Binds to the plus end of microtubules and regulates the dynamics of the microtubule cytoskeleton. Promotes microtubule growth and microtubule bundling. Links cytoplasmic vesicles to microtubules and thereby plays an important role in intracellular vesicle trafficking. Plays a role macropinocytosis and endosome trafficking. Interacts with MTOR; phosphorylates and regulates CLIP1 (PubMed:12231510). Interacts (via CAP-Gly domains) with tubulin (PubMed:17563362, PubMed:17889670). Interacts with SLAIN2 (PubMed:21646404). Interacts (via zinc finger) with DCTN1 (PubMed:17828275, PubMed:20679239). Interacts with TUBA1B, MAPRE1 and MAPRE3 (PubMed:17563362). Binds preferentially to tyrosinated microtubules, and only marginally to detyrosinated microtubules (By similarity). Localizes to microtubule plus ends (PubMed:21646404, PubMed:17889670). Localizes preferentially to the ends of tyrosinated microtubules (By similarity). Accumulates in plasma membrane regions with ruffling and protrusions. Associates with the membranes of intermediate macropinocytic vesicles (PubMed:12433698). Detected in dendritic cells (at protein level). Highly expressed in the Reed-Sternberg cells of Hodgkin disease. Intramolecular interaction between the zinc finger domain and the CAP-Gly domains may inhibit interaction with tubulin. Phosphorylated. Phosphorylation induces conformational changes by increasing the affinity of the N-terminus for C-terminus, resulting in inhibition of its function thus decreasing its binding to microtubules and DCTN1. Exhibits a folded, autoinhibited conformation when phosphorylated and an open conformation when dephosphorylated with increased binding affinity to microtubules and DCTN1. Phosphorylation regulates its recruitment to tyrosinated microtubules and the recruitment of vesicular cargo to microtubules in neurons (By similarity). Phosphorylation by MTOR may positively regulate CLIP1 association with microtubules (PubMed:12231510).