Fig 5.

Importance of the EXXXLL motif in the C-terminal flexible loop for the modulation of cellular receptors by primate lentiviral Nef proteins. (A to D) CEM cells expressing the A2-CD8β fusion (A) or SupT1 cells (B to D) were transduced with VSV-G-pseudotyped vpu- and env-defective NL4-3-based constructs expressing the indicated nef alleles and assayed for surface expression of the A2-CD8β fusion (A), CD4 (B), CD28 (C), and MHC-I (D). Quantification was performed as described in Materials and Methods. Data shown are average values ± SD derived from two independent experiments. The inset in panel A shows an amino acid sequence comparison of the various EXXXLL-corresponding regions analyzed. The NL4-3 motif is shown as a reference at the top. Dots indicate amino acid identity. (E) Correlations between efficiencies of down-modulation of the A2-CD8β fusion on CEM cells and modulation of CD8αβ, CD4, CD28, and MHC-I on SupT1 cells.