Targeting Hypoxia-Inducible Factor-1 (HIF-1) in Cancer: Emerging Therapeutic Strategies and Pathway Regulation

Hypoxia-inducible factor-1 (HIF-1) is a key regulator for balancing oxygen in the cells. It is a transcription factor that regulates the expression of target genes involved in oxygen homeostasis in response to hypoxia. Recently, research has demonstrated the multiple roles of HIF-1 in the pathophysiology of various diseases, including cancer. It is a crucial mediator of the hypoxic response and regulator of oxygen metabolism, thus contributing to tumor development and progression. Studies showed that the expression of the HIF-1α subunit is significantly upregulated in cancer cells and promotes tumor survival by multiple mechanisms. In addition, HIF-1 has potential contributing roles in cancer progression, including cell division, survival, proliferation, angiogenesis, and metastasis. Moreover, HIF-1 has a role in regulating cellular metabolic pathways, particularly the anaerobic metabolism of glucose. Given its significant and potential roles in cancer development and progression, it has been an intriguing therapeutic target for cancer research. Several compounds targeting HIF-1-associated processes are now being used to treat different types of cancer. This review outlines emerging therapeutic strategies that target HIF-1 as well as the relevance and regulation of the HIF-1 pathways in cancer. Moreover, it addresses the employment of nanotechnology in developing these promising strategies.

Lipidomics Profiling of Metformin-Induced Changes in Obesity and Type 2 Diabetes Mellitus: Insights and Biomarker Potential

Metformin is the first-line oral medication for treating type 2 diabetes mellitus (T2DM). In the current study, an untargeted lipidomic analytical approach was used to investigate the alterations in the serum lipidome of a cohort of 89 participants, including healthy lean controls and obese diabetic patients, and to examine the alterations associated with metformin administration. A total of 115 lipid molecules were significantly dysregulated (64 up-regulated and 51 down-regulated) in the obese compared to lean controls. However, the levels of 224 lipid molecules were significantly dysregulated (125 up-regulated and 99 down-regulated) in obese diabetic patients compared to the obese group. Metformin administration in obese diabetic patients was associated with significant dysregulation of 54 lipid molecule levels (20 up-regulated and 34 down-regulated). Levels of six molecules belonging to five lipid subclasses were simultaneously dysregulated by the effects of obesity, T2DM, and metformin. These include two putatively annotated triacylglycerols (TGs), one plasmenyl phosphatidylcholine (PC), one phosphatidylglycerol (PGs), one sterol lipid (ST), and one Mannosyl-phosphoinositol ceramide (MIPC). This study provides new insights into our understanding of the lipidomics alterations associated with obesity, T2DM, and metformin and offers a new platform for potential biomarkers for the progression of diabetes and treatment response in obese patients.

Metabolomics in diabetes mellitus: clinical insight

INTRODUCTION

Diabetes Mellitus (DM) is a chronic heterogeneous metabolic disorder characterized by hyperglycemia due to the destruction of insulin-producing pancreatic β cells and/or insulin resistance. It is now considered a global epidemic disease associated with serious threats to a patient's life. Understanding the metabolic pathways involved in disease pathogenesis and progression is important and would improve prevention and management strategies. Metabolomics is an emerging field of research that offers valuable insights into the metabolic perturbation associated with metabolic diseases, including DM.

AREA COVERED

Herein, we discussed the metabolomics in type 1 and 2 DM research, including its contribution to understanding disease pathogenesis and identifying potential novel biomarkers clinically useful for disease screening, monitoring, and prognosis. In addition, we highlighted the metabolic changes associated with treatment effects, including insulin and different anti-diabetic medications.

EXPERT OPINION

By analyzing the metabolome, the metabolic disturbances involved in T1DM and T2DM can be explored, enhancing our understanding of the disease progression and potentially leading to novel clinical diagnostic and effective new therapeutic approaches. In addition, identifying specific metabolites would be potential clinical biomarkers for predicting the disease and thus preventing and managing hyperglycemia and its complications.

Assessment of Moral Development Among Undergraduate Pharmacy Students and Alumni

Objective. This study's principal aim was to assess the moral development of undergraduate pharmacy students and alumni at a university in Jordan.Methods. Using the Professional Ethics in Pharmacy (PEP) test, the moral reasoning of 512 pharmacy students and alumni was assessed in a cross-sectional design. The main assessment measure was the Principled Morality Score, which reflects an individual's level of moral judgment development and is given as a percentage, where higher values indicate greater moral development.Results. The response rate was 49%. The median Principled Morality Score was 16.7, with no significant differences observed across all five cohorts. No significant differences in median Principled Morality Scores were found between men and women (16.7 vs 20, respectively). Also, no significant differences in median Principled Morality scores were observed between students who had completed the ethics course versus those who had not completed the ethics course at the time of data collection (median Principled Morality Score 20 vs 16.7, respectively). No trends in median Principled Morality Scores were observed.Conclusion. In this study, the professional moral reasoning of prospective pharmacists was lower than expected. A further longitudinal study of the cohort, which attempts to correlate moral development with age, sex, education level, and moral education strategy, is warranted.

Characteristics of inpatients with atopic asthma in a tertiary center: Do age and gender have an influence?

Background: Several studies have demonstrated gender influence on asthma prevalence, being higher among males during early childhood. Little is known about the impact of gender and age on asthma exacerbation characteristics in pediatrics. This study aimed to determine the differences in acute asthma between males and females in three different age groups regarding perinatal characteristics of asthmatic patients, comorbidities, medication adherence, level of blood eosinophils, and pattern of hospitalization.Methods: The medical records of 130 pediatric patients with asthma, who presented to the emergency department at Jordan University hospital with asthma exacerbations, were retrospectively reviewed. Demographic information and clinical characteristics were collected.Results: The mean age of patients was 10.7±4.7 years. The age at diagnosis and gestational age were significantly higher in older children. Furthermore, younger children were significantly more likely to experience winter exacerbations and more emergency presentations. Male patients were considerably younger than their female counterparts and were diagnosed younger. In addition, male patients were more likely to have eosinophil levels higher than 3% than female patients.Conclusion: Gender plays a role in the development and outcome of asthma exacerbations at different ages of pediatrics. A better understanding of gender-based and age-based differences in asthma dictates a personalized approach to treatment.

Lipidomics Profiling of Patients with Low Bone Mineral Density (LBMD)

The relationship between lipid metabolism and bone mineral density (BMD) is still not fully elucidated. Despite the presence of investigations using osteoporotic animal models, clinical studies in humans are limited. In this work, untargeted lipidomics profiling using liquid chromatography-mass spectrometry (LC-MS) analysis of human serum samples was performed to identify the lipidomics profile associated with low bone mineral density (LBMD), with a subsequent examination of potential biomarkers related to OP risk prediction or progression. A total of 69 participants were recruited for this cohort study, including the osteoporotic group (OP, n = 25), osteopenia group (ON, n = 22), and control (Ctrl, n = 22). The LBMD group included OP and ON patients. The lipidomics effect of confounding factors such as age, gender, lipid profile, body mass index (BMD), chronic diseases, and medications was excluded from the dataset. The results showed a clear group separation and clustering between LBMD and Ctrl (Q² = 0.944, R² = 0.991), indicating a significant difference in the lipids profile. In addition, 322 putatively identified lipid molecules were dysregulated, with 163 up- and 159 down-regulated in LBMD, compared with the Ctrl. The most significantly dysregulated subclasses were phosphatidylcholines (PC) (n = 81, 25.16% of all dysregulated lipids 322), followed by triacylglycerol (TG) (n = 65, 20.19%), and then phosphatidylethanolamine (PE) (n = 40, 12.42%). In addition, groups of glycerophospholipids, including LPC (7.45%), LPE (5.59%), and PI (2.48%) were also dysregulated as of LBMD. These findings provide insights into the lipidomics alteration involved in bone remodeling and LBMD. and may drive the development of therapeutic targets and nutritional strategies for OP management.

Parents' attitude towards pneumococcal vaccine: an online survey from Jordan

OBJECTIVES

In developing countries, the pneumococcal conjugate vaccine (PCV) has not been incorporated into the national immunization schedule, and the vaccination rate is low. This study aimed to examine parental knowledge, attitudes, and barriers to children receiving the PCV in Jordan.

METHODS

This was a questionnaire-based cross-sectional study. The online survey was written in Arabic and consisted of three main sections. The questionnaire was distributed via social media platforms, such as Facebook, Twitter, and WhatsApp.

RESULTS

In total, 720 responses were analyzed. Only 149 (20.7%) of the parents' children were vaccinated with the PCV. However, almost half 356 (49.4%) of the respondents were willing to vaccinate their children. Most (563, 78.1%) parents stated that the vaccine would protect their children from pneumococcal disease. More than two thirds (516, 71.6%) of them strongly agreed or agreed that the cost of the PCV is high. Parents who had vaccinated their children had a higher monthly income than parents who had not vaccinated their children.

CONCLUSIONS

This study shows a lack of knowledge regarding pneumococcal infection and the PCV among Jordanian parents. This is the main barrier to vaccinating children. Therefore, improving parental knowledge would increase the rate of vaccination among Jordanian children.

Proteomics Profiling of Osteoporosis and Osteopenia Patients and Associated Network Analysis

Bone mass reduction due to an imbalance in osteogenesis and osteolysis is characterized by low bone mineral density (LBMD) and is clinically classified as osteopenia (ON) or osteoporosis (OP), which is more severe. Multiple biomarkers for diagnosing OP and its progression have been reported; however, most of these lack specificity. This cohort study aimed to investigate sensitive and specific LBMD-associated protein biomarkers in patients diagnosed with ON and OP. A label-free liquid chromatography-mass spectrometry (LC-MS) proteomics approach was used to analyze serum samples. Patients’ proteomics profiles were filtered for potential confounding effects, such as age, sex, chronic diseases, and medication. A distinctive proteomics profile between the control, ON, and OP groups (Q² = 0.7295, R² = 0.9180) was identified, and significant dysregulation in a panel of proteins (n = 20) was common among the three groups. A comparison of these proteins showed that the levels of eight proteins were upregulated in ON, compared to those in the control and the OP groups, while the levels of eleven proteins were downregulated in the ON group compared to those in the control group. Interestingly, only one protein, myosin heavy chain 14 (MYH14), showed a linear increase from the control to the ON group, with the highest abundance in the OP group. A significant separation in the proteomics profile between the ON and OP groups (Q² = 0.8760, R² = 0.991) was also noted. Furthermore, a total of twenty-six proteins were found to be dysregulated between the ON and the OP groups, with fourteen upregulated and twelve downregulated proteins in the OP, compared to that in the ON group. Most of the identified dysregulated proteins were immunoglobulins, complement proteins, cytoskeletal proteins, coagulation factors, and various enzymes. Of these identified proteins, the highest area under the curve (AUC) in the receiver operating characteristic (ROC) analysis was related to three proteins (immunoglobulin Lambda constant 1 (IGLC1), RNA binding protein (MEX3B), and fibulin 1 (FBLN1)). Multiple reaction monitoring (MRM), LC-MS, was used to validate some of the identified proteins. A network pathway analysis of the differentially abundant proteins demonstrated dysregulation of inflammatory signaling pathways in the LBMD patients, including the tumor necrosis factor (TNF), toll-like receptor (TL4), and interferon-γ (IFNG) signaling pathways. These results reveal the existence of potentially sensitive protein biomarkers that could be used in further investigations of bone health and OP progression.

The impact of using a mobile application to improve asthma patients' adherence to medication in Jordan

The main aim of this study is to assess the effectiveness of using a developed asthma mobile application to enhance medication adherence in Jordan. Asthma patients visiting outpatient respiratory clinics and using inhalers were recruited. Patients were assigned into two groups: intervention and control. The intervention group was instructed to download and use the application. Asthma control was assessed using Asthma Control Test (ACT) at baseline and at follow-up of 3 months for both groups. A total of 171 patients (control, n = 83, and intervention, n = 88) participated in the study. After 3 months of usage, patients in the intervention group achieved a significant improvement in ACT score compared to control (p-value <0.05), and reported a significant satisfaction of the application use. Therefore, the asthma mobile application is found as an effective tool to enhance medication adherence in asthma patients.

Coronavirus disease 2019 (COVID-19): a brief overview of features and current treatment

Since the report of the first cases of pneumonia caused by SARS-CoV-2 in December 2019, COVID-19 has become a pandemic and is globally overwhelming healthcare systems. The symptoms of COVID-19 vary from asymptomatic infection to severe complicated pneumonia with acute respiratory distress syndrome (ARDS) and multiple organ failure leading to death. The estimated case-fatality rate among infected patients in Wuhan, the city where the first case appeared, was 1.4%, with 5.1 times increase in the death rate among those aged above 59 years than those aged 30-59 years. In the absence of a proven effective and licensed treatment, many agents that showed activity against previous coronavirus outbreaks such as SARS and MERS have been used to treat SARS-CoV-2 infection. The SARS-CoV-2 is reported to be 80% homologous with SARS-CoV, and some enzymes are almost 90% homologous. Antiviral drugs are urgently required to reduce case fatality-rate and hospitalizations to relieve the burden on healthcare systems worldwide. Randomized controlled trials are ongoing to assess the efficacy and safety of several treatment regimens.

Influenza Viral Infections Surveillance and Clinical Presentations in Hospitalized Children: A Cross-sectional Study

Background:

Influenza virus and other respiratory viruses have been identified as an essential cause of acute respiratory infections (ARIs) in children worldwide. However, there are few data on its frequency and clinical presentation in Jordan.

Objectives:

We aimed to identify the viral etiology of acute respiratory infections and the various clinical presentations in hospitalized children, especially those with influenza viruses compared to other respiratory viruses.

Methods:

A retrospective study was conducted at the Jordan University Hospital. All the positive nasopharyngeal aspirates that were collected from hospitalized children aged 0-19 years from January 2017 to January 2019 were reviewed.

Results:

A total of 338 nasopharyngeal aspirates (NPAs) with positive viral serology results were reviewed. Among the patients younger than four years, the RSV virus was the most frequently detected. However, the Influenza B virus was the most commonly seen in patients older than 5 years, H1N1 was more frequent in autumn (29.5%), and RSV was the most frequent virus in winter. Bronchopneumonia was the most frequent diagnosis among all hospitalized patients, followed by bronchiolitis. Out of 338 patients, 50.3% had tachypnea, 70.7% of patients were admitted to the pediatric floor, while 18.6% presented with a severe illness and required admission to the pediatric intensive care unit (PICU). Infants under the age of one were more likely to have higher co-infection rates with other viruses compared to children over five years that had influenza.

Conclusion:

Presentations of influenza and other respiratory viruses vary between different age groups, such as sepsis in children younger than one year.

Obesity Connected Metabolic Changes in Type 2 Diabetic Patients Treated With Metformin

Metformin is widely used in the treatment of Type 2 Diabetes Mellitus (T2DM). However, it is known to have beneficial effects in many other conditions, including obesity and cancer. In this study, we aimed to investigate the metabolic effect of metformin in T2DM and its impact on obesity. A mass spectrometry (MS)-based metabolomics approach was used to analyze samples from two cohorts, including healthy lean and obese control, and lean as well as obese T2DM patients on metformin regimen in the last 6 months. The results show a clear group separation and sample clustering between the study groups due to both T2DM and metformin administration. Seventy-one metabolites were dysregulated in diabetic obese patients (30 up-regulated and 41 down-regulated), and their levels were unchanged with metformin administration. However, 30 metabolites were dysregulated (21 were up-regulated and 9 were down-regulated) and then restored to obese control levels by metformin administration in obese diabetic patients. Furthermore, in obese diabetic patients, the level of 10 metabolites was dysregulated only after metformin administration. Most of these dysregulated metabolites were dipeptides, aliphatic amino acids, nucleic acid derivatives, and urea cycle components. The metabolic pattern of 62 metabolites was persistent, and their levels were affected by neither T2DM nor metformin in obesity. Interestingly, 9 metabolites were significantly dysregulated between lean and obese cohorts due to T2DM and metformin regardless of the obesity status. These include arginine, citrulline, guanidoacetic acid, proline, alanine, taurine, 5-hydroxyindoleacetic acid, and 5-hydroxymethyluracil. Understanding the metabolic alterations taking place upon metformin treatment would shed light on possible molecular targets of metformin, especially in conditions like T2DM and obesity.

Impact of COVID-19 lockdown on children with asthma in Jordan: a parental questionnaire

OBJECTIVE

To evaluate the impact of a 10-week lockdown on children with asthma aged 4-17 years in terms of presentations to the emergency department (ED), frequency of admissions, compliance with medications and changes in pulmonary function testing results.

DESIGN AND SETTING

A questionnaire-based cross-sectional study using Google Forms to collect parents' and caregivers' responses after they consented to participation.

RESULTS

A total of 374 parents/caregivers were contacted and 297 (79%) responded. The majority of the children were male (188 or 63%) and 49.8% were aged 7-12 years. More than half of the participants (194 or 65%) reported improved compliance with medications and spacer use. There was a significant reduction in the number of presentations to the ED from 137 to 80 and admissions to hospital from 56 to 24 during the 10-week lockdown period compared with the same time period in the previous year (p≤0.0001). Around 25% of the participants used telemedicine by phone and social media applications for communication with their treating physician and 59 (80%) described it as easy and smooth.

CONCLUSION

The national lockdown in Jordan due to the COVID-19 pandemic was associated with a fall in emergency presentations and hospital admissions for acute asthma exacerbations. Parental responses indicate that fears focused around COVID-19 were associated with enhanced compliance with use preventer medications during the lockdown.

Before and after case reporting: A comparison of the knowledge, attitude and practices of the Jordanian population towards COVID-19

Coronavirus disease- 2019 (COVID-19) is an emerging contagious infectious disease. It is pandemic and has affected more than 21 million people and resulted in more than 750,000 deaths worldwide (https://www.worldometers.info/coronavirus/#countries; 14/08/20). Our research group initiated a study to ascertain the knowledge, attitude and practices (KAP) of Jordanians toward COVID-19 prior to any initial case report in Jordan. This project was underway when the first Jordanian case was reported. We extended our study to identify how case reporting would alter public KAP towards COVID-19. This cross-sectional study randomly selected and recruited 2104 Jordanian adults. A four-section questionnaire was devised to address the sociodemographic characteristics of the subjects and their KAP toward COVID-19. The mean knowledge score for the study population was 15.9 ± 2.2 (out of the 20 knowledge questions), with 60.9% of the participants having good knowledge about COVID-19. Participants’ practices to prevent transmission of COVID-19 were adequate in more than 60% of participants. Most participants had positive attitudes regarding their role in preventing COVID-19 and many of the participants’ attitudes and practices changed to more appropriate ones after reporting the first case of COVID-19 in Jordan. The percentage of participants who trust the government in confronting COVID-19 increased significantly (p value < 0.001). However, one alarming and unexpected finding was that the prevention practice score of participants working in the medical field was similar to those from the general population. This may necessitate stricter training and guidelines for this group who will be in the frontline in combating the disease. Impact of this study: The data generated from this study shows that when cases of disease were reported, the public’s attitudes and practices improved in many aspects, and that confidence in the government to contain the disease was boosted. We believe that this study is important in allowing other, international governments to develop an understanding of public KAP during pandemic disease outbreaks.

The impact of pharmaceutical care on the efficacy and safety of transdermal glucosamine sulfate and capsaicin for joint pain

Background Arthritis is a common chronic joint disease. It progressively causes joint pain, stiffness, and disability. Glucosamine sulfate has been shown to be an effective symptom-relieving biological agent. Pharmaceutical care, including patient counseling, is very important to overcome inconsistencies in compliance and adherence. Objective The aim of this study is to evaluate the impact of pharmaceutical care on the efficacy and safety of transdermal glucosamine sulfate and capsaicin (TGC-Plus cream) in the management of chronic joint pain. Settings A rheumatology outpatient clinic, Jordan University Hospital, Amman, Jordan. Methods A cross sectional study with a single treatment group was conducted. One hundred (100) patients diagnosed with either osteoarthritis, rheumatoid arthritis or chronic joint pains were recruited. Patients started on TGC-Plus cream applied twice daily for duration of 12 weeks. Patients received pharmaceutical care services during the study duration. Main outcome measure Efficacy and safety of TGC-Plus cream in pain relief and joint function improvement (alleviating joint stiffness) the need of alternative analgesics and number of doctor's visits. Results There was a significant reduction of numerical pain score (7 ± 1.40 vs. 3.53 ± 2.13, p < 0.05), with significant reduction in the limitation of joint movement (6.18 ± 2.14 vs. 3.47 ± 2.23, p < 0.05) after 12 weeks. In addition, the need for analgesics and the number of doctor's visits were significantly reduced (1.99 ± 2.77 vs. 0.71 ± 1.90, p < 0.05), (1.11 ± 1.28 vs. 0.06 ± 0.293, p < 0.05) respectively. Conclusion Pharmacist supervised treatment with the TGC-Plus cream significantly reduces pain and enhances locomotor function in patients with chronic pain who failed to achieve adequate prior pain relief.

Pregabalin inhibits in vivo and in vitro cytokine secretion and attenuates spleen inflammation in Lipopolysaccharide/Concanavalin A -induced murine models of inflammation

Immune system alteration has been implicated in the pathogenesis of chronic pain conditions, epilepsy and generalized anxiety disorder. Targeting cytokines has recently been proposed for the management of such conditions. Pregabalin (PGB) is an antiepileptic agent used for the management of these conditions. However, little is known about its immunomodulatory effects on cytokine secretion in vivo and in vitro. Hence, a mitogen (Lipopolysaccharide [LPS] or Concanavalin A [ConA])-induced murine model of inflammation was used to investigate the effect of PGB on in vivo and in vitro IL-1β, IL-6, TNF-α and IL-2 cytokine secretion using ELISA. In addition, PGB effect on spleen histology, as a lymphoid organ, was examined. Our results revealed that PGB significantly inhibited the secretion of ConA-induced IL-6 secretion, basal and ConA-induced TNF-α and IL-2 secretion in splenocytes in vitro. In vivo, PGB inhibited basal and LPS/ConA-induced IL-6 and TNF-α secretion in addition to LPS-induced IL-1β and ConA-induced IL-2 secretion. Moreover, PGB attenuated mitogen-induced inflammatory changes in the spleen. These findings provide an evidence of the anti-inflammatory properties of PGB on cytokine secretion and lymphoid organ inflammation. This might give insights into the role of PGB in the management of the inflammatory state in PGB-indicated conditions.

Serum level of insulin-like growth factor-I in type 2 diabetic patients: impact of obesity

Background Insulin-like growth factor-I (IGF-I) is homologous to proinsulin and possesses glucose reducing activity. The association between the level of IGF-I and diabetes has been highlighted. However, this association is controversial due to the influence of different factors including obesity. The aim of the study was to evaluate serum level of IGF-I in type 2 diabetic patients compared to control subjects. Materials and methods A cross-sectional study involving 100 participants was conducted. Serum levels of IGF-I were measured using enzyme-linked immunosorbent assay (ELISA) and the fasting plasma glucose (FPG) levels were measured using the glucose oxidase method. Results IGF-I levels in the diabetic patients were significantly lower than in non-diabetic control subjects (105.13 ± 6.34 vs. 159.96 ± 9.62 ng/mL, p < 0.0001). Among the diabetic group, there was no significant difference in IGF-I levels between obese diabetic patients and non-obese diabetic patients, p = 0.18. Similarly, among the non-diabetic group, a non-significant difference was found in IGF-I levels between obese non-diabetic and non-obese non-diabetic subjects, p = 0.156. However, among the obese group, obese diabetic patients had significantly lower IGF-I serum levels compared to obese non-diabetic subjects (112.07 ± 7.97 vs. 147.07 ± 13.05 ng/mL, p = 0.02). Furthermore, among the non-obese group, the non-obese diabetic patients had significantly lower IGF-I serum levels compared to the non-obese non-diabetic subjects (91.66 ± 9.93 vs. 171.86 ± 13.86 ng/mL, p < 0.0001). No significant associations were observed between IGF-I level and any of the age, gender, body mass index (BMI), FPG levels, or the duration of diabetes. Conclusions Type 2 diabetes mellitus is associated with lower levels of IGF-I regardless to the presence or absence of obesity.

The Adaptor Protein Alix is Involved in the Interaction Between the Ubiquitin Ligase NEDD4-1 and its Targets, ABCG1 and ABCG4

Several ATP-Binding Cassette (ABC) transporters, including ABCG1 and the related ABCG4, are essential regulators of cellular lipid homeostasis. ABCG1 is expressed ubiquitously and is functional in the context of atherosclerosis. However, ABCG4 is expressed almost exclusively in brain and has been linked to Alzheimer's disease (AD). These transporters are highly regulated post-translationally by E3 ubiquitin ligases, with the ligase NEDD4-1 (Neural precursor cell-expressed developmentally downregulated gene 4) implicated in their protein stability. In this study, we investigated interacting partners of ABCG1 using peptide-mass spectrometry and identified the potential adaptor protein, Alix (apoptosis-linked gene 2-interacting protein X). In this paper, we hypothesized and investigated whether Alix could facilitate the interaction between NEDD4-1 and the ABC transporters. We showed that Alix and NEDD4-1 proteins were co-expressed in several commonly used cell lines. Knockdown of Alix in cells overexpressing ABCG1 or ABCG4 increased transporter protein expression while co-immunoprecipitation experiments showed interaction between NEDD4-1, Alix, and ABC transporters. In summary, we provide evidence that Alix serves as a co-factor for the interaction between the E3-ubiquitin ligase NEDD4-1 and the ABC transporter targets, ABCG1 and ABCG4.

The E3 ubiquitin ligases, HUWE1 and NEDD4-1, are involved in the post-translational regulation of the ABCG1 and ABCG4 lipid transporters

The ATP-binding cassette transporter ABCG1 has an essential role in cellular cholesterol homeostasis, and dysregulation has been associated with a number of high burden diseases. Previous studies reported that ABCG1 is ubiquitinated and degraded via the ubiquitin proteasome system. However, so far the molecular mechanism, including the identity of any of the rate-limiting ubiquitination enzymes, or E3 ligases, is unknown. Using liquid chromatography mass spectrometry, we identified two HECT domain E3 ligases associated with ABCG1, named HUWE1 (HECT, UBA, and WWE domain containing 1, E3 ubiquitin protein ligase) and NEDD4-1 (Neural precursor cell-expressed developmentally down regulated gene 4), of which the latter is the founding member of the NEDD4 family of ubiquitin ligases. Silencing both HUWE1 and NEDD4-1 in cells overexpressing human ABCG1 significantly increased levels of the ABCG1 monomeric and dimeric protein forms, however ABCA1 protein expression was unaffected. In addition, ligase silencing increased ABCG1-mediated cholesterol export to HDL in cells overexpressing the transporter as well as in THP-1 macrophages. Reciprocally, overexpression of both ligases resulted in a significant reduction in protein levels of both the ABCG1 monomeric and dimeric forms. Like ABCG1, ABCG4 protein levels and cholesterol export activity were significantly increased after silencing both HUWE1 and NEDD4-1 in cells overexpressing this closely related ABC half-transporter. In summary, we have identified for the first time two E3 ligases that are fundamental enzymes in the post-translational regulation of ABCG1 and ABCG4 protein levels and cellular cholesterol export activity.