Biogenesis of hepatocyte plasma-membrane domains. Incorporation of (3H)fucose into plasma-membrane and golgi-apparatus glycoproteins.
1. Rats were injected intracaudally with [3H]fucose and its rate of incorporation into the fucoproteins of serum, Golgi and plasma-membrane subfractions was followed for up tp 2h. 2. Incorporation into the Golgi dictyosome and secretory-vesicular fractions reached a maximum at 15 min or less, but most of the radioactivity was associated with classes of secretory glycoproteins. Incorporation into sinusoidal plasma-membrane fractions reached a maximum at 30 min, coinciding with the maximum release of fucoproteins into the serum. Contiguous and canalicular plasma-membrane fractions were labelled slightly later and at a lower rate and specific radioactivity. 3. Fluorography of fucoproteins separated by polyacrylamide-gel electrophoresis helped to distinguish between the major secretory and membrane-bound glycoproteins. The results show that a major biogenetic sequence is probably from Golgi dictyosomes to Golgi secretory elements to a sinusoidal plasma membrane. 4. The kinetics of incorporation make it unlikely that there is rapid and direct insertion of glycoproteins into the bile-canalicular plasma membrane. A route involving direct transfer of glycoproteins via a membrane-mediated intracellular path from the blood sinusoidal to the bile-canalicular plasma membranes is proposed.
D000818:Animals; D001345:Autoradiography; D002462:Cell Membrane / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D005643:Fucose / Q000378:metabolism*; D006023:Glycoproteins / Q000096:biosynthesis* / Q000097:blood; D006056:Golgi Apparatus / Q000378:metabolism; D007700:Kinetics; D008099:Liver / Q000378:metabolism*; D008297:Male; D008565:Membrane Proteins / Q000096:biosynthesis; D051381:Rats
D006023:Glycoproteins; D008565:Membrane Proteins; D005643:Fucose