MOLECULAR MATURATION AND FUNCTIONAL EXPRESSION OF MOUSE POLYMERIC IMMUNOGLOBULIN RECEPTOR

Mouse polymeric immunoglobulin receptor (pIgR) cDNA was stably introdu ced into a hamster-derived fibroblastic cell line, Chinese hamster ova ry (CHO) cell, by the calcium phosphate method. Surface expression of pIgR was detected by immunostaining and FAGS analysis. The immunopreci pitated products of cell lysates revealed that the molecular mass of t he most mature form of pIgR was approximately 120 kDa, Western blottin g and metabolic labeling experiments followed by immunoprecipitation w ith an anti-mouse secretory component (SC) Ab demonstrated the existen ce of a 110 kDa immature form of pIgR. The reason for the existence of two forms of pIgR molecule was examined by conducting pulse-chase exp eriments which revealed the pIgR underwent molecular maturation. Durin g this process, the 110 kDa form of pIgR was converted into a 120 kDa form by glycosylation. Moreover, tunicamycin treatment revealed the co re form of pIgR had a molecular mass of approximately 100 kDa. The pIg R expressed on the surface of the transfectant could specifically bind and take up mouse polymeric IgA (MOPC 315), suggesting that, at least in this mouse system, cell type-specific molecules are not necessary for surface pIgR expression and polymeric immunoglobulin (pIg) binding and uptake. (C) 1998 Published by Elsevier Science B.V. All rights re served.