KIF16B delivers for transcytosis

Abstract

EMBO J 32 15, 2125–2139 doi:; DOI: 10.1038/emboj.2013.130; published online June 07 2013

Protein sorting pathways control correct delivery of membrane proteins to specific compartments of the plasma membrane and are required to maintain the physiological functions in all epithelia. Most clathrin-dependent cargoes require the adaptor protein complexes AP-1A and AP-1B for proper sorting to the basolateral plasma membrane. In this issue of The EMBO Journal, Perez Bay et al (2013) shed light on the mechanism of basal-to-apical protein transport, or transcytosis, of the transferrin receptor in natively AP-1B-deficient epithelia. In AP-1B-deficient epithelia, the transferrin receptor transcytoses through the apical recycling endosome, and requires Rab11. Furthermore, they characterize a novel and specific role for the endosomal microtubule motor Kinesin KIF16B in transferrin receptor apical transport. These findings constitute the first characterization of a specific microtubule motor involved in basal-to-apical transcytosis in epithelia.

Figure 1

KIF16B controls basal-to-apical transcytosis of transferrin receptor in AP-1B-deficient epithelia. In AP-1B-expressing epithelia (such as MDCK cells), transferrin receptor (TfR) is endocytosed and sorted to common recycling endosomes, where AP-1B-clathrin-vesicles assemble and transport the protein to the basolateral plasma membrane. In AP-1B-deficient epithelia (such as RPE cells), internalized TfR is instead sorted by the plus-end directed microtubule motor KIF16B towards the ARE, and then transcytosed to the apical plasma membrane through a Rab11-regulated pathway. Polymeric IgA receptor is internalized into the same basolateral endosomes, but it uses a KIF16B-independent pathway to reach the apical membrane.