Fig. 5
The TM domain supports formation of nonameric complexes in the absence of TRIM. a Left; schematic representation of DRα, DRβmyc and DRβKKAA. Right; illustration of the rational behind formation of pentamers and nonamers using the DRβKKAA. If pentameric (DRαβ)1(Ii)3 complexes can egress the ER, the ER-retained (DRα + DRβKKAA)1(IiTRIM)3 complex will not impact WT (DRα + DRβ)1(IiTRIM)3 complexes. In contrast, if formation of nonamers is the only outcome due to the expression of Iip35, the ER-retained DRKKAA will trap a co-expressed WT DR that is incorporated in a same complex. b–f HEK293T cells were transiently transfected with DRα and DRβmyc (DR) and/or DRα + DRβKKAA (DRKKAA) together Δ20TRIM or p35LIMLTRIM. After 48 h, cells were analyzed by flow cytometry to evaluate surface to total expression ratio of MHCII using L243 (b). c Representative histograms showing surface expression of Ii and d bar graph shows surface to total expression ratio of Ii using BU45. e Representative histograms showing CLIP surface expression and f bar graph shows surface of CLIP using Cer-CLIP.1. Ctrl represent isotype control antibodies. b, d, e Error bars indicate the SD from at least three independent experiments. Student t-tests were performed; *p ≤ 0.001 and **p ≤ 0.05