Intracellular processing of epidermal growth factor. I. Acidification of 125I-epidermal growth factor in intracellular organelles.
We previously reported that 125I-labeled epidermal growth factor is processed intracellularly to acidic macromolecules in Rat-1 fibroblasts. The present study defines the precursor-product relationship and localization of the processing steps to subcellular organelles by the use of a single isoelectric species of 125I-epidermal growth factor and Percoll gradient fractionation. The native pI 4.55 125I-epidermal growth factor was rapidly processed to a pI 4.2 species on or near the cell surface and in organelles corresponding to clathrin-coated vesicles, Golgi, and endoplasmic reticulum. This species was then processed to a pI 4.35 species in similar organelles. The pI 4.2 and 4.35 species were converted to a pI 4.0 species in dense, lysosome-like organelles. This species was ultimately degraded and exocytosed from the cell as low molecular weight products.
D000818:Animals; D002458:Cell Fractionation; D002460:Cell Line; D002499:Centrifugation, Density Gradient; D004815:Epidermal Growth Factor / Q000378:metabolism*; D005347:Fibroblasts / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007457:Iodine Radioisotopes; D007525:Isoelectric Focusing; D007700:Kinetics; D051379:Mice; D009940:Organoids / Q000378:metabolism*; D011205:Povidone; D051381:Rats; D012822:Silicon Dioxide; D013363:Submandibular Gland
D007457:Iodine Radioisotopes; D004815:Epidermal Growth Factor; C016039:Percoll; D012822:Silicon Dioxide; D011205:Povidone