HSC70 Inhibits Spring Viremia of Carp Virus Replication by Inducing MARCH8-Mediated Lysosomal Degradation of G Protein

Abstract

As a fierce pathogen, spring viremia of carp virus (SVCV) can cause high mortality in the common carp, and its glycoprotein (G protein) is a component of the viral structure on the surface of virion, which is crucial in viral life cycle. This report adopted tandem affinity purification (TAP), mass spectrometry analysis (LC-MS/MS), immunoprecipitation, and confocal microscopy assays to identify Heat shock cognate protein 70 (HSC70) as an interaction partner of SVCV G protein. It was found that HSC70 overexpression dramatically inhibited SVCV replication, whereas its loss of functions elicited opposing effects on SVCV replication. Mechanistic studies indicate that HSC70 induces lysosomal degradation of ubiquitinated-SVCV G protein. This study further demonstrates that Membrane-associated RING-CH 8 (MARCH8), an E3 ubiquitin ligase, is critical for SVCV G protein ubiquitylation and leads to its lysosomal degradation. Furthermore, the MARCH8 mediated ubiquitylation of SVCV G protein required the participation of HSC70 through forming a multicomponent complex. Taken together, these results demonstrate that HSC70 serves as a scaffold for MARCH8 and SVCV G, which leads to the ubiquitylation and degradation of SVCV G protein and thus inhibits viral replication. These findings have established a novel host defense mechanism against SVCV.

The emerging roles of MARCH8 in viral infections: A double-edged Sword

“…Under the CTD mode, MARCH8 generally ubiquitinates the viral glycoproteins via recognition of their cytoplasmic tails, mediating their endocytosis and targeting them for lysosome degradation, which was reported by many studies [ 27 , 33 – 35 , 37 ].…”

“…In a recent study, Li and colleagues found that heat shock cognate protein 70 (HSC70) negatively regulated SVCV replication [ 37 ]. Their research identified that HSC70 interacted with SVCV-G and promoted its degradation in a dose-dependent manner.…”

“…In contrast, SVCV-G CT truncation abrogated z-MARCH8-induced degradation. The SVCV-G CT harbored 2 lysines, both crucial for z-MARCH8 recognition because only substituting one of the 2 lysines in SVCV-G CT made it still sensitive to z-MARCH8-induced degradation [ 37 ]. These lines of evidence proved that MARCH8 reduced SVCV replication via the CTD antiviral mode.…”

Human MARCH1, 2, and 8 Block Ebola Virus Envelope Glycoprotein Cleavage via Targeting Furin P Domain

“…Subsequently, MARCH1 and MARCH2 were also found to inhibit viral replication potentially (25)(26)(27)(28). The viral proteins targeted by MARCH proteins now are extended to envelope glycoproteins of EBOV (27,29,30), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (27,28,30), murine leukemia virus (MLV) (24,27), influenza virus (IAV) (27,29,31), Nipah virus (NiV) (27), spring viremia of carp virus (SVCV) (32) and rabies virus (RABV) (28), M2 protein of IAV (33), and N protein of porcine epidemic diarrhea virus (PEDV) (15). Interestingly, in contrast to the negative role on viral replication, MARCH8 was also critically supportive of hepatitis C virus (HCV) replication (34).…”

Human MARCH1, 2, and 8 block Ebola virus envelope glycoprotein cleavage via targeting furin P domain

“…24 Subsequently, MARCH1 and MARCH2 were also found to inhibit viral replication. [25][26][27][28] The viral proteins targeted by MARCH proteins now are extended to include envelope GPs of EBOV, 27,29,30 severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), 27,28,30 murine leukemia virus (MLV), 24,27 influenza virus (IAV), 27,29,31 Nipah virus (NiV), 27 spring viremia of carp virus (SVCV) 32 and rabies virus (RABV), 28 M2 protein of IAV, 33 and N protein of porcine epidemic diarrhea virus (PEDV). 15 Interestingly, in contrast to the negative role on viral infection, MARCH8 also critically supported hepatitis C virus (HCV) replication.…”