Phosphorylated MAP1B may play a role in the cytoskeletal changes that accompany neurite extension. Possibly MAP1B binds to at least two tubulin subunits in the polymer, and this bridging of subunits might be involved in nucleating microtubule polymerization and in stabilizing microtubules. Acts as a positive cofactor in DAPK1-mediated autophagic vesicle formation and membrane blebbing. Facilitates tyrosination of alpha-tubulin in neuronal microtubules. Required for synaptic maturation (By similarity). Interacts with TMEM185A (By similarity). 3 different light chains, LC1, LC2 and LC3, can associate with MAP1A and MAP1B proteins. LC1 interacts with the amino-terminal region of MAP1B. Interacts with ANP32A and TIAM2. Interacts with the tubulin tyrosine TTL (By similarity). Interacts (via C-terminus) with GAN (via Kelch domains). Interacts (via N-terminus) with DAPK1. Interacts with TMEM185A. Interacts with MAP1LC3B. Interacts with KIRREL3 (By similarity). MAP1 light chain LC1 (via C-terminus): Interacts with ELAVL4; the interaction contributes to the association of ELAVL4 with microtubules (By similarity). MAP1 light chain LC1: Interacts with ELAVL2 and ELAVL3 (By similarity). Colocalizes with DAPK1 in the microtubules and cortical actin fibers. Nervous system (spinal cord, brain stem, cerebellum and cerebrum). Not expressed in liver, spleen, kidney, heart or muscle. In cerebral cortex, spinal cord and sciatic nerve levels are high early in development but decrease during postnatal development and are low in adults. In dorsal root ganglia levels remain high throughout development. By nerve growth factor. Has a highly basic region with many copies of the sequence KKEE and KKEI/V, repeated but not at fixed intervals, which is responsible for the binding of MAP1B to microtubules. LC1 is coexpressed with MAP1B. It is a polypeptide generated from MAP1B by proteolytic processing. It is free to associate with both MAP1A and MAP1B. It interacts with the N-terminal region of MAP1B (By similarity). S-nitrosylation at Cys-2457 enhances interaction with microtubules, and may act as an effector modification for neuronal nitric oxide synthase control of growth-cone size, growth-cone collapse and axon retraction. Belongs to the MAP1 family. A C-terminal fragment of this protein (residues 1599 to 2461) was originally described as neuraxin in PubMed:2555150. Contaminating sequence. Potential poly-A sequence. Truncated N-terminus.