Plays a role in endocytic trafficking. Required for receptor recycling from endosomes, both to the trans-Golgi network and the plasma membrane. Forms homodimers and heterodimers with PHETA2 (By similarity). Interacts with INPP5B (By similarity) (PubMed:20133602). Interacts with OCRL. Interaction with OCRL may be important for endosomal morphology and function (By similarity) (PubMed:20133602). Interaction with OCRL may be crucial for targeting to endosome and to the trans-Golgi network. Also found on macropinosomes. Not detected in late endosomes, nor in lysosomes. The F&H motif, an approximately 12-13 amino-acid sequence centered around Phe and His residues, is essential for binding to OCRL and INPP5B. Was named after 'sesquipedalian', an unnecessarily long description of a simple thing. Belongs to the sesquipedalian family.