The multiple faces of caveolae

Effect of size and pH-sensitivity of liposomes on cellular uptake pathways and pharmacokinetics of encapsulated gemcitabine

To enhance cytoplasmic delivery efficiency, pH-sensitive liposomes (PSL) have been proposed as a novel strategy. To facilitate clinical translation, this study aims to understand the impact of both size and pH-sensitivity on cellular uptake pathways, intracellular trafficking and pharmacokinetics of liposomes. The large liposomes (130-160 nm) were prepared using thin-film hydration method, while small liposomes (∼60 nm) were fabricated using microfluidics, for both PSL and non-pH-sensitive liposomes (NPSL). Cellular uptake pathways and intracellular trafficking was investigated through confocal imaging with aid of various endocytosis inhibitors. Intracellular gemcitabine delivery by various liposomal formulations was quantified using HPLC, and the cytotoxicity was assessed via cell viability assays. Pharmacokinetics of gemcitabine loaded in various liposomes was evaluated in rats following intravenous administration. Larger liposomes had a higher loading capacity for hydrophilic gemcitabine (7% vs 4%). Small PSL exhibited superior cellular uptake compared to large PSL or NPSLs. Moreover, the alkalization of endosomes significantly attenuated the cellular uptake of PSL. Large liposomes (PSL and NPSL) predominantly entered cells via clathrin-dependent pathway, whereas small liposomes partially utilized caveolae-dependent pathway. However, the long circulation of the liposomes, as measured by the encapsulated gemcitabine, was compromised by both pH-sensitivity and size reduction (9.5 h vs 5.3 h). Despite this drawback, our results indicate that small PSL holds promise as vectors for the next generation of liposomal nanomedicine, owing to their superior cytoplasmic delivery efficiency.

Mechanisms of stretch-induced electro-anatomical remodeling and atrial arrhythmogenesis

Atrial fibrillation (AF) is the most common cardiac rhythm disorder, often occurring in the setting of atrial distension and elevated myocardialstretch. While various mechano-electrochemical signal transduction pathways have been linked to AF development and progression, the underlying molecular mechanisms remain poorly understood, hampering AF therapies. In this review, we describe different aspects of stretch-induced electro-anatomical remodeling as seen in animal models and in patients with AF. Specifically, we focus on cellular and molecular mechanisms that are responsible for mechano-electrochemical signal transduction and the development of ectopic beats triggering AF from pulmonary veins, the most common source of paroxysmal AF. Furthermore, we describe structural changes caused by stretch occurring before and shortly after the onset of AF as well as during AF progression, contributing to longstanding forms of AF. We also propose mechanical stretch as a new dimension to the concept "AF begets AF", in addition to underlying diseases. Finally, we discuss the mechanisms of these electro-anatomical alterations in a search for potential therapeutic strategies and the development of novel antiarrhythmic drugs targeted at the components of mechano-electrochemical signal transduction not only in cardiac myocytes, but also in cardiac non-myocyte cells.

Circulating low-molecular-weight (poly)phenol metabolites in the brain: unveiling in vitro and in vivo blood-brain barrier transport

Circulating metabolites resulting from colonic metabolism of dietary (poly)phenols are highly abundant in the bloodstream, though still marginally explored, particularly concerning their brain accessibility. Our goal is to disclose (poly)phenol metabolites' blood-brain barrier (BBB) transport, in vivo and in vitro, as well as their role at BBB level. For three selected metabolites, benzene-1,2-diol-3-sulfate/benzene-1,3-diol-2-sulfate (pyrogallol-sulfate - Pyr-sulf), benzene-1,3-diol-6-sulfate (phloroglucinol-sulfate - Phlo-sulf), and phenol-3-sulfate (resorcinol-sulfate - Res-sulf), BBB transport was assessed in human brain microvascular endothelial cells (HBMEC). Their potential in modulating in vitro BBB properties at circulating concentrations was also studied. Metabolites' fate towards the brain, liver, kidney, urine, and blood was disclosed in Wistar rats upon injection. Transport kinetics in HBMEC highlighted different BBB permeability rates, where Pyr-sulf emerged as the most in vitro BBB permeable metabolite. Pyr-sulf was also the most potent regarding BBB properties improvement, namely increased beta(β)-catenin membrane expression and reduction of zonula occludens-1 membrane gaps. Whereas no differences were observed for transferrin, increased expression of caveolin-1 upon Pyr-sulf and Res-sulf treatments was found. Pyr-sulf was also capable of modulating gene and protein expression of some solute carrier transporters. Notably, each of the injected metabolites exhibited a unique tissue distribution in vivo, with the remarkable ability to almost immediately reach the brain.

Timing and Mechanisms of Nanodiamond Uptake in Colon Cancer Cells

Introduction

As nanodiamonds become more and more widely used for intracellular labelling and measurements, the task of delivering these nanoparticles inside cells becomes more and more important. Certain cell types easily take up nanodiamonds, while others require special procedures.

Methods

In previous research, we found that HT-29 cells (a colon cancer cell line), which are notoriously difficult in the context of nanodiamond internalization, show increased uptake rates, when pre-treated with trypsin- ethylenediaminetetraacetic acid (trypsin-EDTA). However, the uptake mechanism has not been studied before. This article focuses on a more detailed investigation of the reasons underlying this phenomenon. We start by identifying the timing of fluorescent nanodiamond (FND) uptake in trypsin-EDTA pre-treated cells. We then use a combination of chemical inhibitors and Immunocytochemistry to identify the main pathways employed by HT-29 cells in the internalization process.

Results and Discussion

We investigate how these pathways are affected by the trypsin-EDTA pre-treatment and conclude by offering possible explanations for this phenomenon. We found that nanodiamonds are internalized via different pathways. Clathrin-mediated endocytosis proves to be the dominating mechanism. Trypsin-EDTA treatment increases particle uptake and affects the uptake mechanism.

Role of endothelial glycocalyx in central nervous system diseases and evaluation of the targeted therapeutic strategies for its protection: a review of clinical and experimental data

Central nervous system (CNS) diseases, such as stroke, traumatic brain injury, dementia, and demyelinating diseases, are generally characterized by high morbidity and mortality, which impose a heavy economic burden on patients and their caregivers throughout their lives as well as on public health. The occurrence and development of CNS diseases are closely associated with a series of pathophysiological changes including inflammation, blood-brain barrier disruption, and abnormal coagulation. Endothelial glycocalyx (EG) plays a key role in these changes, making it a novel intervention target for CNS diseases. Herein, we review the current understanding of the role of EG in common CNS diseases, from the perspective of individual pathways/cytokines in pathophysiological and systematic processes. Furthermore, we emphasize the recent developments in therapeutic agents targeted toward protection or restoration of EG. Some of these treatments have yielded unexpected pharmacological results, as previously unknown mechanisms underlying the degradation and destruction of EG has been brought to light. Furthermore, the anti-inflammatory, anticoagulative, and antioxidation effects of EG and its protective role exerted via the blood-brain barrier have been recognized.

Human Umbilical Vein Endothelial Cells as a Versatile Cellular Model System in Diverse Experimental Paradigms: An Ultrastructural Perspective

Human umbilical vein endothelial cells (HUVECs) are primary cells isolated from the vein of an umbilical cord, extensively used in cardiovascular studies and medical research. These cells, retaining the characteristics of endothelial cells in vivo, serve as a valuable cellular model system for understanding vascular biology, endothelial dysfunction, pathophysiology of diseases such as atherosclerosis, and responses to different drugs or treatments. Transmission electron microscopy (TEM) has been a cornerstone in revealing the detailed architecture of multiple cellular model systems including HUVECs, allowing researchers to visualize subcellular organelles, membrane structures, and cytoskeletal elements. Among them, the endoplasmic reticulum, Golgi apparatus, mitochondria, and nucleus can be meticulously examined to recognize alterations indicative of cellular responses to various stimuli. Importantly, Weibel-Palade bodies are characteristic secretory organelles found in HUVECs, which can be easily distinguished in the TEM. These distinctive structures also dynamically react to different factors through regulated exocytosis, resulting in complete or selective release of their contents. This detailed review summarizes the ultrastructural features of HUVECs and highlights the utility of TEM as a pivotal tool for analyzing HUVECs in diverse research frameworks, contributing valuable insights into the comprehension of HUVEC behavior and enriching our knowledge into the complexity of vascular biology.

Post-translational modifications in prion diseases

More than 650 reversible and irreversible post-translational modifications (PTMs) of proteins have been listed so far. Canonical PTMs of proteins consist of the covalent addition of functional or chemical groups on target backbone amino-acids or the cleavage of the protein itself, giving rise to modified proteins with specific properties in terms of stability, solubility, cell distribution, activity, or interactions with other biomolecules. PTMs of protein contribute to cell homeostatic processes, enabling basal cell functions, allowing the cell to respond and adapt to variations of its environment, and globally maintaining the constancy of the milieu interieur (the body's inner environment) to sustain human health. Abnormal protein PTMs are, however, associated with several disease states, such as cancers, metabolic disorders, or neurodegenerative diseases. Abnormal PTMs alter the functional properties of the protein or even cause a loss of protein function. One example of dramatic PTMs concerns the cellular prion protein (PrPC), a GPI-anchored signaling molecule at the plasma membrane, whose irreversible post-translational conformational conversion (PTCC) into pathogenic prions (PrPSc) provokes neurodegeneration. PrPC PTCC into PrPSc is an additional type of PTM that affects the tridimensional structure and physiological function of PrPC and generates a protein conformer with neurotoxic properties. PrPC PTCC into PrPSc in neurons is the first step of a deleterious sequence of events at the root of a group of neurodegenerative disorders affecting both humans (Creutzfeldt-Jakob diseases for the most representative diseases) and animals (scrapie in sheep, bovine spongiform encephalopathy in cow, and chronic wasting disease in elk and deer). There are currently no therapies to block PrPC PTCC into PrPSc and stop neurodegeneration in prion diseases. Here, we review known PrPC PTMs that influence PrPC conversion into PrPSc. We summarized how PrPC PTCC into PrPSc impacts the PrPC interactome at the plasma membrane and the downstream intracellular controlled protein effectors, whose abnormal activation or trafficking caused by altered PTMs promotes neurodegeneration. We discussed these effectors as candidate drug targets for prion diseases and possibly other neurodegenerative diseases.

Understanding the role of DNA methylation in colorectal cancer: Mechanisms, detection, and clinical significance

Colorectal cancer (CRC) is one of the deadliest malignancies worldwide, ranking third in incidence and second in mortality. Remarkably, early stage localized CRC has a 5-year survival rate of over 90%; in stark contrast, the corresponding 5-year survival rate for metastatic CRC (mCRC) is only 14%. Compounding this problem is the staggering lack of effective therapeutic strategies. Beyond genetic mutations, which have been identified as critical instigators of CRC initiation and progression, the importance of epigenetic modifications, particularly DNA methylation (DNAm), cannot be underestimated, given that DNAm can be used for diagnosis, treatment monitoring and prognostic evaluation. This review addresses the intricate mechanisms governing aberrant DNAm in CRC and its profound impact on critical oncogenic pathways. In addition, a comprehensive review of the various techniques used to detect DNAm alterations in CRC is provided, along with an exploration of the clinical utility of cancer-specific DNAm alterations.

Scaffolds and the scaffolding domain: an alternative paradigm for caveolin-1 signaling

Caveolin-1 (Cav1) is a 22 kDa intracellular protein that is the main protein constituent of bulb-shaped membrane invaginations known as caveolae. Cav1 can be also found in functional non-caveolar structures at the plasma membrane called scaffolds. Scaffolds were originally described as SDS-resistant oligomers composed of 10-15 Cav1 monomers observable as 8S complexes by sucrose velocity gradient centrifugation. Recently, cryoelectron microscopy (cryoEM) and super-resolution microscopy have shown that 8S complexes are interlocking structures composed of 11 Cav1 monomers each, which further assemble modularly to form higher-order scaffolds and caveolae. In addition, Cav1 can act as a critical signaling regulator capable of direct interactions with multiple client proteins, in particular, the endothelial nitric oxide (NO) synthase (eNOS), a role believed by many to be attributable to the highly conserved and versatile scaffolding domain (CSD). However, as the CSD is a hydrophobic domain located by cryoEM to the periphery of the 8S complex, it is predicted to be enmeshed in membrane lipids. This has led some to challenge its ability to interact directly with client proteins and argue that it impacts signaling only indirectly via local alteration of membrane lipids. Here, based on recent advances in our understanding of higher-order Cav1 structure formation, we discuss how the Cav1 CSD may function through both lipid and protein interaction and propose an alternate view in which structural modifications to Cav1 oligomers may impact exposure of the CSD to cytoplasmic client proteins, such as eNOS.

Biomechanics-mediated endocytosis in atherosclerosis

Biomechanical forces, including vascular shear stress, cyclic stretching, and extracellular matrix stiffness, which influence mechanosensitive channels in the plasma membrane, determine cell function in atherosclerosis. Being highly associated with the formation of atherosclerotic plaques, endocytosis is the key point in molecule and macromolecule trafficking, which plays an important role in lipid transportation. The process of endocytosis relies on the mobility and tension of the plasma membrane, which is sensitive to biomechanical forces. Several studies have advanced the signal transduction between endocytosis and biomechanics to elaborate the developmental role of atherosclerosis. Meanwhile, increased plaque growth also results in changes in the structure, composition and morphology of the coronary artery that contribute to the alteration of arterial biomechanics. These cross-links of biomechanics and endocytosis in atherosclerotic plaques play an important role in cell function, such as cell phenotype switching, foam cell formation, and lipoprotein transportation. We propose that biomechanical force activates the endocytosis of vascular cells and plays an important role in the development of atherosclerosis.

Newcastle disease virus activates diverse signaling pathways via Src to facilitate virus entry into host macrophages

As an intrinsic cellular mechanism responsible for the internalization of extracellular ligands and membrane components, caveolae-mediated endocytosis (CavME) is also exploited by certain pathogens for endocytic entry [e.g., Newcastle disease virus (NDV) of paramyxovirus]. However, the molecular mechanisms of NDV-induced CavME remain poorly understood. Herein, we demonstrate that sialic acid-containing gangliosides, rather than glycoproteins, were utilized by NDV as receptors to initiate the endocytic entry of NDV into HD11 cells. The binding of NDV to gangliosides induced the activation of a non-receptor tyrosine kinase, Src, leading to the phosphorylation of caveolin-1 (Cav1) and dynamin-2 (Dyn2), which contributed to the endocytic entry of NDV. Moreover, an inoculation of cells with NDV-induced actin cytoskeletal rearrangement through Src to facilitate NDV entry via endocytosis and direct fusion with the plasma membrane. Subsequently, unique members of the Rho GTPases family, RhoA and Cdc42, were activated by NDV in a Src-dependent manner. Further analyses revealed that RhoA and Cdc42 regulated the activities of specific effectors, cofilin and myosin regulatory light chain 2, responsible for actin cytoskeleton rearrangement, through diverse intracellular signaling cascades. Taken together, our results suggest that an inoculation of NDV-induced Src-mediated cellular activation by binding to ganglioside receptors. This process orchestrated NDV endocytic entry by modulating the activities of caveolae-associated Cav1 and Dyn2, as well as specific Rho GTPases and downstream effectors.

IMPORTANCE

In general, it is known that the paramyxovirus gains access to host cells through direct penetration at the plasma membrane; however, emerging evidence suggests more complex entry mechanisms for paramyxoviruses. The endocytic entry of Newcastle disease virus (NDV), a representative member of the paramyxovirus family, into multiple types of cells has been recently reported. Herein, we demonstrate the binding of NDV to induce ganglioside-activated Src signaling, which is responsible for the endocytic entry of NDV through caveolae-mediated endocytosis. This process involved Src-dependent activation of the caveolae-associated Cav1 and Dyn2, as well as specific Rho GTPase and downstream effectors, thereby orchestrating the endocytic entry process of NDV. Our findings uncover a novel molecular mechanism of endocytic entry of NDV into host cells and provide novel insight into paramyxovirus mechanisms of entry.

Nanomaterials in Medicine: Understanding Cellular Uptake, Localization, and Retention for Enhanced Disease Diagnosis and Therapy

Nanomaterials (NMs) have emerged as promising tools for disease diagnosis and therapy due to their unique physicochemical properties. To maximize the effectiveness and design of NMs-based medical applications, it is essential to comprehend the complex mechanisms of cellular uptake, subcellular localization, and cellular retention. This review illuminates the various pathways that NMs take to get from the extracellular environment to certain intracellular compartments by investigating the various mechanisms that underlie their interaction with cells. The cellular uptake of NMs involves complex interactions with cell membranes, encompassing endocytosis, phagocytosis, and other active transport mechanisms. Unique uptake patterns across cell types highlight the necessity for customized NMs designs. After internalization, NMs move through a variety of intracellular routes that affect where they are located subcellularly. Understanding these pathways is pivotal for enhancing the targeted delivery of therapeutic agents and imaging probes. Furthermore, the cellular retention of NMs plays a critical role in sustained therapeutic efficacy and long-term imaging capabilities. Factors influencing cellular retention include nanoparticle size, surface chemistry, and the cellular microenvironment. Strategies for prolonging cellular retention are discussed, including surface modifications and encapsulation techniques. In conclusion, a comprehensive understanding of the mechanisms governing cellular uptake, subcellular localization, and cellular retention of NMs is essential for advancing their application in disease diagnosis and therapy. This review provides insights into the intricate interplay between NMs and biological systems, offering a foundation for the rational design of next-generation nanomedicines.

Intravesicular Solute Delivery and Surface Area Regulation in Giant Unilamellar Vesicles Driven by Cycles of Osmotic Stresses

Phospholipid bilayers are dynamic cellular components that undergo constant changes in their topology, facilitating a broad diversity of physiological functions including endo- and exocytosis, cell division, and intracellular trafficking. These shape transformations consume energy, supplied invariably by the activity of proteins. Here, we show that cycles of oppositely directed osmotic stresses─unassisted by any protein activity─can induce well-defined remodeling of giant unilamellar vesicles, minimally recapitulating the phenomenologies of surface area homeostasis and macropinocytosis. We find that a stress cycle consisting of deflationary hypertonic stress followed by an inflationary hypotonic one prompts an elaborate sequence of membrane shape changes ultimately transporting molecular cargo from the outside into the intravesicular milieu. The initial osmotic deflation produces microscopic spherical invaginations. During the subsequent inflation, the first subpopulation contributes area to the swelling membrane, thereby providing a means for surface area regulation and tensional homeostasis. The second subpopulation vesiculates into the lumens of the mother vesicles, producing pinocytic vesicles. Remarkably, the gradients of solute concentrations between the GUV and the daughter pinocytic vesicles create cascades of water current, inducing pulsatory transient poration that enable solute exchange between the buds and the GUV interior. This results in an efficient water-flux-mediated delivery of molecular cargo across the membrane boundary. Our findings suggest a primitive physical mechanism for communication and transport across protocellular compartments driven only by osmotic stresses. They also suggest plausible physical routes for intravesicular, and possibly intracellular, delivery of ions, solutes, and molecular cargo stimulated simply by cycles of osmotic currents of water.

Dietary Insulin Index (DII) and Dietary Insulin load (DIL) and Caveolin gene variant interaction on cardiometabolic risk factors among overweight and obese women: a cross-sectional study

BACKGROUND AND OBJECTIVE

Studies have shown that Caveolin gene polymorphisms (CAV-1) are involved in chronic diseases, such as metabolic syndrome. Moreover, the dietary insulin index (DII) and dietary insulin load (DIL) have been shown to potentially elicit favorable effects on cardiovascular disease (CVD) risk. Therefore, this study sought to investigate the effect of DII DIL and CAV-1 interaction on CVD risk factors.

METHODS

This cross-sectional study consisted of 333 overweight and obese women aged 18-48 years. Dietary intakes, DII, and DIL were evaluated using the 147-item food frequency questionnaire (FFQ). Serum profiles were measured by standard protocols. The CAV-1 rs 3,807,992 and anthropometric data were measured by the PCR-RFLP method and bioelectrical impedance analysis (BIA), respectively. Participants were also divided into three groups based on DII, DIL score, and rs3807992 genotype.

RESULTS

This comparative cross-sectional study was conducted on 333 women classified as overweight or obese. Participants with A allele for the caveolin genotype and higher DII score showed significant interactions with high-density lipoprotein (HDL) (P for AA = 0.006 and P for AG = 0.019) and CRI-I (P for AA < 0.001 and P for AG = 0.024). In participants with AA genotype and greater DII score, interactions were observed in weight, systolic blood pressure (SBP), diastolic blood pressure (DBP), total cholesterol, CRI-II, fat-free mass (FFM), and skeletal muscle mass (SMM) (P < 0.079). Those with higher DIL scores and AA genotype had higher weight (P = 0.033), FFM (P = 0.022), and SMM (P = 0.024). In addition, DIL interactions for waist/hip ratio (WHR), waist circumference (WC), triglyceride (TG), CRI-I, and body fat mass (BFM) among individuals with AA genotype, while an HDL interaction was observed in individuals with AG and AA (P < 0.066).

CONCLUSION

The findings of the present study indicate that people who carry the caveolin rs3807992 (A) allele and have greater DII and DIL scores are at higher risk for several cardiovascular disease and metabolic syndrome biomarkers. These results highlight that diet, gene variants, and their interaction, should be considered in the risk evaluation of developing CVD.

New insights of platelet endocytosis and its implication for platelet function

Endocytosis constitutes a cellular process in which cells selectively encapsulate surface substances into endocytic vesicles, also known as endosomes, thereby modulating their interaction with the environment. Platelets, as pivotal hematologic elements, play a crucial role not only in regulating coagulation and thrombus formation but also in facilitating tumor invasion and metastasis. Functioning as critical components in the circulatory system, platelets can internalize various endosomal compartments, such as surface receptors, extracellular proteins, small molecules, and pathogens, from the extracellular environment through diverse endocytic pathways, including pinocytosis, phagocytosis, and receptor-mediated endocytosis. We summarize recent advancements in platelet endocytosis, encompassing the catalog of cargoes, regulatory mechanisms, and internal trafficking routes. Furthermore, we describe the influence of endocytosis on platelet regulatory functions and related physiological and pathological processes, aiming to offer foundational insights for future research into platelet endocytosis.

The Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling in pulmonary hypertension by interfering with BMPR2/Caveolin-1 binding

Caveolin-1 (CAV1) and Cavin-1 are components of caveolae, both of which interact with and influence the composition and stabilization of caveolae. CAV1 is associated with pulmonary arterial hypertension (PAH). Bone morphogenetic protein (BMP) type 2 receptor (BMPR2) is localized in caveolae associated with CAV1 and is commonly mutated in PAH. Here, we show that BMP/Smad signaling is suppressed in pulmonary microvascular endothelial cells of CAV1 knockout mice. Moreover, hypoxia enhances the CAV1/Cavin-1 interaction but attenuates the CAV1/BMPR2 interaction and BMPR2 membrane localization in pulmonary artery endothelial cells (PAECs). Both Cavin-1 and BMPR2 are associated with the CAV1 scaffolding domain. Cavin-1 decreases BMPR2 membrane localization by inhibiting the interaction of BMPR2 with CAV1 and reduces Smad signal transduction in PAECs. Furthermore, Cavin-1 knockdown is resistant to CAV1-induced pulmonary hypertension in vivo. We demonstrate that the Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling and is a promising target for the treatment of PAH.

The Recent Advances in the Function and Mechanism of Caveolin-1 in Retinal Neovascularization

Retinal neovascularization diseases have relatively high rates of evitable blindness. Abnormal retinal neovascularization is their main hallmark, which can damage the structure and function of the eye and lead to impaired vision. Caveolin-1 is a membrane protein that is expressed in many types of retinal cells and is involved in retinal neovascularization. This review presents a comprehensive analysis of global research on specific functions of caveolin-1 in retinal neovascularization. We believe that the mechanism of action of caveolin-1 might be related to the regulation of relevant signal pathways and looked ahead the application prospects of modulating caveolin- 1 in retinal neovascularization diseases.

Enhancing the Biopharmacological Characteristics of Asperosaponin VI: Unveiling Dynamic Self-Assembly Phase Transitions in the Gastrointestinal Environment

Purpose

Asperosaponin VI (ASP VI) as an active ingredient of Dipsacus asperoides, which has a wide range of biological and pharmacological activity. However, its development and application are restricted due to the poor gastrointestinal permeability and oral bioavailability. This investigation aims to reveal the influence of the self-assembled structure by the interaction between ASP VI and endogenous components NaTC and/or DOPC in the gastrointestinal environment on its biopharmaceutical properties, and novelty elucidated the molecular mechanism for the formation of self-assembled nanomicelles.

Methods

This change in phase state in gastrointestinal fluids is characterized by dynamic light scattering (DLS) and transmission electron microscope (TEM). UPLC-Q-TOF-MS was used to analyze the composition of phase components and the exposure of nanomicelles in vivo. Molecular dynamics simulation (MDS) was applied to preliminarily elucidate the self-assembly mechanism of ASP VI in the gastrointestinal environment. Furthermore, theS8 promoting absorption mechanism of nanomicelles were investigated through in vivo pharmacokinetic experiments, parallel artificial membrane permeability assay (PAMPA), quadruple single-pass intestinal perfusion in rats, and Caco-2 cell monolayer model.

Results

We demonstrated that the ASP VI could spontaneously form dynamic self-assembled structures with sodium taurocholate (NaTC) and dipalmitoyl phosphatidylcholine (DOPC) during gastrointestinal solubilization, which promoted the gastrointestinal absorption and permeability of ASP VI and increased its exposure in vivo, thus improving the biopharmacological characteristics of ASP VI. Moreover, ASP VI-NaTC-DOPC-self-assembled nanostructures (ASP VI-NaTC-DOPC-SAN) manifested higher cellular uptake in Caco-2 cells as evidenced by flow cytometry and confocal microscopy, and this study also preliminarily revealed the mechanism of self-assembly formation of ASP VI with endogenous components NaTC and DOPC driven by electrostatic and hydrogen bonding interactions.

Conclusion

This study provides evidence that the dynamic self-assembled phase transition may play a key role in improving the biopharmacological characteristics of insoluble or low permeability active ingredients during the gastrointestinal dissolution of Chinese medicines.

Unraveling the Cave: A Seventy-Year Journey into the Caveolar Network, Cellular Signaling, and Human Disease

In the mid-1950s, a groundbreaking discovery revealed the fascinating presence of caveolae, referred to as flask-shaped invaginations of the plasma membrane, sparking renewed excitement in the field of cell biology. Caveolae are small, flask-shaped invaginations in the cell membrane that play crucial roles in diverse cellular processes, including endocytosis, lipid homeostasis, and signal transduction. The structural stability and functionality of these specialized membrane microdomains are attributed to the coordinated activity of scaffolding proteins, including caveolins and cavins. While caveolae and caveolins have been long appreciated for their integral roles in cellular physiology, the accumulating scientific evidence throughout the years reaffirms their association with a broad spectrum of human disorders. This review article aims to offer a thorough account of the historical advancements in caveolae research, spanning from their initial discovery to the recognition of caveolin family proteins and their intricate contributions to cellular functions. Furthermore, it will examine the consequences of a dysfunctional caveolar network in the development of human diseases.

Molecular Mechanisms of Glaucoma Pathogenesis with Implications to Caveolin Adaptor Protein and Caveolin-Shp2 Axis

Glaucoma is a common retinal disorder characterized by progressive optic nerve damage, resulting in visual impairment and potential blindness. Elevated intraocular pressure (IOP) is a major risk factor, but some patients still experience disease progression despite IOP-lowering treatments. Genome-wide association studies have linked variations in the Caveolin1/2 (CAV-1/2) gene loci to glaucoma risk. Cav-1, a key protein in caveolae membrane invaginations, is involved in signaling pathways and its absence impairs retinal function. Recent research suggests that Cav-1 is implicated in modulating the BDNF/TrkB signaling pathway in retinal ganglion cells, which plays a critical role in retinal ganglion cell (RGC) health and protection against apoptosis. Understanding the interplay between these proteins could shed light on glaucoma pathogenesis and provide potential therapeutic targets.

Regulation of the proteostasis network by the neuronal system

The protein homeostasis (proteostasis) network is a nexus of molecular mechanisms that act in concert to maintain the integrity of the proteome and ensure proper cellular and organismal functionality. Early in life the proteostasis network efficiently preserves the functionality of the proteome, however, as the organism ages, or due to mutations or environmental insults, subsets of inherently unstable proteins misfold and form insoluble aggregates that accrue within the cell. These aberrant protein aggregates jeopardize cellular viability and, in some cases, underlie the development of devastating illnesses. Hence, the accumulation of protein aggregates activates different nodes of the proteostasis network that refold aberrantly folded polypeptides, or direct them for degradation. The proteostasis network apparently functions within the cell, however, a myriad of studies indicate that this nexus of mechanisms is regulated at the organismal level by signaling pathways. It was also discovered that the proteostasis network differentially responds to dissimilar proteotoxic insults by tailoring its response according to the specific challenge that cells encounter. In this mini-review, we delineate the proteostasis-regulating neuronal mechanisms, describe the indications that the proteostasis network differentially responds to distinct proteotoxic challenges, and highlight possible future clinical prospects of these insights.

Caveolae-associated cAMP/Ca2+-mediated mechano-chemical signal transduction in mouse atrial myocytes

Caveolae are tiny invaginations in the sarcolemma that buffer extra membrane and contribute to mechanical regulation of cellular function. While the role of caveolae in membrane mechanosensation has been studied predominantly in non-cardiomyocyte cells, caveolae contribution to cardiac mechanotransduction remains elusive. Here, we studied the role of caveolae in the regulation of Ca2+ signaling in atrial cardiomyocytes. In Langendorff-perfused mouse hearts, atrial pressure/volume overload stretched atrial myocytes and decreased caveolae density. In isolated cells, caveolae were disrupted through hypotonic challenge that induced a temporal (<10 min) augmentation of Ca2+ transients and caused a rise in Ca2+ spark activity. Similar changes in Ca2+ signaling were observed after chemical (methyl-β-cyclodextrin) and genetic ablation of caveolae in cardiac-specific conditional caveolin-3 knock-out mice. Acute disruption of caveolae, both mechanical and chemical, led to the elevation of cAMP level in the cell interior, and cAMP-mediated augmentation of protein kinase A (PKA)-phosphorylated ryanodine receptors (at Ser2030 and Ser2808). Caveolae-mediated stimulatory effects on Ca2+ signaling were abolished via inhibition of cAMP production by adenyl cyclase antagonists MDL12330 and SQ22536, or reduction of PKA activity by H-89. A compartmentalized mathematical model of mouse atrial myocytes linked the observed changes to a microdomain-specific decrease in phosphodiesterase activity, which disrupted cAMP signaling and augmented PKA activity. Our findings add a new dimension to cardiac mechanobiology and highlight caveolae-associated cAMP/PKA-mediated phosphorylation of Ca2+ handling proteins as a novel component of mechano-chemical feedback in atrial myocytes.

Miriplatin-loaded liposome, as a novel mitophagy inducer, suppresses pancreatic cancer proliferation through blocking POLG and TFAM-mediated mtDNA replication

Pancreatic cancer is a more aggressive and refractory malignancy. Resistance and toxicity limit drug efficacy. Herein, we report a lower toxic and higher effective miriplatin (MPt)-loaded liposome, LMPt, exhibiting totally different anti-cancer mechanism from previously reported platinum agents. Both in gemcitabine (GEM)-resistant/sensitive (GEM-R/S) pancreatic cancer cells, LMPt exhibits prominent anti-cancer activity, led by faster cellular entry-induced larger accumulation of MPt. The level of caveolin-1 (Cav-1) determines entry rate and switch of entry pathways of LMPt, indicating a novel role of Cav-1 in nanoparticle entry. After endosome-lysosome processing, in unchanged metabolite, MPt is released and targets mitochondria to enhance binding of mitochondria protease LONP1 with POLG and TFAM, to degrade POLG and TFAM. Then, via PINK1-Parkin axis, mitophagy is induced by POLG and TFAM degradation-initiated mitochondrial DNA (mtDNA) replication blocking. Additionally, POLG and TFAM are identified as novel prognostic markers of pancreatic cancer, and mtDNA replication-induced mitophagy blocking mediates their pro-cancer activity. Our findings reveal that the target of this liposomal platinum agent is mitochondria but not DNA (target of most platinum agents), and totally distinct mechanism of MPt and other formulations of MPt. Self-assembly offers LMPt special efficacy and mechanisms. Prominent action and characteristic mechanism make LMPt a promising cancer candidate.

Neutral sphingomyelinase regulates mechanotransduction in human engineered cardiac tissues and mouse hearts

Cardiovascular disease is the leading cause of death in the USA and is known to be exacerbated by elevated mechanical stress from hypertension. Caveolae are plasma membrane structures that buffer mechanical stress but have been found to be reduced in pathological conditions associated with chronically stretched myocardium. To explore the physiological implications of the loss of caveolae, we used human engineered cardiac tissue (ECT) constructs, composed of human induced pluripotent stem cell (hiPSC)-derived cardiomyocytes and hiPSC-derived cardiac fibroblasts, to develop a long-term cyclic stretch protocol that recapitulates the effects of hypertension on caveolae expression, membrane tension, and the β-adrenergic response. Leveraging this new stretch protocol, we identified neutral sphingomyelinases (nSMase) as mechanoregulated mediators of caveolae loss, ceramide production and the blunted β-adrenergic response in this human cardiac model. Specifically, in our ECT model, nSMase inhibition via GW4869 prevented stretch-induced loss of caveolae-like structures, mitigated nSMase-dependent ceramide production, and maintained the ECT contractile kinetic response to isoprenaline. These findings are correlated with a blood lipidomic analysis in middle-aged and older adults, which revealed an increase of the circulating levels of ceramides in adults with hypertension. Furthermore, we found that conduction slowing from increased pressure loading in mouse left ventricle was abolished in the context of nSMase inhibition. Collectively, these findings identify nSMase as a potent drug target for mitigating stretch-induced effects on cardiac function. KEY POINTS: We have developed a new stretch protocol for human engineered cardiac tissue that recapitulates changes in plasma membrane morphology observed in animal models of pressure/volume overload. Stretch of engineered cardiac tissue induces activation of neutral sphingomyelinase (nSMase), generation of ceramide, and disassembly of caveolae. Activation of nSMase blunts cardiac β-adrenergic contractile kinetics and mediates stretch-induced slowing of conduction and upstroke velocity. Circulating ceramides are increased in adults with hypertension, highlighting the clinical relevance of stretch-induced nSMase activity.

Chemical Biology Approach to Reveal the Importance of Precise Subcellular Targeting for Intracellular Staphylococcus aureus Eradication

Intracellular bacterial pathogens, such as Staphylococcus aureus, that may hide in intracellular vacuoles represent the most significant manifestation of bacterial persistence. They are critically associated with chronic infections and antibiotic resistance, as conventional antibiotics are ineffective against such intracellular persisters due to permeability issues and mechanistic reasons. Direct subcellular targeting of S. aureus vacuoles suggests an explicit opportunity for the eradication of these persisters, but a comprehensive understanding of the chemical biology nature and significance of precise S. aureus vacuole targeting remains limited. Here, we report an oligoguanidine-based peptidomimetic that effectively targets and eradicates intracellular S. aureus persisters in the phagolysosome lumen, and this oligomer was utilized to reveal the mechanistic insights linking precise targeting to intracellular antimicrobial efficacy. The oligomer has high cellular uptake via a receptor-mediated endocytosis pathway and colocalizes with S. aureus persisters in phagolysosomes as a result of endosome-lysosome interconversion and lysosome-phagosome fusion. Moreover, the observation of a bacterium's altered susceptibility to the oligomer following a modification in its intracellular localization offers direct evidence of the critical importance of precise intracellular targeting. In addition, eradication of intracellular S. aureus persisters was achieved by the oligomer's membrane/DNA dual-targeting mechanism of action; therefore, its effectiveness is not hampered by the hibernation state of the persisters. Such precise subcellular targeting of S. aureus vacuoles also increases the agent's biocompatibility by minimizing its interaction with other organelles, endowing excellent in vivo bacterial targeting and therapeutic efficacy in animal models.

Surf4 collaborates with derlin-2 and derlin-1 to mediate cyclooxygenase-2 translocation to the cytosol for degradation

Derlin family members participate in the retrotranslocation of endoplasmic reticulum (ER) lumen proteins to the cytosol for ER-associated degradation (ERAD); however, the proteins facilitating this retrotranslocation remain to be explored. Using CRISPR library screening, we have found that derlin-2 and surfeit locus protein 4 (Surf4) are candidates to facilitate degradation of cyclooxygenase-2 (COX-2, also known as PTGS2). Our results show that derlin-2 acts upstream of derlin-1 and that Surf4 acts downstream of derlin-2 and derlin-1 to facilitate COX-2 degradation. Knockdown of derlin-2 or Surf4 impedes the ubiquitylation of COX-2 and the interaction of COX-2 with caveolin-1 (Cav-1) and p97 (also known as VCP) in the cytosol. Additionally, COX-2 degradation is N-glycosylation dependent. Although derlin-2 facilitates degradation of N-glycosylated COX-2, the interaction between derlin-2 and COX-2 is independent of COX-2 N-glycosylation. Derlin-1, Surf4 and p97 preferentially interact with non-glycosylated COX-2, whereas Cav-1 preferentially interacts with N-glycosylated COX-2, regardless of the N-glycosylation pattern. Collectively, our results reveal that Surf4 collaborates with derlin-2 and derlin-1 to mediate COX-2 translocation from the ER lumen to the cytosol. The derlin-2-derlin-1-Surf4-Cav-1 machinery might represent a unique pathway to accelerate COX-2 degradation in ERAD.

Polymer/Nanoceria Hybrid Polyplexes for Gene and Antioxidant Delivery

Various diseases, including cancers and inflammatory diseases, are characterized by a disruption of redox homeostasis, suggesting the need for synergistic treatments involving co-delivery of gene therapies and free radical scavengers. In this report, polyethylenimine (PEI), nanoceria (NC), and DNA were complexed to form nanoparticles providing simultaneous delivery of a gene and an antioxidant. NC was coated in citric acid to provide stable, 4 nm particles that electrostatically bound PEI/DNA polyplexes. The resulting ternary particles transfected HeLa cells with similar efficiency to that of ternary polyplexes comprising 15 kDa poly-l-α-glutamic acid/PEI/DNA while providing smaller particle sizes by more than 100 nm. NC/PEI/DNA polyplexes exhibited enhanced radical-scavenging activity compared to free NC, and oxidative stress from the superoxide-generating agent, menadione, could be completely reversed by the delivery of NC/PEI/DNA polyplexes. Transfection by NC/PEI/DNA polyplexes was demonstrated to occur efficiently through caveolin-mediated endocytosis and macropinocytosis. Co-delivery of genes encoding reactive oxygen species-scavenging proteins, transcription factors, growth factors, tumor suppressors, or anti-inflammatory genes with NC, therefore, may be a promising strategy in synergistic therapeutics.

CircGNB1 drives osteoarthritis pathogenesis by inducing oxidative stress in chondrocytes

BACKGROUND

Circular RNAs (circRNAs) have risen to prominence as important regulators of biological processes. This study investigated whether circGNB1 functions as a competitive endogenous RNA to regulate the pathological process of oxidative stress in age-related osteoarthritis (OA).

METHODS

The relationship between circGNB1 expression and oxidative stress/OA severity was determined in cartilages from OA patients at different ages. The biological roles of circGNB1 in oxidative stress and OA progression, and its downstream targets were determined using gain- and loss-of-function experiments in various biochemical assays in human chondrocytes (HCs). The in vivo effects of circGNB1 overexpression and knockdown were also determined using a destabilization of the medial meniscus (DMM) mouse model.

RESULTS

Increased circGNB1 expression was detected in HCs under oxidative and inflammatory stress and in the cartilage of older individuals. Mechanistically, circGNB1 sponged miR-152-3p and thus blocked its interaction with its downstream mRNA target, ring finger protein 219 (RNF219), which in turn stabilized caveolin-1 (CAV1) by preventing its ubiquitination at the K47 residue. CircGNB1 inhibited IL-10 signalling by antagonizing miR-152-3p-mediated RNF219 and CAV1 inhibition. Consequently, circGNB1 overexpression promoted OA progression by enhancing catabolic factor expression and oxidative stress and by suppressing anabolic genes in vitro and in vivo. Furthermore, circGNB1 knockdown alleviated the severity of OA, whereas circGNB1 overexpression had the opposite effect in a DMM mouse model of OA.

CONCLUSION

CircGNB1 regulated oxidative stress and OA progression via the miR-152-3p/RNF219/CAV1 axis. Modulating circGNB1 could be an effective strategy for treating OA.

Encapsulation and adhesion of nanoparticles as a potential biomarker for TNBC cells metastatic propensity

Metastasis is the main cause of cancer-related mortality; therefore, the ability to predict its propensity can remarkably affect survival rate. Metastasis development is predicted nowadays by lymph-node status, tumor size, histopathology, and genetic testing. However, all these methods may have inaccuracies, and some require weeks to complete. Identifying novel prognostic markers will open an essential source for risk prediction, possibly guiding to elevated patient treatment by personalized strategies. Cancer cell invasion is a critical step in metastasis. The cytoskeletal mechanisms used by metastatic cells for the invasion process are very similar to the utilization of actin cytoskeleton in the endocytosis process. In the current study, the adhesion and encapsulation efficiency of low-cost carboxylate-modified fluorescent nanoparticles by breast cancer cells with high (HM) and low metastatic potential (LM) have been evaluated; benign cells were used as control. Using high-content fluorescence imaging and analysis, we have revealed (within a short time of 1 h), that efficiency of nanoparticles adherence and encapsulation is sufficiently higher in HM cells compared to LM cells, while benign cells are not encapsulating or adhering the particles during experiment time at all. We have utilized custom-made automatic image analysis algorithms to find quantitative co-localization (Pearson's coefficients) of the nanoparticles with the imaged cells. The method proposed here is straightforward; it does not require especial equipment or expensive materials nor complicated cell manipulations, it may be potentially applicable for various cells, including patient-derived cells. Effortless and quantitative determination of the metastatic likelihood has the potential to be performed using patient-specific biopsy/surgery sample, which will directly influence the choice of protocols for cancer patient's treatment and, as a result, increase their life expectancy.

Mechanisms of Nanoparticle Transport across Intestinal Tissue: An Oral Delivery Perspective

Oral drug administration has been a popular choice due to patient compliance and limited clinical resources. Orally delivered drugs must circumvent the harsh gastrointestinal (GI) environment to effectively enter the systemic circulation. The GI tract has a number of structural and physiological barriers that limit drug bioavailability including mucus, the tightly regulated epithelial layer, immune cells, and associated vasculature. Nanoparticles have been used to enhance oral bioavailability of drugs, as they can act as a shield to the harsh GI environment and prevent early degradation while also increasing uptake and transport of drugs across the intestinal epithelium. Evidence suggests that different nanoparticle formulations may be transported via different intracellular mechanisms to cross the intestinal epithelium. Despite the existence of a significant body of work on intestinal transport of nanoparticles, many key questions remain: What causes the poor bioavailability of the oral drugs? What factors contribute to the ability of a nanoparticle to cross different intestinal barriers? Do nanoparticle properties such as size and charge influence the type of endocytic pathways taken? In this Review, we summarize the different components of intestinal barriers and the types of nanoparticles developed for oral delivery. In particular, we focus on the various intracellular pathways used in nanoparticle internalization and nanoparticle or cargo translocation across the epithelium. Understanding the gut barrier, nanoparticle characteristics, and transport pathways may lead to the development of more therapeutically useful nanoparticles as drug carriers.

Unique features of the arterial blood-brain barrier

CNS vasculature differs from vascular networks of peripheral organs by its ability to tightly control selective material exchange across capillary barriers. Capillary permeability is mostly defined by unique cellular components of the endothelium. While capillaries are extensively investigated, the barrier properties of larger vessels are understudied. Here, we investigate barrier properties of CNS arterial walls. Using tracer challenges and various imaging modalities, we discovered that at the mouse cortex, the arterial barrier does not reside at the classical level of the endothelium. The arterial wall's unique permeability acts bi-directionally; CSF substances travel along the glymphatic path and can penetrate from the peri-vascular space through arteriolar walls towards the lumen. We found that caveolae vesicles in arteriole endothelial are functional transcytosis machinery components, and that a similar mechanism is evident in the human brain. Our discoveries highlight vascular heterogeneity investigations as a potent approach to uncover new barrier mechanisms.

The origin of T-tubules

Ring-like structures made up of caveolae appear to drive the development of membrane invaginations called T-tubules which are important for muscle contraction.

Molecular and clinical characterization of PTRF in glioma via 1,022 samples

Polymerase I and transcript release factor (PTRF) plays a role in the regulation of gene expression and the release of RNA transcripts during transcription, which have been associated with various human diseases. However, the role of PTRF in glioma remains unclear. In this study, RNA sequencing (RNA-seq) data (n = 1022 cases) and whole-exome sequencing (WES) data (n = 286 cases) were used to characterize the PTRF expression features. Gene ontology (GO) functional enrichment analysis was used to assess the biological implication of changes in PTRF expression. As a result, the expression of PTRF was associated with malignant progression in gliomas. Meanwhile, somatic mutational profiles and copy number variations (CNV) revealed the glioma subtypes classified by PTRF expression showed distinct genomic alteration. Furthermore, GO functional enrichment analysis suggested that PTRF expression was associated with cell migration and angiogenesis, particularly during an immune response. Survival analysis confirmed that a high expression of PTRF is associated with a poor prognosis. In summary, PTRF may be a valuable factor for the diagnosis and treatment target of glioma.

Cavin-2 loss exacerbates hypoxia-induced pulmonary hypertension with excessive eNOS phosphorylation and protein nitration

Pulmonary hypertension (PH) is associated with a poor prognosis even in recent years. Caveolin-1 (CAV1), a caveolae-associated protein, is a causal gene in PH. Cavin-2, one of the other caveolae-associated proteins, forms protein complexes with CAV1 and influences each other's functions. However, the role of Cavin-2 in PH has not been thoroughly investigated. To clarify the role of Cavin-2 in PH, we exposed Cavin-2-deficient (Cavin-2 KO) mice to hypoxia. A part of the analyses was confirmed in human pulmonary endothelial cells (HPAECs). After 4-week 10% O₂ hypoxic exposure, we performed physiological, histological, and immunoblotting analyses. Right ventricular (RV) systolic pressure elevation and RV hypertrophy were exacerbated in Cavin-2 KO mice with hypoxia-induced PH (Cavin-2 KO PH mice). The vascular wall thickness of pulmonary arterioles was aggravated in Cavin-2 KO PH mice. Cavin-2 loss reduced CAV1 and induced sustained endothelial nitric oxide synthase (eNOS) hyperphosphorylation in the Cavin-2 KO PH lungs and HPAECs. NOx production associated with eNOS phosphorylation was also increased in the Cavin-2 KO PH lung and HPAECs. Furthermore, the nitration of proteins, including protein kinase G (PKG), was raised in the Cavin-2 KO PH lungs. In conclusion, we revealed that Cavin-2 loss exacerbated hypoxia-induced PH. Our results suggest that Cavin-2 loss leads to sustained eNOS hyperphosphorylation in pulmonary artery endothelial cells via CAV1 reduction, resulting in Nox overproduction-mediated nitration of proteins, including PKG, in smooth muscle cells.

Extracellular vesicle-matrix interactions

The extracellular matrix in microenvironments harbors a variety of signals to control cellular functions and the materiality of tissues. Most efforts to synthetically reconstitute the matrix by biomaterial design have focused on decoupling cell-secreted and polymer-based cues. Cells package molecules into nanoscale lipid membrane-bound extracellular vesicles and secrete them. Thus, extracellular vesicles inherently interact with the meshwork of the extracellular matrix. In this Review, we discuss various aspects of extracellular vesicle-matrix interactions. Cells receive feedback from the extracellular matrix and leverage intracellular processes to control the biogenesis of extracellular vesicles. Once secreted, various biomolecular and biophysical factors determine whether extracellular vesicles are locally incorporated into the matrix or transported out of the matrix to be taken up by other cells or deposited into tissues at a distal location. These insights can be utilized to develop engineered biomaterials where EV release and retention can be precisely controlled in host tissue to elicit various biological and therapeutic outcomes.

Early Endothelial Signaling Transduction in Developing Lung Edema

The lung promptly responds to edemagenic conditions through functional adaptations that contrast the increase in microvascular filtration. This review presents evidence for early signaling transduction by endothelial lung cells in two experimental animal models of edema, hypoxia exposure, and fluid overload (hydraulic edema). The potential role of specialized sites of the plasma membranes considered mobile signaling platforms, referred to as membrane rafts, that include caveolae and lipid rafts, is presented. The hypothesis is put forward that early changes in the lipid composition of the bilayer of the plasma membrane might trigger the signal transduction process when facing changes in the pericellular microenvironment caused by edema. Evidence is provided that for an increase in the extravascular lung water volume not exceeding 10%, changes in the composition of the plasma membrane of endothelial cells are evoked in response to mechanical stimuli from the interstitial compartment as well as chemical stimuli relating with changes in the concentration of the disassembled portions of structural macromolecules. In hypoxia, thinning of endothelial cells, a decrease in caveolae and AQP-1, and an increase in lipid rafts are observed. The interpretation of this response is that it favors oxygen diffusion and hinder trans-cellular water fluxes. In hydraulic edema, which generates greater capillary water leakages, an increase in cell volume and opposite changes in membrane rafts were observed; further, the remarkable increase in caveolae suggests a potential abluminal-luminal vesicular-dependent fluid reabsorption.

Endocytosis in cancer and cancer therapy

Endocytosis is a complex process whereby cell surface proteins, lipids and fluid from the extracellular environment are packaged, sorted and internalized into cells. Endocytosis is also a mechanism of drug internalization into cells. There are multiple routes of endocytosis that determine the fate of molecules, from degradation in the lysosomes to recycling back to the plasma membrane. The overall rates of endocytosis and temporal regulation of molecules transiting through endocytic pathways are also intricately linked with signalling outcomes. This process relies on an array of factors, such as intrinsic amino acid motifs and post-translational modifications. Endocytosis is frequently disrupted in cancer. These disruptions lead to inappropriate retention of receptor tyrosine kinases on the tumour cell membrane, changes in the recycling of oncogenic molecules, defective signalling feedback loops and loss of cell polarity. In the past decade, endocytosis has emerged as a pivotal regulator of nutrient scavenging, response to and regulation of immune surveillance and tumour immune evasion, tumour metastasis and therapeutic drug delivery. This Review summarizes and integrates these advances into the understanding of endocytosis in cancer. The potential to regulate these pathways in the clinic to improve cancer therapy is also discussed.

Porcine Enteric Alphacoronavirus Entry through Multiple Pathways (Caveolae, Clathrin, and Macropinocytosis) Requires Rab GTPases for Endosomal Transport

Porcine enteric alphacoronavirus (PEAV) is a new bat HKU2-like porcine coronavirus, and its endemic outbreak has caused severe economic losses to the pig industry. Its broad cellular tropism suggests a potential risk of cross-species transmission. A limited understanding of PEAV entry mechanisms may hinder a rapid response to potential outbreaks. This study analyzed PEAV entry events using chemical inhibitors, RNA interference, and dominant-negative mutants. PEAV entry into Vero cells depended on three endocytic pathways: caveolae, clathrin, and macropinocytosis. Endocytosis requires dynamin, cholesterol, and a low pH. Rab5, Rab7, and Rab9 GTPases (but not Rab11) regulate PEAV endocytosis. PEAV particles colocalize with EEA1, Rab5, Rab7, Rab9, and Lamp-1, suggesting that PEAV translocates into early endosomes after internalization, and Rab5, Rab7, and Rab9 regulate trafficking to lysosomes before viral genome release. PEAV enters porcine intestinal cells (IPI-2I) through the same endocytic pathway, suggesting that PEAV may enter various cells through multiple endocytic pathways. This study provides new insights into the PEAV life cycle. IMPORTANCE Emerging and reemerging coronaviruses cause severe human and animal epidemics worldwide. PEAV is the first bat-like coronavirus to cause infection in domestic animals. However, the PEAV entry mechanism into host cells remains unknown. This study demonstrates that PEAV enters into Vero or IPI-2I cells through caveola/clathrin-mediated endocytosis and macropinocytosis, which does not require a specific receptor. Subsequently, Rab5, Rab7, and Rab9 regulate PEAV trafficking from early endosomes to lysosomes, which is pH dependent. The results advance our understanding of the disease and help to develop potential new drug targets against PEAV.

Uptake of Tropheryma whipplei by Intestinal Epithelia

Background: Tropheryma whipplei (TW) can cause different pathologies, e.g., Whipple’s disease and transient gastroenteritis. The mechanism by which the bacteria pass the intestinal epithelial barrier, and the mechanism of TW-induced gastroenteritis are currently unknown. Methods: Using ex vivo disease models comprising human duodenal mucosa exposed to TW in Ussing chambers, various intestinal epithelial cell (IEC) cultures exposed to TW and a macrophage/IEC coculture model served to characterize endocytic uptake mechanisms and barrier function. Results: TW exposed ex vivo to human small intestinal mucosae is capable of autonomously entering IECs, thereby invading the mucosa. Using dominant-negative mutants, TW uptake was shown to be dynamin- and caveolin-dependent but independent of clathrin-mediated endocytosis. Complementary inhibitor experiments suggested a role for the activation of the Ras/Rac1 pathway and actin polymerization. TW-invaded IECs underwent apoptosis, thereby causing an epithelial barrier defect, and were subsequently subject to phagocytosis by macrophages. Conclusions: TW enters epithelia via an actin-, dynamin-, caveolin-, and Ras-Rac1-dependent endocytosis mechanism and consecutively causes IEC apoptosis primarily in IECs invaded by multiple TW bacteria. This results in a barrier leak. Moreover, we propose that TW-packed IECs can be subject to phagocytic uptake by macrophages, thereby opening a potential entry point of TW into intestinal macrophages.

Resistance to antibody-drug conjugates in breast cancer: mechanisms and solutions

Antibody-drug conjugates (ADCs) are a rapidly developing therapeutic approach in cancer treatment that has shown remarkable activity in breast cancer. Currently, there are two ADCs approved for the treatment of human epidermal growth factor receptor 2-positive breast cancer, one for triple-negative breast cancer, and multiple investigational ADCs in clinical trials. However, drug resistance has been noticed in clinical use, especially in trastuzumab emtansine. Here, the mechanisms of ADC resistance are summarized into four categories: antibody-mediated resistance, impaired drug trafficking, disrupted lysosomal function, and payload-related resistance. To overcome or prevent resistance to ADCs, innovative development strategies and combination therapy options are being investigated. Analyzing predictive biomarkers for optimal therapy selection may also help to prevent drug resistance.

Caveolin-1-Mediated Cholesterol Accumulation Contributes to Exaggerated mGluR-Dependent Long-Term Depression and Impaired Cognition in Fmr1 Knockout Mice

Fragile X syndrome (FXS) is one of the most common inherited mental retardation diseases and is caused by the loss of fragile X mental retardation protein (FMRP) expression. The metabotropic glutamate receptor (mGluR) theory of FXS states that enhanced mGluR-dependent long-term depression (LTD) due to FMRP loss is involved in aberrant synaptic plasticity and autistic-like behaviors, but little is known about the underlying molecular mechanism. Here, we found that only hippocampal mGluR-LTD was exaggerated in adolescent Fmr1 KO mice, while N-methyl-D-aspartate receptor (NMDAR)-LTD was intact in mice of all ages. This development-dependent alteration was related to the differential expression of caveolin-1 (Cav1), which is essential for caveolae formation. Knockdown of Cav1 restored the enhanced mGluR-LTD in Fmr1 KO mice. Moreover, hippocampal Cav1 expression in Fmr1 KO mice induced excessive endocytosis of the α-amino-3-hydroxyl-5-methyl-4-isoxazolepropionate (AMPA) receptor subunit GluA2. This process relied on mGluR1/5 activation rather than NMDAR. Interference with Cav1 expression reversed these changes. Furthermore, massive cholesterol accumulation contributed to redundant caveolae formation, which provided the platform for mGluR-triggered Cav1 coupling to GluA2. Importantly, injection of the cholesterol scavenger methyl-β-cyclodextrin (Mβ-CD) recovered AMPA receptor trafficking and markedly alleviated hyperactivity, hippocampus-dependent fear memory, and spatial memory defects in Fmr1 KO mice. Together, our findings elucidate the important role of Cav1 in mediating mGluR-LTD enhancement and further inducing AMPA receptor endocytosis and suggest that cholesterol depletion by Mβ-CD during caveolae formation may be a novel and safe strategy to treat FXS.

New insights into the role of dietary triglyceride absorption in obesity and metabolic diseases

The incidence of obesity and associated metabolic diseases is increasing globally, adversely affecting human health. Dietary fats, especially triglycerides, are an important source of energy for the body, and the intestine absorbs lipids through a series of orderly and complex steps. A long-term high-fat diet leads to intestinal dysfunction, inducing obesity and metabolic disorders. Therefore, regulating dietary triglycerides absorption is a promising therapeutic strategy. In this review, we will discuss diverse aspects of the dietary triglycerides hydrolysis, fatty acid uptake, triglycerides resynthesis, chylomicron assembly, trafficking, and secretion processes in intestinal epithelial cells, as well as potential targets in this process that may influence dietary fat-induced obesity and metabolic diseases. We also mention the possible shortcomings and deficiencies in modulating dietary lipid absorption targets to provide a better understanding of their administrability as drugs in obesity and related metabolic disorders.

Regulation of membrane protein structure and function by their lipid nano-environment

Transmembrane proteins comprise ~30% of the mammalian proteome, mediating metabolism, signalling, transport and many other functions required for cellular life. The microenvironment of integral membrane proteins (IMPs) is intrinsically different from that of cytoplasmic proteins, with IMPs solvated by a compositionally and biophysically complex lipid matrix. These solvating lipids affect protein structure and function in a variety of ways, from stereospecific, high-affinity protein-lipid interactions to modulation by bulk membrane properties. Specific examples of functional modulation of IMPs by their solvating membranes have been reported for various transporters, channels and signal receptors; however, generalizable mechanistic principles governing IMP regulation by lipid environments are neither widely appreciated nor completely understood. Here, we review recent insights into the inter-relationships between complex lipidomes of mammalian membranes, the membrane physicochemical properties resulting from such lipid collectives, and the regulation of IMPs by either or both. The recent proliferation of high-resolution methods to study such lipid-protein interactions has led to generalizable insights, which we synthesize into a general framework termed the 'functional paralipidome' to understand the mutual regulation between membrane proteins and their surrounding lipid microenvironments.

Nanoscale membrane curvature sorts lipid phases and alters lipid diffusion

The precise spatiotemporal control of nanoscale membrane shape and composition is the result of a complex interplay of individual and collective molecular behaviors. Here, we employed single-molecule localization microscopy and computational simulations to observe single-lipid diffusion and sorting in model membranes with varying compositions, phases, temperatures, and curvatures. Supported lipid bilayers were created over 50-nm-radius nanoparticles to mimic the size of naturally occurring membrane buds, such as endocytic pits and the formation of viral envelopes. The curved membranes recruited liquid-disordered lipid phases while altering the diffusion and sorting of tracer lipids. Disorder-preferring fluorescent lipids sorted to and experienced faster diffusion on the nanoscale curvature only when embedded in a membrane capable of sustaining lipid phase separation at low temperatures. The curvature-induced sorting and faster diffusion even occurred when the sample temperature was above the miscibility temperature of the planar membrane, implying that the nanoscale curvature could induce phase separation in otherwise homogeneous membranes. Further confirmation and understanding of these results are provided by continuum and coarse-grained molecular dynamics simulations with explicit and spontaneous curvature-phase coupling, respectively. The curvature-induced membrane compositional heterogeneity and altered dynamics were achieved only with a coupling of the curvature with a lipid phase separation. These cross-validating results demonstrate the complex interplay of lipid phases, molecular diffusion, and nanoscale membrane curvature that are critical for membrane functionality.

PI(4,5)P2 and Cholesterol: Synthesis, Regulation, and Functions

Phosphatidylinositol 4,5-bisphosphate (PI(4,5)P₂) is the most abundant membrane phosphoinositide and cholesterol is an essential component of the plasma membrane (PM). Both lipids play key roles in a variety of cellular functions including as signaling molecules and major regulators of protein function. This chapter provides an overview of these two important lipids. Starting from a brief description of their structure, synthesis, and regulation, the chapter continues to describe the primary functions and signaling processes in which PI(4,5)P₂ and cholesterol are involved. While PI(4,5)P₂ and cholesterol can act independently, they often act in concert or affect each other's impact. The chapters in this volume on "Cholesterol and PI(4,5)P₂ in Vital Biological Functions: From Coexistence to Crosstalk" focus on the emerging relationship between cholesterol and PI(4,5)P₂ in a variety of biological systems and processes. In this chapter, the next section provides examples from the ion channel field demonstrating that PI(4,5)P₂ and cholesterol can act via common mechanisms. The chapter ends with a discussion of future directions.

Increased Caveolin-2 Expression in Brain Endothelial Cells Promotes Age-Related Neuroinflammation

Aging is a major risk factor for common neurodegenerative diseases. Although multiple molecular, cellular, structural, and functional changes occur in the brain during aging, the involvement of caveolin-2 (Cav-2) in brain ageing remains unknown. We investigated Cav-2 expression in brains of aged mice and its effects on endothelial cells. The human umbilical vein endothelial cells (HUVECs) showed decreased THP-1 adhesion and infiltration when treated with Cav-2 siRNA compared to control siRNA. In contrast, Cav-2 overexpression increased THP-1 adhesion and infiltration in HUVECs. Increased expression of Cav-2 and iba-1 was observed in brains of old mice. Moreover, there were fewer iba-1-positive cells in the brains of aged Cav-2 knockout (KO) mice than of wild-type aged mice. The levels of several chemokines were higher in brains of aged wild-type mice than in young wild-type mice; moreover, chemokine levels were significantly lower in brains of young mice as well as aged Cav-2 KO mice than in their wild-type counterparts. Expression of PECAM1 and VE-cadherin proteins increased in brains of old wild-type mice but was barely detected in brains of young wild-type and Cav-2 KO mice. Collectively, our results suggest that Cav-2 expression increases in the endothelial cells of aged brain, and promotes leukocyte infiltration and age-associated neuroinflammation.

Structural determinants of REMORIN nanodomain formation in anionic membranes

Remorins are a family of multigenic plasma membrane phosphoproteins involved in biotic and abiotic plant interaction mechanisms, partnering in molecular signaling cascades. Signaling activity of remorins depends on their phosphorylation states and subsequent clustering into nanosized membrane domains. The presence of a coiled-coil domain and a C-terminal domain is crucial to anchor remorins to negatively charged membrane domains; however, the exact role of the N-terminal intrinsically disordered domain (IDD) on protein clustering and lipid interactions is largely unknown. Here, we combine chemical biology and imaging approaches to study the partitioning of group 1 remorin into anionic model membranes mimicking the inner leaflet of the plant plasma membrane. Using reconstituted membranes containing a mix of saturated and unsaturated phosphatidylcholine, phosphatidylinositol phosphates, and sterol, we investigate the clustering of remorins to the membrane and monitor the formation of nanosized membrane domains. REM1.3 promoted membrane nanodomain organization on the exposed external leaflet of both spherical lipid vesicles and flat supported lipid bilayers. Our results reveal that REM1.3 drives a mechanism allowing lipid reorganization, leading to the formation of remorin-enriched nanodomains. Phosphorylation of the N-terminal IDD by the calcium protein kinase CPK3 influences this clustering and can lead to the formation of smaller and more disperse domains. Our work reveals the phosphate-dependent involvement of the N-terminal IDD in the remorin-membrane interaction process by driving structural rearrangements at lipid-water interfaces.

Effects of morphology and size of nanoscale drug carriers on cellular uptake and internalization process: a review

In the field of targeted drug delivery, the effects of size and morphology of drug nanocarriers are of great importance and need to be discussed in depth. To be concise, among all the various shapes of nanocarriers, rods and tubes with a narrow cross-section are the most preferred shapes for the penetration of a cell membrane. In this regard, several studies have focused on methods to produce nanorods and nanotubes with controlled optimized size and aspect ratio (AR). Additionally, a non-spherical orientation could affect the cellular uptake process while a tangent angle of less than 45° is better at penetrating the membrane, and Ω = 90° is beneficial. Moreover, these nanocarriers show different behaviors when confronting diverse cells whose fields should be investigated in future studies. In this survey, a comprehensive classification based on carrier shape is first submitted. Then, the most commonly used methods for control over the size and shape of the carriers are reviewed. Finally, influential factors on the cellular uptake and internalization processes and related analytical methods for evaluating this process are discussed.

Interaction between caveolin-1 polymorphism and dietary fat quality indexes on visceral adiposity index (VAI) and body adiposity index (BAI) among overweight and obese women: a cross-sectional study

BACKGROUND AND AIMS

Caveolin-1 (CAV-1) in adipocyte tissue and other body parts possesses numerous biological functions. In the present study, we sought to investigate the interaction between CAV-1 polymorphism and dietary fat quality indexes on visceral adiposity index (VAI) and body adiposity index (BAI) among overweight and obese women.

METHODS

This study was conducted on 386 women aged 18-48 years old. Biochemical measurements were assessed by standard protocols. We used a food frequency questionnaire (FFQ) to calculate the dietary intake and the indexes of dietary fat quality intake. Anthropometric values and body composition were measured by standard methods. Finally, the CAV-1 genotype was measured using the PCR-RFLP method.

RESULTS

We found marginally significant differences between AA and GG genotypes of waist-to-hip ratio (WHR) (P = 0.06) and BAI (P = 0.06) of participants after adjusting for potential confounders. For dietary intakes, after adjusting with the energy intake, mean differences in biotin (P = 0.04) and total fiber (P = 0.06) were significant and marginally significant, respectively. The interaction between two risk alleles (AA) with omega-6 to omega-3 ratio (W6/W3) on BAI, after adjustment for potential confounders (age, physical activity, energy intake, education), was marginally positive (β = 14.08, 95% CI = - 18.65, 46.81, P = 0.07). In comparison to the reference group (GG), there was a positive interaction between the two risk alleles (AA) with W6/W3 ratio on VAI (β = 2.81, 95% CI = 1.20, 8.84, P = 0.06) in the adjusted model.

CONCLUSIONS

We found that there might be an interaction between CAV-1 genotypes with dietary quality fat indexes on VAI and BAI among overweight and obese women.