Localization of a novel 252-kDa plasma membrane protein that binds Cry1A toxins in the midgut epithelia of Bombyx mori

In hepatocytes, newly synthesized apical plasma membrane proteins are first delivered to the basolateral surface and are supposed to reach the apical surface by transcytosis. The transcytotic pathway of apical membrane proteins and its relationship with other endosomal pathways has not been demonstrated morphologically. We compared the intracellular route of an apical plasma membrane protein, B10, with that of polymeric IgA (pIgA), which is transcytosed, transferrin (Tf) which is recycled, and asialoorosomucoid (ASOR) which is delivered to lysosomes. Ligands and anti-B10 monoclonal IgG were linked to fluorochromes or with peroxidase. The fate of each ligand was followed by confocal and electron microscopy in polarized primary monolayers of rat hepatocytes. When fluorescent anti-B10 IgG and fluorescent pIgA were simultaneously endocytosed for 15–30 minutes, they both uniformly labelled a juxtanuclear compartment. By 30–60 minutes, they reached the bile canaliculi. Tf and ASOR were also routed to the juxtanuclear area, but their fluorescence patterns were more punctate. Microtubule disruption prevented all ligands from reaching the juxtanuclear area. This area corresponded, at least partially, to the localization of the mannose 6-phosphate receptor, an endosomal marker. By electron microscopy, the juxtanuclear compartment was made up of anastomosing tubules connected to vacuoles, and was organized around the centrioles. B10 and pIgA were mainly found in the tubules, whereas ASOR was segregated inside the vacuolar elements and Tf within thinner, recycling tubules. In conclusion, transcytosis of the apical membrane protein B10 occurs inside tubules similar to those carrying pIgA, and involves passage via the pericentriolar area. In the pericentriolar area, the transcytotic tubules appear to maintain connections with other endosomal elements where sorting between recycled and degraded ligands occurs.

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Sendai-viral HN and F glycoproteins as probes of plasma-membrane protein catabolism in HTC cells. Studies with fusogenic reconstituted Sendai-viral envelopes

Biochemical Journal ◽

10.1042/bj2410801 ◽

1987 ◽

Vol 241 (3) ◽

pp. 801-807 ◽

Cited By ~ 5

Author(s):

R T Earl ◽

E E Billett ◽

I M Hunneyball ◽

R J Mayer

Keyword(s):

Plasma Membrane ◽

Membrane Protein ◽

Plasma Membranes ◽

Viral Proteins ◽

Plasma Membrane Protein ◽

Lysosomal Degradation ◽

Cell Plasma ◽

Degradation Rates ◽

Htc Cells ◽

Viral Envelopes

Reconstituted Sendai-viral envelopes (RSVE) were produced by the method of Vainstein, Hershkovitz, Israel & Loyter [(1984) Biochim. Biophys. Acta 773, 181-188]. RSVE are fusogenic unilamellar vesicles containing two transmembrane glycoproteins: the HN (haemagglutinin-neuraminidase) protein and the F (fusion) factor. The fate of the viral proteins after fusion-mediated transplantation of RSVE into hepatoma (HTC) cell plasma membranes was studied to probe plasma-membrane protein degradation. Both protein species are degraded at similar, relatively slow, rates (t1/2 = 67 h) in HTC cells fused with RSVE in suspension. Even slower degradation rates for HN and F proteins (t1/2 = 93 h) were measured when RSVE were fused with HTC cells in monolayer. Lysosomal degradation of the transplanted viral proteins is strongly implicated by the finding that degradation of HN and F proteins is sensitive to inhibition by 10 mM-NH4Cl (81%) and by 50 micrograms of leupeptin/ml (70%).

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Correct insertion of a simple eukaryotic plasma-membrane protein into the cytoplasmic membrane of Escherichia coli

Gene ◽

10.1016/0378-1119(90)90340-w ◽

1990 ◽

Vol 96 (1) ◽

pp. 51-57 ◽

Cited By ~ 28

Author(s):

Yianbiao Zhang ◽

Jenny K. Broome-Smith

Keyword(s):

Escherichia Coli ◽

Plasma Membrane ◽

Membrane Protein ◽

Cytoplasmic Membrane ◽

Plasma Membrane Protein

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The Candida albicans plasma membrane protein Rch1p, a member of the vertebrate SLC10 carrier family, is a novel regulator of cytosolic Ca2+ homoeostasis

Biochemical Journal ◽

10.1042/bj20112166 ◽

2012 ◽

Vol 444 (3) ◽

pp. 497-502 ◽

Cited By ~ 26

Author(s):

Linghuo Jiang ◽

Joerg Alber ◽

Jihong Wang ◽

Wei Du ◽

Xuexue Yang ◽

...

Keyword(s):

Functional Analysis ◽

Candida Albicans ◽

Plasma Membrane ◽

Membrane Protein ◽

Solute Carrier Family ◽

Plasma Membrane Protein ◽

Cellular Functions ◽

Downstream Target ◽

Solute Carrier ◽

High Concentrations

Candida albicans RCH1 (regulator of Ca2+ homoeostasis 1) encodes a protein of ten TM (transmembrane) domains, homologous with human SLC10A7 (solute carrier family 10 member 7), and Rch1p localizes in the plasma membrane. Deletion of RCH1 confers hypersensitivity to high concentrations of extracellular Ca2+ and tolerance to azoles and Li+, which phenocopies the deletion of CaPMC1 (C. albicans PMC1) encoding the vacuolar Ca2+ pump. Additive to CaPMC1 mutation, lack of RCH1 alone shows an increase in Ca2+ sensitivity, Ca2+ uptake and cytosolic Ca2+ level. The Ca2+ hypersensitivity is abolished by cyclosporin A and magnesium. In addition, deletion of RCH1 elevates the expression of CaUTR2 (C. albicans UTR2), a downstream target of the Ca2+/calcineurin signalling. Mutational and functional analysis indicates that the Rch1p TM8 domain, but not the TM9 and TM10 domains, are required for its protein stability, cellular functions and subcellular localization. Therefore Rch1p is a novel regulator of cytosolic Ca2+ homoeostasis, which expands the functional spectrum of the vertebrate SLC10 family.

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