Degradation of transplanted rat liver mitochondrial-outer-membrane proteins in hepatoma cells.
Reductively [3H]methylated 3H mitochondrial-outer-membrane vesicles from rat liver and vesicles where monoamine oxidase has been derivatized irreversibly by [3H]-pargyline have been deliberately miscompartmentalized by heterologous transplantation into hepatoma (HTC) cells by poly(ethylene glycol)-mediated vesicle-cell fusion. Fluorescein-conjugated mitochondrial-outer-membrane vesicles have also been used to show that transplanted material is patched, capped and internalized. Reductively methylated outer-membrane proteins and monoamine oxidase are destroyed at the same rate (t1/2 24 h). Mitochondrial-outer-membrane proteins are not degraded at the same rate as HTC plasma-membrane proteins, endogenous cell protein, or endocytosed protein. Transplanted radiolabelled mitochondrial-outer-membrane proteins accumulate intracellularly in structures that are distinct from plasma membrane and lysosomes. However, when mitochondrial-outer-membrane vesicles derivatized with [14C]sucrose are transplanted, the acid-soluble degradation products accumulate in the lysosomal fraction. [14C]Sucrose-conjugated HTC cell plasma membrane accumulates in intracellular structures that are again distinct from plasma membrane and lysosomes. In contrast with the above observations, homologously transplanted mitochondrial-outer-membrane proteins from rat liver are destroyed in hepatocytes at rates that are remarkably similar (t1/2 60-70 h) to the rates in rat liver in vivo [Evans & Mayer (1982) Biochem. Biophys. Res. Commun. 107, 51-58].
D000818:Animals; D002478:Cells, Cultured; D002498:Centrifugation; D004591:Electrophoresis, Polyacrylamide Gel; D007425:Intracellular Membranes / Q000378:metabolism / Q000637:transplantation; D007700:Kinetics; D008114:Liver Neoplasms, Experimental / Q000378:metabolism*; D008565:Membrane Proteins / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D008930:Mitochondria, Liver / Q000378:metabolism* / Q000637:transplantation; D051381:Rats; D011919:Rats, Inbred Strains; D013367:Submitochondrial Particles / Q000378:metabolism
D008565:Membrane Proteins