Non-neuronal microtubule-associated protein. Promotes microtubule assembly (By similarity). Interacts with SEPTIN2; this interaction impedes tubulin-binding. Interacts with TRAF3IP1 (By similarity). Interacts with KNSTRN (By similarity). Recruitment to microtubule is inhibited by microtubules polyglutamylation. Phosphorylation on Ser-761 negatively regulates MAP4 activity to promote microtubule assembly. Phosphorylated at serine residues in K-X-G-S motifs by MAP/microtubule affinity-regulating kinase (MARK1 or MARK2), causing detachment from microtubules, and their disassembly.