Figure 2.

Endoplasmic reticulum-associated degradation of CD4 by Vpu protein: Vpu interacts with CD4 by transmembrane–transmembrane domain in the ER and promotes binding with SKP1-cullin1-F-Box (SCF) E3 ubiquitin ligase through the SCF subunits β-TrCP1 and β-TrCP2. Vpu and SCF β-TrCP complex induces proteasomal degradation of CD4 by the ERAD pathway by extracting it from ER. Abbreviations: Vpu: viral protein U, CD4: cluster differentiation 4, Ub: ubiquitination, SCF β-TrCP: SKP1-cullin1-F-Box-β-transducin repeat-containing proteins, UFDL1: ubiquitin fusion degradation 1-like, NPL4: nuclear protein localization protein 4, ERAD: endoplasmic reticulum-associated degradation, VCP: valosin-containing protein.