Microtubule plus-end tracking protein that promotes the stabilization of dynamic microtubules. Involved in the nucleation of noncentrosomal microtubules originating from the trans-Golgi network (TGN). Required for the polarization of the cytoplasmic microtubule arrays in migrating cells towards the leading edge of the cell. May act at the cell cortex to enhance the frequency of rescue of depolymerizing microtubules by attaching their plus-ends to cortical platforms composed of ERC1 and PHLDB2. This cortical microtubule stabilizing activity is regulated at least in part by phosphatidylinositol 3-kinase signaling. Also performs a similar stabilizing function at the kinetochore which is essential for the bipolar alignment of chromosomes on the mitotic spindle. Acts as a mediator of ERBB2-dependent stabilization of microtubules at the cell cortex. Interacts with microtubules (PubMed:11290329). Interacts with MAPRE1; probably required for targeting to growing microtubule plus ends. Interacts with ERC1, MAPRE3 and PHLDB2. The interaction with ERC1 may be mediated by PHLDB2. Interacts with GCC2; recruits CLASP2 to Golgi membranes (By similarity). Interacts with CLIP2 and RSN (PubMed:11290329). Interacts with MACF1 (PubMed:18854161). Localizes to microtubule plus ends (PubMed:11290329). Localizes to centrosomes, kinetochores and the mitotic spindle from prometaphase. Subsequently localizes to the spindle midzone from anaphase and to the midbody from telophase. In migrating cells localizes to the plus ends of microtubules within the cell body and to the entire microtubule lattice within the lamella. Localizes to the cell cortex and this requires ERC1 and PHLDB2 (By similarity). Also localizes to meiotic spindle poles. The MEMO1-RHOA-DIAPH1 signaling pathway controls localization of the phosphorylated form to the cell membrane (By similarity). Highly expressed in brain and at low levels in heart, kidney and lung. Expressed in oocytes and early embryos. The two SXIP sequence motifs mediate interaction with MAPRE1; this is necessary for targeting to growing microtubule plus ends. Two TOG regions display structural characteristics similar to HEAT repeat domains and mediate interaction with microtubules. Phosphorylated by GSK3B. Phosphorylation by GSK3B may negatively regulate binding to microtubule lattices in lamella. Isoform 2 is phosphorylated on Ser-241. Belongs to the CLASP family.