Caveola-mediated Endocytosis Research Articles

Reciprocal regulation of eNOS and caveolin-1 functions in endothelial cells.

We hypothesized that the maintenance of vascular homeostasis is critically dependent on the expression and reciprocal regulation of caveolin-1 (Cav-1) and endothelial nitric oxide synthase (eNOS) in endothelial cells (ECs). Skeletal muscle biopsies from subjects with type 2 diabetes showed 50% less Cav-1 and eNOS than those from lean healthy controls. The Cav-1:eNOS expression ratio was 200:1 in primary culture human ECs. Cav-1 small interfering RNA (siRNA) reduced eNOS protein and gene expression in association with a twofold increase in eNOS phosphorylation and nitrate production per molecule of eNOS, which was reversed in cells overexpressing Adv-Cav-1-GFP. Upon addition of the Ca2+ ionophore A23187 to activate eNOS, we observed eNOS Ser1177 phosphorylation, its translocation to β-catenin-positive cell–cell junctions, and increased colocalization of eNOS and Cav-1 within 5 min. We also observed Cav-1 S-nitrosylation and destabilization of Cav-1 oligomers in cells treated with A23187 as well as insulin or albumin, and this could be blocked by L-NAME, PP2, or eNOS siRNA. Finally, caveola-mediated endocytosis of albumin or insulin was reduced by Cav-1 or eNOS siRNA, and the effect of Cav-1 siRNA was rescued by Adv-Cav-1-GFP. Thus, Cav-1 stabilizes eNOS expression and regulates its activity, whereas eNOS-derived NO promotes caveola-mediated endocytosis.

N-mercapto acetyl-N′-octyl-O, N″-glycol chitosan as an efficiency oral delivery system of paclitaxel

Herein, thioglycolic acid modified N-octyl-O, N′-glycol chitosan (N-mercapto acetyl-N′-octyl-O, N″-glycol chitosan, abbreviated as SH-OGC) was synthesized to improve the oral bioavailability of paclitaxel (PTX). PTX was readily solubilized into the hydrophobic inner core of SH-OGC. Pharmacokinetic studies demonstrated that the bioavailability of PTX was greatly enhanced when delivered by SH-OGC compared to Taxol® or non-sulfhydrylated OGC micelles. Caco-2 cell experiments confirmed PTX or rhodamine-123-loaded SH-OGC demonstrated effective cellular accumulation via caveola-mediated endocytosis along with the inhibition of P-gp efflux. Furthermore, Caco-2 transport studies demonstrated that the mechanistic basis of SH-OGC efficacy was attributed to P-gp inhibition, enhanced permeability of tight junctions and clathrin-mediated transcytosis across the endothelium. In addition, SH-OGC exhibited increased intestinal retention through thiol-mediated mucoadhesion compared with OGC according to results of mucoadhesion evaluation on freshly excised rat intestine. In summary, SH-OGC micelles may present as a promising delivery vehicle for enhancing the oral bioavailability of P-gp substrates.

Abstract 72: Human Vascular Smooth Muscle Gene Expression Profiling Between Incracranial and Extracranial Vasculature

Background: Intracranial arteries (IA) have unique histological, pharmacological, and pathological characteristics when compared to extracranial arteris (EA). Despite its importance, little is known about the molecular characteristics of those vessels. In this study, we carried out a genome-wide characterization on expressions of mRNAs, and performed integrative analyses in conjunction with changes of the transcriptome between IA and EA vascular smooth muscle cells. Methods: mRNA expression screening was performed from same autopsied body (n=3) using Agilent Human mRNA arrays for IA (middle cerebral a.) and EA (left ant. descending a. of coronary a.) vascular smooth muscle (vSMC) layer. Total gene expression compared with intracranial vs. extracranial vSMC. Results: As compared to EA, we identified 304 mRNA that were differentially expressed in the IA vSMC (p<0.05 and fold change >2), including 224 upregulated and 80 downregulated. Through this comparison we have identified angiogenesis, cell migration, cell proliferation, neurogenesis, and inflammatory response genes whose expression is enriched in IA vSMC. This analysis has identified that RAR activation, and Caveolar-mediated endocytosis signaling cascade is specifically enriched at the IA vSMC, implicating this pathway in regulating this arterial system. Conclusions: This dataset provides a resource for understanding the different arterial regulation and disease susceptibility in IA and EA, especially atherosclerosis and diabetes.Funding: This study was supported by a grant from the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Kim HS, NRF-2016R1A2B4008316).

Membrane-Bound Estrogen Receptor Alpha Initiated Signaling is Dynamin Dependent in MCF-7 Cells

Although membrane-associated estrogen receptors (mERs) have been known to play important role in steroid induced signal transmission, we still know little about their function in the estrogen induced proliferation of breast cancer cells. In our current work we tried to separate membrane initiated estrogen receptor (ERα,) signaling from the overall estrogenic effect in MCF7 breast carcinoma cells. Re-analyzing expression data from multiple microarray experiments, we selected a set of key regulatory genes involved in proliferation regulation and estrogen signaling. Our quantitative real time-PCR results confirmed that the selective membrane receptor agonist, estrogen-BSA induces similarly pronounced expression changes regarding these genes as 17β-estradiol. Our light and electronmicroscopical studies revealed that the membrane-bound form of classical estrogen receptor alpha is internalized after ligand binding via dynamin dependent, caveola-mediated endocytosis. Inhibition of this internalization with dynamin inhibitor, dynasore practically abolished the regulatory effect of E2-BSA, suggesting that interaction and internalization with the scaffold protein is necessary for effective signaling. The physiological role of plasma membrane estrogen receptor alpha is intensively studied, yet there are still several aspects of it to be resolved. The dynamin-dependent, ligand mediated internalization of mERs seems to play an important role in estrogen signaling. Our results may serve as another example how membrane initiated and nuclear receptor signaling well-orchestrated is and form an integrated system.

Renal carcinoma/kidney progenitor cell chimera organoid as a novel tumorigenesis gene discovery model.

ABSTRACTThree-dimensional (3D) organoids provide a new way to model various diseases, including cancer. We made use of recently developed kidney-organ-primordia tissue-engineering technologies to create novel renal organoids for cancer gene discovery. We then tested whether our novel assays can be used to examine kidney cancer development. First, we identified the transcriptomic profiles of quiescent embryonic mouse metanephric mesenchyme (MM) and of MM in which the nephrogenesis program had been induced ex vivo. The transcriptome profiles were then compared to the profiles of tumor biopsies from renal cell carcinoma (RCC) patients, and control samples from the same kidneys. Certain signature genes were identified that correlated in the developmentally induced MM and RCC, including components of the caveolar-mediated endocytosis signaling pathway. An efficient siRNA-mediated knockdown (KD) of Bnip3, Gsn, Lgals3, Pax8, Cav1, Egfr or Itgb2 gene expression was achieved in mouse RCC (Renca) cells. The live-cell imaging analysis revealed inhibition of cell migration and cell viability in the gene-KD Renca cells in comparison to Renca controls. Upon siRNA treatment, the transwell invasion capacity of Renca cells was also inhibited. Finally, we mixed E11.5 MM with yellow fluorescent protein (YFP)-expressing Renca cells to establish chimera organoids. Strikingly, we found that the Bnip3-, Cav1- and Gsn-KD Renca-YFP+ cells as a chimera with the MM in 3D organoid rescued, in part, the RCC-mediated inhibition of the nephrogenesis program during epithelial tubules formation. Altogether, our research indicates that comparing renal ontogenesis control genes to the genes involved in kidney cancer may provide new growth-associated gene screens and that 3D RCC-MM chimera organoids can serve as a novel model with which to investigate the behavioral roles of cancer cells within the context of emergent complex tissue structures.

Positively Charged Surface-Modified Solid Lipid Nanoparticles Promote the Intestinal Transport of Docetaxel through Multifunctional Mechanisms in Rats.

Solid lipid nanoparticles (SLNs) are one of the most promising nanocarriers to increase the oral absorption of drugs with poor solubility and low permeability. However, the absorption mechanism of SLNs remains incomplete and thus requires further careful consideration. In this study, positively charged chitosan (CS) modified SLNs or hydroxypropyl trimethylammonium chloride chitosan (HACC) modified SLNs were designed and their absorption mechanisms were fully clarified to improve the oral absorption of docetaxel (DTX). The HACC-DTX-SLNs showed the highest cellular uptake in Caco-2 cell monolayer; the transport efficacy in the follicle-associated epithelium cell monolayer was higher than that in the Caco-2 cell monolayer. The CS- or HACC-modified SLNs could reversibly regulate the transepithelial electrical resistance and the expressions of tight junction (TJ) associated proteins, such as claudin-1, occludin, and zonula occludens-1. The uptake of HACC-DTX-SLNs through Peyer's patches was higher than that of the normal tissue of the small intestine in rats. The enhanced absorption mechanisms of HACC-DTX-SLNs were mainly related to the caveola-mediated endocytosis, M cell phagocytosis, and reversible TJ opening.

Host cell virus entry mechanisms enhance anti-JCV-antibody switch in natalizumab-treated multiple sclerosis patients.

Estimating the individual risk for the development of progressive multifocal leukoencephalopathy (PML) in anti-John Cunningham virus (JCV) antibody-negative patients with multiple sclerosis (MS) treated with natalizumab is a major challenge. A serological conversion occurring under treatment from anti-JCV antibody-negative to positive status may significantly increase this risk. We investigated changes in peripheral blood cells' gene expression induced by natalizumab treatment in anti-JCV antibody-negative MS patients and tested blood transcriptional profile that characterizes patients predisposed to antibody switch under natalizumab treatment. After 3years of natalizumab treatment, 24.6% of anti-JCV antibody-negative MS patients switched to become anti-JCV antibody-positive (JCV switchers). Natalizumab induced 946 and 1186 significantly differentiating genes in JCV switchers and non-switchers, respectively. In JCV switchers, the signature was enriched by over-expression of genes associated with the first stages of viral entry to host cells including macropinocytosis (p = 1.82E-06), virus entry via endocytosis (p = 1.60E-06), clathrin-mediated endocytosis (p = 1.13E-04), and caveolar-mediated endocytosis (p = 4.50E-04) pathways. Further analysis to identify pre-existing transcriptional differences that characterize future JCV switchers prior to treatment initiation also demonstrated a transcriptional signature enriched by similar viral entry mechanisms. These findings, verified in an additional independent cohort of natalizumab-treated patients, could lead to future identification of patients that remain anti-JCV antibody-negative thus allowing safe continuation of treatment, as well as the development of future targeted therapeutic interventions to reduce the risk of PML.

Photothermal Ablation of in Situ Renal Tumor by PEG-IR780-C13 Micelles and Near-Infrared Irradiation.

PEG-IR780-C13 micelles have been demonstrated to be a novel photothermal agent with tumor-targeting property. This study was designed to explore the feasibility of applying PEG-IR780-C13 micelles and near-infrared (NIR) irradiation for thermal ablation of renal tumor by using an in situ tumor model. In addition, the potential thermal injury to normal renal tissue was evaluated. PEG-IR780-C13 micelles were intended to accumulate in renal tumor after systemic delivery. In vitro results revealed that PEG-IR780-C13 micelles were uptaken by RENCA cells mainly through caveola-mediated endocytosis and mainly distributed in late endosomes and lysosomes. Upon NIR irradiation, PEG-IR780-C13 micelles generated heat effectively both in vitro and in vivo, exhibiting a promising photothermal therapeutic property. The photothermal effect of PEG-IR780-C13 micelles could effectively destroy RENCA cells in vitro and adequately inhibit growth of in situ renal tumor in vivo. Meanwhile, PEG-IR780-C13 micelles mediated photothermal therapy (PTT) resulting in only limited injury to normal renal tissue surrounding tumor sites. Our data indicated that PEG-IR780-C13 micelles mediating PTT could generate tumor-specific heat for destruction of renal tumor in a minimally invasive way, providing a novel strategy for thermal ablation of renal tumor.

Comparative Profiling of Triple-Negative Breast Carcinomas Tissue Glycoproteome by Sequential Purification of Glycoproteins and Stable Isotope Labeling

Background: Women with triple negative breast cancers (TNBCs) have a poor prognosis due to lack of suitable targeted therapies. Changes in the protein glycosylation are increasingly being recognized as an important modification associated with cancer etiology. Methods: In an attempt to identify TNBC biomarkers with greater diagnostic and prognostic capabilities, hydrazide- based chemistry method combined with LC-MS/MS were used to purify and identify N-linked glycopeptides or glycoproteins of tissues from TNBC patients. Results: A total of 550 unique N-linked glycoproteins were identified, among these proteins, 72 unique N-linked glycoproteins were significantly regulated in tumor tissues, of which 56 proteins were upregulated and 16 proteins were downregulated. To assess the validity of the results, three selected proteins including Vascular endothelial growth factor receptor 1, Insulin receptor, Tissue factor pathway inhibitor were selected for western blot analysis, and these proteins were found as potential biomarkers of TNBC. The top three pathways of differentially expressed glycoproteins participated in were caveolar-mediated endocytosis signaling, agrin interactions at neuromuscular junction and LXR/RXR activation. Conclusion: This work provides potential glycoprotein markers to function as a novel tissue-based biomarker for TNBC.

Scavenger receptor class B, type I-mediated uptake of A1AT by pulmonary endothelial cells

In addition to exerting a potent anti-elastase function, α-1 antitrypsin (A1AT) maintains the structural integrity of the lung by inhibiting endothelial inflammation and apoptosis. A main serpin secreted in circulation by hepatocytes, A1AT requires uptake by the endothelium to achieve vasculoprotective effects. This active uptake mechanism, which is inhibited by cigarette smoking (CS), involves primarily clathrin- but also caveola-mediated endocytosis and may require active binding to a receptor. Because circulating A1AT binds to high-density lipoprotein (HDL), we hypothesized that scavenging receptors are candidates for endothelial uptake of the serpin. Although the low-density lipoprotein (LDL) receptor-related protein 1 (LRP1) internalizes only elastase-bound A1AT, the scavenger receptor B type I (SR-BI), which binds and internalizes HDL and is modulated by CS, may be involved in A1AT uptake. Transmission electron microscopy imaging of colloidal gold-labeled A1AT confirmed A1AT endocytosis in both clathrin-coated vesicles and caveolae in endothelial cells. SR-BI immunoprecipitation identified binding to A1AT at the plasma membrane. Pretreatment of human lung microvascular endothelial cells with SR-B ligands (HDL or LDL), knockdown of SCARB1 expression, or neutralizing SR-BI antibodies significantly reduced A1AT uptake by 30-50%. Scarb1 null mice exhibited decreased A1AT lung content following systemic A1AT administration and reduced lung anti-inflammatory effects of A1AT supplementation during short-term CS exposure. In turn, A1AT supplementation increased lung SR-BI expression and modulated circulating lipoprotein levels in wild-type animals. These studies indicate that SR-BI is an important mediator of A1AT endocytosis in pulmonary endothelium and suggest a cross talk between A1AT and lipoprotein regulation of vascular functions.

The subcellular compartmentalization of TGFβ-RII and the dynamics of endosomal formation during the signaling events: An in vivo study on rat mesothelial cells

We previously showed that intraperitoneal administration of Freund's adjuvant treatment resulted in acute peritonitis and TGF-β was found to be one of the main organizers of the subsequent EMT in mesothelial cells. In the present study, we investigated whether TGF-β signaling molecules are present in mesothelial cells and how their compartmentalization pattern changes with the dynamics of inflammatory events in vivo. In addition, we tried to evaluate the turnover of endosomal compartments concomitant with the internalization of signaling molecules and examine whether caveola-mediated internalization might play a role in the termination of TGF-β signaling.Using immunocytochemical approach, we could detect TβRII in EEA1 positive compartments and as the inflammation progressed, at D3, the receptor appeared in caveolin-1 positive intracellular structures as well. The latter event was accompanied by the appearance of negative regulatory protein, Smad7 in caveolae. We also found EEA1 and caveolin-1 double positive vesicular structures that were corresponded to forming MVBs affirmed by our immuno-electron microscopical results. Fine structural, morphometric and immunoblot analysis proved that Cd63 positive multivesicular body (MVB) formation was significantly increased by D3 and the IP results confirmed that TβRII as well as caveolin-1 were strongly associated with these endosomal compartments at this time. In contrast, by the termination of inflammation, by D5, caveolin-1 was found to be associated with late endosomal marker, Rab7 and entirely degraded from the system.Despite the limitations of an in vivo system, our results provide both morphological and biochemical data about the endosomal compartments involved in the internalization of TβRII upon inflammatory stimuli. Furthermore, our study implies the possible role of caveola-mediated endocytosis in the attenuation of TGF-β signaling and highlight the significance of endosomal compartments via which caveolae might meet the classical endocytic pathway under in vivo inflammatory conditions.

Gene network and canonical pathway analysis in canine myxomatous mitral valve disease: A microarray study

Myxomatous mitral valve disease (MMVD) is the single most common acquired heart disease of the dog and is particularly common in small pedigree breed dogs such as the Cavalier King Charles spaniel (CKCS). There are limited data on the mitral valve transcriptome and the aim of this study was to use the microarray technology in conjunction with bioinformatics platforms to analyse transcript changes in MMVD in CKCS compared to normal dogs (non-CKCS). Differentially expressed genes (n = 5397) were identified using cut-off settings of fold change, false discovery rate (FDR) and P < 0.05. In total, 4002 genes were annotated to a specific transcript in the Affymetrix canine database, and after further filtering, 591 annotated canine genes were identified: 322 (55%) were up-regulated and 269 (45%) were down-regulated. Canine microRNAs (cfa-miR; n = 59) were also identified.Gene ontology and network analysis platforms identified between six and 10 significantly different biological function clusters from which the following were selected as relevant to MMVD: inflammation, cell movement, cardiovascular development, extracellular matrix organisation and epithelial-to-mesenchymal (EMT) transition. Ingenuity Pathway Analysis identified three canonical pathways relevant to MMVD: caveolar-mediated endocytosis, remodelling of epithelial adherens junctions, and endothelin-1 signalling. Considering the biological relevance to MMVD, the gene families of importance with significant difference between groups included collagens, ADAMTS peptidases, proteoglycans, matrix metalloproteinases (MMPs) and their inhibitors, basement membrane components, cathepsin S, integrins, tight junction cell adhesion proteins, cadherins, other matrix-associated proteins, and members of the serotonin (5-HT)/transforming growth factor -β signalling pathway.

Identification of phosphatidylcholine transfer protein-like in the parasite Entamoeba histolytica.

Caveolin is the protein marker of caveola-mediated endocytosis. Previously, we demonstrated by immunoblotting and immunofluorescence that an anti-chick embryo caveolin-1 monoclonal antibody (mAb) recognizes a protein in amoeba extracts. Nevertheless, the caveolin-1 gene is absent in the Entamoeba histolytica genome database. In this work, the goal was to isolate, identify and characterize the protein that cross-reacts with chick embryo caveolin-1. We identified the protein using a proteomic approach, and the complete gene was cloned and sequenced. The identified protein, E.histolytica phosphatidylcholine transfer protein-like (EhPCTP-L), is a member of the StAR-related lipid transfer (START) protein superfamily. The human homolog binds and transfers phosphatidylcholine (PC) and phosphatidylethanolamine (PE) between model membranes invitro; however, the physiological role of PCTP-L remains elusive. Studies in silico showed that EhPCTP-L has a central START domain and also contains a C-terminal intrinsically disordered region. The anti-rEhPCTP-L antibody demonstrated that EhPCTP-L is found in the plasma membrane and cytosol, which is in agreement with previous reports on the human counterpart. This result points to the plasma membrane as one possible target membrane for EhPCTP-L. Furthermore, assays using filipin and nystatin showed down regulation of EhPCTP-L, in an apparently cholesterol-independent way. Interestingly, EhPCTP-L binds primarily to anionic phospholipids phosphatidylserine (PS) and phosphatidic acid (PA), while its mammalian counterpart HsPCTP-L binds neutral phospholipids PC and PE. The present study provides information that helps reveal the possible function and regulation of PCTP-L expression in the primitive eukaryotic parasite E.histolytica.

Estrogen Receptor Alpha Is Expressed in Mesenteric Mesothelial Cells and Is Internalized in Caveolae upon Freund's Adjuvant Treatment

Transformation of epithelial cells into connective tissue cells (epithelial-mesenchymal transition, EMT) is a complex mechanism involved in tumor metastasis, and in normal embryogenesis, while type II EMT is mainly associated with inflammatory events and tissue regenaration.In this study we examined type II EMT at the ultrastructural and molecular level during the inflammatory process induced by Freund's adjuvant treatment in rat mesenteric mesothelial cells. We found that upon the inflammatory stimulus mesothelial cells lost contact with the basal lamina and with each other, and were transformed into spindle-shaped cells. These morphological changes were accompanied by release of interleukins IL-1alpha, -1beta and IL-6 and by secretion of transforming growth factor beta (TGF-β) into the peritoneal cavity. Mesothelial cells also expressed estrogen receptor alpha (ER-α) as shown by immunolabeling at the light and electron microscopical levels, as well as by quantitative RT-PCR. The mRNA level of ER-α showed an inverse correlation with the secretion of TGF-β. At the cellular and subcellular levels ER-α was colocalized with the coat protein caveolin-1 and was found in the plasma membrane of mesothelial cells, in caveolae close to multivesicular bodies (MVBs) or in the membrane of these organelles, suggesting that ER-α is internalized via caveola-mediated endocytosis during inflammation. We found asymmetric, thickened, electron dense areas on the limiting membrane of MVBs (MVB plaques) indicating that these sites may serve as platforms for collecting and organizing regulatory proteins. Our morphological observations and biochemical data can contribute to form a potential model whereby ER-α and its caveola-mediated endocytosis might play role in TGF-β induced type II EMT in vivo.

Effect of surface charge on the colloidal stability and in vitro uptake of carboxymethyl dextran-coated iron oxide nanoparticles.

Nanoparticle physicochemical properties such as surface charge are considered to play an important role in cellular uptake and particle-cell interactions. In order to systematically evaluate the role of surface charge on the uptake of iron oxide nanoparticles, we prepared carboxymethyl-substituted dextrans with different degrees of substitution, ranging from 38 to 5 groups per chain, and reacted them using carbodiimide chemistry with amine-silane-coated iron oxide nanoparticles with narrow size distributions in the range of 33-45 nm. Surface charge of carboxymethyl-substituted dextran-coated nano-particles ranged from -50 to 5 mV as determined by zeta potential measurements, and was dependent on the number of carboxymethyl groups incorporated in the dextran chains. Nanoparticles were incubated with CaCo-2 human colon cancer cells. Nanoparticle-cell interactions were observed by confocal laser scanning microscopy and uptake was quantified by elemental analysis using inductively coupled plasma mass spectroscopy. Mechanisms of internalization were inferred using pharmacological inhibitors for fluid-phase, clathrin-mediated, and caveola-mediated endocytosis. Results showed increased uptake for nanoparticles with greater negative charge. Internalization patterns suggest that uptake of the most negatively charged particles occurs via non-specific interactions.

The Role of Endocytic Pathways in TGF-β Signaling

Transforming growth factor β (TGF-β) superfamily consists of numerous cytokins that regulate various cellular processes. TGF-β, the prototype of the family, signals through its cell surface serine/threonin kinase receptors and besides its role in cell differentiation, migration, adhesion etc. it is also able to induce epithelial-mesenchymal (EMT) transition via both Smad- pathway and MAPK- pathway. Among the different types of epithelial-mesenchymal transition, type II that is described to be associated with wound healing, tissue regeneration, organ fibrosis and is induced upon inflammatory stimuli. It can be triggered by secretion of growth factors such as TGF-β, EGF. Different endocytic routes are used for the internalization of TGF-β ligand and its receptors and these pathways can control the activity of downstream events. Internalization via clathrin-coated vesicles promotes the signaling while the caveola-mediated endocytosis plays important role in the termination of the events, although the steps of the latter event are less clear. The early endosome is considered a clue compartment in promoting the signaling. Recently published data suggest that the early endosome plays crucial role in the termination of the TGFβ signaling as well. It is not only maintain a special environment for the effective signaling but can direct the internalized cargos towards degradative pathways (multivesicular bodies, lysosomes).

Rift Valley Fever Virus Strain MP-12 Enters Mammalian Host Cells via Caveola-Mediated Endocytosis

Rift Valley fever virus (RVFV) is a zoonotic pathogen capable of causing serious morbidity and mortality in both humans and livestock. The lack of efficient countermeasure strategies, the potential for dispersion into new regions, and the pathogenesis in humans and livestock make RVFV a serious public health concern. The receptors, cellular factors, and entry pathways used by RVFV and other members of the family Bunyaviridae remain largely uncharacterized. Here we provide evidence that RVFV strain MP-12 uses dynamin-dependent caveola-mediated endocytosis for cell entry. Caveolae are lipid raft domains composed of caveolin (the main structural component), cholesterol, and sphingolipids. Caveola-mediated endocytosis is responsible for the uptake of a wide variety of host ligands, as well as bacteria, bacterial toxins, and a number of viruses. To determine the cellular entry mechanism of RVFV, we used small-molecule inhibitors, RNA interference (RNAi), and dominant negative (DN) protein expression to inhibit the major mammalian cell endocytic pathways. Inhibitors and RNAi specific for macropinocytosis and clathrin-mediated endocytosis had no effect on RVFV infection. In contrast, inhibitors of caveola-mediated endocytosis, and RNAi targeted to caveolin-1 and dynamin, drastically reduced RVFV infection in multiple cell lines. Expression of DN caveolin-1 also reduced RVFV infection significantly, while expression of DN EPS15, a protein required for the assembly of clathrin-coated pits, and DN PAK-1, an obligate mediator of macropinocytosis, had no significant impact on RVFV infection. These results together suggest that the primary mechanism of RVFV MP-12 uptake is dynamin-dependent, caveolin-1-mediated endocytosis.

Integration of maternal genome into the neonate genome through breast milk mRNA transcripts and reverse transcriptase

Human milk samples contain microvesicles similar to the retroviruses. These microvesicles contain mRNA transcripts and possess reverse transcriptase activity. They contain about 14,000 transcripts representing the milk transcriptome. Microvesicles are also enriched with proteins related to “caveolar-mediated endocytosis signaling” pathway. It has recently been reported that microvesicles could be transferred to other cells by endocytosis and their RNA content can be translated and be functional in their new location. A significant percentage of the mammalian genome appears to be the product of reverse transcription, containing sequences whose characteristics point to RNA as a template precursor. These are mobile elements that move by way of transposition and are called retrotransposons. We thought that retrotransposons may stem from about 14,000 transcriptome of breast milk microvesicles, and reviewed the literature.The enhanced acceptance of maternal allografts in children who were breast-fed and tolerance to the maternal MHC antigens after breastfeeding may stem from RNAs of the breast milk microvesicles that can be taken up by the breastfed infant and receiving maternal genomic information. We conclude that milk microvesicles may transfer genetic signals from mother to neonate during breastfeeding. Moreover, transfer of wild type RNA from a healthy wet-nurse to the suckling neonate through the milk microvesicles and its subsequent reverse transcription and integration into the neonate genome could result in permanent correction of the clinical manifestations in genetic diseases.

Theranostic liposomes loaded with quantum dots and apomorphine for brain targeting and bioimaging

Quantum dots (QDs) and apomorphine were incorporated into liposomes to eliminate uptake by the liver and enhance brain targeting. We describe the preparation, physicochemical characterization, in vivo bioimaging, and brain endothelial cell uptake of the theranostic liposomes. QDs and the drug were mainly located in the bilayer membrane and inner core of the liposomes, respectively. Spherical vesicles with a mean diameter of ~140 nm were formed. QDs were completely encapsulated by the vesicles. Nearly 80% encapsulation percentage was achieved for apomorphine. A greater fluorescence intensity was observed in mouse brains treated with liposomes compared to free QDs. This result was further confirmed by ex vivo imaging of the organs. QD uptake by the heart and liver was reduced by liposomal incorporation. Apomorphine accumulation in the brain increased by 2.4-fold after this incorporation. According to a hyperspectral imaging analysis, multifunctional liposomes but not the aqueous solution carried QDs into the brain. Liposomes were observed to have been efficiently endocytosed into bEND3 cells. The mechanisms involved in the cellular uptake were clathrin- and caveola-mediated endocytosis, which were energy-dependent. To the best of our knowledge, our group is the first to develop liposomes with a QD-drug hybrid for the aim of imaging and treating brain disorders.

Infectious Spleen and Kidney Necrosis Virus (a Fish Iridovirus) Enters Mandarin Fish Fry Cells via Caveola-Dependent Endocytosis

Infectious spleen and kidney necrosis virus (ISKNV) is the type species of the genus Megalocytivirus from the family Iridoviridae. Megalocytiviruses have been implicated in more than 50 fish species infections and currently threaten the aquaculture industry, causing great economic losses in China, Japan, and Southeast Asia. However, the cellular entry mechanisms of megalocytiviruses remain largely uncharacterized. In this study, the main internalization mechanism of ISKNV was investigated by using mandarin fish fry (MFF-1) cells. The progression of ISKNV infection is slow, and infection is not inhibited when the cells are treated with ammonium chloride (NH(4)Cl), chloroquine, sucrose, and chlorpromazine, which are inhibitors of clathrin-dependent endocytosis. The depletion of cellular cholesterol by methyl-β-cyclodextrin results in the significant inhibition of ISKNV infection; however, the infection is resumed with cholesterol replenishment. Inhibitors of caveolin-1-involved signaling events, including phorbol 12-myristate 13-acetate (PMA), genistein, and wortmannin, impair ISKNV entry into MFF-1 cells. Moreover, ISKNV entry is dependent on dynamin and the microtubule cytoskeleton. Cofraction analysis of ISKNV and caveolin-1 showed that ISKNV colocates with caveolin-1 during virus infection. These results indicate that ISKNV entry into MFF-1 cells proceeds via classical caveola-mediated endocytosis and is dependent on the microtubules that serve as tracks along which motile cavicles may move via a caveola-caveosome-endoplasmic reticulum (ER) pathway. As a fish iridovirus, ISKNV entry into MFF-1 cells is different from the clathrin-mediated endocytosis of frog virus 3 entry into mammalian cells (BHK-21) at 28°C, which has been recognized as a model for iridoviruses. Thus, our work may help further the understanding of the initial steps of iridovirus infection.