Mammalian two-hybrid assays with wild-type and mutant LRP1. NPXY motifs of the cytoplasmic domain of LRP1 were mutated and the interaction of the cytoplasmic domain with Nyggf4 was assessed as described in Fig. 2. NATA represents the mutation of the NPXY motif of LRP1-C1 and NAVA represents the mutation of NPXY motif of LRP1-C2. Nyggf4 binds to wild-type LRP1 and to LRP1-NATA but not to LRP1-NAVA. *, P < 0.01; ***, P < 0.001.