FIGURE 2.

The GXXXG dimerization motif is not a major determinant for the intramembrane cleavage of Bri2. A, GXXXG to AXXXG mutation does not change Bri2 ICD generation. Co-expression of Bri2 wt or Bri2 G67A with SPPL2b wt or the inactive SPPL2b D421A revealed similar ICD production from both Bri2 variants. All proteolytic products were detected as described in Fig. 1C. B, quantitative analysis of the experiment shown in A. Data represent the means ± S.D. of eight independent experiments. C, GXXXG to IXXXG mutation slightly reduced SPPL2b dependent Bri2 ICD generation. Co-expression of Bri2 wt or Bri2 G67I with SPPL2b wt or the inactive SPPL2b D421A revealed a slightly reduced ICD production from Bri2 G67I. All proteolytic products were detected as described in Fig. 1C. D, quantitative analysis of the experiment shown in C. Data represent the means ± S.D. of eighteen independent experiments. E, mutations in GXXXG motif did not affect subcellular localization of Bri2. Immunohistochemistry of HEK293 TR cells transfected with Bri2 wt, Bri2 G67A, or Bri2 G67I reveals similar localization of all Bri2 protein variants at the plasma membrane (staining without Triton X-100) and within the secretory pathway (staining with Triton X-100). Scale bar, 10 μm.