Identification of a novel Eps 15 homology domain-containing protein 1 (EHD1) and EHD4-binding motif in phostensin.

Phostensin (PTS) encoded by KIAA1949 binds to protein phosphatase 1, F-actin, Eps 15 homology domain-containing protein 1 (EHD1) and EHD4. Most EHD-binding proteins contain a consensus motif, Asn-Pro-Phe (NPF), which interacts with the C-terminal EH domain of EHD proteins. Nevertheless, the NPF motif is absent in PTS. The binding motif for PTS to interact with EHD1 (or EHD4) remains unknown. Here, we identified that PTS-α binds to EHD1 (or EHD4) through the region of residues 51-80, which contains a consensus motif, 64ILV(X)4(L/V)RL74S. This novel consensus motif is also found in vacuolar protein sorting-35 (vps35). Replacement of 64ILV(X)4(L/V)RL74S with 64AAA(X)4(L/V)RL74S or with 64ILV(X)4AEA74A significantly reduces the binding efficiency of PTS-α to either EHD1 or EHD4 in GST pull-down assay and far western blotting assay. In addition, replacement of 218ILV(X)4VRL228S with 218AAA(X)4AEA228A decreases the binding ability of vps35 to EHD4 in far western blotting assay. Overexpression of the PTS-β in 293 T cells attenuated the endocytic trafficking of transferrin. However, this attenuation of transferrin in endocytic trafficking was disrupted when 293 T cells overexpressed the mutant PTS-β with a defective EHD-binding motif, suggesting that PTS-β can regulate the endocytic recycling via associating with EHD1 or EHD4.