Abstract
Purpose: :
Rab11, a member of the Ras–like small GTP–binding protein superfamily, is considered to regulate various cellular functions, including plasma membrane recycling, phagocytosis, and cytokinesis. In this study, we preliminarily characterize the role of rab11 in the regulation of polymeric immunoglobulin receptor (pIgR) trafficking in primary cultured rabbit lacrimal gland acinar cells (LGAC).
Methods: :
Primary rabbit LGAC cultured for 3 days were processed for confocal fluorescence microscopy utilizing appropriate primary and secondary antibodies to rab11 and pIgR. Co–immunoprecipitation experiments were performed from lysates of resting or 100 µM carbachol–stimulated LGAC using established procedures.
Results: :
Confocal fluorescence microscopy revealed that the apical endosomal marker rab11 exhibited significant colocalization with the pIgR beneath the apical plasma membrane in LGAC, suggesting that rab11 participates in pIgR transcytosis. The pIgR can be co–immunoprecipitated from lysates of resting LGAC with either monoclonal or polyclonal anti–rab11 antibodies, indicating that rab11 interacts with pIgR. When co–immunoprecipitation was conducted using lysates from LGAC stimulated with 100 µM carbachol, a cholinergic agonist, for 15 min and 30min, the co–immunoprecipitated amount of pIgR appeared to increase. This is the first demonstration of co–immunoprecipitation of pIgR with rab11 from any cell type.
Conclusions: :
These findings suggest that rab11 is involved in the regulation of pIgR trafficking in LGAC in a stimulation–dependent manner.
Keywords: lacrimal gland • receptors • protein structure/function