P21-activated kinase 1 (PAK1)-mediated cytoskeleton rearrangement promotes SARS-CoV-2 entry and ACE2 autophagic degradation

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2),the causative agent of coronavirus disease 2019(COVID-19),has had a significant impact on healthcare systems and economies worldwide.The continuous emergence of new viral strains presents a major challenge in the development of effective antiviral agents.Strategies that possess broad-spectrum antiviral activities are desirable to control SARS-CoV-2 infection.ACE2,an angiotensin-containing enzyme that prevents the overactivation of the renin angiotensin system,is the receptor for SARS-CoV-2.ACE2 interacts with the spike protein and facilitates viral attachment and entry into host cells.Yet,SARS-CoV-2 infection also promotes ACE2 degradation.Whether restoring ACE2 surface expression has an impact on SARS-CoV-2 infection is yet to be determined.Here,we show that the ACE2-spike complex is endocytosed and degraded via autophagy in a manner that depends on clathrin-mediated endocytosis and PAK1-mediated cytoskeleton rearrangement.In contrast,free cellular spike protein is selectively cleaved into S1 and s2 subunits in a lysosomal-dependent manner.Importantly,we show that the pan-PAK inhibitor FRAX-486 restores ACE2 surface expression and suppresses infection by different SARS-CoV-2 strains.FRAX-486-treated Syrian hamsters exhibit significantly decreased lung viral load and alleviated pulmonary inflammation compared with untreated hamsters.In summary,our findings have identified novel pathways regulating viral entry,as well as therapeutic targets and candidate compounds for controlling the emerging strains of SARS-CoV-2 infection.

Potential therapeutic effects of dipyridamole in the severely ill patients with COVID-19

Severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)infection can cause acute respiratory distress syndrome,hypercoagulability,hypertension,and multiorgan dysfunction.Effective antivirals with safe clinical profile are urgently needed to improve the overall prognosis.In an analysis of a randomly collected cohort of 124 patients with COVID-19,we found that hypercoagulability as indicated by elevated concentrations of D-dimers was associated with disease severity.By virtual screening of a U.S.FDA approved drug library,we identified an anticoagulation agent dipyridamole(DIP)in silico,which suppressed SARS-CoV-2 replication in vitro.In a proof-of-concept trial involving 31 patients with COVID-19,DIP supplementation was associated with significantly decreased concentrations of D-dimers(P<0.05),increased lymphocyte and platelet recovery in the circulation,and markedly improved clinical outcomes in comparison to the control patients.In particular,all 8 of the DIP-treated severely ill patients showed remarkable improvement:7 patients(87.5%)achieved clinical cure and were discharged from the hospitals while the remaining 1 patient(12.5%)was in clinical remission.

非锚定泛素链调控RIG-I介导的I型干扰素通路的持续激活及其下游基因的选择性表达

泛素化修饰在抗病毒免疫的信号网络调控中起重要作用.作为RNA病毒的关键受体,RIG-I分子既能发生共价结合的泛素化,也能和非锚定的泛素链结合,但是这两种修饰方式对于RIG-I通路的具体调控作用还不清楚.本研究通过免疫共沉淀、定量PCR、双荧光酶报告基因系统、转录组学以及免疫荧光等实验,发现RIG-I的非锚定泛素链介导了I型干扰素通路的持续激活,并调控其下游基因的选择性表达.此外,去泛素酶USP21和USP3可以分别通过负向调节RIG-I的泛素化和其对非锚定泛素链的结合,动态调控RIG-I介导信号通路的激活方式.综上所述,本研究揭示了RIG-I的不同泛素修饰模式精确调控抗病毒的I型干扰素通路的新机制.