RESUMEN
The intracellular pathway of polymeric immunoglobulin receptor (pIgR) is governed by multiple signals that lead to constitutive transcytosis. In addition, in transfected polarized MDCK cells, polymeric immunoglobulin A (pIgA) binding stimulates rabbit pIgR-transcytosis, owing to phospholipase-C gamma 1 activation and increase of intracellular calcium. Transcytosis of rat pIgR across hepatocytes is similarly accelerated by pIgA injection. In contrast we show here that human Madrin-Darby Canine Kidney (pIgR)-transcytosis, in human Calu-3 and human pIgR-transfected MDCK cells, is not promoted by pIgA, as monitored by a continuous apical release of its secreted ectodomain. However, the incubation of cells expressing human or rabbit pIgR with pIgA induces a comparable IP3 production, and pIgR-transcytosis of either species is accelerated by the protein kinase C (PKC)-activator phorbol myristate acetate. Without pIgA, mimicking phospholipase-C activation by combining low concentrations of phorbol myristate acetate with ionomycin, or high concentrations of ionomycin alone, stimulates the rabbit, but not the human, pIgR transcytosis. These data suggest that the species difference in pIgA-induced pIgR-transcytosis does not stem from the defective production of second messengers, but from a different sensitivity of pIgR to intracellular calcium. Our results outline the danger of extrapolating to humans the abundant data obtained from mucosal vaccination of laboratory animals.
Asunto(s)
Inmunoglobulina A/metabolismo , Receptores de Inmunoglobulina Polimérica/metabolismo , Transducción de Señal/fisiología , Adenocarcinoma/patología , Animales , Señalización del Calcio/efectos de los fármacos , Línea Celular/efectos de los fármacos , ADN Complementario/genética , Perros , Activación Enzimática/efectos de los fármacos , Humanos , Inmunoglobulina A/genética , Inmunoglobulina A/inmunología , Inositol 1,4,5-Trifosfato/metabolismo , Ionomicina/farmacología , Ionóforos/farmacología , Túbulos Renales Proximales/citología , Neoplasias Pulmonares/patología , Proteína Quinasa C/efectos de los fármacos , Proteína Quinasa C/fisiología , Transporte de Proteínas/efectos de los fármacos , Conejos , Ratas , Receptores de Inmunoglobulina Polimérica/genética , Receptores de Inmunoglobulina Polimérica/fisiología , Proteínas Recombinantes de Fusión/inmunología , Proteínas Recombinantes de Fusión/metabolismo , Sistemas de Mensajero Secundario/fisiología , Especificidad de la Especie , Acetato de Tetradecanoilforbol/farmacología , Transfección , Células Tumorales Cultivadas , VacunaciónRESUMEN
Mouse polymeric immunoglobulin receptor (pIgR) cDNA was stably introduced into a hamster-derived fibroblastic cell line, Chinese hamster ovary (CHO) cell, by the calcium phosphate method. Surface expression of pIgR was detected by immunostaining and FACS analysis. The immunoprecipitated products of cell lysates revealed that the molecular mass of the most mature form of pIgR was approximately 120 kDa. Western blotting and metabolic labeling experiments followed by immunoprecipitation with an anti-mouse secretory component (SC) Ab demonstrated the existence 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 experiments which revealed the pIgR underwent molecular maturation. During this process, the 110 kDa form of pIgR was converted into a 120 kDa form by glycosylation. Moreover, tunicamycin treatment revealed the core form of pIgR had a molecular mass of approximately 100 kDa. The pIgR 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.