Small GTP-binding protein which cycles between a GDP-bound inactive and a GTP-bound active form. In its active form interacts with and regulates several effectors including MAP4K4, MINK1 and TNIK. Part of a signaling complex composed of NEDD4, RAP2A and TNIK which regulates neuronal dendrite extension and arborization during development. More generally, it is part of several signaling cascades and may regulate cytoskeletal rearrangements, cell migration, cell adhesion and cell spreading. GTP + H2O = GDP + H(+) + phosphate Activated by the guanine nucleotide-exchange factors RAPGEF3 and RAPGEF4 in a cAMP-dependent manner. Nucleotide exchange is also specifically stimulated by RAPGEF5, RASGEF1A and RASGEF1B (By similarity). Interacts with PLCE1. Interacts with ARHGAP29, SGSM1, SGSM2 and SGSM3. Interacts (GTP-bound form preferentially) with MAP4K4. Interacts with MINK1. Interacts with cytoskeletal actin (By similarity). Interacts (GTP-bound form) with RUNDC3A. Interacts (GTP-bound form preferentially) with TNIK (via the CNH domain); the interaction is direct and recruits RAP2A to the E3 ubiquitin ligase NEDD4. Interacts with RGS14; the interaction is GTP-dependent. Localizes to midbody at telophase. May also localize to the Golgi and the gelatinase-containing granules of neutrophils. Expressed in granular layer of the cerebellum, forebrain, striatum, layer V of the cortex, olfactory cortex, tubercules, subthalamic and hippocampus, particularly in the CA2 region, to a lesser extent in the CA1 region and the external layer of the dentate gyrus. Expressed in neurons. The effector domain mediates the interaction with RUNDC3A. Ubiquitinated; undergoes 'Lys-63' monoubiquitination and diubiquitination by NEDD4. Multiple lysine residues are probably modified. Ubiquitination requires TNIK, prevents interaction with effectors and inactivates RAP2A. Palmitoylated. Palmitoylation is required for association with recycling endosome membranes and activation of TNIK. Transgenic mice expressing a constitutively active form of Rap2a display impaired spatial learning and defective extinction of contextual fear. Belongs to the small GTPase superfamily. Ras family.