Phostensin carries a novel Eps 15 homology domain-containing protein 1
(EHD1) and EHD4-binding motif to regulate endocytic recycling
Abstract
Phostensin (PTS) encoded by KIAA1949 is a scaffold protein. It
can bind to protein phosphatase 1 (PP1), F-actin, Eps 15 homology
domain-containing protein 1 (EHD1) and EHD4. PTS contains both
PP1-binding and actin-binding motifs. Most EHD-binding proteins contain
a consensus motif, Asn-Pro-Phe (NPF) motif, 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 associate with EHD1 (or
EHD4) remains unknown. Here, we used structure-function, far western
blotting and GST pull-down assays to investigate this issue and
identified that PTS-α binds to EHD1 (or EHD4) through the region of
residues 60-80 which contains a consensus motif,
64ILV(X) 4(L/V)RL
74S. This novel motif was also found in the vacuolar
protein sorting 35 (vps35) of retromer, an EHD1-associating complex and
regulating retrograde trafficking, Replacement of
64ILV(X) 4(L/V)RL
74S with 64AAA(X)
4(L/V)RL 74S or with
64ILV(X) 4AEA 74A
significantly reduces the binding efficiency of PTS-α to either EHD1 or
EHD4. Overexpression of the PTS-β in 293T cells attenuated the endocytic
trafficking of transferrin. However, this attenuation of transferrin in
endocytic trafficking was disrupted when 293T 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.