Ras-related protein Rap-2a

RAP2A (Ras-related protein Rap-2a) is a small GTP-binding protein that cycles between inactive GDP-bound and active GTP-bound states to regulate cellular signaling (UniProt: P10114). The protein acts as a molecular switch controlling several effectors including MAP4K4, MINK1, and TNIK, and participates in a signaling complex with NEDD4 and TNIK that regulates neuronal dendrite extension and arborization during development. More broadly, RAP2A regulates cytoskeletal rearrangements, cell migration, cell adhesion, and cell spreading across multiple signaling pathways (UniProt: P10114).

RAP2A functions in neuronal development and cell morphology regulation, with particular importance in dendrite formation during neural development. The protein operates within interconnected signaling cascades affecting fundamental cellular processes required for proper neuronal architecture and synaptic function.

In Alzheimer's disease, RAP2A shows decreased expression in post-mortem AD brain tissue compared to age-matched controls (Chaparral AD proteomics), with a mean log2 fold-change of −0.606 across one subcellular fraction in TMT-labeled quantitative proteomics (Chaparral AD proteomics). The downregulation of this dendrite-extension regulator may contribute to neuronal structural pathology characteristic of AD.