Tzaban, SalitMassol, RamiroYen, Elizabeth HechavarriaHamman, WendyFrank, ScottLapierre, Lynne A.Hansen, SteenGoldenring, James R.Blumberg, RichardLencer, Wayne2012-01-242009Tzaban, Salit, Ramiro H. Massol, Elizabeth Yen, Wendy Hamman, Scott R. Frank, Lynne A. Lapierre, Steen H. Hansen, James R. Goldenring, Richard S. Blumberg, and Wayne I. Lencer. 2009. The recycling and transcytotic pathways for IgG transport by FcRn are distinct and display an inherent polarity. Journal of Cell Biology 185(4): 673-684.0021-9525http://nrs.harvard.edu/urn-3:HUL.InstRepos:8015281The Fc receptor FcRn traffics immunoglobulin G (IgG) in both directions across polarized epithelial cells that line mucosal surfaces, contributing to host defense. We show that FcRn traffics IgG from either apical or basolateral membranes into the recycling endosome (RE), after which the actin motor myosin Vb and the GTPase Rab25 regulate a sorting step that specifies transcytosis without affecting recycling. Another regulatory component of the RE, Rab11a, is dispensable for transcytosis, but regulates recycling to the basolateral membrane only. None of these proteins affect FcRn trafficking away from lysosomes. Thus, FcRn transcytotic and recycling sorting steps are distinct. These results are consistent with a single structurally and functionally heterogeneous RE compartment that traffics FcRn to both cell surfaces while discriminating between recycling and transcytosis pathways polarized in their direction of transport.en-USJournal Article2012-01-2410.1083/jcb.200809122