Plus end-directed microtubule-dependent motor protein involved in endosome transport and receptor recycling and degradation. Regulates the plus end motility of early endosomes and the balance between recycling and degradation of receptors such as EGF receptor (EGFR) and FGF receptor (FGFR). Regulates the Golgi to endosome transport of FGFR-containing vesicles during early development, a key process for developing basement membrane and epiblast and primitive endoderm lineages during early postimplantation development. Interacts with PTPN21 (By similarity). Interacts with RAB14. It is unclear whether association with endosomes is mediated via phosphatidylinositol 3-phosphate (PtdIns(3)P)-binding or via its interaction with RAB14. The PX domain mediates binding to phosphatidylinositol 3-phosphate (PtdIns(3)P), phosphatidylinositol 3,4-bisphosphate (PtdIns(3,4)P2), phosphatidylinositol 3,5-bisphosphate (PtdIns(3,5)P2) and phosphatidylinositol 3,4,5-trisphosphate (PtdIns(3,4,5)P3). Does not bind phosphatidylinositol 4,5-bisphosphate (PtdIns(4,5)P2) (By similarity). Embryonic death. Embryos are arrested at the blastocyst stage: the primitive endoderm and epiblast cannot be distinguished and appear as cell clumps resembling the inner cell mass (ICM) of the blastocyst. Embryos do not develop an epiblast epithelium and the uterine reaction appears to be incomplete. Development of the primitive endoderm and a basement membrane derived from it are severely affected in embryos at 4.5 dpc. Belongs to the TRAFAC class myosin-kinesin ATPase superfamily. Kinesin family. Partially unspliced pre-RNA.