VLDLR interacts with the PTB1 domain of FE65 A. Constructs of FE65 with C-terminal Myc tags containing PTB1 and PTB2 (construct 1, ~65 KD), WW and PTB1 (construct 2, ~85 KD), only PTB2 (construct 3, ~15 KD), and full length FE65 (construct 4, ~95 KD). B. Western blot analysis showing comparable expression levels of the different FE65 constructs (upper panel). The VLDLR immunoblotting (bottom panel) showed similar expression levels of VLDLR in all transfected cells. C. COS7 cells were transfected with plasmids expressing different FE65 constructs (indicated along the top of the panel) and full length VLDLR. Cell lysates (200 ug) were immunoprecipitated with anti-HA antibody (for VLDLR) and probed with an anti-myc antibody (for FE65). FE65 constructs containing the PTB1 domain (constructs 1, 2, 4) co-immunoprecipitated with VLDLR, but not constructs containing only the PTB2 domain (construct 3).