Biology subjects

Bernal, J. A.

Publications and source records attributed to Bernal, J. A..

3 recordsLinked to original sources

bioRxiv2020

Neuronal NOX4 knockdown alleviates pathological tau-related alterations in a humanized mouse model of tauopathy

Approximately 44 million people worldwide live with Alzheimers disease (AD) or a related form of dementia. Aggregates of the microtubule-associated protein tau are a common marker of these neurodegenerative diseases collectively termed as tauopathies. However, all therapeutic attempts based on tau have failed, suggesting that tau may only indicate a higher-level causal mechanism. For example, increasing levels of reactive oxygen species (ROS) may trigger protein aggregation or modulate protein degradation. Here we show that type 4 NADPH oxidase (NOX), the most abundant isoform of the only dedicated reactive oxygen producing enzyme family, is upregulated in dementia and AD patients and in a humanized mouse model of tauopathy. Both global knockout and neuronal knockdown of the Nox4 gene in mice, diminished the accumulation of pathological tau and positively modified established tauopathy by a mechanism that implicates modulation of the autophagy-lysosomal pathway (ALP). Moreover, neuronal-targeted NOX4 knockdown was sufficient to reduce neurotoxicity and prevented cognitive decline, suggesting a direct and causal role for neuronal NOX4. Thus, NOX4 is a previously unrecognized causal, mechanism-based target in tauopathies and blood-brain barrier permeable specific NOX4 inhibitors could have therapeutic potential even in established disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=83 SRC="FIGDIR/small/338954v1_ufig1.gif" ALT="Figure 1"> View larger version (26K): org.highwire.dtl.DTLVardef@1dac496org.highwire.dtl.DTLVardef@1a07dd5org.highwire.dtl.DTLVardef@1a5653aorg.highwire.dtl.DTLVardef@198f3e4_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2020

SARS-CoV-2 protein Nsp1 alters actomyosin cytoskeleton and phenocopies arrhythmogenic cardiomyopathy-related PKP2 mutant

Mutations in desmosomal Plakophilin-2 (PKP2) are the most prevalent drivers of arrhythmogenic cardiomyopathy (ACM) and a common cause of sudden cardiac death in young athletes. However, partner proteins that elucidate PKP2 cellular mechanism to understand cardiac dysfunction in ACM are mostly unknown. Here we identify the actin-based motor proteins Myh9 and Myh10 as key PKP2 interactors, and demonstrate that the expression of the ACM-related PKP2 mutant R735X alters actin fiber organization and cell mechanical stiffness. We also show that SARS-CoV-2 Nsp1 protein acts similarly to this known pathogenic R735X mutant, altering the actomyosin component distribution on cardiac cells. Our data reveal that the viral Nsp1 hijacks PKP2 into the cytoplasm and mimics the effect of delocalized R735X mutant. These results demonstrate that cytoplasmic PKP2, wildtype or mutant, induces the collapse of the actomyosin network, since shRNA-PKP2 knockdown maintains the cell structure, validating a critical role of PKP2 localization in the regulation of actomyosin architecture. The fact that Nsp1 and PKP2 mutant R735X share similar phenotypes also suggests that direct SARS-CoV-2 heart infection could induce a transient ACM-like disease in COVID-19 patients, which may contribute to right ventricle dysfunction, observed in patients with poor survival prognosis. HighlightsThe specific cardiac isoform Plakophilin-2a (PKP2) interacts with Myh9 and Myh10. PKP2 delocalization alters actomyosin cytoskeleton component organization. SARS-CoV-2 Nsp1 protein hijacks PKP2 from the desmosome into the soluble fraction where it is downregulated. Viral Nsp1 collapses the actomyosin cytoskeleton and phenocopies the arrhythmogenic cardiomyopathy-related mutant R735X.

molecular biology↗

bioRxiv2020

Conserved cysteines in titin sustain the mechanical function of cardiomyocytes

The protein titin determines cardiomyocyte contraction and truncating variants in the titin gene (TTN) are the most common cause of dilated cardiomyopathy (DCM). Different to truncations, missense variants in TTN are currently classified as variants of uncertain significance due to their high frequency in the population and the absence of functional annotation. Here, we report the regulatory role of conserved, mechanically active titin cysteines, which, contrary to current views, we uncover to be reversibly oxidized in basal conditions leading to isoform- and force-dependent modulation of titin stiffness and dynamics. Building on our functional studies, we demonstrate that missense mutations targeting a conserved titin cysteine alter myocyte contractile function and cause DCM in humans. Our findings have a direct impact on genetic counselling in clinical practice. One sentence summaryMutations targeting cysteines key to the mechanoredox control of titin cause human dilated cardiomyopathy

physiology↗