Tubulin-folding protein; involved in the first step of the tubulin folding pathway. Modulates microtubule dynamics by capturing GTP-bound beta-tubulin (TUBB). Acts as a GTPase-activating protein (GAP) for ARL2. Its ability to interact with beta tubulin is regulated via its interaction with ARL2. Induces microtubule disruption in absence of ARL2. Increases degradation of beta tubulin, when overexpressed in polarized cells. Promotes epithelial cell detachment, a process antagonized by ARL2. Induces tight adherens and tight junctions disassembly at the lateral cell membrane.