Liver plasma membrane domains and endocytic trafficking

1989 ◽  
Vol 17 (4) ◽  
pp. 619-622 ◽  
Author(s):  
W. HOWARD EVANS ◽  
CARLOS ENRICH
1989 ◽  
Vol 261 (3) ◽  
pp. 905-912 ◽  
Author(s):  
N Ali ◽  
G Milligan ◽  
W H Evans

1. The distribution of the alpha- and beta-subunits of nucleotide-binding G-proteins among rat liver sinusoidal, lateral and canalicular plasma membranes, endosomes, Golgi membranes and lysosomes was investigated. 2. Pertussis-toxin-catalysed ADP-ribosylation identified a 41 kDa inhibitory alpha-subunit in all liver plasma-membrane functional domains as well as in endosomes. An antibody to a synthetic peptide corresponding to a C-terminal sequence of the inhibitory alpha-subunit also identified the 41 kDa polypeptide in all plasma-membrane domains, in ‘early’ and ‘late’ endosomes and in Golgi membranes; this polypeptide was not detected in lysosomes. The antibody-binding studies showed that bile-canalicular plasma membranes had the highest content of the inhibitory alpha-subunit. 3. Immunofluorescent microscopy confirmed the presence of the inhibitory alpha-subunit in all regions of the hepatocyte's cell surface. 4. An antibody recognizing the beta-subunit showed that a 36 kDa polypeptide was present in all plasma membranes and in ‘early’ and ‘late’ endosomes; it was not detected in lysosomes. The relative distribution among the fractions of this polypeptide was similar to the distribution of the inhibitory alpha-subunit. 5. The presence of high levels of the G-protein inhibitory alpha-subunit in bile-canalicular plasma membranes was confirmed by demonstration of its co-fractionation with marker enzymes in Nycodenz gradients and by free-flow electrophoresis. The significance of this location is discussed.


2002 ◽  
Vol 277 (33) ◽  
pp. 30325-30336
Author(s):  
Daniel Wüstner ◽  
Andreas Herrmann ◽  
Mingming Hao ◽  
Frederick R. Maxfield

2003 ◽  
Vol 278 (22) ◽  
pp. 20389-20394 ◽  
Author(s):  
Lorian C. Hartgroves ◽  
Joseph Lin ◽  
Hanno Langen ◽  
Tobias Zech ◽  
Arthur Weiss ◽  
...  

1989 ◽  
Vol 257 (6) ◽  
pp. F913-F924 ◽  
Author(s):  
R. Bacallao ◽  
L. G. Fine

Information from studies of embryonic nephrons and established renal tubular cell lines in culture can be integrated to derive a picture of how the renal tubule develops and regenerates after acute injury. During development, the formation of a morphologically polarized epithelium from committed nephric mesenchymal cells requires an external signal for mitogenesis and differentiation. Polypeptide growth factors, in some cases mediated through oncogene expression, act in an autocrine or paracrine fashion to stimulate the production of extracellular matrix proteins that probably provide the earliest orientation signal for the cell. Interaction of these proteins with cell surface receptors leads to early organization of the cytoskeletal actin network, which is the major scaffolding for further differentiation and for definition of plasma membrane domains. The formation of cell-cell contacts via specialized adhesion molecules integrates the epithelium into a polarized monolayer and maintains its fence function, i.e., separation of plasma membrane domains. Microtubules probably participate in the delivery of vesicles to specific plasma membrane domains and in the spatial organization of intracellular organelles. Following acute renal injury, this sequence of events appears to be reversed, resulting in partial or complete loss of differentiated features. Regeneration seems to follow the same pattern of sequential differentiation steps as nephrogenesis. The integrity of the epithelium is restored by reestablishing only those stages of differentiation that have been lost. Where cell death occurs, mitogenesis in adjacent cells restores the continuity of the epithelium and the entire sequence of differentiation events is initiated in the newly generated cells.


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