The mitophagy receptor NIX induces vIRF-1 oligomerization and interaction with GABARAPL1 for the promotion of HHV-8 reactivation-induced mitophagy

Abstract

Recently, viruses have been shown to regulate selective autophagy for productive infections. For instance, human herpesvirus 8 (HHV-8), also known as Kaposi’s sarcoma-associated herpesvirus (KSHV), activates selective autophagy of mitochondria, termed mitophagy, thereby inhibiting antiviral innate immune responses during lytic infection in host cells. We previously demonstrated that HHV-8 viral interferon regulatory factor 1 (vIRF-1) plays a crucial role in lytic replication-activated mitophagy by interacting with cellular mitophagic proteins, including NIX and TUFM. However, the precise molecular mechanisms by which these interactions lead to mitophagy activation remain to be determined. Here, we show that vIRF-1 binds directly to mammalian autophagy-related gene 8 (ATG8) proteins, preferentially GABARAPL1 in infected cells, in an LC3-interacting region (LIR)-independent manner. Accordingly, we identified key residues in vIRF-1 and GABARAPL1 required for mutual interaction and demonstrated that the interaction is essential for mitophagy activation and HHV-8 productive replication. Interestingly, the mitophagy receptor NIX promotes vIRF-1-GABARAPL1 interaction, and NIX/vIRF-1-induced mitophagy is significantly inhibited in GABARAPL1-deficient cells. Moreover, a vIRF-1 variant defective in GABARAPL1 binding substantially loses the ability to induce vIRF-1/NIX-induced mitophagy. These results suggest that NIX supports vIRF-1 activity as a mitophagy mediator. In addition, we found that NIX promotes vIRF-1 aggregation and stabilizes aggregated vIRF-1. Together, these findings indicate that vIRF-1 plays a role as a viral mitophagy mediator that can be activated by a cellular mitophagy receptor.

Dysfunction of astrocytic glycophagy exacerbates reperfusion injury in ischemic stroke

“…S5D ). Previous studies suggested that GABARAPL1 might not be specific for glycophagy and might also participate in other types of autophagy, such as mitophagy [ 27 , 28 ]. Accordingly, we further downregulated GAA expression in cultured Ve-GA astrocytes (Ve-GA+sh-GAA, Fig.…”

“…Finally, one study suggested that GABARAPL1 knockdown inhibits mitophagy in breast cancer cells [ 27 ]. Another study revealed that viral interferon regulatory factor 1 of human herpesvirus 8 can interact with GABARAPL1 to activate mitophagy in infected cells [ 28 ]. Here, we observed that GABARAPL1 overexpression had little impact on mitophagy flux in astrocytes ( Fig.…”

NAT10-dependent N4‐acetylcytidine modification mediates PAN RNA stability, KSHV reactivation, and IFI16-related inflammasome activation

“…IL-1β (3A6) mouse mAb (12242; 1:1000) and cleaved Caspase-1 (Asp296) (E2G2I) rabbit mAb (89332; 1:1000) were from Cell Signaling Technology. The monoclonal rabbit anti-vIL-6 antibody (1:500) was kindly provided by Dr. Robert Yarchoan from the Center for Cancer Research, National Cancer Institute (Bethesda, Maryland, USA) 53 , 54 , and polyclonal rabbit anti-vIRF1 antibody (1:300) was from Dr. Gary Hayward from Viral Oncology Program, The Johns Hopkins School of Medicine (Baltimore, Maryland, USA) 55 – 58 .…”

TUFM in health and disease: exploring its multifaceted roles

“…Of note, TUFM-mediated LAP induces MAPKs-AP-1 signal pathway activation for inflammatory cytokine response ( 51 ). In addition, Human Herpesvirus 8 (HHV-8) vIRF-1 is localized to mitochondria and stimulates TUFM dimerization for mitophagy induction which is associated with the inhibition of caspase-8-mediated apoptosis ( 44 , 45 ) ( Table 1 ).…”