Intracellular carrier for long-chain fatty acids and related active lipids, such as endocannabinoids, that regulate the metabolism and actions of the ligands they bind. In addition to the cytosolic transport, selectively delivers specific fatty acids from the cytosol to the nucleus, wherein they activate nuclear receptors (By similarity). Delivers retinoic acid to the nuclear receptor peroxisome proliferator-activated receptor delta; which promotes proliferation and survival. May also serve as a synaptic carrier of endocannabinoid at central synapses and thus controls retrograde endocannabinoid signaling. Modulates inflammation by regulating PTGES induction via NF-kappa-B activation, and prostaglandin E2 (PGE2) biosynthesis during inflammation (By similarity). Has the highest binding affinity for docosahexaenoic acid (DHA) and decreasing relative affinity for eicosapentaenoic acid (EPA), alpha-linolenic acid (ALA), oleic acid, palmitic acid, linoleic acid and stearic acid, respectively (PubMed:26206084). hexadecanoate(out) = hexadecanoate(in) (9Z,12Z)-octadecadienoate(out) = (9Z,12Z)-octadecadienoate(in) (9Z)-octadecenoate(out) = (9Z)-octadecenoate(in) Monomer. Localizes primarily to the cytoplasm. Upon certain ligand binding, a conformation change exposes a nuclear localization motif and the protein is transported into nucleus (By similarity). Secreted by astrocytes, but not by neurons (By similarity). Forms a beta-barrel structure that accommodates the hydrophobic ligand in its interior. Belongs to the calycin superfamily. Fatty-acid binding protein (FABP) family.