Analysis of the role of mitochondrial morphology in autophagy

PARK2 gene encodes for an E3 ubiquitin ligase called Parkin. Loss-of-function mutations in this gene cause early onset of Parkinson’s disease, a neurodegenerative disorder of unknown etiology. The role of Parkin in neuron maintenance is still unknown, however it has been linked to the regulation of mitochondria dynamic. Recent works show that Parkin is selectively recruited to dysfunctional mitochondria, where it mediates their elimination via autophagy. Parkin translocation and Parkin-mediated autophagy depend on the Serine/Threonine-protein kinase PINK1 (PTEN-induced putative kinase 1), which is selectively stabilized on dysfunctional mitochondria where it recruits Parkin. However, it remains unknown which cellular signals or covalent modifications directly regulate Parkin translocation. Confocal microscopy of EYFP-Parkin transfected MEFs shows that Parkin has a cytoplasmic localization. After treatment with the mitochondrial uncoupling agent Carbonyl cyanide m-chlorophenyl hydrazine (CCCP), Parkin appears as spots that co-localize with mitochondria. We found that pretreatment with the Ca2+ selective chelator BAPTA completely blocked Parkin translocation. We also found that inhibition of Ca2+ dependent phosphatase Calcineurin A (CnA) impaired Parkin recruitment and that CaN constitutive active expression was able to induce Parkin translocation per se, independently from PINK1. In accordance to the in vitro data, we showed that in the Drosophila fruit fly, Calcineurin constitutive active expression is able to rescue the climbing ability of a PINK1 in vivo model of Parkinson’s Disease

SARS-CoV-2 susceptibility and COVID-19 disease severity are associated with genetic variants affecting gene expression in a variety of tissues

Variability in SARS-CoV-2 susceptibility and COVID-19 disease severity between individuals is partly due to genetic factors. Here, we identify 4 genomic loci with suggestive associations for SARS-CoV-2 susceptibility and 19 for COVID-19 disease severity. Four of these 23 loci likely have an ethnicity-specific component. Genome-wide association study (GWAS) signals in 11 loci colocalize with expression quantitative trait loci (eQTLs) associated with the expression of 20 genes in 62 tissues/cell types (range: 1:43 tissues/gene), including lung, brain, heart, muscle, and skin as well as the digestive system and immune system. We perform genetic fine mapping to compute 99% credible SNP sets, which identify 10 GWAS loci that have eight or fewer SNPs in the credible set, including three loci with one single likely causal SNP. Our study suggests that the diverse symptoms and disease severity of COVID-19 observed between individuals is associated with variants across the genome, affecting gene expression levels in a wide variety of tissue types

A first update on mapping the human genetic architecture of COVID-19

peer reviewe

Analysis of the role of mitochondrial morphology in autophagy

PARK2 gene encodes for an E3 ubiquitin ligase called Parkin. Loss-of-function mutations in this gene cause early onset of Parkinson’s disease, a neurodegenerative disorder of unknown etiology. The role of Parkin in neuron maintenance is still unknown, however it has been linked to the regulation of mitochondria dynamic. Recent works show that Parkin is selectively recruited to dysfunctional mitochondria, where it mediates their elimination via autophagy. Parkin translocation and Parkin-mediated autophagy depend on the Serine/Threonine-protein kinase PINK1 (PTEN-induced putative kinase 1), which is selectively stabilized on dysfunctional mitochondria where it recruits Parkin. However, it remains unknown which cellular signals or covalent modifications directly regulate Parkin translocation. Confocal microscopy of EYFP-Parkin transfected MEFs shows that Parkin has a cytoplasmic localization. After treatment with the mitochondrial uncoupling agent Carbonyl cyanide m-chlorophenyl hydrazine (CCCP), Parkin appears as spots that co-localize with mitochondria. We found that pretreatment with the Ca2+ selective chelator BAPTA completely blocked Parkin translocation. We also found that inhibition of Ca2+ dependent phosphatase Calcineurin A (CnA) impaired Parkin recruitment and that CaN constitutive active expression was able to induce Parkin translocation per se, independently from PINK1. In accordance to the in vitro data, we showed that in the Drosophila fruit fly, Calcineurin constitutive active expression is able to rescue the climbing ability of a PINK1 in vivo model of Parkinson’s Disease.Il gene PARK2 codifica per un’E3-ubiquitin ligasi chiamata Parkin. Mutazioni con perdita di funzione in questo gene e’ causa di forme precoci del morbo di Parkinson, una malattia neurodegenerativa di etiologia sconosciuta. Il ruolo di Parkin nel mantenimento dei neuroni e’ ancora sconosciuto, tuttavia la sua funzione e’ stata legata alla regolazione della dinamica mitocondriale. Lavori recenti mostrano come Parkin sia selettivamente recrutato ai mitocondri non funzionali, dove media la loro eliminazione tramite autofagia. La traslocazione di Parkin e la mitofagia indotta da Parkin dipendono dalla Serin/Treonin chinasi PINK1 (PTEN-induced putative kinase 1), che e’ selettivamente stabilizzata sui mitocondri non funzionali, dove recruta Parkin. Tuttavia, rimane ancora sconosciuto che segnale cellulare o che modificazioni posttrascrizionali regolano direttamente la traslocazione di Parkin. Tramite microscopia confocale, abbiamo cisto come in MEFs trasfettate con mCherry-Parkin, Parkin abbia una localizzazione citosolica. Tuttavia, dopo trattamento con l’agente disacoppiante mitocondriale agent Carbonyl cyanide m-chlorophenyl hydrazine (CCCP), Parkin appare con punti che colocalizzano con i mitondri. Abbiamo visto che trattando le cellule con il chelatore di calcio BAPTA bloccava completamente la traslocazione di Parkin indotta da CCCP. Inoltre l’inibizione della Calcio-dipendente fosfatasi Calcineurina (CaN) bloccava il recrutamento di Parkin, mentre l’espressione della CaN costitutivamente attiva era in grado di indurre la traslocazione di Parkin per se, indipendentemente dalla presenza di PINK1. Abbiamo dimostrato, inoltre, come l’espressione della CaN costitutivamente attiva sia in grado di migliorare l’abilita’ di arrampicare delle Drosophile, in un modello di Parkinson dipendente d a mutazioni di PINK1

Counteracting PINK/Parkin Deficiency in the Activation of Mitophagy: A Potential Therapeutic Intervention for Parkinson\u2019s Disease

Parkinson’s Disease (PD) related genes PINK1, a protein kinase [1], and Parkin, an E3 ubiquitin ligase [2], operate within the same pathway [3-5], which controls, via specific elimination of dysfunctional mitochondria, the quality of the organelle network [6]. Parkin translocates to impaired mitochondria and drives their elimination via autophagy, a process known as mitophagy [6]. PINK1 regulates Parkin translocation through a not yet completely understood mechanism [7, 8]. Mitochondrial outer membrane proteins Mitofusin (MFN), VDAC, Fis1 and TOM20 were found to be targets for Parkin mediated ubiquitination [9-11]. By adding ubiquitin molecules to its targets expressed on mitochondria, Parkin tags and selects dysfunctional mitochondria for clearance, contributing to maintain a functional and healthy mitochondrial network. Abnormal accumulation of misfolded proteins and unfunctional mitochondria is a characteristic hallmark of PD pathology. Therefore a therapeutic approach to enhance clearance of misfolded proteins and potentiate the ubiquitin-proteosome system (UPS) could be instrumental to ameliorate the progression of the disease. Recently, much effort has been put to identify specific de-ubiquitinating enzymes (DUBs) that oppose Parkin in the ubiquitination of its targets. Similar to other post-translational modifications, such as phosphorylation and acetylation, ubiquitination is also a reversible modification, mediated by a large family of DUBs [12]. DUBs inhibitors or activators can affect cellular response to stimuli that induce mitophagy via ubiquitination of mitochondrial outer membrane proteins MFN, VDAC, Fis1 and TOM20. In this respect, the identification of a Parkin-opposing DUB in the regulation of mitophagy, might be instrumental to develop specific isopeptidase inhibitors or activators that can modulate the fundamental biological process of mitochondria clearance and impact on cell survival