SARS-CoV-2 E and 3a Proteins Are Inducers of Pannexin Currents

Controversial reports have suggested that SARS-CoV E and 3a proteins are plasma membrane viroporins. Here, we aimed at better characterizing the cellular responses induced by these proteins. First, we show that expression of SARS-CoV-2 E or 3a protein in CHO cells gives rise to cells with newly acquired round shapes that detach from the Petri dish. This suggests that cell death is induced upon expression of E or 3a protein. We confirmed this by using flow cytometry. In adhering cells expressing E or 3a protein, the whole-cell currents were not different from those of the control, suggesting that E and 3a proteins are not plasma membrane viroporins. In contrast, recording the currents on detached cells uncovered outwardly rectifying currents much larger than those observed in the control. We illustrate for the first time that carbenoxolone and probenecid block these outwardly rectifying currents; thus, these currents are most probably conducted by pannexin channels that are activated by cell morphology changes and also potentially by cell death. The truncation of C-terminal PDZ binding motifs reduces the proportion of dying cells but does not prevent these outwardly rectifying currents. This suggests distinct pathways for the induction of these cellular events by the two proteins. We conclude that SARS-CoV-2 E and 3a proteins are not viroporins expressed at the plasma membrane.

A need for exhaustive and standardized characterization of ion channels activity. The case of KV11.1

hERG, the pore-forming subunit of the rapid component of the delayed rectifier K⁺ current, plays a key role in ventricular repolarization. Mutations in the KCNH2 gene encoding hERG are associated with several cardiac rhythmic disorders, mainly the Long QT syndrome (LQTS) characterized by prolonged ventricular repolarization, leading to ventricular tachyarrhythmias, sometimes progressing to ventricular fibrillation and sudden death. Over the past few years, the emergence of next-generation sequencing has revealed an increasing number of genetic variants including KCNH2 variants. However, the potential pathogenicity of the majority of the variants remains unknown, thus classifying them as variants of uncertain significance or VUS. With diseases such as LQTS being associated with sudden death, identifying patients at risk by determining the variant pathogenicity, is crucial. The purpose of this review is to describe, on the basis of an exhaustive examination of the 1322 missense variants, the nature of the functional assays undertaken so far and their limitations. A detailed analysis of 38 hERG missense variants identified in Long QT French patients and studied in electrophysiology also underlies the incomplete characterization of the biophysical properties for each variant. These analyses lead to two conclusions: first, the function of many hERG variants has never been looked at and, second, the functional studies done so far are excessively heterogeneous regarding the stimulation protocols, cellular models, experimental temperatures, homozygous and/or the heterozygous condition under study, a context that may lead to conflicting conclusions. The state of the literature emphasizes how necessary and important it is to perform an exhaustive functional characterization of hERG variants and to standardize this effort for meaningful comparison among variants. The review ends with suggestions to create a unique homogeneous protocol that could be shared and adopted among scientists and that would facilitate cardiologists and geneticists in patient counseling and management.

A standardised hERG phenotyping pipeline to evaluate KCNH2 genetic variant pathogenicity

BACKGROUND AND AIMS

Mutations in KCNH2 cause long or short QT syndromes (LQTS or SQTS) predisposing to life-threatening arrhythmias. Over 1000 hERG variants have been described by clinicians, but most remain to be characterised. The objective is to standardise and accelerate the phenotyping process to contribute to clinician diagnosis and patient counselling. In silico evaluation was also included to characterise the structural impact of the variants.

METHODS

We selected 11 variants from known LQTS patients and two variants for which diagnosis was problematic. Using the Gibson assembly strategy, we efficiently introduced mutations in hERG cDNA despite GC-rich sequences. A pH-sensitive fluorescent tag was fused to hERG for efficient evaluation of channel trafficking. An optimised 35-s patch-clamp protocol was developed to evaluate hERG channel activity in transfected cells. R software was used to speed up analyses.

RESULTS

In the present work, we observed a good correlation between cell surface expression, assessed by the pH-sensitive tag, and current densities. Also, we showed that the new biophysical protocol allows a significant gain of time in recording ion channel properties and provides extensive information on WT and variant channel biophysical parameters, that can all be recapitulated in a single parameter defined herein as the repolarisation power. The impacts of the variants on channel structure were also reported where structural information was available. These three readouts (trafficking, repolarisation power and structural impact) define three pathogenicity indexes that may help clinical diagnosis.

CONCLUSIONS

Fast-track characterisation of KCNH2 genetic variants shows its relevance to discriminate mutants that affect hERG channel activity from variants with undetectable effects. It also helped the diagnosis of two new variants. This information is meant to fill a patient database, as a basis for personalised medicine. The next steps will be to further accelerate the process using an automated patch-clamp system.

Effect of narghile and cigarette smoking on newborn birthweight

OBJECTIVE

To assess the effect of narghile smoking on the weight of newborns.

DESIGN

Historical retrospective cohort.

SETTING

Six major hospitals in Greater Beirut, Lebanon.

POPULATION

Consecutive singleton newborns delivered from August 2000 to August 2003.

METHODS

Obstetric and nursery charts were reviewed to obtain information about maternal and neonatal variables. Information concerning initiation of smoking, dose of smoking, smoking habits during pregnancy, and socio-demographic characteristics was collected through interviews with mothers.

MAIN OUTCOME MEASURES

Low birthweight and newborn birthweight.

RESULTS

Exclusive narghile smokers constituted 4.4% (378/8592) of women. Multiparas were significantly more likely to smoke cigarettes and narghile. Mothers smoking narghile more than once per day were at 2.4 increased odds of having low birthweight infants compared with nonsmoking mothers (OR 2.4; 95% CI 1.2-5.0) after adjusting for confounding variables. No difference was noted between women smoking narghile in the first trimester and those initiating smoking in subsequent trimesters regarding low birthweight.

CONCLUSIONS

Narghile smoking more than once per day increases the odds of low birthweight by a 2.4-fold compared with nonsmokers, although to a lesser extent than cigarette smoking.

Low socioeconomic status and neonatal outcomes in an urban population in a developing country

OBJECTIVE

To investigate the effect of low socioeconomic status indicators, specifically parental educational and occupational characteristics on neonatal health outcomes.

METHODS

Analysis of 3372 newborn infants admitted to five National Collaborative Perinatal Neonatal Network centers (1 February 2000 to 31 January 2002). Outcomes included birth weight, gestational age, admission to the neonatal intensive care unit (NICU) and length of hospital stay. The independent effects of mother's education and occupation as well as father's occupation on health outcomes were assessed by means of stepwise logistic regression analysis.

RESULTS

A total of 271 (8.0%) infants were of low birth weight, 306 (9.1%) were preterm, 410 (12.2%) had NICU admissions and 240 (7.1%) were hospitalized for more than a week. After adjusting for maternal gravidity, age, smoking during pregnancy and pregnancy-related complications, parental socioeconomic characteristics had no significant impact on low birth weight or preterm birth. NICU admission and prolonged hospitalization were significantly correlated with skilled, semi-skilled and unskilled paternal occupations. Illiterate mothers had nearly 3-5 times the risk of NICU admission and prolonged hospitalization.

CONCLUSION

Both father's occupation and mother's education play an important role as determinants of neonatal morbidity characteristics.