N-Glycan Moieties in Neonatal Fc Receptor Determine Steady-state Membrane Distribution and Directional Transport of IgG.
The neonatal Fc receptor (FcRn) is a major histocompatibility complex class I-related molecule known to protect IgG and albumin from catabolism and transport IgG across polarized epithelial cells in a bidirectional manner. Previous studies have shown species-specific differences in ligand binding, IgG transport direction, and steady-state membrane distribution when expressed in polarized epithelial cells. We hypothesized that these differences may be due to the additional N-glycans expressed on the rat FcRn, because N-glycans have been proposed to function as apical targeting signals, and that two of the N-glycan moieties have been shown to contribute to the IgG binding of rat FcRn. A panel of mutant human FcRn variants was generated to resemble the N-glycan expression of rat FcRn in various combinations and subsequently transfected into Madin-Darby canine kidney II cells together with human beta2-microglobulin. Mutant human FcRn clones that contained additional N-glycan side-chain modifications, including that which was fully rodentized, still exhibited specificity for human IgG and failed to bind to mouse IgG. At steady state, the mutant human FcRn with additional N-glycans redistributed to the apical cell surface similar to that of rat FcRn. Furthermore, the rodentized human FcRn exhibited a reversal of IgG transport with predominant transcytosis from an apical-to-basolateral direction, which resembled that of the rat FcRn isoform. These studies show that the N-glycans in FcRn contribute significantly to the steady-state membrane distribution and direction of IgG transport in polarized epithelia.
Kuo
Timothy T
TT
Department of Gastroenterology, Brigham & Women's Hospital and Harvard Medical School, USA.
de Muinck
Eric J
EJ
Claypool
Steven M
SM
Yoshida
Masaru
M
Nagaishi
Takashi
T
Aveson
Victoria G
VG
Lencer
Wayne I
WI
Blumberg
Richard S
RS
D000418:Albumins / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D000818:Animals; D002460:Cell Line; D002462:Cell Membrane / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D016764:Cell Polarity / Q000502:physiology*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000276:immunology / Q000378:metabolism*; D015395:Histocompatibility Antigens Class I / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D009154:Mutation / Q000276:immunology; D011134:Polysaccharides / Q000235:genetics / Q000378:metabolism*; D011499:Protein Processing, Post-Translational / Q000502:physiology*; D021381:Protein Transport / Q000502:physiology; D051381:Rats; D011961:Receptors, Fc / Q000235:genetics / Q000276:immunology / Q000378:metabolism*
D000418:Albumins; D015395:Histocompatibility Antigens Class I; D007074:Immunoglobulin G; D011134:Polysaccharides; D011961:Receptors, Fc; C100688:Fc receptor, neonatal