Chloroquine inhibits autophagic flux by decreasing autophagosome-lysosome fusion

Abstract

Macroautophagy/autophagy is a conserved transport pathway where targeted structures are sequestered by phagophores, which mature into autophagosomes, and then delivered into lysosomes for degradation. Autophagy is involved in the pathophysiology of numerous diseases and its modulation is beneficial for the outcome of numerous specific diseases. Several lysosomal inhibitors such as bafilomycin A (BafA), protease inhibitors and chloroquine (CQ), have been used interchangeably to block autophagy in in vitro experiments assuming that they all primarily block lysosomal degradation. Among them, only CQ and its derivate hydroxychloroquine (HCQ) are FDA-approved drugs and are thus currently the principal compounds used in clinical trials aimed to treat tumors through autophagy inhibition. However, the precise mechanism of how CQ blocks autophagy remains to be firmly demonstrated. In this study, we focus on how CQ inhibits autophagy and directly compare its effects to those of BafA. We show that CQ mainly inhibits autophagy by impairing autophagosome fusion with lysosomes rather than by affecting the acidity and/or degradative activity of this organelle. Furthermore, CQ induces an autophagy-independent severe disorganization of the Golgi and endo-lysosomal systems, which might contribute to the fusion impairment. Strikingly, HCQ-treated mice also show a Golgi disorganization in kidney and intestinal tissues. Altogether, our data reveal that CQ and HCQ are not bona fide surrogates for other types of late stage lysosomal inhibitors for in vivo experiments. Moreover, the multiple cellular alterations caused by CQ and HCQ call for caution when interpreting results obtained by blocking autophagy with this drug.

Structural and molecular modelling studies reveal a new mechanism of action of chloroquine and hydroxychloroquine against SARS-CoV-2 infection

“…In addition, the antiviral potential of CLQ and its derivative hydroxychloroquine (CLQ-OH) against SARS-CoV-2 were compared. Overall, this study found that CLQ and CLQ-OH may be used to fight pathogenic human coronaviruses [3][4][5][6] , including SARS-CoV-2 [12] .…”

“…However, the mechanism of action of CLQ against SARS-CoV-2 is unclear as the drug seems to exert a broad range of potential antiviral effects [5] . Therefore, although CLQ is classically considered as an inhibitor of endocytic pathways through elevation of endoso-mal pH [6] , its detailed molecular mechanism of action as an antiviral compound remains unclear [3 , 5] . Interestingly, CLQ has been shown to interfere with the terminal glycosylation of angiotensinconverting enzyme-2 (ACE-2) [7] , which acts as a plasma membrane receptor for both SARS-CoV [8] and SARS-CoV-2 [9] , and CLQ could act at several steps of the coronavirus replication cycle [7] .…”

COVID-19 for the Cardiologist

“…The antiviral properties of chloroquine (CQ) were previously observed in HIV and other viruses (134,135). CQ and HCQ are thought to inhibit endosomal maturation, a process by which endosomes are translocated from the perimembrane regions of the cell to central hubs (136,137) ( Figure 1). CQ prevented viral replication of SARS-CoV1 in vitro (138).…”

Dissecting pharmacological effects of chloroquine in cancer treatment: interference with inflammatory signaling pathways

“…15,70,71 Pharmacological inhibitors of autophagy have been used extensively in various cellular conditions to delineate the molecular mechanism of autophagy and the effect of these inhibitors on autophagy. 49 It inhibits late stages of autophagy and may induce cell death even under conditions where inhibitors of early autophagy cannot 72 (Fig.…”