The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and ...increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people.
Esta tesis doctoral está dedicada fundamentalmente a la identificación y caracterización de transportadores de nitrato/nitrito de la levadura Hansenula polymorpha. El uso de las herramientas ...bioinformáticas nos ha permitido identificar en el genoma de H. polymorphasólo dos proteínas denominadas Nar1 y Chl1 que comparten similitud de secuencia con los respectivos transportadores de nitrito y nitrato descritos en otros organismos. Los resultados del presente trabajo indican que Nar1 es una proteína ubicada en la membrana plasmática que regula la concentración intracelular de nitrito mediante su excreción. De esta forma, las células toman el nitrato del medio principalmente a través del transportador de nitrato y nitrito de alta afinidad, Ynt1. Una vez en el citoplasma, el nitrato se reduce a nitrito, cuyo excedente es devuelto al medio extracelular a través de Nar1, y de otro(s) sistema(s). Pensamos que este mecanismo permite mantener el nitrito intracelular por debajo de niveles tóxicos para la levadura. Por otra parte, Chl1 participa en la excreción de aminoácidos. La acumulación intracelular de fuentes reducidas en ∆chl1promueven la represión catabólica por nitrógeno, que junto con la menor activación de la vía calcineurina, disminuyen los niveles de expresión de los genes de la vía de asimilación de nitrato. En conjunto, estos resultados nos han permitido conocer nuevos elementos que participan en la asimilación de nitrato, si bien ninguno de ellos parece mediar directamente el transporte de nitrato o nitrito al interior de la célula.
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Transepithelial sodium reabsorption through ENaC plays a key role in electrolyte and extracellular volume homeostasis and regulation of blood pressure. ENaC is a heterotrimeric ion ...channel formed by α, β and γ subunits. Channel activity is tightly regulated by many local and circulating factors, which in turn control channel cell surface expression (N) and open probability (Po). ENaC upregulation resulting from decreased endocytosis or enhanced delivery to the membrane have been described. However, there are several technical challenges in the study of ENaC trafficking, including low levels of plasma membrane expression. The aim of this study was to develop a new tool to directly study the dynamics of ENaC trafficking to and from the plasma membrane. To that end we inserted an α‐bungarotoxin (BTX) binding site (BBS) in the extracellular domain of the a subunit and used fluorescently labeled BTX to study ENaC plasma membrane expression and trafficking in
Xenopus laevis
oocytes. Mutant α
BBS
βγ channels do not shown any functional abnormality in the absence or presence of the toxin. Confocal imaging of Alexa Fluor 488 (AF488)‐labeled BTX showed specific labeling in plasma membrane of oocytes expressing α
BBS
βγ channels. ENaC retrieval was detected by imaging AF488‐BTX labeled oocytes at different time points whereas ENaC insertion rate was detected by blocking α
BBS
βγ‐expressing oocytes with unlabeled BTX and then staining with AF488‐BTX at different times. Our results suggest that tagged α
BBS
subunits provide a useful tool to study plasma membrane ENaC abundance and trafficking to and from the membrane.
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