Identification and characterization of an alternatively spliced variant of the MHC class I-related porcine neonatal Fc receptor for IgG

Abstract

The neonatal Fc receptor for IgG (FcRn) functions to transport maternal IgG to the fetal/neonatal animals and protects IgG from catabolism. The present study identified two pFcRn cDNAs (1.071 kb and 0.795 kb) from intestinal epithelial cells. The corresponding mRNA transcripts were detected in porcine kidney cell line LLC-PK1, peripheral blood mononuclear cells and porcine tissues by RT-PCR and Northern blot. Sequence analysis showed that the 1.071 kb cDNA encodes the full-length pFcRn (pFcRn-L); whereas the 0.795 kb cDNA codes for a truncated pFcRn (pFcRn-S) with deletion of 92 amino acids matching to the alpha2 domain of pFcRn-L. The pFcRn-L was constitutively expressed by epithelial cells; however, pFcRn-S was not detectable in porcine tissues and cell lines although its transcript was abundant. Despite of the lack of native pFcRn-S, pFcRn-S was readily detected in transfected cells. Recombinant pFcRn-L was confirmed to bind IgG at pH 6.0, but not pH 7.5; however, pFcRn-S failed to bind IgG at both pH 5.0-6.0 and 7.5. The pFcRn-L was expressed on the cell surface and mainly localized in early endosomes. In contrast, pFcRn-S was absent from cell surface and primarily localized in the lysosome and pFcRn-S trafficking to lysosomes was independent of β2m. The accumulation of pFcRn-S in the lysosome may explain the absence detection of native pFcRn-S protein expression. In addition, the trafficking of pFcRn-S to the lysosomal compartment suggests that in addition to sorting signals in its cytoplasmic tail, the FcRn structural integrity may be important for proper intracellular trafficking and function.

The intracellular localization and association of porcine Ia-associated invariant chain with the MHC class I-related porcine neonatal Fc receptor for IgG

“…The Ii chain interacted with the FcRn H chain alone or with the FcRn-β2m complex (Fig. 5), indicating that the Ii chain may retain the FcRn H chain in the ER until its assembly into a complex with β2m (Ye et al, 2008a(Ye et al, , 2008b. This is consistent with studies finding that the Ii chain retains incompletely folded CD1d H chain in the ER (Jayawardena- Wolf et al, 2001), but inconsistent with studies showing that the Ii chain combines with fully folded MHC class I in the ER because Ii cannot associate with a single MHC I molecule, or the α or β2m chain (Powis, 2006;Vigna et al, 1996;Xu et al, 2013aXu et al, , 2013b.…”

“…The stable cells, P815 FcRn and P815 Ii , have been described previously (Ye et al, 2008a(Ye et al, , 2008bZhu et al, 2002). Briefly, P815 cells were cultured in RPMI-1640 including 25 mM HEPES, 2 mM glutamine, 10% heat-inactivated fetal bovine serum (Gibco), 100 units/ml penicillin, and 100 pg/ml streptomycin.…”

“…FcRn is composed of an H chain noncovalently associated with an L chain β2m (Simister and Mostov, 1989;Burmeister et al, 1994). Similar to MHC class I, FcRn consists of three extracellular alpha (α) domains, a single-pass transmembrane domain, and a short cytoplasmic tail (Ye et al, 2008a(Ye et al, , 2008b. FcRn may play a major role in the passive acquisition of immunity in fetuses of some species and in newborns of most mammals, allowing newborns to obtain humoral immunity against Ags encountered by the mother before they develop their own immune system (Firan et al, 2001;Ghetie and Ward, 2000;Simister, 2000).…”

“…Ye et al reported that Ii was capable of associating with FcRn and regulating FcRn trafficking (Ye et al, 2008a(Ye et al, , 2008b. Basha et al reported that Ii associated with MHC class I in the ER of dendritic cells (DCs) and mediated the trafficking of MHC class I to endolysosomal compartments for loading with exogenous peptides (Basha et al, 2012).…”

Intestinal gene expression profiles of piglets benefit from maternal supplementation with a yeast mannan-rich fraction during gestation and lactation

“…Supplementing maternal diets with MRF has been shown to improve colostrum yield and improve immunoglobulin concentrations during early life in offspring (Crosby et al, 2005). Sufficient immunoglobulin G (IgG) in the maternal milk is fundamental to neonatal pigs for the passive transfer of immunity that improves survival (Ye et al, 2008). In addition, sow supplementation with MRF has been linked to positive responses in the progeny † E-mail: kbrennan@alltech.com Animal (2015), 9:4, pp 622-628 © The Animal Consortium 2014 doi:10.1017/S1751731114002961 animal 622 production performance including decreased incidence of diarrhea (Zanello et al, 2013), increased number of weaned pigs and increased efficiency in weight gain of pigs (Jurgens et al, 1997).…”