The COVID-19 pandemic is currently a severe challenge for healthcare workers, with a considerable impact on their mental health. In order to focus preventive and rehabilitation measures it's ...fundamental to identify risk factors of such psychological impairment. We designed an observational longitudinal study to systematically examine the psychological wellbeing of all employees in a large University Hospital in Italy, using validated psychometric scales in the context of the occupational physician's health surveillance, in collaboration with Psychiatric Unit.
The study started after ethical approval in August 2020. For each worker, the psychological wellbeing is screened in two steps. The first level questionnaire collects sociodemographic characteristics, personal and occupational COVID-19 exposure, worries and concerns about COVID-19, general psychological discomfort (GHQ-12), post-traumatic stress symptoms (IES-R) and anxiety (GAD-7). Workers who score above the cut-off in at least one scale are further investigated by the second level questionnaire composed by PHQ-9, DES-II and SCL-90. If second level shows psychological impairments, we offer individual specialist treatment (third level). We plan to follow-up all subjects to monitor symptoms and possible chronicization; we aim to investigate potential risk factors through univariate analysis and multivariate logistic regressions.
Preliminary results refer to a sample of 550 workers who completed the multi-step evaluation from August to December 2020, before vaccination campaign started. The participation rate was 90%. At first level screening, 39% of the subjects expressed general psychological discomfort (GHQ-12), 22% post-traumatic stress symptoms (IES-R), and 21% symptoms of anxiety (GAD-7). Women, nurses, younger workers, subjects with COVID-19 working exposure and with an infected family member showed significantly higher psychological impairment compared to colleagues. After the second level screening, 12% and 7% of all workers showed, respectively, depressive and dissociative symptoms; scorings were significantly associated with gender and occupational role. We are currently extending sample size and evaluating subjects over a period of further 12 months.
The possibility to perform a systematic follow-up of psychological wellbeing of all hospital workers, directly or indirectly exposed to pandemic consequences, constitutes a unique condition to detect individual, occupational, and non-occupational risk factors for psychological impairment in situations of prolonged stress, as well as variables associated with symptoms chronicization.
The voltage-gated proton channel (Hv1) is homologous to the voltage-sensing domain (VSD) of voltage-gated potassium (Kv) channels but lacks a separate pore domain. The Hv1 monomer has dual functions: ...it gates the proton current and also serves as the proton conduction pathway. To gain insight into the structure and dynamics of the yet unresolved proton permeation pathway, we performed all-atom molecular dynamics simulations of two different Hv1 homology models in a lipid bilayer in excess water. The structure of the Kv1.2–Kv2.1 paddle-chimera VSD was used as template to generate both models, but they differ in the sequence alignment of the S4 segment. In both models, we observe a water wire that extends through the membrane, whereas the corresponding region is dry in simulations of the Kv1.2–Kv2.1 paddle-chimera. We find that the kinetic stability of the water wire is dependent upon the identity and location of the residues lining the permeation pathway, in particular, the S4 arginines. A measurement of water transport kinetics indicates that the water wire is a relatively static feature of the permeation pathway. Taken together, our results suggest that proton conduction in Hv1 may occur via Grotthuss hopping along a robust water wire, with exchange of water molecules between inner and outer ends of the permeation pathway minimized by specific water–protein interactions. This article is part of a Special Issue entitled: Membrane protein structure and function.
► Two homology models of the Hv1 proton channel are presented. ► The models are based on two alignments with the voltage-sensing domain of a potassium channel of known structure. ► Both models support water wires, but the wire is more stable in one of the models. ► No water flux is observed in the model with the most robust water wire. ► The model with the most robust wire is supported by experimental studies and modeling of a mutant.
Mitochondrial porin, or voltage-dependent anion channel, is a pore-forming protein first discovered in the outer mitochondrial membrane. Later investigations have provided indications for its ...presence also in other cellular membranes, including the plasma membrane, and in caveolae. This extra-mitochondrial localization is debated and no clear-cut conclusion has been reached up to now. In this work, we used biochemical and electrophysiological techniques to detect and characterize porin within isolated caveolae and caveolae-like domains (low density Triton-insoluble fractions). A new procedure was used to isolate porin from plasma membrane. The outer surface of cultured CEM cells was biotinylated by an impermeable reagent. Low density Triton-insoluble fractions were prepared from the labeled cells and used as starting material to purify a biotinylated protein with the same electrophoretic mobility and immunoreactivity of mitochondrial porin. In planar bilayers, the porin from these sources formed slightly anion-selective pores with properties indistinguishable from those of mitochondrial porin. This work thus provides a strong indication of the presence of porin in the plasma membrane, and specifically in caveolae and caveolae-like domains.
Mitochondrial porin, or VDAC, is a pore-forming protein abundant in the outer mitochondrial membrane. Several publications have reported extramitochondrial localizations as well, but the evidence was ...considered insufficient by many, and the presence of porin in nonmitochondrial cellular compartments has remained in doubt for a long time. We have now obtained new data indicating that the plasma membrane of hematopoietic cells contains porin, probably located mostly in caveolae or caveolae-like domains. Porin was purified from the plasma membrane of intact cells by a procedure utilizing the membrane-impermeable labeling reagent NH-SS-biotin and streptavidin affinity chromatography, and shown to have the same properties as mitochondrial porin. A channel with properties similar to that of isolated VDAC was observed by patch-clamping intact cells. This review discusses the evidence supporting extramitochondrial localization, the putative identification of the plasma membrane porin with the "maxi" chloride channel, the hypothetical mechanisms of sorting porin to various cellular membrane structures, and its possible functions.
The transport of genetic material across biomembranes is a process of great relevance for several fields of study. However, much remains to be learned about the mechanisms underlying transport, one ...of which implies the involvement of proteic DNA‐conducting pores. Entry of genetic material into mitochondria has been observed under both physiological and pathological conditions. We report here that double‐stranded DNA can move through a planar bilayer membrane containing isolated mitochondrial porin (voltage‐dependent anion channel). The transport is driven by the applied electrical field, and the presence of DNA is associated with a decrease of current conduction by the pores. The passage of DNA does not take place if the bilayer has not been doped with any protein or in the presence of both reconstituted porin and anti‐porin antibody. Translocation does not occur if the bilayer contains Shigella sonnei maltoporin, gramicidin A channels, or a 30 pS anion‐selective channel plus other proteins. These results show that mitochondrial porin is capable of mediating the transport of genetic material, revealing a new property of this molecule and futher confirming the idea that DNA can move through proteic pores.—Szabò, I., Bàthori, G., Tombola, F., Coppola, A., Schmehl, I., Brini, M., Ghazi, A., De Pinto, V., Zoratti, M. Double‐stranded DNA can be translocated across a planar membrane containing purified mitochondrial porin. FASEB J. 12, 495–502 (1998)
The recent findings that mitochondrial porin, VDAC, participates in supramolecular complexes and is present in the plasmamembrane need to be reconciled with its biophysical properties. We report here ...that VDAC often displays previously unobserved or unappreciated behaviors. Reconstituted VDAC can: a) exhibit fast gating when in any of many conductance substates; b) close completely, although briefly, on its own; c) close for long periods, in the presence of König's polyanion; d) take several milliseconds to re-open when an applied transmembrane potential is switched off; e) be desensitized by prolonged exposure to high voltages, so that it will not re-open to the full conductance state upon subsequent return to zero voltage; f) display polarity-dependent voltage-induced closure. These behaviors are especially noticeable when the observations are conducted on a single reincorporated channel, suggesting that interactions between copies of VDAC may play a role in determining its electrophysiological properties. Any model of VDAC's structure, gating and function should take these observations into account.
PDF
