Porcine Fc gamma RIIb sub-isoforms are generated by alternative splicing

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• 作者：Pingan Xia¹ ; Xiaoping Liu¹ ; Yina Zhang ; Erzhen Duan ; Zhiyuan Zhang ; Jing Chen ; Chunlong Mu ; Baoan Cui ; ^{xpa88@163.com}
• 关键词：Fc¦Ã receptor ; Fc¦ÃRIIb ; Sub-isoforms ; Alternative splicing ; Pig
• 刊名：Veterinary Immunology and Immunopathology
• 出版年：2012
• 出版时间：15 January 2012
• 年：2012
• 卷：145
• 期：1-2
• 页码：386-394
• 全文大小：2366 K

文摘

Receptors for the Fc portion of IgG (Fc¦ÃRs) are expressed on various leukocytes and they modulate both humoral and cell-mediated immune responses with different capacities for IgG binding and phagocytosis. Four different types of Fc¦ÃRs, Fc¦ÃRI (CD64), Fc¦ÃRII (CD32), Fc¦ÃRIII (CD16) and Fc¦ÃRIV, have been identified. There are three Fc¦ÃRII isoforms (activating Fc¦ÃRIIa and Fc¦ÃRIIc, and inhibitory Fc¦ÃRIIb) in humans, one isoform (inhibitory Fc¦ÃRIIb) in mice, and two isoforms (inhibitory Fc¦ÃRIIb and activating Fc¦ÃRIIc) in cattle. Two alternativly spliced isoforms of Fc¦ÃRIIb, b1 and b2, have been identified in humans, mice and cattle, however, only two porcine Fc¦ÃRIIb transcripts have been reported. In this study, we report the identification of three new porcine Fc¦ÃRIIb transcript and analyze the sequences of five porcine Fc¦ÃRIIb transcript generated by alternative splicing. The porcine transcript 1 and porcine transcript 2 have a high homology and structural similarity with human b1 and b2, respectively, while there is only one alanine residue difference at the signal peptide region between porcine transcript 1 and transcript 4, as well as porcine transcript 2 and transcript 3. This is the first time that an alternativly spliced isoform of porcine transcript 5 is described in pigs rather than humans or other animals. All the five transcripts have the consensus sequence of an ITIM (ITYSLL) in their cytoplasmic tails. Analysis results indicate that the five transcripts serve as inhibitory receptors and are these sub-isoforms or alternativly spliced isoforms. Immunoglobulin-binding assays show that transcript 1, transcript 2, transcript 3 and transcript 4 have binding activity for IgG immune complexes, whereas transcripts 5 without domain 2 can not bind IgG-complexes. It is now clear that porcine Fc¦ÃRIIb exists as five sub-isoforms at least. These sub-isoforms may individually modulate Fc¦ÃRIIb-mediated immune responses in the porcine immune system.