The SARS-CoV-2 SSHHPS Recognized by the Papain-like Protease.

Viral proteases are highly specific and recognize conserved cleavage site sequences of ∼6-8 amino acids. Short stretches of homologous host-pathogen sequences (SSHHPS) can be found spanning the viral protease cleavage sites. We hypothesized that these sequences corresponded to specific host protein targets since >40 host proteins have been shown to be cleaved by Group IV viral proteases and one Group VI viral protease. Using PHI-BLAST and the viral protease cleavage site sequences, we searched the human proteome for host targets and analyzed the hit results. Although the polyprotein and host proteins related to the suppression of the innate immune responses may be the primary targets of these viral proteases, we identified other cleavable host proteins. These proteins appear to be related to the virus-induced phenotype associated with Group IV viruses, suggesting that information about viral pathogenesis may be extractable directly from the viral genome sequence. Here we identify sequences cleaved by the SARS-CoV-2 papain-like protease (PLpro) in vitro within human MYH7 and MYH6 (two cardiac myosins linked to several cardiomyopathies), FOXP3 (an X-linked Treg cell transcription factor), ErbB4 (HER4), and vitamin-K-dependent plasma protein S (PROS1), an anticoagulation protein that prevents blood clots. Zinc inhibited the cleavage of these host sequences in vitro. Other patterns emerged from multispecies sequence alignments of the cleavage sites, which may have implications for the selection of animal models and zoonosis. SSHHPS/nsP is an example of a sequence-specific post-translational silencing mechanism.

Sudden Cardiac Death Caused by a Fatal Association of Hypertrophic Cardiomyopathy (MYH7, p.Arg719Trp), Heterozygous Familial Hypercholesterolemia (LDLR, p.Gly343Lys) and SARS-CoV-2 B.1.1.7 Infection.

Hypertrophic cardiomyopathy (HCM) and heterozygous familial hypercholesterolemia (HeFH), two of the most common genetic cardiovascular disorders, can lead to sudden cardiac death. These conditions could be complicated by concomitant severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection as in the case herein described. A young amateur soccer player died in late October 2020 after a fatal arrhythmia and the autopsy revealed the presence of HCM with diffuse non-obstructive coronary disease. The molecular autopsy revealed a compound condition with a first mutation in the MYH7 gene (p.Arg719Trp) and a second mutation in the LDLR gene (p.Gly343Cys): both have already been described as associated with HCM and HeFH, respectively. In addition, molecular analyses showed the presence of SARS-CoV-2 lineage B.1.1.7 (UK variant with high titer in the myocardium. Co-segregation analysis within the family (n = 19) showed that heterozygous LDLR mutation was maternally inherited, while the heterozygous MYH7 genetic lesion was de novo. All family member carriers of the LDLR mutation (n = 13) had systematic higher LDL plasma concentrations and positive records of cardiac and vascular ischemic events at young age. Considering that HCM mutations are in themselves involved in the predisposition to malignant arrhythmogenicity and HeFH could cause higher risk of cardiac complications in SARS-CoV-2 infection, this case could represent an example of a potential SARS-CoV-2 infection role in triggering or unmasking inherited cardiovascular disease, whose combination might represent the cause of fatal arrhythmia at such a young age. Additionally, it can provide clues in dating the presence of the SARS-CoV-2 lineage B.1.1.7 in Northern Italy in the early phases of the second pandemic wave.