Plasma Membrane Protein Clusters Appear in CFTR-Expressing Xenopus Laevis Oocytes after cAMP Stimulation

2001 ◽  
Vol 180 (3) ◽  
pp. 205-212 ◽  
Author(s):  
H. Schillers ◽  
T. Danker ◽  
M. Madeja ◽  
H. Oberleithner
Keyword(s):  
Plasma Membrane ◽  
Membrane Protein ◽  
Xenopus Laevis ◽  
Xenopus Laevis Oocytes ◽  
Plasma Membrane Protein ◽  
Protein Clusters ◽  
Camp Stimulation

The transcytotic pathway of an apical plasma membrane protein (B10) in hepatocytes is similar to that of IgA and occurs via a tubular pericentriolar compartment

1996 ◽  
Vol 109 (6) ◽  
pp. 1215-1227 ◽  
Author(s):  
I. Hemery ◽  
A.M. Durand-Schneider ◽  
G. Feldmann ◽  
J.P. Vaerman ◽  
M. Maurice
Keyword(s):  
Electron Microscopy ◽  
Plasma Membrane ◽  
Membrane Proteins ◽  
Membrane Protein ◽  
Apical Membrane ◽  
Rat Hepatocytes ◽  
Apical Plasma Membrane ◽  
Apical Surface ◽  
Plasma Membrane Protein ◽  
Microtubule Disruption

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.

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

1987 ◽  
Vol 241 (3) ◽  
pp. 801-807 ◽  
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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