Human and viral membrane-associated E3 ubiquitin ligases MARCH1 and MIR2 recognize different features of CD86 to downregulate surface expression
- Author(s)
- Trenker, R; Wu, X; Nguyen, JV; Wilcox, S; Rubin, AF; Call, ME; Call, MJ;
- Journal Title
- Journal of Biological Chemistry
- Publication Type
- epub ahead of print
- Abstract
- Immune-stimulatory ligands, such as major histocompatibility complex (MHC) molecules and the T-cell costimulatory ligand CD86 are central to productive immunity. Endogenous mammalian membrane-associated RING-CHs (MARCH) act on these and other targets to regulate antigen presentation and activation of adaptive immunity, while virus-encoded homologs target the same molecules to evade immune responses. Substrate specificity is encoded in or near the membrane-embedded domains of MARCHs and the proteins they regulate, but the exact sequences that distinguish substrates from non-substrates are poorly understood. Here we examined the requirements for recognition of the costimulatory ligand CD86 by two different MARCH-family proteins, human MARCH1 and Kaposi's sarcoma herpesvirus (KSHV) modulator of immune recognition (MIR)2, using deep mutational scanning (DMS). We identified a highly specific recognition surface in the hydrophobic core of the CD86 TM domain that is required for recognition by MARCH1 and prominently features a proline at position 254. In contrast, MIR2 requires no specific sequences in the CD86 TM domain, but relies primarily on an aspartic acid at position 244 in the CD86 extracellular juxtamembrane region. Surprisingly, while MIR2 recognized CD86 with a TM domain composed entirely of valine, many different single-amino-acid substitutions in the context of the native TM sequence conferred MIR2 resistance. These results show that the human and viral proteins evolved completely different recognition modes for the same substrate. That some TM sequences are incompatible with MIR2 activity, even when no specific recognition motif is required, suggests a more complicated mechanism of immune modulation via CD86 than was previously appreciated.
- Publisher
- Elsevier
- Keywords
- Kaposi Sarcoma Virus; Membrane-associated E3 ubiquitin ligase; deep mutational scanning; immune regulation; membrane protein; protein:protein interactions;
- Research Division(s)
- Structural Biology; Advanced Technology And Biology
- PubMed ID
- 34157285
- Publisher's Version
- https://doi.org/10.1016/j.jbc.2021.100900
- Open Access at Publisher's Site
https://doi.org/10.1016/j.jbc.2021.100900- Terms of Use/Rights Notice
- Refer to copyright notice on published article.
Creation Date: 2021-06-25 01:41:43
Last Modified: 2021-06-25 01:49:10