GABARAP, a microtuble-associated protein, is identified to interact with GABAA receptor. Anchoring of the GABAA receptor to GABARAP helps to cluster the receptor at the synaptic termini and to mediate fast synaptic transmission. GABARAP may mediate interaction of gephyrin with the GABAA receptor to stabilize clusters by forming multimeric structures. Furthermore, GABARAP and gephyrin may play more of a role in receptor sorting and transport to the cell surface than in anchoring to the cytoplasm, because at inhibitory synapses GABARAP appears to associate with transport vesicles rather than the cell surface. The association of GABARAP with NSF (N-ethylmaleimide sensitive factor), a protein involved in intracellular vesicle transport, supports this hypothesis. We cloned cDNA encoding full-length human GABARAP by nested PCR and inserted it into eukaryon expression vector pcDNA6HA and GST fusion protein expression vector pGEX4T2. The recombinant plasmid pGEX4T2-hGABARAP was transformed into E. coli BL21, from which GST-hGABARAP fusion protein was purified after IPTG induction by affinity chromatography with glutathione Sepharose-4B column. The antiserum against GABARAP was generated by immunizing rabbits with the purified GST-hGABARAP and was purified with GST-hGABARAP coupled NHS-activated Sepherose 4 column. The purified polyclonal antibody was effective for Western blotting and immunostaining. The hGABARAP was located both in the cytoplasm and nucleus with an abundant distribution around the peripheral nucleus.