Journal Article

Expression and physical association of Fc alpha receptor and Fc receptor gamma chain in human mesangial cells.

Y Suzuki, C Ra, K Saito, S Horikoshi, S Hasegawa, T Tsuge, K Okumura and Y Tomino

in Nephrology Dialysis Transplantation

Published on behalf of European Renal Association - European Dialysis and Transplant Assoc

Volume 14, issue 5, pages 1117-1123
Published in print May 1999 | ISSN: 0931-0509
Published online May 1999 | e-ISSN: 1460-2385 | DOI: http://dx.doi.org/10.1093/ndt/14.5.1117
Expression and physical association of Fc alpha receptor and Fc receptor gamma chain in human mesangial cells.

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BACKGROUND: Most intensive investigations on the pathogenesis of IgA nephropathy have focused on the process before IgA deposition and the characteristics of IgA/IgA immune complex (IgA IC), but it still remains uncertain whether mesangial IgA ICs may cause glomerular injuries directly or are only secondary events of another pathological process. To assess the role of IgA ICs in IgA nephropathy, we investigated the characteristics of Fc alpha receptor (Fc alphaR) and FcR gamma chain which is a signalling subunit of FcR in human mesangial cells (MCs). METHODS: Gene expression of Fc alphaR and FcR gamma chain of human cultured MCs was examined by RT-PCR and subsequent Southern blot analyses. Sequence analyses after subcloning were also performed for further confirmation. Expression of Fc alphaR and FcR gamma chain at the protein level and their physical association in MCs were determined by immunoprecipitation after stimulation of the cells with heat-aggregated IgA. RESULTS: Two distinct cDNA products were amplified from each cultured MC line. The sequence of the major product of approximately 900 bp was completely identical to that of Fc alphaR previously described. The smaller product had a 288 bp deletion which corresponded to exon 2 encoding the extracellular domain 2 of Fc alphaR. Gene expression of FcR gamma chain was also confirmed. Furthermore, we proved the physical association of Fc alphaR with the FcR gamma chain by co-immunoprecipitation under stimulation with a high dose of the heat-aggregated IgA. CONCLUSION: These findings suggested that polymeric IgA and/or IgA IC can directly activate MCs via Fc alphaR associated with the gamma chain. Our data also indicated that phenotypic variations of Fc alphaR occur on MC, such as splicing forms, the chain association and/or the alpha chain expression itself, which may contribute to the pathogenesis of IgA nephropathy.

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Subjects: Nephrology

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