Characterization of the human polymeric immunoglobulin receptor(PIGR) 3'UTR and differential expression ofPIGR mRNA during colon tumorigenesis

Transcytosis is used alone (e.g., hepatoma HepG2 cells) or in combination with a direct pathway from the Golgi (e.g., epithelial MDCK cells) as an indirect route for targeting proteins to the apical surface. The raft-associated MAL protein is an essential element of the machinery for the direct route in MDCK cells. Herein, we present the functional characterization of MAL2, a member of the MAL protein family, in polarized HepG2 cells. MAL2 resided selectively in rafts and is predominantly distributed in a compartment localized beneath the subapical F-actin cytoskeleton. MAL2 greatly colocalized in subapical endosome structures with transcytosing molecules en route to the apical surface. Depletion of endogenous MAL2 drastically blocked transcytotic transport of exogenous polymeric immunoglobulin receptor and endogenous glycosylphosphatidylinositol-anchored protein CD59 to the apical membrane. MAL2 depletion did not affect the internalization of these molecules but produced their accumulation in perinuclear endosome elements that were accessible to transferrin. Normal transcytosis persisted in cells that expressed exogenous MAL2 designed to resist the depletion treatment. MAL2 is therefore essential for transcytosis in HepG2 cells.

Download Full-text

Distribution and processing of the polymeric immunoglobulin receptor in the rat hepatocyte: morphological and biochemical characterization of subcellular fractions.

Journal of Histochemistry & Cytochemistry ◽

10.1177/34.1.3941264 ◽

1986 ◽

Vol 34 (1) ◽

pp. 17-23 ◽

Cited By ~ 13

Author(s):

R Solari ◽

L Racine ◽

C Tallichet ◽

J P Kraehenbuhl

Keyword(s):

Biochemical Characterization ◽

Secretory Component ◽

Transepithelial Transport ◽

Apical Plasma Membrane ◽

Polymeric Immunoglobulin Receptor ◽

Cell Fractionation ◽

Immunoglobulin Receptor ◽

Membrane Anchoring ◽

Polymeric Immunoglobulins

The transepithelial transport of polymeric immunoglobulins is an essential process in the mucosal immune system. Transport across the epithelial cells of mucous or exocrine glands is affected by an integral membrane glycoprotein receptor known as membrane secretory component (SCm) or as polymeric immunoglobulin receptor (pIgR). This receptor binds polymeric immunoglobulins at the basolateral cell surface and mediates their transcellular translocation and their release from the apical plasma membrane into external secretions. Release depends on cleavage of the membrane-anchoring domain of the receptor, resulting in liberation of polymeric immunoglobulin bound to the ectoplasmic domain of the receptor (secreted SC or SCs) into extracellular secretions. Using a monoclonal antibody directed against the cytoplasmic tail of the receptor and a polyclonal antibody directed against the secreted ectoplasmic domain, we have combined cell fractionation and Western blotting techniques to examine the fate of these receptor domains in the hepatocyte. In this study, we characterize biochemically and morphologically the various subcellular components separated by our fractionation scheme, and correlate this with biochemical analysis of the receptor in each fraction.

Download Full-text