Analytical Performance Evaluation of Three Point-of-Care CBC Analyzers for Management of Clozapine Therapy in Ambulatory Psychiatry Clinics.

BACKGROUND: Clozapine is a first-line therapy and the only FDA-approved drug for patients with treatment-resistant schizophrenia (TRS). However, frequent measurement of absolute neutrophil count (ANC) is required to monitor for potential adverse severe neutropenia from clozapine therapy. We evaluated 3 point-of-care (POC) instruments that perform the complete blood count (CBC) with differential to assess their analytical performance and potential to meet the clinical need for clozapine therapy management. METHODS: A CBC with differential was performed on 104 residual whole blood specimens using 3 CBC analyzers (Sight OLO, PixCell HemoScreen, and Sysmex pocH-100i) to assess analytical precision, linearity, and accuracy vs the ADVIA 2120i and manual differential reference methods. Clinical concordance of ANC between POC devices and manual differential at medical decision points for mild, moderate, or severe neutropenia, and the threshold for clozapine therapy discontinuation (1.0 × 109/L) were determined. RESULTS: For CBC parameters, a CV ≤ 6.4% was observed on the OLO, CV ≤ 6.2% for the HemoScreen, and CV ≤ 5.1% with the pocH-100i. Each device accurately identified ANC with the greatest mean bias ±0.42 × 109/L using the pocH-100i vs manual differential. For results near the medical decision points (ANC <1.5 × 109/L), clinical concordance of ANC results was 55.6% for the OLO, 89.5% for the HemoScreen, and 82.4% for the pocH-100i. CONCLUSIONS: The HemoScreen device demonstrated the best clinical concordance in ANC values at medical decision thresholds for clozapine therapy management.

The E2 ubiquitin-conjugating enzymes UBE2D1 and UBE2D2 regulate VEGFR2 dynamics and endothelial function.

Vascular endothelial growth factor receptor 2 (VEGFR2, encoded by KDR) regulates endothelial function and angiogenesis. VEGFR2 undergoes ubiquitination that programs this receptor for trafficking and proteolysis, but the ubiquitin-modifying enzymes involved are ill-defined. Herein, we used a reverse genetics screen for the human E2 family of ubiquitin-conjugating enzymes to identify gene products that regulate VEGFR2 ubiquitination and proteolysis. We found that depletion of either UBE2D1 or UBE2D2 in endothelial cells caused a rise in steady-state VEGFR2 levels. This rise in plasma membrane VEGFR2 levels impacted on VEGF-A-stimulated signalling, with increased activation of canonical MAPK, phospholipase Cγ1 and Akt pathways. Analysis of biosynthetic VEGFR2 is consistent with a role for UBE2D enzymes in influencing plasma membrane VEGFR2 levels. Cell-surface-specific biotinylation and recycling studies showed an increase in VEGFR2 recycling to the plasma membrane upon reduction in UBE2D levels. Depletion of either UBE2D1 or UBE2D2 stimulated endothelial tubulogenesis, which is consistent with increased VEGFR2 plasma membrane levels promoting the cellular response to exogenous VEGF-A. Our studies identify a key role for UBE2D1 and UBE2D2 in regulating VEGFR2 function in angiogenesis.

Exploring Determinants of HIV/AIDS Self-Testing Uptake in South Africa Using Generalised Linear Poisson and Geographically Weighted Poisson Regression.

Increased HIV/AIDS testing is of paramount importance in controlling the HIV/AIDS pandemic and subsequently saving lives. Despite progress in HIV/AIDS testing programmes, most people are still reluctant to test and thus are still unaware of their status. Understanding the factors associated with uptake levels of HIV/AIDS self-testing requires knowledge of people's perceptions and attitudes, thus informing evidence-based decision making. Using the South African National HIV Prevalence, HIV Incidence, Behaviour and Communication Survey of 2017 (SABSSM V), this study assessed the efficacy of Generalised Linear Poisson Regression (GLPR) and Geographically Weighted Poisson Regression (GWPR) in modelling the spatial dependence and non-stationary relationships of HIV/AIDS self-testing uptake and covariates. The models were calibrated at the district level across South Africa. Results showed a slightly better performance of GWPR (pseudo R2 = 0.91 and AICc = 390) compared to GLPR (pseudo R2 = 0.88 and AICc = 2552). Estimates of local intercepts derived from GWPR exhibited differences in HIV/AIDS self-testing uptake. Overall, the output of this study displays interesting findings on the levels of spatial heterogeneity of factors associated with HIV/AIDS self-testing uptake across South Africa, which calls for district-specific policies to increase awareness of the need for HIV/AIDS self-testing.

Factors Affecting Access to Public Healthcare Facilities in the City of Tshwane, South Africa.

Access to healthcare services is largely determined by socioeconomic factors, with economically well-off individuals obtaining healthcare services more efficiently than those who are disadvantaged. This paper aims to assess the effects of socioeconomic and other related factors on access to healthcare facilities in the City of Tshwane, South Africa, during the COVID-19 pandemic. Data were sourced from the Gauteng City-Region Observatory (GCRO) quality of life survey (2020/2021). Multivariate logistic regression was applied. Results showed that 66.3% of the respondents reported that they had access to public healthcare facilities within their area. Furthermore, results showed that those who lived in informal houses were significantly (OR = 0.55, 95% CI [0.37-0.80], p < 0.01) less likely to report that they had access to public healthcare facilities in their area compared to those who lived in formal houses. More efforts need to be undertaken to ensure that all citizens have access to public healthcare facilities, especially among those who are disadvantaged, such as informal dwellers. In addition, future research should encompass locality in relation to the factors that affect access to public healthcare facilities, especially during pandemics such as the COVID-19 pandemic, in order to have geographically targeted interventions.

Introducing the hormonal Intrauterine Device in Madagascar, Nigeria, and Zambia: results from a pilot study.

BACKGROUND: The hormonal Intrauterine Device (IUD) is a highly effective contraceptive option growing in popularity and availability in many countries. The hormonal IUD has been shown to have high rates of satisfaction and continuation among users in high-income countries. The study aims to understand the profiles of clients who choose the hormonal IUD in low- and middle-income countries (LMICs) and describe their continuation and satisfaction with the method after 12 months of use. METHODS: A prospective longitudinal study of hormonal IUD acceptors was conducted across three countries-Madagascar, Nigeria, and Zambia-where the hormonal IUD had been introduced in a pilot setting within the of a broad mix of available methods. Women were interviewed at baseline immediately following their voluntary hormonal IUD insertion, and again 3 and 12 months following provision of the method. A descriptive analysis of user characteristics and satisfaction with the method was conducted on an analytic sample of women who completed baseline, 3-month, and 12-month follow-up questionnaires. Kaplan-Meier time-to-event models were used to estimate the cumulative probability of method continuation rates up to 12 months post-insertion. RESULTS: Each country had a unique demographic profile of hormonal IUD users with different method-use histories. Across all three countries, women reported high rates of satisfaction with the hormonal IUD (67-100%) and high rates of continuation at the 12-month mark (82-90%). CONCLUSIONS: Rates of satisfaction and continuation among hormonal IUD users in the study suggest that expanding method choice with the hormonal IUD would provide a highly effective, long-acting method desirable to many different population segments, including those with high unmet need.

Implementation of SARS-CoV-2 Monoclonal Antibody Infusion Sites at Three Medical Centers in the United States: Strengths and Challenges Assessment to Inform COVID-19 Pandemic and Future Public Health Emergency Use.

Monoclonal antibody therapeutics to treat coronavirus disease (COVID-19) have been authorized by the US Food and Drug Administration under Emergency Use Authorization (EUA). Many barriers exist when deploying a novel therapeutic during an ongoing pandemic, and it is critical to assess the needs of incorporating monoclonal antibody infusions into pandemic response activities. We examined the monoclonal antibody infusion site process during the COVID-19 pandemic and conducted a descriptive analysis using data from 3 sites at medical centers in the United States supported by the National Disaster Medical System. Monoclonal antibody implementation success factors included engagement with local medical providers, therapy batch preparation, placing the infusion center in proximity to emergency services, and creating procedures resilient to EUA changes. Infusion process challenges included confirming patient severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) positivity, strained staff, scheduling, and pharmacy coordination. Infusion sites are effective when integrated into pre-existing pandemic response ecosystems and can be implemented with limited staff and physical resources.

Does community-based distribution of HIV self-tests increase uptake of HIV testing? Results of pair-matched cluster randomised trial in Zambia.

OBJECTIVES: Ending HIV by 2030 is a global priority. Achieving this requires alternative HIV testing strategies, such as HIV self-testing (HIVST) to reach all individuals with HIV testing services (HTS). We present the results of a trial evaluating the impact of community-based distribution of HIVST in community and facility settings on the uptake of HTS in rural and urban Zambia. DESIGN: Pair-matched cluster randomised trial. METHODS: In catchment areas of government health facilities, OraQuick HIVST kits were distributed by community-based distributors (CBDs) over 12 months in 2016-2017. Within matched pairs, clusters were randomised to receive the HIVST intervention or standard of care (SOC). Individuals aged ≥16 years were eligible for HIVST. Within communities, CBDs offered HIVST in high traffic areas, door to door and at healthcare facilities. The primary outcome was self-reported recent testing within the previous 12 months measured using a population-based survey. RESULTS: In six intervention clusters (population 148 541), 60 CBDs distributed 65 585 HIVST kits. A recent test was reported by 66% (1622/2465) in the intervention arm compared with 60% (1456/2429) in SOC arm (adjusted risk ratio 1.08, 95% CI 0.94 to 1.24; p=0.15). Uptake of the HIVST intervention was low: 24% of respondents in the intervention arm (585/2493) used an HIVST kit in the previous 12 months. No social harms were identified during implementation. CONCLUSION: Despite distributing a large number of HIVST kits, we found no evidence that this community-based HIVST distribution intervention increased HTS uptake. Other models of HIVST distribution, including secondary distribution and community-designed distribution models, provide alternative strategies to reach target populations. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT02793804).

Objectively measured chronic disease risk among food pantry patrons.

OBJECTIVES AND DESIGN: This cross-sectional, observational study examined the prevalence of objectively measured chronic disease risk factors among a diverse group of food pantry patrons. SAMPLE AND MEASUREMENT: Public health nurses performed biometric screenings in community settings for 1,685 unduplicated adults attending food pantries. RESULTS: Over three fourths of participants (81.1%) were overweight or obese. High cholesterol and high blood pressure were detected in 38.4% and 37.7% of participants, respectively. Over half (58%) of the participants were referred to a local community health clinic for follow-up services. CONCLUSION: Interventions should target food pantry patrons to reduce the prevalence of chronic disease conditions among this vulnerable population.

Impact of cigarette versus electronic cigarette aerosol conditioned media on aortic endothelial cells in a microfluidic cardiovascular model.

Atherosclerosis is a complex process involving progressive pathological events, including monocyte adhesion to the luminal endothelial surface. We have developed a functional in vitro adhesion assay using BioFlux microfluidic technology to investigate THP-1 (human acute monocytic leukaemia cell) monocyte adhesion to human aortic endothelial cells (HAECs). The effect of whole smoke conditioned media (WSCM) generated from University of Kentucky reference cigarette 3R4F, electronic cigarette vapour conditioned media (eVCM) from an electronic nicotine delivery system (ENDS) product (Vype ePen) and nicotine on monocyte adhesion to HAECs was evaluated. Endothelial monolayers were grown in microfluidic channels and exposed to 0-1500 ng/mL nicotine or nicotine equivalence of WSCM or eVCM for 24 h. Activated THP-1 cells were perfused through the channels and a perfusion, adhesion period and wash cycle performed four times with increasing adhesion period lengths (10, 20, 30 and 40 min). THP-1 cell adhesion was quantified by counting adherent cells. WSCM induced dose-dependent increases in monocyte adhesion compared to vehicle control. No such increases were observed for eVCM or nicotine. Adhesion regulation was linked to increased ICAM-1 protein expression. Staining of ICAM-1 in HAECs and CD11b (MAC-1) in THP-1 cells demonstrated adhesion molecule co-localisation in BioFlux plates. The ICAM-1 adhesion response to WSCM was downregulated by transfecting HAECs with ICAM-1 siRNA. We conclude that the BioFlux system is able to model human monocyte adhesion to primary human endothelial cells in vitro and WSCM drives the greatest increase in monocyte adhesion via a mechanism involving endothelial ICAM-1 expression.

Increasing the availability of quality human tissue for research.

Advances in 3D and other in vitro tissue model platforms have led to fundamental improvements in research on human disease, development of novel therapies, and safety testing. In addition, histological and cellular investigations of human tissues continue to serve as keystones in understanding disease and health processes. In recognition of the importance of human tissues in research, the Physicians Committee for Responsible Medicine held a workshop. Working closely with key stakeholders from the research community, regulatory agencies, and organ procurement organizations, the goal was to explore, understand, and address the barriers to increased use of human organs, tissues, and cells in research. Workshop participants were tasked with identifying the challenges of accessing and qualifying tissues for research purposes and creating a strategy to help meet the needs of the research communities to increase the availability and quality of human tissues in biomedical and translational research. Break-out groups identified significant challenges in the areas of policy, scientific development, and public engagement with respect to the provision and application of tissues and cells for scientific advancement. Following working group recommendations, stakeholders concluded that there is a need to facilitate the availability and quality of human tissues for the research community, as well as provide a framework for education of the public, medical professionals, and researchers to foster donation and utilization for research in place of animal models. The success of these new initiatives will facilitate greater access to high-quality human tissues for biomedical and translational research and help ensure the transition away from the dependence on animal models.

The evaluation of the Woman's Condom marketing approach: What value did peer-led interpersonal communication add to the promotion of a new female condom in urban Lusaka?

During a mass media campaign accompanying the launch of the Maximum Diva Woman's Condom (WC) in Lusaka, Zambia, a cluster-randomized evaluation was implemented to measure the added impact of a peer-led interpersonal communication (IPC) intervention on the awareness and uptake of the new female condom (FC). The WC and mass media campaign were introduced simultaneously in 40 urban wards in April 2016; half of the wards were randomly assigned to the treatment (IPC intervention) with cross-sectional surveys conducted before (n = 2,364) and one year after (n = 2,430) the start of the intervention. A pre-specified intention-to-treat (ITT) analysis measured the impact of randomization to IPC at the community level. In adjusted ITT models, there were no statistically significant differences between intervention and control groups. Due to significant implementation challenges, we also conducted exploratory secondary analyses to estimate effects among those who attended an IPC event (n = 66) using instrumental variable and inverse probability weighting analyses. In addition to increases in FC identification (IPC attendees had higher reported use of any condom, improved perceptions of FC's, and were more likely to have discussed contraceptive use with their partner as compared to non-attendees). The introduction of a new FC product combined with an IPC intervention significantly increased general knowledge and awareness in the community as compared to media alone, but did not lead to detectable community level impacts on other primary outcomes of interest. Observational evidence from our study suggests that IPC attendance is associated with increased use and negotiation. Future studies should explore the intensity and duration of IPC programming necessary to achieve detectable community level impacts on behavior. Trial Registration: AEARCTR-0000899.

Mechanisms of whole smoke conditioned media induced cytotoxicity to human aortic endothelial cells.

Chronic exposure to cigarette smoke can lead to endothelial dysfunction and potentially endothelial cell death. Here, we exposed Human Aortic Endothelial Cells (HAECs) to whole smoke conditioned media (WSCM) over a range of nicotine equivalence (n.e.) concentrations (0-8000 ng/mL n.e.). After 24 h, Neutral Red Uptake (NRU) and reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) to formazan was determined for each exposure concentration and compared to control. IC50 values in the NRU assay were: 4582 ng/mL n.e. ± 1074, 4587 ng/mL n.e. ± 951, 4993 ng/mL n.e. ± 1239 and 4691 ng/mL n.e. ± 402 for four HAEC donors. IC50 values in the MTT assay were: 4885 ng/mL n.e. ± 1341, 4584 ng/mL n.e. ± 806, 5749 ng/mL n.e. ± 783 and 5228 ng/mL n.e. ± 593 for the four donors. To examine the mechanism responsible for WSCM-induced cytotoxicity in HAECs, flow cytometry using necrosis (Propidium Iodide) and apoptosis (Annexin V) markers were used. Annexin V-positive cell populations increased in a dose dependent manner while increases in PI-positive cell populations occurred at the highest doses of WSCM (5000-8000 ng/mL n.e.). Western blotting for cleaved caspase-3 confirmed that apoptosis occurs at >5000 ng/mL n.e. WSCM, coinciding with reduced HAEC survival.

HIV self-testing: breaking the barriers to uptake of testing among men and adolescents in sub-Saharan Africa, experiences from STAR demonstration projects in Malawi, Zambia and Zimbabwe.

INTRODUCTION: Social, structural and systems barriers inhibit uptake of HIV testing. HIV self-testing (HIVST) has shown promising uptake by otherwise underserved priority groups including men, young people and first-time testers. Here, we use characteristics of HIVST kit recipients to investigate delivery to these priority groups during HIVST scale-up in three African countries. METHODS: Kit distributors collected individual-level age, sex and testing history from all clients. These data were aggregated and analysed by country (Malawi, Zambia and Zimbabwe) for five distribution models: local community-based distributor (CBD: door-to-door, street and local venues), workplace distribution (WD), integration into HIV testing services (IHTS), or public health facilities (IPHF) and during demand creation for voluntary male medical circumcision (VMMC). Used kits were collected and re-read from CBD and IHTS recipients. RESULTS: Between May 2015 and July 2017, 628,705 HIVST kits were distributed in Malawi (172,830), Zambia (190,787) and Zimbabwe (265,091). Community-based models, the first to be established, accounted for 519,658 (82.7%) of kits distributed, with 275,419 (53.0%) used kits returned. Subsequent model diversification delivered 54,453 (8.7%) test-kits through IHTS, 23,561 (3.7%) through VMMC, 21,183 (3.4%) through IPHF and 9850 (1.7%) through WD. Men took 294,508 (48.2%) kits, and 263,073 (43.1%) went to young people (16 to 24 years). A higher proportion of male self-testers (65,577; 22.3%) were first-time testers than women (54,096; 17.1%) with this apparent in Zimbabwe (16.2% vs. 11.4%), Zambia (25.4% vs. 17.7%) and Malawi (27.9% vs. 25.9%). The highest proportions of first-time testers were in young (16 to 24 years) and older (>50 years) men (country-ranges: 18.7% to 35.9% and 13.8% to 26.8% respectively). Most IHTS clients opted for HIVST in preference to standard HTS in each of 12 delivery sites, with those selecting HIVST having lower HIV prevalence, potentially due to self-selection. CONCLUSIONS: HIVST delivered at scale using several different models reached a high proportion of men, young people and first-time testers in Malawi, Zambia and Zimbabwe, some of whom may not have tested otherwise. As men and young people have limited uptake under standard facility-and community-based HIV testing, innovative male- and youth-sensitive approaches like HIVST may be essential to reaching UNAIDS fast-track targets for 2020.

The Views of Mental Health Manager Towards the Use of a Family Work Model for Psychosis in Guangzhou, China.

Family Interventions in Psychosis (FIP) have been promoted internationally but have been criticised for being based on western cultural models. This paper reports on a focus group study with 10 Integrated Mental Health Service Managers in Guangzhou, China using thematic analysis. Managers believed FIP might benefit families but identified potential difficulties due to (a) families avoiding services due to the 'shame' of mental illness (b) unrealistic expectations of services amongst families (c) deferral to 'key decision-makers' within families when discussing family issues with workers. The findings indicate that FIP work should focus on interaction between carers in the first instance with service users being introduced into sessions at a later date and that more attention needs to be given by the research community to how FIP may be adapted to cultural norms within China.

Human aortic endothelial cells respond to shear flow in well-plate microfluidic devices.

Although chronic progressive cardiovascular diseases such as atherosclerosis are often challenging to fully model in vitro, it has been shown that certain in vitro methods can effectively evaluate some aspects of disease progression. This has been demonstrated in in vitro and in vivo studies of endothelial cells that have illustrated the effects of nitric oxide (NO) production, filamentous actin (F-actin) formation, and cell and actin angle alignment on vascular function and homeostasis. Systems utilising shear flow have been established, in order to create a physiologically relevant environment for cells that require shear flow for homeostasis. Here, we investigated the use of a well-plate microfluidic system and associated devices (0-20dyn/cm²) to demonstrate applied shear effects on primary Human Aortic Endothelial Cells (HAECs). Changes in cell and actin alignment in the direction of flow, real-time production of NO and gross cell membrane shape changes in response to physiological shear flow were observed. These commercial systems have a range of potential applications, including within the consumer and pharmaceutical industries, thereby reducing the dependency on animal testing for regulatory safety assessments.

Ubiquitination of basal VEGFR2 regulates signal transduction and endothelial function.

Cell surface receptors can undergo recycling or proteolysis but the cellular decision-making events that sort between these pathways remain poorly defined. Vascular endothelial growth factor A (VEGF-A) and vascular endothelial growth factor receptor 2 (VEGFR2) regulate signal transduction and angiogenesis, but how signaling and proteolysis is regulated is not well understood. Here, we provide evidence that a pathway requiring the E1 ubiquitin-activating enzyme UBA1 controls basal VEGFR2 levels, hence metering plasma membrane receptor availability for the VEGF-A-regulated endothelial cell response. VEGFR2 undergoes VEGF-A-independent constitutive degradation via a UBA1-dependent ubiquitin-linked pathway. Depletion of UBA1 increased VEGFR2 recycling from endosome-to-plasma membrane and decreased proteolysis. Increased membrane receptor availability after UBA1 depletion elevated VEGF-A-stimulated activation of key signaling enzymes such as PLCγ1 and ERK1/2. Although UBA1 depletion caused an overall decrease in endothelial cell proliferation, surviving cells showed greater VEGF-A-stimulated responses such as cell migration and tubulogenesis. Our study now suggests that a ubiquitin-linked pathway regulates the balance between receptor recycling and degradation which in turn impacts on the intensity and duration of VEGF-A-stimulated signal transduction and the endothelial response.

Affimer proteins are versatile and renewable affinity reagents.

Molecular recognition reagents are key tools for understanding biological processes and are used universally by scientists to study protein expression, localisation and interactions. Antibodies remain the most widely used of such reagents and many show excellent performance, although some are poorly characterised or have stability or batch variability issues, supporting the use of alternative binding proteins as complementary reagents for many applications. Here we report on the use of Affimer proteins as research reagents. We selected 12 diverse molecular targets for Affimer selection to exemplify their use in common molecular and cellular applications including the (a) selection against various target molecules; (b) modulation of protein function in vitro and in vivo; (c) labelling of tumour antigens in mouse models; and (d) use in affinity fluorescence and super-resolution microscopy. This work shows that Affimer proteins, as is the case for other alternative binding scaffolds, represent complementary affinity reagents to antibodies for various molecular and cell biology applications.

Dynamics of a plasmon-activated p-mercaptobenzoic acid layer deposited over Au nanoparticles using time-resolved SERS.

Time-dependent SERS intensity recorded over a drop-coated coffee-ring pattern of p-MBA with gold colloids was investigated as a function of the specific laser power applied. Pure electromagnetic enhancement produced stochastic intensity variations of the whole SER spectra, which were mainly correlated with evolutions of the background intensity. Besides long-term, non-reversible spectral changes caused by plasmon-induced decarboxylation of p-MBA, transient original spectral profiles showing additional lines were also observed as the specific power reached 5.5 × 10(4) W cm(-2). An unprecedented qualitative and quantitative study of SERS intensity variations based on the complementary use of both extreme deviation and cross-correlation statistics is provided, which resulted in an improved understanding of SERS mechanisms. More precisely, cross-correlation analysis made it possible to follow the evolution of groups of modes assigned to one species or sharing the same symmetry while so-called individual events denote particular resonance structures, whose occurrence was tentatively related to a photo-thermally activated motion of the gold nanostructures.

VEGF-A isoforms program differential VEGFR2 signal transduction, trafficking and proteolysis.

Vascular endothelial growth factor A (VEGF-A) binding to the receptor tyrosine kinase VEGFR2 triggers multiple signal transduction pathways, which regulate endothelial cell responses that control vascular development. Multiple isoforms of VEGF-A can elicit differential signal transduction and endothelial responses. However, it is unclear how such cellular responses are controlled by isoform-specific VEGF-A-VEGFR2 complexes. Increasingly, there is the realization that the membrane trafficking of receptor-ligand complexes influences signal transduction and protein turnover. By building on these concepts, our study shows for the first time that three different VEGF-A isoforms (VEGF-A165, VEGF-A121 and VEGF-A145) promote distinct patterns of VEGFR2 endocytosis for delivery into early endosomes. This differential VEGFR2 endocytosis and trafficking is linked to VEGF-A isoform-specific signal transduction events. Disruption of clathrin-dependent endocytosis blocked VEGF-A isoform-specific VEGFR2 activation, signal transduction and caused substantial depletion in membrane-bound VEGFR1 and VEGFR2 levels. Furthermore, such VEGF-A isoforms promoted differential patterns of VEGFR2 ubiquitylation, proteolysis and terminal degradation. Our study now provides novel insights into how different VEGF-A isoforms can bind the same receptor tyrosine kinase and elicit diverse cellular outcomes.

Extracellular and Luminal pH Regulation by Vacuolar H+-ATPase Isoform Expression and Targeting to the Plasma Membrane and Endosomes.

Plasma membrane vacuolar H(+)-ATPase (V-ATPase) activity of tumor cells is a major factor in control of cytoplasmic and extracellular pH and metastatic potential, but the isoforms involved and the factors governing plasma membrane recruitment remain uncertain. Here, we examined expression, distribution, and activity of V-ATPase isoforms in invasive prostate adenocarcinoma (PC-3) cells. Isoforms 1 and 3 were the most highly expressed forms of membrane subunit a, with a1 and a3 the dominant plasma membrane isoforms. Correlation between plasma membrane V-ATPase activity and invasiveness was limited, but RNAi knockdown of either a isoform did slow cell proliferation and inhibit invasion in vitro Isoform a1 was recruited to the cell surface from the early endosome-recycling complex pathway, its knockdown arresting transferrin receptor recycling. Isoform a3 was associated with the late endosomal/lysosomal compartment. Both a isoforms associated with accessory protein Ac45, knockdown of which stalled transit of a1 and transferrin-transferrin receptor, decreased proton efflux, and reduced cell growth and invasiveness; this latter effect was at least partly due to decreased delivery of the membrane-bound matrix metalloproteinase MMP-14 to the plasma membrane. These data indicate that in prostatic carcinoma cells, a1 and a3 isoform populations predominate in different compartments where they maintain different luminal pH. Ac45 plays a central role in navigating the V-ATPase to the plasma membrane, and hence it is an important factor in expression of the invasive phenotype.