Adaptor Related Protein Complex 3 Sigma 1 (AP3s1)

CLAPS3 (for clathrin-associated/assembly/adaptor protein, small 3, 22-kD), contains an open reading frame of 579 bp encoding 193 amino acids. Northern blot analysis revealed expression of a 1.35-kb transcript in all human tissues examined.the ear domain of the AP3 delta subunit (AP3D1) interacts with both isoforms of the sigma-3 subunit, sigma-3A and sigma-3B (AP3S2). An extended C-terminal segment of sigma-3 was necessary for the interaction with the delta subunit. The delta-sigma-3 interaction interfered with the binding of AP3 to ARF, but not with its binding to dileucine-based sorting signals. As a consequence, the delta subunit ear inhibited the recruitment of AP3 to membranes both in vitro and in vivo and impaired the sorting of lysosomal membrane proteins.