ABSTRACT
OBJECTIVE: It is unclear how often anxiety is diagnosed and treated and whether anxiety treatment is associated with improved viral suppression in persons with HIV. In this study, we characterized the anxiety care continuum and its association with viral suppression in a large urban HIV clinic in the United States. DESIGN: Observational cohort study. METHODS: We described the anxiety care continuum by combining data on self-reported anxiety symptoms, engagement in mental health care, clinical diagnoses and prescriptions from 1,967 persons receiving HIV care and treatment in Baltimore, Maryland, from 2014-23. We examined cross-sectional associations with viral suppression. All analyses were stratified by sex and race/ethnicity; a secondary analysis adjusted for age, years in care, and depressive symptoms. RESULTS: Nearly 1 in 5 patients reported mild-severe symptoms of anxiety but were not currently receiving mental health care or pharmacologic treatment for anxiety; 6% of patients reported anxiety symptoms but were receiving treatment, and 7% had been treated for anxiety that was currently in remission. The prevalence of viral suppression ranged from 87-89% across the anxiety care continuum except among patients with untreated moderate-severe anxiety, only 81% of whom were virally suppressed (95% CI: 80, 83). In adjusted models, untreated moderate-severe anxiety remained associated with viral non-suppression across demographic groups. CONCLUSION: We observed a robust association between untreated anxiety and viral non-suppression in a large urban cohort of persons with HIV. Screening for anxiety may identify patients with unmet mental health care needs who face barriers to maintaining viral suppression.
ABSTRACT
Extracellular vesicles (EVs) have emerged as a promising drug delivery system. Connectosomes are a specialized type of EVs that contain connexins in their membranes. Connexin is a surface transmembrane protein that forms connexin hemichannels. When a connexin hemichannel on a connectosome docks with another connexin hemichannel of a target cell, they form a gap junction that allows direct intracellular delivery of therapeutic cargos from within the connectosome to the cytoplasm of the recipient cell. In the present study, we tested the feasibility of converting connectosomes into dry powders by (thin-film) freeze-drying to enable their potential storage in temperatures higher than the recommended -80 °C, while maintaining their activity. Connectosomes were isolated from a genetically engineered HeLa cell line that overexpressing connexin-43 subunit protein tagged with red fluorescence protein. To facilitate the testing of the function of the connectosomes, they were loaded with calcein green dye. Calcein green-loaded connectosomes were thin-film freeze-dried with trehalose alone or trehalose and a polyvinylpyrrolidone polymer as lyoprotectant(s) to produce amorphous powders with high glass transition temperatures (>100 °C). Thin-film freeze-drying did not significantly change the morphology and structure of the connectosomes, nor their particle size distribution. Based on data from confocal microscopy, flow cytometry, and fluorescence spectrometry, the connexin hemichannels in the connectosomes reconstituted from the thin-film freeze-dried powder remained functional, allowing the passage of calcein green through the hemichannels and the release of the calcein green from the connectosomes when the channels were opened by chelating calcium in the reconstituted medium. The function of connectosomes was assessed after one month storage at different temperatures. The connexin hemichannels in connectosomes in liquid lost their function when stored at -19.5 ± 2.2 °C or 6.0 ± 0.5 °C for a month, while those in dry powder form remained functional under the same storage conditions. Finally, using doxorubicin-loaded connectosomes, we showed that the connectosomes reconstituted from thin-film freeze-dried powder remained pharmacologically active. These findings demonstrate that (thin-film) freeze-drying represents a viable method to prepare stable and functional powders of EVs that contain connexins in their membranes.
ABSTRACT
Depletion interactions are thought to significantly contribute to the organization of intracellular structures in the crowded cytosol. The strength of depletion interactions depends on physical parameters such as the depletant number density and the depletant size ratio. Cells are known to dynamically regulate these two parameters by varying the copy number of proteins of a wide distribution of sizes. However, mammalian cells are also known to keep the total protein mass density remarkably constant, to within 0.5% throughout the cell cycle. We thus ask how the strength of depletion interactions varies when the total depletant mass is held fixed, a.k.a. fixed-mass depletion. We answer this question via scaling arguments, as well as by studying depletion effects on networks of reconstituted semiflexible actin in silico and in vitro. We examine the maximum strength of the depletion interaction potential U∗ as a function of q, the size ratio between the depletant and the matter being depleted. We uncover a scaling relation U∗ â¼ qζ for two cases: fixed volume fraction φ and fixed mass density ρ. For fixed volume fraction, we report ζ < 0. For the fixed mass density case, we report ζ > 0, which suggests that the depletion interaction strength increases as the depletant size ratio is increased. To test this prediction, we prepared our filament networks at fixed mass concentrations with varying sizes of the depletant molecule poly(ethylene glycol) (PEG). We characterize the depletion interaction strength in our simulations via the mesh size. In experiments, we observe two distinct actin network morphologies, which we call weakly bundled and strongly bundled. We identify a mass concentration where different PEG depletant sizes lead to weakly bundled or strongly bundled morphologies. For these conditions, we find that the mesh size and intra-bundle spacing between filaments across the different morphologies do not show significant differences, while the dynamic light scattering relaxation time and storage modulus between the two states do show significant differences. Our results demonstrate the ability to tune actin network morphology and mechanics by controlling depletant size and give insights into depletion interaction mechanisms under the fixed-depletant-mass constraint relevant to living cells.
Subject(s)
Actins , Actins/chemistry , Actins/metabolism , Polyethylene Glycols/chemistry , Animals , Actin Cytoskeleton/chemistry , Actin Cytoskeleton/metabolismABSTRACT
A popular strategy for therapeutic delivery to cells and tissues is to encapsulate therapeutics inside particles that cells internalize via endocytosis. The efficacy of particle uptake by endocytosis is often studied in bulk using flow cytometry and Western blot analysis and confirmed using confocal microscopy. However, these techniques do not reveal the detailed dynamics of particle internalization and how the inherent heterogeneity of many types of particles may impact their endocytic uptake. Toward addressing these gaps, here we present a live-cell imaging-based method that utilizes total internal reflection fluorescence microscopy to track the uptake of a large ensemble of individual particles in parallel, as they interact with the cellular endocytic machinery. To analyze the resulting data, we employ an open-source tracking algorithm in combination with custom data filters. This analysis reveals the dynamic interactions between particles and endocytic structures, which determine the probability of particle uptake. In particular, our approach can be used to examine how variations in the physical properties of particles (size, targeting, rigidity), as well as heterogeneity within the particle population, impact endocytic uptake. These data impact the design of particles toward more selective and efficient delivery of therapeutics to cells.
Subject(s)
Clathrin , Endocytosis , Endocytosis/physiology , Humans , Clathrin/metabolism , Microscopy, Fluorescence/methods , Animals , AlgorithmsABSTRACT
OBJECTIVE: Integrase strand transfer inhibitors (INSTI) are associated with weight gain in people with HIV (PWH), but their impact on diabetes is unclear. We evaluated the association between switching from nonnucleoside reverse-transcriptase inhibitors (NNRTI) or protease inhibitors (PI) to INSTI and incident diabetes. DESIGN: Longitudinal cohort study. METHODS: We included PWH aged ≥18âyears from the Johns Hopkins HIV Clinical Cohort (2007-2023) without history of diabetes who had used NNRTI or PI for ≥180âdays. We followed participants up to 10âyears from HIV primary care visits where they switched to INSTI or continued NNRTI or PI. We estimated the hazard of incident diabetes associated with switching to INSTI using weighted Cox regression with robust variance estimator. RESULTS: We included 2075 PWH who attended 22 116 visits where they continued NNRTI or PI and 631 visits where they switched to INSTI. Switching to INSTI was associated with a weighted hazard ratio (wHR) of 1.11 [95% confidence interval (CI), 0.77-1.59] for incident diabetes. The association if no weight gain occurred during the first two years was not qualitatively different (wHR 1.22; 95% CI, 0.82-1.80). In a posthoc analysis, switching to INSTI conferred a significant wHR of 1.79 (95% CI, 1.13-2.84) for diabetes within the first two years but not after. CONCLUSIONS: Switching from NNRTI or PI to INSTI did not significantly increase overall diabetes incidence in PWH, although there may be elevated risk in the first two years. These findings can inform considerations when switching to INSTI-based regimens.
Subject(s)
Diabetes Mellitus , HIV Infections , HIV Integrase Inhibitors , Humans , Male , HIV Infections/drug therapy , HIV Infections/complications , Female , Adult , Middle Aged , Longitudinal Studies , Diabetes Mellitus/epidemiology , HIV Integrase Inhibitors/therapeutic use , HIV Integrase Inhibitors/adverse effects , Incidence , Drug Substitution/statistics & numerical data , Weight Gain , Reverse Transcriptase Inhibitors/adverse effects , Reverse Transcriptase Inhibitors/therapeutic useABSTRACT
Liquid-like protein condensates perform diverse physiological functions. Previous work showed that VASP, a processive actin polymerase, forms condensates that polymerize and bundle actin. To minimize their curvature, filaments accumulated at the inner condensate surface, ultimately deforming the condensate into a rod-like shape, filled with a bundle of parallel filaments. Here we show that this behavior does not require proteins with specific polymerase activity. Specifically, we found that condensates composed of Lamellipodin, a protein that binds actin but is not an actin polymerase, were also capable of polymerizing and bundling actin filaments. To probe the minimum requirements for condensate-mediated actin bundling, we developed an agent-based computational model. Guided by its predictions, we hypothesized that any condensate-forming protein that binds actin could bundle filaments through multivalent crosslinking. To test this idea, we added an actin-binding motif to Eps15, a condensate-forming protein that does not normally bind actin. The resulting chimera formed condensates that drove efficient actin polymerization and bundling. Collectively, these findings broaden the family of proteins that could organize cytoskeletal filaments to include any actin-binding protein that participates in protein condensation.
ABSTRACT
BACKGROUND: Prostate cancer is projected to account for the greatest proportion of cancer-related burden among men with HIV. However, incidence is reportedly lower than in men without HIV, potentially due to differences in screening. Factors influencing receipt of screening in men with HIV are unknown. We described receipt of prostate-specific antigen (PSA) testing and assessed factors for association with receipt of PSA test. METHODS: Demographics, measures of HIV and related care, and non-HIV care were assessed for association with receipt of first PSA test in men ≥40 years old each calendar year in 2000-2020 using univariable and multivariable Poisson regression. Models were additionally stratified by calendar period to identify changes in determinants of PSA test as prostate cancer screening guidelines changed. RESULTS: Men (n = 2,063) 72% Non-Hispanic Black, median age of 47 (IQR: 41, 53), contributed median of 4.7 years (IQR: 2.3, 10.0) of follow-up. Receipt of antiretroviral therapy (aIRR = 1.33; 95% CI: 1.14, 1.55), engagement in HIV care (aIRR = 2.09; 95% CI: 1.66, 2.62), history of testosterone-replacement therapy (aIRR = 1.34; 95% CI: 1.19, 1.50), urologist evaluation (aIRR = 1.66; 95% CI: 1.35, 2.05), and receipt of PSA test in preceding two years (no elevated PSA aIRR = 2.37; 95% CI: 2.16, 2.61; elevated PSA aIRR = 4.35; 95% CI: 3.24, 5.84) were associated with PSA testing in men aged 50 or older. Associations varied across calendar time. CONCLUSION: Findings suggest men with greater interaction with healthcare are more likely to receive PSA test. Measures of control of HIV did not appear to influence the decision to screen.
Subject(s)
Early Detection of Cancer , HIV Infections , Prostate-Specific Antigen , Prostatic Neoplasms , Humans , Male , Middle Aged , HIV Infections/diagnosis , Prostatic Neoplasms/diagnosis , Early Detection of Cancer/statistics & numerical data , Prostate-Specific Antigen/blood , United States/epidemiology , Adult , Mass Screening/statistics & numerical data , Urban Population/statistics & numerical dataABSTRACT
Several actin-binding proteins (ABPs) phase separate to form condensates capable of curating the actin network shapes. Here, we use computational modeling to understand the principles of actin network organization within VASP condensate droplets. Our simulations reveal that the different actin shapes, namely shells, rings, and mixture states are highly dependent on the kinetics of VASP-actin interactions, suggesting that they arise from kinetic trapping. Specifically, we show that reducing the residence time of VASP on actin filaments reduces degree of bundling, thereby promoting assembly of shells rather than rings. We validate the model predictions experimentally using a VASP-mutant with decreased bundling capability. Finally, we investigate the ring opening within deformed droplets and found that the sphere-to-ellipsoid transition is favored under a wide range of filament lengths while the ellipsoid-to-rod transition is only permitted when filaments have a specific range of lengths. Our findings highlight key mechanisms of actin organization within phase-separated ABPs.
Subject(s)
Actin Cytoskeleton , Actins , Actins/metabolism , Actin Cytoskeleton/metabolism , Microfilament Proteins/genetics , Microfilament Proteins/metabolism , Cytoskeleton/metabolismABSTRACT
INTRODUCTION: Postsurgical opioid utilization may be directly and indirectly associated with a range of patient-related and surgery-related factors, above and beyond pain intensity. However, most studies examine postsurgical opioid utilization without accounting for the multitude of co-occurring relationships among predictors. Therefore, this study aimed to identify factors associated with opioid utilization in the first 2 weeks after arthroscopic surgery and examine the relationship between discharge opioid prescription doses and acute postsurgical outcomes. METHODS: In this prospective longitudinal observational study, 110 participants undergoing shoulder or knee arthroscopies from August 2016 to August 2018 at Walter Reed National Military Medical Center completed self-report measures before and at 14 days postoperatively. The association between opioid utilization and both patient-level and surgery-related factors was modeled using structural equation model path analysis. RESULTS: Participants who were prescribed more opioids took more opioids, which was associated with worse physical function and sleep problems at day 14, as indicated by the significant indirect effects of discharge opioid dose on day 14 outcomes. Additional patient-level and surgery-related factors were also significantly related to opioid utilization dose and day 14 outcomes. Most participants had opioid medications leftover at day 14. CONCLUSION: Excess opioid prescribing was common, did not result in improved pain alleviation, and was associated with poorer physical function and sleep 14 days after surgery. As such, higher prescribed opioid doses could reduce subacute functioning after surgery, without benefit in reducing pain. Future patient-centered studies to tailor opioid postsurgical prescribing are needed.
Subject(s)
Analgesics, Opioid , Arthroscopy , Military Personnel , Pain, Postoperative , Humans , Male , Analgesics, Opioid/therapeutic use , Analgesics, Opioid/administration & dosage , Female , Prospective Studies , Arthroscopy/methods , Arthroscopy/statistics & numerical data , Arthroscopy/adverse effects , Adult , Pain, Postoperative/drug therapy , Pain, Postoperative/etiology , Longitudinal Studies , Military Personnel/statistics & numerical data , Middle Aged , United States/epidemiology , Patient Discharge/statistics & numerical data , Patient Discharge/standards , Shoulder/surgery , Shoulder/physiopathology , Knee/surgery , Knee/abnormalities , Knee/physiopathologyABSTRACT
Membrane-associated protein phase separation plays critical roles in cell biology, driving essential cellular phenomena from immune signaling to membrane traffic. Importantly, by reducing dimensionality from three to two dimensions, lipid bilayers can nucleate phase separation at far lower concentrations compared with those required for phase separation in solution. How might other intracellular lipid substrates, such as lipid droplets, contribute to nucleation of phase separation? Distinct from bilayer membranes, lipid droplets consist of a phospholipid monolayer surrounding a core of neutral lipids, and they are energy storage organelles that protect cells from lipotoxicity and oxidative stress. Here, we show that intrinsically disordered proteins can undergo phase separation on the surface of synthetic and cell-derived lipid droplets. Specifically, we find that the model disordered domains FUS LC and LAF-1 RGG separate into protein-rich and protein-depleted phases on the surfaces of lipid droplets. Owing to the hydrophobic nature of interactions between FUS LC proteins, increasing ionic strength drives an increase in its phase separation on droplet surfaces. The opposite is true for LAF-1 RGG, owing to the electrostatic nature of its interprotein interactions. In both cases, protein-rich phases on the surfaces of synthetic and cell-derived lipid droplets demonstrate molecular mobility indicative of a liquid-like state. Our results show that lipid droplets can nucleate protein condensates, suggesting that protein phase separation could be key in organizing biological processes involving lipid droplets.
Subject(s)
Lipid Droplets , Lipid Droplets/chemistry , Lipid Droplets/metabolism , Intrinsically Disordered Proteins/chemistry , Intrinsically Disordered Proteins/metabolism , Humans , RNA-Binding Protein FUS/chemistry , RNA-Binding Protein FUS/metabolism , Phase Transition , Hydrophobic and Hydrophilic Interactions , Protein Domains , Phase SeparationABSTRACT
BACKGROUND: Few studies have examined which subgroups of people with HIV (PWH) carry the greatest burden of internalized HIV stigma (IHS), which may be important to care provision and interventions. METHODS: PWH in the CFAR Network of Integrated Clinical Systems (CNICS) longitudinal, US-based, multisite, clinical care cohort completed tablet-based assessments during clinic visits including a four-item, Likert scale (low 1-5 high), IHS instrument. Associations between sociodemographic characteristics and IHS scores were assessed in adjusted linear regression models. RESULTS: Twelve thousand six hundred and fifty-six PWH completed the IHS assessment at least once from February 2016 to November 2022, providing 28â559 IHS assessments. At baseline IHS assessment, the mean age was 49âyears, 41% reported White, 38% Black/African American, and 16% Latine race/ethnicity, and 80% were cisgender men. The mean IHS score was 2.04, with all subgroups represented among those endorsing IHS. In regression analyses, younger PWH and those in care fewer years had higher IHS scores. In addition, cisgender women vs. cisgender men, PWH residing in the West vs. the Southeast, and those with sexual identities other than gay/lesbian had higher IHS scores. Compared with White-identifying PWH, those who identified with Black/African American or Latine race/ethnicity had lower IHS scores. Age stratification revealed patterns related to age category, including specific age-related differences by gender, geographic region and race/ethnicity. DISCUSSION: IHS is prevalent among PWH, with differential burden by subgroups of PWH. These findings highlight the benefits of routine screening for IHS and suggest the need for targeting/tailoring interventions to reduce IHS among PWH.
Subject(s)
HIV Infections , Social Stigma , Humans , Male , Female , HIV Infections/psychology , Middle Aged , United States/epidemiology , Adult , Longitudinal Studies , Young Adult , Aged , AdolescentABSTRACT
Cellular remodeling of actin networks underlies cell motility during key morphological events, from embryogenesis to metastasis. In these transformations, there is an inherent competition between actin branching and bundling, because steric clashes among branches create a mechanical barrier to bundling. Recently, liquid-like condensates consisting purely of proteins involved in either branching or bundling of the cytoskeleton have been found to catalyze their respective functions. Yet in the cell, proteins that drive branching and bundling are present simultaneously. In this complex environment, which factors determine whether a condensate drives filaments to branch or become bundled? To answer this question, we added the branched actin nucleator, Arp2/3, to condensates composed of VASP, an actin bundling protein. At low actin to VASP ratios, branching activity, mediated by Arp2/3, robustly inhibited VASP-mediated bundling of filaments, in agreement with agent-based simulations. In contrast, as the actin to VASP ratio increased, addition of Arp2/3 led to formation of aster-shaped structures, in which bundled filaments emerged from a branched actin core, analogous to filopodia emerging from a branched lamellipodial network. These results demonstrate that multi-component, liquid-like condensates can modulate the inherent competition between bundled and branched actin morphologies, leading to organized, higher-order structures, similar to those found in motile cells.
Subject(s)
Actins , Microfilament Proteins , Actins/metabolism , Microfilament Proteins/genetics , Microfilament Proteins/metabolism , Cytoskeleton/metabolism , Cell Movement/physiology , Actin Cytoskeleton/metabolism , Actin-Related Protein 2-3 Complex/genetics , Actin-Related Protein 2-3 Complex/chemistryABSTRACT
Access to direct acting antivirals (DAAs) may be associated with reductions in hepatitis C virus (HCV) viremia prevalence among people with human immunodeficiency virus (PWH). Among 3755 PWH, estimated HCV viremia prevalence decreased by 94.0% from 36% (95% confidence interval [CI], 27%-46%) in 2009 (pre-DAA era) to 2% (95% CI, 0%-4%) in 2021 (DAA era). Male sex, black race, and older age were associated with HCV viremia in 2009 but not in 2021. Injection drug use remained associated with HCV viremia in 2009 and 2021. Targeted interventions are needed to meet the HCV care needs of PWH who use drugs.
Subject(s)
HIV Infections , Hepatitis C, Chronic , Hepatitis C , Humans , Male , HIV , Antiviral Agents/therapeutic use , Viremia/drug therapy , Viremia/epidemiology , Hepatitis C, Chronic/drug therapy , Hepatitis C/complications , Hepatitis C/drug therapy , Hepatitis C/epidemiology , Hepacivirus , HIV Infections/complications , HIV Infections/drug therapy , HIV Infections/epidemiologyABSTRACT
BACKGROUND: This study aims to evaluate the agreement in substance use on both binary and ordinal scales between 3-month and 6-month recall periods with samples from different communities, demographic backgrounds, and HIV status. METHODS: We administered the Alcohol, Smoking and Substance Involvement Screening Test (ASSIST) to 799 participants from three different North American cohorts focused on substance use and HIV. We conducted a within-person agreement analysis by calculating the agreement levels and Kappa statistic between data collected using the 3-month recall ASSIST and 6-month custom substance use surveys as well as different terminology for each substance in multiple cohorts. RESULTS: For all drugs studied, the agreement on the binary use or ordinal frequency of use metrics showed a high agreement level between 80.4% and 97.9% and an adequate adjusted kappa value between 0.61 and 0.96, suggesting substantial agreement. According to the agreement criteria we proposed, substance use data collected using different recall periods and with variation in drug names can be harmonized across cohorts. CONCLUSIONS: This study is the first to evaluate the feasibility of data harmonization of substance use by demonstrating high level of agreement between different recall periods in different cohorts. The results can inform data harmonization efforts in consortia where data are collected from cohorts using different questions and recall periods.
Subject(s)
HIV Infections , Substance-Related Disorders , Humans , Surveys and Questionnaires , Smoking , Substance-Related Disorders/diagnosis , Substance-Related Disorders/epidemiology , Tobacco Smoking , HIV Infections/diagnosis , HIV Infections/epidemiologyABSTRACT
Liquid-liquid phase separation of proteins occurs on both surfaces of cellular membranes during diverse physiological processes. In vitro reconstitution could provide insight into the mechanisms underlying these events. However, most existing reconstitution techniques provide access to only one membrane surface, making it difficult to probe transmembrane phenomena. To study protein phase separation simultaneously on both membrane surfaces, we developed an array of freestanding planar lipid membranes. Interestingly, we observed that liquid-like protein condensates on one side of the membrane colocalized with those on the other side, resulting in transmembrane coupling. Our results, based on lipid probe partitioning and mobility of lipids, suggest that protein condensates locally reorganize membrane lipids, a process which could be explained by multiple effects. These findings suggest a mechanism by which signals originating on one side of a biological membrane, triggered by protein phase separation, can be transferred to the opposite side.
Subject(s)
Lipids , Proteins , Proteins/metabolism , Cell Membrane/metabolismABSTRACT
Background: During the 2022 mpox outbreak most patients were managed as outpatients, but some required hospitalization. Uncontrolled human immunodeficiency virus (HIV) has been identified as a risk factor for severe mpox. Methods: Patients with mpox diagnosed or treated within the Johns Hopkins Health System between 1 June and 15 December 2022 were included. The primary outcome of interest was risk of hospitalization. Demographic features, comorbid conditions, treatment, and clinical outcomes were determined. Results: A total of 353 patients were tested or treated for mpox; 100 had mpox diagnosed or treated (median age, 35.3 years; 97.0% male; 57.0% black and 10.0% Hispanic; 46.0% people with HIV [PWH]). Seventeen patients (17.0%) required hospitalization, 10 of whom were PWH. Age >40 years, race, ethnicity, HIV status, insurance status, and body mass index >30 (calculated as weight in kilograms divided by height in meters squared) were not associated with hospitalization. Eight of 9 patients (88.9%) with immunosuppression were hospitalized. Immunosuppression was associated with hospitalization in univariate (odds ratio, 69.3 [95% confidence interval, 7.8-619.7]) and adjusted analysis (adjusted odds ratio, 94.8 [8.5-1060.1]). Two patients (11.8%) who were hospitalized required intensive care unit admission and died; both had uncontrolled HIV infection and CD4 T-cell counts <50/µL. Median cycle threshold values for the first positive mpox virus sample did not differ between those who were hospitalized and those who were not. Conclusions: Immunosuppression was a significant risk factor for hospitalization with mpox. PWH with CD4 T-cell counts <50/µL are at high risk of death due to mpox infection. Patients who are immunosuppressed should be considered for early and aggressive treatment of mpox, given the increased risk of hospitalization.
ABSTRACT
Cell surface receptors facilitate signaling and nutrient uptake. These processes are dynamic, requiring receptors to be actively recycled by endocytosis. Due to their differential expression in disease states, receptors are often the target of drug-carrier particles, which are adorned with ligands that bind specifically to receptors. These targeted particles are taken into the cell by multiple routes of internalization, where the best-characterized pathway is clathrin-mediated endocytosis. Most studies of particle uptake have utilized bulk assays rather than observing individual endocytic events. As a result, the detailed mechanisms of particle uptake remain obscure. To address this gap, we employed a live-cell imaging approach to study the uptake of individual liposomes as they interact with clathrin-coated structures. By tracking individual internalization events, we find that the size of liposomes rather than the density of the ligands on their surfaces primarily determines their probability of uptake. Interestingly, targeting has the greatest impact on endocytosis of liposomes of intermediate diameters, with the smallest and largest liposomes being internalized or excluded, respectively, regardless of whether they are targeted. These findings, which highlight a previously unexplored limitation of targeted delivery, can be used to design more effective drug carriers.
Subject(s)
Endocytosis , Liposomes , Liposomes/chemistry , Drug Carriers/pharmacology , Biological Transport , Clathrin/chemistrySubject(s)
Curriculum , Schools, Dental , United States , Educational Status , American Dental Association , Education, DentalABSTRACT
This paper provides an overview of my research programme for the past 37 years. The focus of my work has been on identifying productive in-session processes to enhance treatment outcomes and therapist responsiveness. Two foci will be reviewed, first, my research on client and therapist interpersonal process and second, productive processing in psychotherapy in three different therapeutic approaches including EFT, CBT and CCT. Given that many competing theoretical perspectives are effective, I was curious about change processes that are common and unique to each. In my work, I employed a variety of research methodologies drawing on frameworks with alternative epistemological and ontological assumptions to capture specific in-session change processes in an attempt to reveal the richness and complexity of the phenomena being studied and illuminate the process of change.
ABSTRACT
Clathrin-mediated endocytosis is an essential cellular pathway that enables signaling and recycling of transmembrane proteins and lipids. During endocytosis, dozens of cytosolic proteins come together at the plasma membrane, assembling into a highly interconnected network that drives endocytic vesicle biogenesis. Recently, multiple labs have reported that early endocytic proteins form liquid-like condensates, which provide a flexible platform for the efficient assembly of endocytic vesicles. Given the importance of this network in the dynamics of endocytosis, how might cells regulate its stability? Many receptors and endocytic proteins are ubiquitylated, while early endocytic proteins such as Eps15 contain ubiquitin-interacting motifs. Therefore, we examined the influence of ubiquitin on the stability of the early endocytic protein network. In vitro, we found that recruitment of small amounts of polyubiquitin dramatically increased the stability of Eps15 condensates, suggesting that ubiquitylation could nucleate endocytic sites. In live cell imaging experiments, a version of Eps15 that lacked the ubiquitin-interacting motif failed to rescue defects in endocytic initiation created by Eps15 knockout. Furthermore, fusion of Eps15 to a deubiquitinase enzyme destabilized nascent endocytic sites within minutes. These results suggest that ubiquitylation drives assembly of the flexible protein network responsible for catalyzing endocytic events. More broadly, this work illustrates a biophysical mechanism by which ubiquitylated transmembrane proteins at the plasma membrane could regulate the efficiency of endocytic recycling.