Signal peptide peptidase is required for dislocation from the endoplasmic reticulum

Area of Science:

• Virology
• Immunology
• Molecular Biology

Background:

• Human cytomegalovirus (HCMV) employs immunoevasins like US2 and US11 to evade immune surveillance.
• These proteins disrupt the presentation of MHC class I peptide complexes on infected cell surfaces.
• US11 utilizes Derlin-1, but the mechanism and partners for US2-mediated dislocation remain unclear.

Purpose of the Study:

• To identify host proteins interacting with the HCMV US2 immunoevasin.
• To elucidate the specific pathway employed by US2 for MHC class I heavy chain dislocation.
• To investigate the role of identified partners in US2-mediated immune evasion.

Main Methods:

• Co-immunoprecipitation to identify US2 interacting partners.
• RNA-mediated interference to assess the impact of protein depletion on US2 function.
• Analysis of MHC class I heavy chain localization and degradation.

Main Results:

• Signal peptide peptidase (SPP) was identified as a binding partner for the active form of US2.
• Reduced SPP levels via RNA interference significantly inhibited US2-mediated heavy chain dislocation.
• SPP depletion did not affect dislocation mediated by the US11 immunoevasin.

Conclusions:

• Signal peptide peptidase (SPP) is implicated as a key component of the US2-dependent dislocation pathway.
• This finding suggests a novel role for SPP, an intramembrane-cleaving protease, in endoplasmic reticulum-associated degradation.
• Understanding the US2-SPP interaction provides new insights into HCMV immune evasion strategies.