title: Mechanisms of intracellular protein catabolism. Intracellular fate of microinjected polypeptides translated in vitro.
abstract: Erythrocyte-mediated microinjection was used to introduce [35S]polypeptides translated in vitro into 3T3-L1 cells. Such [35S]polypeptides are not degraded after loading into erythrocytes and are stable for the first 2 h after microinjection into growing 3T3-L1 cells. Similarly, little or no degradation of microinjected [35S]polypeptides is observed in either growing or confluent 3T3-L1 cells over a 70 h period. Microinjection of reticulocyte lysate alone does not affect the rate of degradation of long-lived endogenous protein. Reductively [3H]methylated lysate haemoglobin is degraded after microinjection by a cytosolic mechanism. Microinjected 125I-labelled bovine serum albumin is rapidly degraded by a cytosolic mechanism at the same rate in the absence or presence of reticulocyte lysate. The data do not support the notion that the observed lack of degradation of microinjected [35S]polypeptides translated in vitro is due to the presence of proteolytic inhibitors in reticulocyte lysates which can inhibit the degradation of microinjected or cellular proteins.
mesh_terms: D002460:Cell Line; D004912:Erythrocytes / Q000378:metabolism; D006454:Hemoglobins / Q000378:metabolism; D007424:Intracellular Fluid / Q000378:metabolism; D008715:Methionine / Q000378:metabolism; D008845:Microinjections; D010455:Peptides / Q000378:metabolism*; D014176:Protein Biosynthesis; D011498:Protein Precursors / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D012710:Serum Albumin, Bovine / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D006454:Hemoglobins; D010455:Peptides; D011498:Protein Precursors; D012333:RNA, Messenger; D012710:Serum Albumin, Bovine; D008715:Methionine