Microtubule-associated factor involved in the late phase of epithelial polarization and microtubule dynamics regulation. Plays a role in the development and maintenance of non-centrosomal microtubule bundles at the lateral membrane in polarized epithelial cells. Isoform 1 interacts with MARK2; the interaction increases MARK2 microtubule-binding ability (By similarity). Homodimer. Associates (via N- and C-terminus domains) with microtubule filaments. Isoform 2 interacts with MARK2; the interaction is direct. Colocalized with microtubules at the base of cilia. Gradually accumulates on the apicobasal microtubule bundles during epithelial cell polarization (By similarity). Colocalized with the apicobasal microtubule bundles running beneath the lateral membrane. Colocalized with microtubule bundles in the spindle pole in mitotic cells and in the midbodies at the end of cytokinesis. Belongs to the SOGA family. Extended N-terminus.