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. Interacts with OCRL and INPP5B (By similarity). Interaction with OCRL may be important for endosomal morphology and function (By similarity). 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.