Figure 6.
Tetraspanins CD9, CD81, and CD82 can stabilize CD4. (A) CD9 is relatively stable. COS-1 cells transfected with the control pcDNA3 plasmid (lane 1), CD9 cDNA (lanes 2–6), or CD9 plus CD4 cDNAs (lanes 7–11) were labeled with [35S]methionine for 1 h, chased, and analyzed by immunoprecipitation using an anti-CD9 antibody. (B) CD4 can be partially stabilized by CD9. COS-1 cells transfected with pcDNA3 (lane 1), CD4 cDNA (lanes 2–6), or CD4 plus CD9 cDNAs (lanes 7–11) were radio-labeled, chased, and analyzed by immunoprecipitation using an anti-CD4 antibody. (C) The bands in A and B were quantified by densitometry. Data from three independent experiments were presented (mean ± SD). (D) CD81 is relatively stable. COS-1 cells transfected with pcDNA3 (lane 1), CD81 cDNA (lanes 2–6), or CD81 plus CD4 cDNAs (lanes 7–11) were radiolabeled, chased, and analyzed by immunoprecipitation using an anti-CD81 antibody. (E) CD4 can be partially stabilized by CD81. COS-1 cells transfected with pcDNA3 (lane 1), CD4 cDNA (lanes 2–6), or CD4 plus CD81 cDNAs (lanes 7–11) were radiolabeled, chased, and analyzed by immunoprecipitation using the anti-CD4 antibody. (F) The bands in D and E were quantified. Data from three independent experiments were presented (mean ± SD). (G) CD82 is quite unstable. COS-1 cells transfected with pcDNA3 (lane 1), CD82 cDNA (lanes 2–6), or CD82 plus CD4 cDNAs (lanes 7–11) were radiolabeled, chased, and analyzed by immunoprecipitation using an anti-CD82 antibody. (H) CD4 can be partially stabilized by CD82. COS-1 cells transfected with pcDNA3 (lane 1), CD4 cDNA (lanes 2–6), or CD4 plus CD82 cDNAs (lanes 7–11) were radiolabeled, chased, and analyzed by immunoprecipitation using the anti-CD4 antibody. (I) The bands in G and H were quantified. Data from three independent experiments were presented (mean ± SD).