proteins by distinct mechanisms. They provide new insights into mechanisms governing endocytosis and α-granule deficiencies in RUNX1- haplodeficiency.

Key points

Platelet content and endocytosis of α-granule proteins, albumin, fibrinogen and IgG, are decreased in germline RUNX1 haplodeficiency. In RUNX1 -deficient HEL cells and primary MK endocytosis is enhanced with defective trafficking leading to decreased protein levels.

Light-dependent inhibition of clathrin-mediated endocytosis in yeast unveils conserved functions of the AP2 complex

Clathrin-mediated endocytosis (CME) is an essential cellular process, conserved among eukaryotes. Yeast constitutes a powerful genetic model to dissect the complex endocytic machinery, yet there is a lack of specific pharmacological agents to interfere with CME in these organisms. TL2 is a light-regulated peptide inhibitor targeting the AP2-β-adaptin/β-arrestin interaction and that can photocontrol CME with high spatiotemporal precision in mammalian cells. Here, we study endocytic protein dynamics by live-cell imaging of the fluorescently tagged coat-associated protein Sla1-GFP, demonstrating that TL2 retains its inhibitory activity in S. cerevisiae spheroplasts. This is despite the β-adaptin/β-arrestin interaction not being conserved in yeast. Our data indicate that the AP2 α-adaptin is the functional target of activated TL2. We identified as interacting partners for the α-appendage, the Eps15 and epsin homologues Ede1 and Ent1. This demonstrates that endocytic cargo loading and sensing can be executed by conserved molecular interfaces, regardless of the proteins involved.

Nanotechnology-empowered strategies in treatment of skin cancer

In current scenario skin cancer is a serious condition that has a significant impact on world health. Skin cancer is divided into two categories: melanoma skin cancer (MSC) and non-melanoma skin cancer (NMSC). Because of its significant psychosocial effects and need for significant investment in new technology and therapies, skin cancer is an illness of global health relevance. From the patient's perspective chemotherapy considered to be the most acceptable form of treatment. However, significant negatives of chemotherapy such as severe toxicities and drug resistance pose serious challenges to the treatment. The field of nanomedicine holds significant promise for enhancing the specificity of targeting neoplastic cells through the facilitation of targeted drug delivery to tumour cells. The integration of multiple therapeutic modalities to selectively address cancer-promoting or cell-maintaining pathways constitutes a fundamental aspect of cancer treatment. The use of mono-therapy remains prevalent in the treatment of various types of cancer, it is widely acknowledged in the academic community that this conventional approach is generally considered to be less efficacious compared to the combination treatment strategy. The employment of combination therapy in cancer treatment has become increasingly widespread due to its ability to produce synergistic anticancer effects, mitigate toxicity associated with drugs, and inhibit multi-drug resistance by means of diverse mechanisms. Nanotechnology based combination therapy represents a promising avenue for the development of efficacious therapies for skin cancer within the context of this endeavour. The objective of this article is to provide a description of distinct challenges for efficient delivery of drugs via skin. This article also provides a summary of the various nanotechnology based combinatorial therapy available for skin cancer with their recent advances. This review also focuses on current status of clinical trials of such therapies.

Force redistribution in clathrin-mediated endocytosis revealed by coiled-coil force sensors

Forces are central to countless cellular processes, yet in vivo force measurement at the molecular scale remains difficult if not impossible. During clathrin-mediated endocytosis, forces produced by the actin cytoskeleton are transmitted to the plasma membrane by a multiprotein coat for membrane deformation. However, the magnitudes of these forces remain unknown. Here, we present new in vivo force sensors that induce protein condensation under force. We measured the forces on the fission yeast Huntingtin-Interacting Protein 1 Related (HIP1R) homolog End4p, a protein that links the membrane to the actin cytoskeleton. End4p is under ~19-piconewton force near the actin cytoskeleton, ~11 piconewtons near the clathrin lattice, and ~9 piconewtons near the plasma membrane. Our results demonstrate that forces are collected and redistributed across the endocytic machinery.

Biodistribution of Fluorescent Albumin Nanoparticles among Organs of Laboratory Animals after Intranasal and Peroral Administration

Natural, environmental and engineered nanoparticles (NP) penetrate into cells by endocytosis and induce innate immunity. The behaviour of the nanomaterials both in vitro and in vivo should be assessed. Our goal was to study protein NP stability in biological fluids and distribution in organs of animals after intranasal and oral administration. Bovine serum albumin (BSA) was labelled with the fluorescent dye RhoB and NP were fabricated by nanoprecipitation. The fluorescent protein NPwere administered intranasally and orally in laboratory-outbred mice ICR and rabbits. RhoB-BSA NP distribution in organs was detected using spectrofluorometry and fluorescent microscopy. Innate immunity was evaluated using reverse transcription with random hexanucleotide primer and subsequent real-time PCR with specific fluorescent hydrolysis probes. The labelled BSA NP were shown to remain stable in blood sera and nasopharyngeal swabs for 5 days at +37 °C. In vivo the maximal accumulation was found in the brain in 2 days posttreatment without prevalent accumulation in olfactory bulbs. For the intestine, heart and liver, the BSA NP accumulation was similar in 1 and 2 days, whereas for kidney samples even decreased after 1 day. Both intranasal and peroral administration of RhoB-BSA NP did not induce innate immunity. Thus, after intranasal or oral instillation RhoB-BSA NP were found mainly in the brain and intestine without interferon gene expression.

Cell lipid biology in infections: an overview

Lipids are a big family of molecules with a vast number of functions in the cell membranes, within the cytoplasm, and extracellularly. Lipid droplets (LDs) are the most common storage organelles and are present in almost every tissue type in the body. They also have structural functions serving as building blocks of cellular membranes and may be precursors of other molecules such as hormones, and lipoproteins, and as messengers in signal transduction. Fatty acids (FAs), such as sterol esters and triacylglycerols, are stored in LDs and are used in β-oxidation as fuel for tricarboxylic acid cycle (TCA) and adenosine triphosphate (ATP) generation. FA uptake and entrance in the cytoplasm are mediated by membrane receptors. After a cytoplasmic round of α- and β-oxidation, FAs are guided into the mitochondrial matrix by the L-carnitine shuttle system, where they are fully metabolized, and enter the TCA cycle. Pathogen infections may lead to impaired lipid metabolism, usage of membrane phospholipids, and LD accumulation in the cytoplasm of infected cells. Otherwise, bacterial pathogens may use lipid metabolism as a carbon source, thus altering the reactions and leading to cellular and organelles malfunctioning. This review aims to describe cellular lipid metabolism and alterations that occur upon infections.

MYL3 protects chondrocytes from senescence by inhibiting clathrin-mediated endocytosis and activating of Notch signaling

As the unique cell type in articular cartilage, chondrocyte senescence is a crucial cellular event contributing to osteoarthritis development. Here we show that clathrin-mediated endocytosis and activation of Notch signaling promotes chondrocyte senescence and osteoarthritis development, which is negatively regulated by myosin light chain 3. Myosin light chain 3 (MYL3) protein levels decline sharply in senescent chondrocytes of cartilages from model mice and osteoarthritis (OA) patients. Conditional deletion of Myl3 in chondrocytes significantly promoted, whereas intra-articular injection of adeno-associated virus overexpressing MYL3 delayed, OA progression in male mice. MYL3 deficiency led to enhanced clathrin-mediated endocytosis by promoting the interaction between myosin VI and clathrin, further inducing the internalization of Notch and resulting in activation of Notch signaling in chondrocytes. Pharmacologic blockade of clathrin-mediated endocytosis-Notch signaling prevented MYL3 loss-induced chondrocyte senescence and alleviated OA progression in male mice. Our results establish a previously unknown mechanism essential for cellular senescence and provide a potential therapeutic direction for OA.

Integration of Protein Nanocage with CpG Motifs: A Virus-Mimicked Core-Shell Nanostructure to Ignite Antitumor Immunity

The tumor microenvironment typically possesses immunosuppressive properties that hinder the effectiveness of antitumor immune responses, even in the context of immunotherapies. However, it is observed that pathogenic microorganisms can trigger strong immune responses during infection, offering a potential means to counteract the immunosuppressive environment of tumors. In this study, a protein nanocage called CpG@HBc nanocages (NCs) is developed, which mimics the structure of the hepatitis B virus and combines with an immunostimulatory component known as cytosine phosphoguanosine oligonucleotide (CpG). By delivering these immunostimulatory agents, CpG@HBc NCs are able to effectively reverse the suppressive tumor microenvironment, resulting in the inhibition of poorly immunogenic tumors in mice. Through high-dimensional mass cytometry (CyTOF) analysis, remarkable alterations in immune responses is observed induced by CpG@HBc. Treatment with immunogenic CpG@HBc NCs, along with co-injection of an OX40 agonist, sensitized colorectal cancer tumors to T cell immune responses, resulting in significant impairment of tumor growth and robust immune activation. Furthermore, CpG@HBc NCs induced long-term antitumor immunological memory, protecting tumor-cured mice from tumor rechallenge. Overall, these findings highlight the potential of a virus-inspired protein nanocage to mimic anti-viral immunity and offer a unique therapeutic approach for cancer immunotherapy.

Placenta-Derived Extracellular Vesicles From Preeclamptic Pregnancies Impair Vascular Endothelial Function via Lectin-Like Oxidized LDL Receptor-1

BACKGROUND

Preeclampsia is a complex syndrome that includes maternal vascular dysfunction. Syncytiotrophoblast-derived extracellular vesicles from preeclampsia placentas (preeclampsia-STBEVs) were shown to induce endothelial dysfunction, but an endothelial transmembrane mediator is still unexplored. The LOX-1 (lectin-like oxidized low-density lipoprotein receptor-1) is a transmembrane scavenger receptor that can cause endothelial dysfunction, and its expression is increased in the endothelium of preeclampsia women. In this study, we hypothesized that LOX-1 mediates the effects of preeclampsia-STBEVs on endothelial function.

METHODS

Preeclampsia-STBEVs were collected by perfusion of placentas from women with preeclampsia and in vitro and ex vivo endothelial cell function were assessed.

RESULTS

In human umbilical vein endothelial cells, inhibition of LOX-1 with LOX-1 blocking antibody (TS20) reduced the uptake of preeclampsia-STBEVs (61.3±8.8%). TS20 prevented the activation of ERK (extracellular signal-regulated kinase, a kinase downstream of LOX-1) and reduced the activation of NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells; 21.1±8.0%) and nitrative stress (23.2±10.3%) that was induced by preeclampsia-STBEVs. Vascular function was assessed by wire myography in isolated mesenteric arteries from pregnant rats that were incubated overnight with preeclampsia-STBEVs±TS20. TS20 prevented endothelium-dependent vasodilation impairment induced by preeclampsia-STBEVs. Nitric oxide contribution to the relaxation was reduced by preeclampsia-STBEVs, which was prevented by TS20. Superoxide dismutase or apocynin, an inhibitor of NOX (nicotinamide adenine dinucleotide phosphate oxidase), restored the impaired endothelium-dependent vasodilation in arteries exposed to preeclampsia-STBEVs.

CONCLUSIONS

Taken together, our findings demonstrate that LOX-1 mediates the endothelial dysfunction induced by preeclampsia-STBEVs. Our study further expands on the mechanisms that may lead to adverse outcomes in preeclampsia and proposes LOX-1 as a potential target for future interventions.

Cold atmospheric plasma mediated cell membrane permeation and gene delivery-empirical interventions and pertinence

Delivery of genetic material to cells is an integral tool to analyze and reveal the genetic interventions in normal cellular processes and differentiation, disease development and for gene therapy. It has profound applications in pharmaceutical, agricultural, environmental and biotechnological sectors. The major methods relied for gene delivery or transfection requires either viral vectors or xenogenic carrier molecules, which renders probabilistic carcinogenic, immunogenic and toxic effects. A newly evolved physical method, Cold atmospheric plasma induced transfection neither needs vector nor carriers. The 4th state of matter 'Plasma' is a quasineutral ionized gas-containing ions, neutral atoms, electrons and reactive radical molecules; and possess electric and magnetic field, along with emanating photons and UV radiations. Plasma produced at atmospheric pressure conditions, and having room temperature is conferred as Low temperature plasma or Cold atmospheric plasma. Selective and controlled application of cold atmospheric plasma on tissues creates temporary, restorable pores on cell membranes that could be diligently manipulated for gene delivery. Research in this regard attained pace since 2016. Cold atmospheric plasma induces transfection by lipid peroxidation, electroporation, and clathrin dependent endocytosis in cell membranes, by virtue of its reactive radicals and electric field. Plasma formed reactive radicals, especially 'OH' penetrates to the cell membrane and cleaves the phosphate head group of membrane lipids, peroxidize and detaches fatty acid tails. This decreases membrane thickness, increases membrane fluidity and permeability. Simultaneously plasma formed ions, electrons and reactive radicals accumulate over cells, generating local electric field and neutralize the negative charge of cell membrane. This induces stress on cell membrane and disrupts its structural integrity, by infringing the dynamic equilibrium between surface tension, spatial repulsion and linear tension between the head groups of phospholipids, generating minute pores. Neutralization of membrane charge promote foreign, external plasmid and gene movement towards cells and its enhanced binding with ligands and receptors on cell membrane, instigating clathrin dependent endocytosis. In vitro and in vivo studies have successfully delivered plasmids, linear DNA, siRNA and miRNA to several established cell lines like, HeLa, PC12, CHL, HUVEC, Jurkat, MCF, SH-SY5Y, HT, B16F10, HaCaT, LP-1, etc., and live C57BL/6 and BALB/c mice, using cold atmospheric plasma. This review delineates the cell surface mechanism of plasma-induced transfection, critically summarizes the research progress in this context, plasma devices used, and the inimitable features of this method. Metabolic activity, cell function, and viability are not adversely affected by this process; moreover, the cell permeating plasma-formed reactive radicals are effectively defended by cellular antioxidant mechanisms like superoxide dismutase, glutathione reductase and cytokines, alleviating its toxicity. A deeper understanding on mechanism of plasma action on cells, its aftermath, and the research status in this field would provide a better insight on future avenues of research.

Cellular uptake and trafficking of peptide-based drug delivery systems for miRNA

Today, macromolecular compounds such as microRNAs (miRNAs) are becoming more and more widespread as leading therapeutics. However, their application is limited mostly due to their poor stability, limited cellular uptake, and poor target specificity. Cell-penetrating peptides (CPPs), a group of positively charged peptides, represent a breakthrough as delivery systems for macromolecules. In the present study, we used two types of nanoparticles which differ in the type of CPP used for their manufacturing. The first type is composed of protamine, an arginine rich CPP, which is highly positively charged. The arginine residues are able to form electrostatic interactions with miRNAs, stabilize them, and deliver them to cells. The second type is composed of the N-Ter peptide (also known as MPG), an amphipathic peptide rich in lysine. The positively charged parts of the N-Ter peptide electrostatically stabilize miRNAs, whereas its amphipathic character allows it to successfully traverse cell membranes. We used miRNA-27a, a negative regulator of adipogenesis, to form nanoparticles with the peptides and traced their uptake in 3T3-L1 preadipocytes. Motivated by the lengthy discourse regarding the uptake mechanism of CPPs, the focus of our study was to analyse and understand the internalization of proticles (protamine nanoparticles) and N-Ter complexes. The nanoparticles were characterized regarding size, size distribution, and zeta potential, and their cytotoxicity was tested in 3T3-L1 cells. The uptake studies were performed by varying the experimental conditions such as time, concentration, and temperature, as well as by applying different inhibitors of endocytosis. Furthermore, we assessed the biological effect of miRNA-27a on the pro-adipogenic machinery. The obtained data have shown that protamine and the N-Ter peptide form positively charged nanoparticles through non-covalent complexation. The uptake of proticles and N-Ter complexes was found to be dependent on time, concentration, and temperature, and different uptake pathways were discovered to be involved in the internalization of the different nanoparticles. Furthermore, both types of nanoparticles induced the anti-adipogenic effect of miRNA-27a, demonstrating that this approach can be used as a novel miRNA replacement therapy in the treatment of obesity and obesity-related disorders.

A clathrin-related protein FaRRP1/SCD2 integrates ABA trafficking and signaling to regulate strawberry fruit ripening

Abscisic acid (ABA) is a critical regulator for nonclimacteric fruit ripening such as in the model plant of strawberry (Fragaria × ananassa). Although FaRRP1 is proposed to participate in clathrin-mediated endocytosis of ABA, its action molecular mechanisms in ABA signaling are not fully understood. Here, using our isolated FaRRP1 (ripening-regulation protein) and candidate ABA receptor FaPYL2 and FaABAR from strawberry fruit, a series of silico and molecular interaction analyses demonstrate that they all bind to ABA, and FaRRP1 binds both FaPYL2 and FaABAR; by contrast, the binding affinity of FaRRP1 to FaPYL2 is relatively higher. Interestingly, the binding of FaRRP1 to FaPYL2 and FaABAR affects the perception affinity to ABA. Furthermore, exogenous ABA application and FaRRP1 transgenic analyses confirm that FaRRP1 participates in clathrin-mediated endocytosis and vesicle transport. Importantly, FaRRP1, FaPYL2, and FaABAR all trigger the initiation of strawberry fruit ripening at physiological and molecular levels. In conclusion, FaRRP1 not only binds to ABA but also affects the binding affinity of FaPYL2 and FaABAR to ABA, thus promoting strawberry fruit ripening. Our findings provide novel insights into the role of FaRRP1 in ABA trafficking and signaling, at least in strawberry, a model plant for nonclimacteric fruit ripening.

A Comparison of Cellular Uptake Mechanisms, Delivery Efficacy, and Intracellular Fate between Liposomes and Extracellular Vesicles

A key aspect for successful drug delivery via lipid-based nanoparticles is their internalization in target cells. Two prominent examples of such drug delivery systems are artificial phospholipid-based carriers, such as liposomes, and their biological counterparts, the extracellular vesicles (EVs). Despite a wealth of literature, it remains unclear which mechanisms precisely orchestrate nanoparticle-mediated cargo delivery to recipient cells and the subsequent intracellular fate of therapeutic cargo. In this review, internalization mechanisms involved in the uptake of liposomes and EVs by recipient cells are evaluated, also exploring their intracellular fate after intracellular trafficking. Opportunities are highlighted to tweak these internalization mechanisms and intracellular fates to enhance the therapeutic efficacy of these drug delivery systems. Overall, literature to date shows that both liposomes and EVs are predominantly internalized through classical endocytosis mechanisms, sharing a common fate: accumulation inside lysosomes. Studies tackling the differences between liposomes and EVs, with respect to cellular uptake, intracellular delivery and therapy efficacy, remain scarce, despite its importance for the selection of an appropriate drug delivery system. In addition, further exploration of functionalization strategies of both liposomes and EVs represents an important avenue to pursue in order to control internalization and fate, thereby improving therapeutic efficacy.

Polyethylenimine (PEI) in gene therapy: Current status and clinical applications

Polyethlyenimine (PEI) was introduced 1995 as a cationic polymer for nucleic acid delivery. PEI and its derivatives are extensively used in basic research and as reference formulations in the field of polymer-based gene delivery. Despite its widespread use, the number of clinical applications to date is limited. Thus, this review aims to consolidate the past applications of PEI in DNA delivery, elucidate the obstacles that hinder its transition to clinical use, and highlight potential prospects for novel iterations of PEI derivatives. The present review article is divided into three sections. The first section examines the mechanism of action employed by PEI, examining fundamental aspects of cellular delivery including uptake mechanisms, release from endosomes, and transport into the cell nucleus, along with potential strategies for enhancing these delivery phases. Moreover, an in-depth analysis is conducted concerning the mechanism underlying cellular toxicity, accompanied with approaches to overcome this major challenge. The second part is devoted to the in vivo performance of PEI and its application in various therapeutic indications. While systemic administration has proven to be challenging, alternative localized delivery routes hold promise, such as treatment of solid tumors, application as a vaccine, or serving as a therapeutic agent for pulmonary delivery. In the last section, the outcome of completed and ongoing clinical trials is summarized. Finally, an expert opinion is provided on the potential of PEI and its future applications. PEI-based formulations for nucleic acid delivery have a promising potential, it will be an important task for the years to come to introduce innovations that address PEI-associated shortcomings by introducing well-designed PEI formulations in combination with an appropriate route of administration.

The hybrid RAVE complex plays V-ATPase-dependent and -independent pathobiological roles in Cryptococcus neoformans

V-ATPase, which comprises 13-14 subunits, is essential for pH homeostasis in all eukaryotes, but its proper function requires a regulator to assemble its subunits. While RAVE (regulator of H+-ATPase of vacuolar and endosomal membranes) and Raboconnectin-3 complexes assemble V-ATPase subunits in Saccharomyces cerevisiae and humans, respectively, the function of the RAVE complex in fungal pathogens remains largely unknown. In this study, we identified two RAVE complex components, Rav1 and Wdr1, in the fungal meningitis pathogen Cryptococcus neoformans, and analyzed their roles. Rav1 and Wdr1 are orthologous to yeast RAVE and human Rabconnectin-3 counterparts, respectively, forming the hybrid RAVE (hRAVE) complex. Deletion of RAV1 caused severe defects in growth, cell cycle control, morphogenesis, sexual development, stress responses, and virulence factor production, while the deletion of WDR1 resulted in similar but modest changes, suggesting that Rav1 and Wdr1 play central and accessary roles, respectively. Proteomics analysis confirmed that Wdr1 was one of the Rav1-interacting proteins. Although the hRAVE complex generally has V-ATPase-dependent functions, it also has some V-ATPase-independent roles, suggesting a unique role beyond conventional intracellular pH regulation in C. neoformans. The hRAVE complex played a critical role in the pathogenicity of C. neoformans, and RAV1 deletion attenuated virulence and impaired blood-brain barrier crossing ability. This study provides comprehensive insights into the pathobiological roles of the fungal RAVE complex and suggests a novel therapeutic strategy for controlling cryptococcosis.

Functional genomics identify causal variant underlying the protective CTSH locus for Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent age-related neurodegenerative disease, which has a high heritability of up to 79%. Exploring the genetic basis is essential for understanding the pathogenic mechanisms underlying AD development. Recent genome-wide association studies (GWASs) reported an AD-associated signal in the Cathepsin H (CTSH) gene in European populations. However, the exact functional/causal variant(s), and the genetic regulating mechanism of CTSH in AD remain to be determined. In this study, we carried out a comprehensive study to characterize the role of CTSH variants in the pathogenesis of AD. We identified rs2289702 in CTSH as the most significant functional variant that is associated with a protective effect against AD. The genetic association between rs2289702 and AD was validated in independent cohorts of the Han Chinese population. The CTSH mRNA expression level was significantly increased in AD patients and AD animal models, and the protective allele T of rs2289702 was associated with a decreased expression level of CTSH through the disruption of the binding affinity of transcription factors. Human microglia cells with CTSH knockout showed a significantly increased phagocytosis of Aβ peptides. Our study identified CTSH as being involved in AD genetic susceptibility and uncovered the genetic regulating mechanism of CTSH in pathogenesis of AD.

Macropinocytosis in Gracilariopsis lemaneiformis (Rhodophyta)

Macropinocytosis is an endocytic process that plays an important role in animal development and disease occurrence but until now has been rarely reported in organisms with cell walls. We investigated the properties of endocytosis in a red alga, Gracilariopsis lemaneiformis. The cells non-selectively internalized extracellular fluid into large-scale endocytic vesicles (1.94 ± 0.51 μm), and this process could be inhibited by 5-(N-ethyl-N-isopropyl) amiloride, an macropinocytosis inhibitor. Moreover, endocytosis was driven by F-actin, which promotes formation of ruffles and cups from the cell surface and facilitates formation of endocytotic vesicles. After vesicle formation, endocytic vesicles could be acidified and acquire digestive function. These results indicated macropinocytosis in G. lemaneiformis. Abundant phosphatidylinositol kinase and small GTPase encoding genes were found in the genome of this alga, while PI3K, Ras, and Rab5, the important participators of traditional macropinocytosis, seem to be lacked. Such findings provide a new insight into endocytosis in organisms with cell walls and facilitate further research into the core regulatory mechanisms and evolution of macropinocytosis.

Emerging roles of proximal tubular endocytosis in renal fibrosis

Endocytosis is a crucial component of many pathological conditions. The proximal tubules are responsible for reabsorbing the majority of filtered water and glucose, as well as all the proteins filtered through the glomerular barrier via endocytosis, indicating an essential role in kidney diseases. Genetic mutations or acquired insults could affect the proximal tubule endocytosis processes, by disturbing or overstressing the endolysosomal system and subsequently activating different pathways, orchestrating renal fibrosis. This paper will review recent studies on proximal tubular endocytosis affected by other diseases and factors. Endocytosis plays a vital role in the development of renal fibrosis, and renal fibrosis could also, in turn, affect tubular endocytosis.

Designed Endocytosis-Triggering Proteins mediate Targeted Degradation

Endocytosis and lysosomal trafficking of cell surface receptors can be triggered by interaction with endogenous ligands. Therapeutic approaches such as LYTAC1,2 and KineTAC3, have taken advantage of this to target specific proteins for degradation by fusing modified native ligands to target binding proteins. While powerful, these approaches can be limited by possible competition with the endogenous ligand(s), the requirement in some cases for chemical modification that limits genetic encodability and can complicate manufacturing, and more generally, there may not be natural ligands which stimulate endocytosis through a given receptor. Here we describe general protein design approaches for designing endocytosis triggering binding proteins (EndoTags) that overcome these challenges. We present EndoTags for the IGF-2R, ASGPR, Sortillin, and Transferrin receptors, and show that fusing these tags to proteins which bind to soluble or transmembrane protein leads to lysosomal trafficking and target degradation; as these receptors have different tissue distributions, the different EndoTags could enable targeting of degradation to different tissues. The modularity and genetic encodability of EndoTags enables AND gate control for higher specificity targeted degradation, and the localized secretion of degraders from engineered cells. The tunability and modularity of our genetically encodable EndoTags should contribute to deciphering the relationship between receptor engagement and cellular trafficking, and they have considerable therapeutic potential as targeted degradation inducers, signaling activators for endocytosis-dependent pathways, and cellular uptake inducers for targeted antibody drug and RNA conjugates.

Unravelling the Mystery inside Cells by Using Single-Molecule Fluorescence Imaging

Live-cell imaging is a powerful technique to study the dynamics and mechanics of various biological molecules like proteins, organelles, DNA, and RNA. With the rapid evolution of optical microscopy, our understanding of how these molecules are implicated in the cells' most critical physiological roles deepens. In this review, we focus on how spatiotemporal nanoscale live-cell imaging at the single molecule level allows for profound contributions towards new discoveries in life science. This review will start by summarizing how single-molecule tracking has been used to analyze membrane dynamics, receptor-ligand interactions, protein-protein interactions, inner- and extra-cellular transport, gene expression/transcription, and whole organelle tracking. We then move on to how current authors are trying to improve single-molecule tracking and overcome current limitations by offering new ways of labeling proteins of interest, multi-channel/color detection, improvements in time-lapse imaging, and new methods and programs to analyze the colocalization and movement of targets. We later discuss how single-molecule tracking can be a beneficial tool used for medical diagnosis. Finally, we wrap up with the limitations and future perspectives of single-molecule tracking and total internal reflection microscopy.

The Chemical Inhibitors of Endocytosis: From Mechanisms to Potential Clinical Applications

Endocytosis is one of the major ways cells communicate with their environment. This process is frequently hijacked by pathogens. Endocytosis also participates in the oncogenic transformation. Here, we review the approaches to inhibit endocytosis, discuss chemical inhibitors of this process, and discuss potential clinical applications of the endocytosis inhibitors.

Engineered Histidine-Rich Peptides Enhance Endosomal Escape for Antibody-Targeted Intracellular Delivery of Functional Proteins

Currently, the clinical application of protein/peptide therapeutics is mainly limited to the modulation of diseases in extracellular spaces. Intracellular targets are hardly accessed, owing largely to the endosomal entrapment of internalized proteins/peptides. Here, we report a strategy to design and construct peptides that enable endosome-to-cytosol delivery based on an extension of the "histidine switch" principle. By substituting the Arg/Lys residues in cationic cell-penetrating peptides (CPPs) with histidine, we obtained peptides with pH-dependent membrane-perturbation activity. These peptides do not randomly penetrate cells like CPPs, but imitate the endosomal escape of CPPs following cellular uptake. Working with one such 16-residue peptide (hsLMWP) with high endosomal escape capacity, we engineered modular fusion proteins and achieved antibody-targeted delivery of diverse protein cargoes-including the pro-apoptotic protein BID (BH3-interacting domain death agonist) and Cre recombinase-into the cytosol of multiple cancer cell types. After extensive in vitro testing, an in vivo analysis with xenograft mice ultimately demonstrated that a trastuzumab-hsLMWP-BID fusion conferred strong anti-tumor efficacy without apparent side effects. Notably, our fusion protein features a modular design, allowing flexible applications for any antibody/cargo combination of choice. Therefore, the potential applications extend throughout life science and biomedicine, including gene editing, cancer treatment, and immunotherapy.

Attachment, Entry, and Intracellular Trafficking of Classical Swine Fever Virus

Classical swine fever virus (CSFV), which is a positive-sense, single-stranded RNA virus with an envelope, is a member of the Pestivirus genus in the Flaviviridae family. CSFV causes a severe and highly contagious disease in pigs and is prevalent worldwide, threatening the pig farming industry. The detailed mechanisms of the CSFV life cycle have been reported, but are still limited. Some receptors and attachment factors of CSFV, including heparan sulfate (HS), laminin receptor (LamR), complement regulatory protein (CD46), MER tyrosine kinase (MERTK), disintegrin, and metalloproteinase domain-containing protein 17 (ADAM17), were identified. After attachment, CSFV internalizes via clathrin-mediated endocytosis (CME) and/or caveolae/raft-dependent endocytosis (CavME). After internalization, CSFV moves to early and late endosomes before uncoating. During this period, intracellular trafficking of CSFV relies on components of the endosomal sorting complex required for transport (ESCRT) and Rab proteins in the endosome dynamics, with a dependence on the cytoskeleton network. This review summarizes the data on the mechanisms of CSFV attachment, internalization pathways, and intracellular trafficking, and provides a general view of the early events in the CSFV life cycle.

Respiratory syncytial virus entry mechanism in host cells: A general overview

Respiratory syncytial virus (RSV) is a virus that causes acute respiratory infections in neonates and older adults. To infect host cells, the attachment glycoprotein (G) interacts with a cell surface receptor. This interaction determines the specific cell types that are susceptible to infection. RSV possesses a type I fusion protein F. Type I fusion proteins are metastable when rearrangement of the prefusion F occurs; the fusion peptide is exposed transforming the protein into postfusion form. The transition between the prefusion form and its postfusion form facilitates the viral envelope and the host cell membrane to fuse, enabling the virus to enter the host cell. Understanding the entry mechanism employed by RSV is crucial for developing effective antiviral therapies. In this review, we will discuss the various types of viral fusion proteins and explore the potential entry mechanisms utilized by RSV. A deeper understanding of these mechanisms will provide valuable insights for the development of novel approaches to treat RSV infections.

Distinct role of TGN-resident clathrin adaptors for Vps21p activation in the TGN-endosome trafficking pathway

Clathrin-mediated vesicle trafficking plays central roles in post-Golgi transport. In yeast (Saccharomyces cerevisiae), the AP-1 complex and GGA adaptors are predicted to generate distinct transport vesicles at the trans-Golgi network (TGN), and the epsin-related proteins Ent3p and Ent5p (collectively Ent3p/5p) act as accessories for these adaptors. Recently, we showed that vesicle transport from the TGN is crucial for yeast Rab5 (Vps21p)-mediated endosome formation, and that Ent3p/5p are crucial for this process, whereas AP-1 and GGA adaptors are dispensable. However, these observations were incompatible with previous studies showing that these adaptors are required for Ent3p/5p recruitment to the TGN, and thus the overall mechanism responsible for regulation of Vps21p activity remains ambiguous. Here, we investigated the functional relationships between clathrin adaptors in post-Golgi-mediated Vps21p activation. We show that AP-1 disruption in the ent3Δ5Δ mutant impaired transport of the Vps21p guanine nucleotide exchange factor Vps9p transport to the Vps21p compartment and severely reduced Vps21p activity. Additionally, GGA adaptors, the phosphatidylinositol-4-kinase Pik1p and Rab11 GTPases Ypt31p and Ypt32p were found to have partially overlapping functions for recruitment of AP-1 and Ent3p/5p to the TGN. These findings suggest a distinct role of clathrin adaptors for Vps21p activation in the TGN-endosome trafficking pathway.

Comparison of endocytosis pathways of Duck Tembusu virus in BHK-21 and duck embryo fibroblasts

The Duck Tembusu virus (DTMUV) is a zoonotic flavivirus characterized by nonsuppurative encephalitis and decreasing egg production that has adversely affected the poultry industry. While the way of invasion of DTMUV into different host cells, especially primary cells, remains elusive. In the present study, the ultrastructural pathological characteristics showed that DTMUV underwent a typical maturation and replication process: progeny virus particles gathered in rough endoplasmic reticulum (RER) cisternae, reached the cell membrane via Golgi body's endocrine channel, then were released in the infected baby hamster kidney-21 (BHK-21) and duck embryo fibroblast (DEF). Endoplasmic reticulum vesicles in BHK-21 were short rods and densely arranged like honeycombs, whereas vesicles in DEF were round and dispersed. Further study showed that the virus replication peak in mammalian BHK-21 cells was at 48 hpi, whereas in avian DEF cells was at 24 hpi. DTMUV entry into BHK-21 and DEF cells was blocked by clathrin inhibitor, chlorpromazine (CPZ), indicating that the flavivirus DTMUV enters BHK-21 and DEF both via a clathrin-mediated endocytosis (CME) pathway rather than caveola-mediated endocytosis or micropinocytosis. The endocytic difference in DTMUV entry into BHK-21 and DEF cells might provide insight into understanding the underlying virulence difference between passaged cells and cultured cells.

Lipid nanodiscs as a template for high-resolution cryo-EM structures of peripheral membrane proteins

Peripheral membrane proteins are ubiquitous throughout cell biology and are required for a variety of cellular processes such as signal transduction, membrane trafficking, and autophagy. Transient binding to the membrane has a profound impact on protein function, serving to induce conformational changes and alter biochemical and biophysical parameters by increasing the local concentration of factors and restricting diffusion to two dimensions. Despite the centrality of the membrane in serving as a template for cell biology, there are few reported high-resolution structures of peripheral membrane proteins bound to the membrane. We analyzed the utility of lipid nanodiscs to serve as a template for cryo-EM analysis of peripheral membrane proteins. We tested a variety of nanodiscs and we report a 3.3 Å structure of the AP2 clathrin adaptor complex bound to a 17-nm nanodisc, with sufficient resolution to visualize a bound lipid head group. Our data demonstrate that lipid nanodiscs are amenable to high-resolution structure determination of peripheral membrane proteins and provide a framework for extending this analysis to other systems.

Tension-tuned receptors for synthetic mechanotransduction and intercellular force detection

Cells interpret mechanical stimuli from their environments and neighbors, but the ability to engineer customized mechanosensing capabilities has remained a synthetic and mechanobiology challenge. Here we introduce tension-tuned synthetic Notch (SynNotch) receptors to convert extracellular and intercellular forces into specifiable gene expression changes. By elevating the tension requirements of SynNotch activation, in combination with structure-guided mutagenesis, we designed a set of receptors with mechanical sensitivities spanning the physiologically relevant picoNewton range. Cells expressing these receptors can distinguish between varying tensile forces and respond by enacting customizable transcriptional programs. We applied these tools to design a decision-making circuit, through which fibroblasts differentiate into myoblasts upon stimulation with distinct tension magnitudes. We also characterize cell-generated forces transmitted between cells during Notch signaling. Overall, this work provides insight into how mechanically induced changes in protein structure can be used to transduce physical forces into biochemical signals. The system should facilitate the further programming and dissection of force-related phenomena in biological systems.

What can we do to optimize mitochondrial transplantation therapy for myocardial ischemia-reperfusion injury?

Mitochondrial transplantation is a promising solution for the heart following ischemia-reperfusion injury due to its capacity to replace damaged mitochondria and restore cardiac function. However, many barriers (such as inadequate mitochondrial internalization, poor survival of transplanted mitochondria, few mitochondria colocalized with cardiac cells) compromise the replacement of injured mitochondria with transplanted mitochondria. Therefore, it is necessary to optimize mitochondrial transplantation therapy to improve clinical effectiveness. By analogy, myocardial ischemia-reperfusion injury is like a withered flower, it needs to absorb enough nutrients to recover and bloom. In this review, we present a comprehensive overview of "nutrients" (source of exogenous mitochondria and different techniques for mitochondrial isolation), "absorption" (mitochondrial transplantation approaches, mitochondrial transplantation dose and internalization mechanism), and "flowering" (the mechanism of mitochondrial transplantation in cardioprotection) for myocardial ischemia-reperfusion injury.

ORFV entry into host cells via clathrin-mediated endocytosis and macropinocytosis

Orf virus (ORFV), also known as infectious pustular virus, leads to an acute contagious zoonotic infectious disease. ORFV can directly contact and infect epithelial cells of skin and mucosa, causing damage to tissue cells. So far, the pathway of ORFV entry into cells is unclear. Therefore, finding the internalization pathway of ORFV will help to elucidate the cellular and molecular mechanisms of ORFV infection and invasion, which in turn will provide a certain reference for the prevention and treatment of ORFV. In the present study, chemical inhibitors were used to analyze the mechanism of ORFV entry into target cells. The results showed that the inhibitor of clathrin-mediated endocytosis could inhibit ORFV entry into cells. However, the inhibitor of caveolae-mediated endocytosis cannot inhibit ORFV entry into cells. In addition, inhibition of macropinocytosis pathway also significantly reduced ORFV internalization. Furthermore, the inhibitors of acidification and dynamin also prevented ORFV entry. However, results demonstrated that inhibitors inhibited ORFV entry but did not inhibit ORFV binding. Notably, extracellular trypsin promoted ORFV entry into cells directly, even when the endocytic pathway was inhibited. In conclusion, ORFV enters into its target cells by clathrin-mediated endocytosis and macropinocytosis, while caveolae-dependent endocytosis has little effects on this process. In addition, the entry into target cells by ORFV required an acid environment and the effect of dynamin. Meanwhile, we emphasize that broad-spectrum antiviral inhibitors and extracellular enzyme inhibitors are likely to be effective strategies for the prevention and treatment of ORFV infection.

Bacterial Membrane Vesicles: Physiological Roles, Infection Immunology, and Applications

Bacterial or fungal membrane vesicles, traditionally considered as microbial metabolic wastes, are secreted mainly from the outer membrane or cell membrane of microorganisms. However, recent studies have shown that these vesicles play essential roles in direct or indirect communications among microorganisms and between microorganisms and hosts. This review aims to provide an updated understanding of the physiological functions and emerging applications of bacterial membrane vesicles, with a focus on their biogenesis, mechanisms of adsorption and invasion into host cells, immune stimulatory effects, and roles in the much-concerned problem of bacterial resistance. Additionally, the potential applications of these vesicles as biomarkers, vaccine candidates, and drug delivery platforms are discussed.

Protein phase separation in plant membrane biology: more than just a compartmentalization strategy

The formation of biomolecular condensates through phase separation is an important strategy to compartmentalize cellular functions. While it is now well established that condensates exist throughout eukaryotic cells, how condensates assemble and function on lipid membranes is only beginning to be understood. In this perspective, we highlight work from plant, animal, and yeast model systems showing that condensates assemble on many endomembrane surfaces to carry out diverse functions. In vesicle trafficking, condensation has reported roles in the formation of endocytic vesicles and autophagosomes and in the inactivation of secretory COPII vesicles. We briefly discuss how membranes and membrane lipids regulate the formation and function of membrane-associated condensates. This includes how membranes act as surfaces for condensate assembly, with lipids mediating the nucleation of condensates during endocytosis and other processes. Additionally, membrane-condensate interactions give rise to the biophysical property of "wetting", which has functional importance in shaping autophagosomal and vacuolar membranes. We also speculate on the existence of membrane-associated condensates during cell polarity in plants and discuss how condensation may help to establish functional plasma membrane domains. Lastly, we provide advice on relevant in vitro and in vivo approaches and techniques to study membrane-associated phase separation.

The battle of lipid-based nanocarriers against blood-brain barrier: a critical review

Central nervous system integrity is the state of brain functioning across sensory, cognitive, emotional-social behaviors, and motor domains, allowing a person to realise his full potential. Thus, brain disorders seriously affect patients' quality of life. Efficient drug delivery to treat brain disorders remains a crucial challenge due to numerous brain barriers, particularly the blood-brain barrier (BBB), which greatly impacts the ultimate drug therapeutic efficacy. Lately, nanocarrier technology has made huge progress in overcoming these barriers by improving drug solubility, ameliorating its retention, reducing its toxicity, and targeting the encapsulated agents to different brain tissues. The current review primarily offers an overview of the different components of BBB and the progress, strategies, and contemporary applications of the nanocarriers, specifically lipid-based nanocarriers (LBNs), in treating various brain disorders.

The multiple links between actin and mitochondria

Actin plays many well-known roles in cells, and understanding any specific role is often confounded by the overlap of multiple actin-based structures in space and time. Here, we review our rapidly expanding understanding of actin in mitochondrial biology, where actin plays multiple distinct roles, exemplifying the versatility of actin and its functions in cell biology. One well-studied role of actin in mitochondrial biology is its role in mitochondrial fission, where actin polymerization from the endoplasmic reticulum through the formin INF2 has been shown to stimulate two distinct steps. However, roles for actin during other types of mitochondrial fission, dependent on the Arp2/3 complex, have also been described. In addition, actin performs functions independent of mitochondrial fission. During mitochondrial dysfunction, two distinct phases of Arp2/3 complex-mediated actin polymerization can be triggered. First, within 5 min of dysfunction, rapid actin assembly around mitochondria serves to suppress mitochondrial shape changes and to stimulate glycolysis. At a later time point, at more than 1 h post-dysfunction, a second round of actin polymerization prepares mitochondria for mitophagy. Finally, actin can both stimulate and inhibit mitochondrial motility depending on the context. These motility effects can either be through the polymerization of actin itself or through myosin-based processes, with myosin 19 being an important mitochondrially attached myosin. Overall, distinct actin structures assemble in response to diverse stimuli to affect specific changes to mitochondria.

Harnessing the Lysosomal Sorting Signals of the Cation-Independent Mannose-6-Phosphate Receptor for Targeted Degradation of Membrane Proteins

Membrane proteins are a crucial class of therapeutic targets that remain challenging to modulate using traditional occupancy-driven inhibition strategies or current proteolysis-targeting degradation approaches. Here, we report that the inherent endolysosomal sorting machinery can be harnessed for the targeted degradation of membrane proteins. A new degradation technique, termed signal-mediated lysosome-targeting chimeras (SignalTACs), was developed by genetically fusing the signaling motif from the cation-independent mannose-6-phosphate receptor (CI-M6PR) to a membrane protein binder. Antibody-based SignalTACs were constructed with the CI-M6PR signal peptides fused to the C-terminus of both heavy and light chains of IgG. We demonstrated the scope of this platform technology by degrading five pathogenesis-related membrane proteins, including HER2, EGFR, PD-L1, CD20, and CD71. Furthermore, two simplified constructs of SignalTACs, nanobody-based and peptide-based SignalTACs, were created and shown to promote the lysosomal degradation of target membrane proteins. Compared to the parent antibodies, SignalTACs exhibited significantly higher efficiency in inhibiting tumor cell growth both in vitro and in vivo. This work provides a simple, general, and robust strategy for degrading membrane proteins with molecular precision and may represent a powerful platform with broad research and therapeutic applications.

Physiologically Based Pharmacokinetic Modeling of Extracellular Vesicles

Extracellular vesicles (EVs) are lipid membrane bound-cell-derived structures that are a key player in intercellular communication and facilitate numerous cellular functions such as tumor growth, metastasis, immunosuppression, and angiogenesis. They can be used as a drug delivery platform because they can protect drugs from degradation and target specific cells or tissues. With the advancement in the technologies and methods in EV research, EV-therapeutics are one of the fast-growing domains in the human health sector. Therapeutic translation of EVs in clinics requires assessing the quality, safety, and efficacy of the EVs, in which pharmacokinetics is very crucial. We report here the application of physiologically based pharmacokinetic (PBPK) modeling as a principal tool for the prediction of absorption, distribution, metabolism, and excretion of EVs. To create a PBPK model of EVs, researchers would need to gather data on the size, shape, and composition of the EVs, as well as the physiological processes that affect their behavior in the body. The PBPK model would then be used to predict the pharmacokinetics of drugs delivered via EVs, such as the rate at which the drug is absorbed and distributed throughout the body, the rate at which it is metabolized and eliminated, and the maximum concentration of the drug in the body. This information can be used to optimize the design of EV-based drug delivery systems, including the size and composition of the EVs, the route of administration, and the dose of the drug. There has not been any dedicated review article that describes the PBPK modeling of EV. This review provides an overview of the absorption, distribution, metabolism, and excretion (ADME) phenomena of EVs. In addition, we will briefly describe the different computer-based modeling approaches that may help in the future of EV-based therapeutic research.

Relevance of multilamellar and multicompartmental vesicles in biological fluids: understanding the significance of proportional variations and disease correlation

Extracellular vesicles (EVs) have garnered significant interest in the field of biomedical science due to their potential applications in therapy and diagnosis. These vesicles participate in cell-to-cell communication and carry a diverse range of bioactive cargo molecules, such as nucleic acids, proteins, and lipids. These cargoes play essential roles in various signaling pathways, including paracrine and endocrine signaling. However, our understanding of the morphological and structural features of EVs is still limited. EVs could be unilamellar or multilamellar or even multicompartmental structures. The relative proportions of these EV subtypes in biological fluids have been associated with various human diseases; however, the mechanism remains unclear. Cryo-electron microscopy (cryo-EM) holds great promise in the field of EV characterization due to high resolution properties. Cryo-EM circumvents artifacts caused by fixation or dehydration, allows for the preservation of native conformation, and eliminates the necessity for staining procedures. In this review, we summarize the role of EVs biogenesis and pathways that might have role on their structure, and the role of cryo-EM in characterization of EVs morphology in different biological samples and integrate new knowledge of the alterations of membranous structures of EVs which could be used as biomarkers to human diseases.

Transferrin-Targeted Liposomes in Glioblastoma Therapy: A Review

Glioblastoma (GBM) is a highly aggressive brain tumor, and its treatment is further complicated by the high selectivity of the blood-brain barrier (BBB). The scientific community is urgently seeking innovative and effective therapeutic solutions. Liposomes are a promising new tool that has shown potential in addressing the limitations of chemotherapy, such as poor bioavailability and toxicity to healthy cells. However, passive targeting strategies based solely on the physicochemical properties of liposomes have proven ineffective due to a lack of tissue specificity. Accordingly, the upregulation of transferrin receptors (TfRs) in brain tissue has led to the development of TfR-targeted anticancer therapeutics. Currently, one of the most widely adopted methods for improving drug delivery in the treatment of GBM and other neurological disorders is the utilization of active targeting strategies that specifically target this receptor. In this review, we discuss the role of Tf-conjugated liposomes in GBM therapy and present some recent studies investigating the drug delivery efficiency of Tf-liposomes; in addition, we address some challenges currently facing this approach to treatment and present some potential improvement possibilities.

Ultrasound meets the cell membrane: for enhanced endocytosis and drug delivery

Endocytosis plays a crucial role in drug delivery for precision therapy. As a non-invasive and spatiotemporal-controllable stimulus, ultrasound (US) has been utilized for improving drug delivery efficiency due to its ability to enhance cell membrane permeability. When US meets the cell membrane, the well-known cavitation effect generated by US can cause various biophysical effects, facilitating the delivery of various cargoes, especially nanocarriers. The comprehension of recent progress in the biophysical mechanism governing the interaction between ultrasound and cell membranes holds significant implications for the broader scientific community, particularly in drug delivery and nanomedicine. This review will summarize the latest research results on the biological effects and mechanisms of US-enhanced cellular endocytosis. Moreover, the latest achievements in US-related biomedical applications will be discussed. Finally, challenges and opportunities of US-enhanced endocytosis for biomedical applications will be provided.

The sulfonadyns: a class of aryl sulfonamides inhibiting dynamin I GTPase and clathrin mediated endocytosis are anti-seizure in animal models

We show that dansylcadaverine (1) a known in-cell inhibitor of clathrin mediated endocytosis (CME), moderately inhibits dynamin I (dynI) GTPase activity (IC50 45 μM) and transferrin (Tfn) endocytosis in U2OS cells (IC50 205 μM). Synthesis gave a new class of GTP-competitive dynamin inhibitors, the Sulfonadyns™. The introduction of a terminal cinnamyl moiety greatly enhanced dynI inhibition. Rigid diamine or amide links between the dansyl and cinnamyl moieties were detrimental to dynI inhibition. Compounds with in vitro inhibition of dynI activity <10 μM were tested in-cell for inhibition of CME. These data unveiled a number of compounds, e.g. analogues 33 ((E)-N-(6-{[(3-(4-bromophenyl)-2-propen-1-yl]amino}hexyl)-5-isoquinolinesulfonamide)) and 47 ((E)-N-(3-{[3-(4-bromophenyl)-2-propen-1-yl]amino}propyl)-1-naphthalenesulfonamide)isomers that showed dyn IC50 <4 μM, IC50(CME) <30 μM and IC50(SVE) from 12-265 μM. Both analogues (33 and 47) are at least 10 times more potent that the initial lead, dansylcadaverine (1). Enzyme kinetics revealed these sulfonamide analogues as being GTP competitive inhibitors of dynI. Sulfonadyn-47, the most potent SVE inhibitor observed (IC50(SVE) = 12.3 μM), significantly increased seizure threshold in a 6 Hz mouse psychomotor seizure test at 30 (p = 0.003) and 100 mg kg-1 ip (p < 0.0001), with similar anti-seizure efficacy to the established anti-seizure medication, sodium valproate (400 mg kg-1). The Sulfonadyn™ class of drugs target dynamin and show promise as novel leads for future anti-seizure medications.

Opportunities and challenges of protein-based targeted protein degradation

In the 20 years since the first report of a proteolysis targeting chimeric (PROTAC) molecule, targeted protein degradation (TPD) technologies have attempted to revolutionize the fields of chemical biology and biomedicine by providing exciting research opportunities and potential therapeutics. However, they primarily focus on the use of small molecules to recruit the ubiquitin proteasome system to mediate target protein degradation. This then limits protein targets to cytosolic domains with accessible and suitable small molecule binding pockets. In recent years, biologics such as proteins and nucleic acids have instead been used as binders for targeting proteins, thereby expanding the scope of TPD platforms to include secreted proteins, transmembrane proteins, and soluble but highly disordered intracellular proteins. This perspective summarizes the recent TPD platforms that utilize nanobodies, antibodies, and other proteins as binding moieties to deplete challenging targets, either through the ubiquitin proteasome system or the lysosomal degradation pathway. Importantly, the perspective also highlights opportunities and remaining challenges of current protein-based TPD technologies.

Extracting nanoscale membrane morphology from single-molecule localizations

Membrane surface reconstruction at the nanometer scale is required for understanding mechanisms of subcellular shape change. This historically has been the domain of electron microscopy, but extraction of surfaces from specific labels is a difficult task in this imaging modality. Existing methods for extracting surfaces from fluorescence microscopy have poor resolution or require high-quality super-resolution data that are manually cleaned and curated. Here, we present NanoWrap, a new method for extracting surfaces from generalized single-molecule localization microscopy data. This makes it possible to study the shape of specifically labeled membranous structures inside cells. We validate NanoWrap using simulations and demonstrate its reconstruction capabilities on single-molecule localization microscopy data of the endoplasmic reticulum and mitochondria. NanoWrap is implemented in the open-source Python Microscopy Environment.

Self-assembly of CIP4 drives actin-mediated asymmetric pit-closing in clathrin-mediated endocytosis

Clathrin-mediated endocytosis is pivotal to signal transduction pathways between the extracellular environment and the intracellular space. Evidence from live-cell imaging and super-resolution microscopy of mammalian cells suggests an asymmetric distribution of actin fibres near the clathrin-coated pit, which induces asymmetric pit-closing rather than radial constriction. However, detailed molecular mechanisms of this 'asymmetricity' remain elusive. Herein, we used high-speed atomic force microscopy to demonstrate that CIP4, a multi-domain protein with a classic F-BAR domain and intrinsically disordered regions, is necessary for asymmetric pit-closing. Strong self-assembly of CIP4 via intrinsically disordered regions, together with stereospecific interactions with the curved membrane and actin-regulating proteins, generates a small actin-rich environment near the pit, which deforms the membrane and closes the pit. Our results provide mechanistic insights into how disordered and structured domain collaboration promotes spatio-temporal actin polymerisation near the plasma membrane.

Sorting of multiple molecular species on cell membranes

Eukaryotic cells maintain their inner order by a hectic process of sorting and distillation of molecular factors taking place on their lipid membranes. A similar sorting process is implied in the assembly and budding of enveloped viruses. To understand the properties of this molecular sorting process, we have recently proposed a physical model [Zamparo et al., Phys. Rev. Lett. 126, 088101 (2021)]10.1103/PhysRevLett.126.088101, based on (1) the phase separation of a single, initially dispersed molecular species into spatially localized sorting domains on the lipid membrane and (2) domain-induced membrane bending leading to the nucleation of submicrometric lipid vesicles, naturally enriched in the molecules of the engulfed sorting domain. The analysis of the model showed the existence of an optimal region of parameter space where sorting is most efficient. Here the model is extended to account for the simultaneous distillation of a pool of distinct molecular species. We find that the mean time spent by sorted molecules on the membrane increases with the heterogeneity of the pool (i.e., the number of distinct molecular species sorted) according to a simple scaling law, and that a large number of distinct molecular species can in principle be sorted in parallel on cell membranes without significantly interfering with each other. Moreover, sorting is found to be most efficient when the distinct molecular species have comparable homotypic affinities. We also consider how valence (i.e., the average number of interacting neighbors of a molecule in a sorting domain) affects the sorting process, finding that higher-valence molecules can be sorted with greater efficiency than lower-valence molecules.

Comparing the effects of proteins with IDRs on membrane system in yeast, mammalian cells, and the model plant Arabidopsis

Membrane vesiculation is an energy-costing process. Previous studies paid much attention to proteins with curvature-inducing motifs. Recent publications reveal that the liquid-like protein assembly on membrane surfaces provides an efficient yet structure-independent mechanism for increasing the membrane curvature, which plays important roles in vesicle transport in many aspects. Intrinsically disordered regions (IDRs) within the proteins are highly potent drivers of membrane curvature by providing large hydrodynamic radii to generate steric pressure. Biomolecular condensates formed by phase separation can provide a reaction platform for sequential processes or generate a wetting surface to sequestrate cargos and trigger membrane remodeling. We review the latest progress in yeast and mammalian cells, focus on the mechanism of clathrin-mediated endocytosis (CME) and autophagy initiation, and compare with what we know in model plant Arabidopsis. The comparison may give important insights into the understanding of basic membrane trafficking mechanisms in plant cells.

Intranasally Administered MSC-Derived Extracellular Vesicles Reverse Cisplatin-Induced Cognitive Impairment

Neurotoxic side effects of chemotherapy include deficits in attention, memory, and executive functioning. Currently, there are no FDA-approved therapies. In mice, cisplatin causes long-term cognitive deficits, white matter damage, mitochondrial dysfunction, and loss of synaptic integrity. We hypothesized that MSC-derived small extracellular vesicles (sEVs) could restore cisplatin-induced cognitive impairments and brain damage. Animals were injected with cisplatin intraperitoneally and treated with MSC-derived sEVs intranasally 48 and 96 h after the last cisplatin injection. The puzzle box test (PBT) and the novel object place recognition test (NOPRT) were used to determine cognitive deficits. Synaptosomal mitochondrial morphology was analyzed by transmission electron microscopy. Immunohistochemistry using antibodies against synaptophysin and PSD95 was applied to assess synaptic loss. Black-Gold II staining was used to quantify white matter integrity. Our data show that sEVs enter the brain in 30 min and reverse the cisplatin-induced deficits in executive functioning and working and spatial memory. Abnormalities in mitochondrial morphology, loss of white matter, and synaptic integrity in the hippocampus were restored as well. Transcriptomic analysis revealed upregulation of regenerative functions after treatment with sEVs, pointing to a possible role of axonal guidance signaling, netrin signaling, and Wnt/Ca²⁺ signaling in recovery. Our data suggest that intranasal sEV treatment could become a novel therapeutic approach for the treatment of chemobrain.

Exploring the Potential of Aptamers in Targeting Neuroinflammation and Neurodegenerative Disorders: Opportunities and Challenges

Neuroinflammation is the precursor for several neurodegenerative diseases (NDDs), such as Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Targeting neuroinflammation has emerged as a promising strategy to address a wide range of CNS pathologies. These NDDs still present significant challenges in terms of limited and ineffective diagnosis and treatment options, driving the need to explore innovative and novel therapeutic alternatives. Aptamers are single-stranded nucleic acids that offer the potential for addressing these challenges through diagnostic and therapeutic applications. In this review, we summarize diagnostic and therapeutic aptamers for inflammatory biomolecules, as well as the inflammatory cells in NDDs. We also discussed the potential of short nucleotides for Aptamer-Based Targeted Brain Delivery through their unique features and modifications, as well as their ability to penetrate the blood-brain barrier. Moreover, the unprecedented opportunities and substantial challenges of using aptamers as therapeutic agents, such as drug efficacy, safety considerations, and pharmacokinetics, are also discussed. Taken together, this review assesses the potential of aptamers as a pioneering approach for target delivery to the CNS and the treatment of neuroinflammation and NDDs.

Cell-Penetrating and Targeted Peptides Delivery Systems as Potential Pharmaceutical Carriers for Enhanced Delivery across the Blood-Brain Barrier (BBB)

Among the challenges to the 21st-century health care industry, one that demands special mention is the transport of drugs/active pharmaceutical agents across the blood-brain barrier (BBB). The epithelial-like tight junctions within the brain capillary endothelium hinder the uptake of most pharmaceutical agents. With an aim to understand more deeply the intricacies of cell-penetrating and targeted peptides as a powerful tool for desirable biological activity, we provide a critical review of both CPP and homing/targeted peptides as intracellular drug delivery agents, especially across the blood-brain barrier (BBB). Two main peptides have been discussed to understand intracellular drug delivery; first is the cell-penetrating peptides (CPPs) for the targeted delivery of compounds of interest (primarily peptides and nucleic acids) and second is the family of homing peptides, which specifically targets cells/tissues based on their overexpression of tumour-specific markers and are thus at the heart of cancer research. These small, amphipathic molecules demonstrate specific physical and chemical modifications aimed at increased ease of cellular internalisation. Because only a limited number of drug molecules can bypass the blood-brain barrier by free diffusion, it is essential to explore all aspects of CPPs that can be exploited for crossing this barrier. Considering siRNAs that can be designed against any target RNA, marking such molecules with high therapeutic potential, we present a synopsis of the studies on synthetic siRNA-based therapeutics using CPPs and homing peptides drugs that can emerge as potential drug-delivery systems as an upcoming requirement in the world of pharma- and nutraceuticals.