Plasma Membrane Profiling Defines an Expanded Class of Cell Surface Proteins Selectively Targeted for Degradation by HCMV US2 in Cooperation with UL141

Abstract

Human cytomegalovirus (HCMV) US2, US3, US6 and US11 act in concert to prevent immune recognition of virally infected cells by CD8+ T-lymphocytes through downregulation of MHC class I molecules (MHC-I). Here we show that US2 function goes far beyond MHC-I degradation. A systematic proteomic study using Plasma Membrane Profiling revealed US2 was unique in downregulating additional cellular targets, including: five distinct integrin α-chains, CD112, the interleukin-12 receptor, PTPRJ and thrombomodulin. US2 recruited the cellular E3 ligase TRC8 to direct the proteasomal degradation of all its targets, reminiscent of its degradation of MHC-I. Whereas integrin α-chains were selectively degraded, their integrin β1 binding partner accumulated in the ER. Consequently integrin signaling, cell adhesion and migration were strongly suppressed. US2 was necessary and sufficient for degradation of the majority of its substrates, but remarkably, the HCMV NK cell evasion function UL141 requisitioned US2 to enhance downregulation of the NK cell ligand CD112. UL141 retained CD112 in the ER from where US2 promoted its TRC8-dependent retrotranslocation and degradation. These findings redefine US2 as a multifunctional degradation hub which, through recruitment of the cellular E3 ligase TRC8, modulates diverse immune pathways involved in antigen presentation, NK cell activation, migration and coagulation; and highlight US2’s impact on HCMV pathogenesis.

Regulation of Immunity by Butyrophilins

“…to be regulated efficiently during viral infection by a mechanism analogous to viral downregulation of MHC class I or NKG2D ligands, implying that immune evasion of BTN-mediated activation of γδ T cells is a requirement for viral infection (76)(77)(78).…”

The Cell Biology of Cytomegalovirus: Implications for Transplantation

“…The HCMV envelope can initiate thrombin generation or interact with the prothrombinase protein complex to facilitate thrombin generation. HCMV gene products include US2, which decreases thrombomodulin expression (141). In animal transplantation models, EC activation by CMV results in consumptive coagulopathy (142,143).…”

NK cell interplay with cytomegaloviruses

“…We have only begun to probe the long term consequences of CMV infection on the immune 14 Viral immunology Nectin-2 is directed to a TRC8-mediated proteasomal degradation pathway by the HCMV US2 [65,67,73 ]. (b) Based on the differential binding affinities of DNAM-1, TIGIT and Tactile for Nectin-2 and PVR, a model for fine tuning of NK-cell cytotoxicity during HCMV infection has been proposed, in which low levels of PVR on the surface of healthy cells maintain NK cells in inhibited state via a high affinity interaction between PVR and inhibitory TIGIT [67].…”

“…Interestingly, TLR2 is expressed mostly inside NK cells and interaction requires endocytosis of virus particles. Quantitative proteomic analysis of HCMV infected HFFs has added several novel NK cell ligands to the list of molecules modulated by HCMV infection [52 ], while HCMV protein US2 has been found to target the host IL-12 receptor, PTPRJ (protein tyrosine phosphatase receptor J aka CD148), thrombomodulin, CD112 and 6 a-integrins for degradation, thereby suppressing cell migration and adhesion [73 ].…”