Identification of a 34,000-dalton mitogenic protein associated with plasma membranes from human A431 epidermoid carcinoma cells.
We present evidence for a discrete 34,000-Da polypeptide with mitogenic activity, associated with plasma membranes from human A431 carcinoma cells. Plasma membranes from A431 cells are highly mitogenic for quiescent fibroblasts. A significant fraction of the membrane-associated activity can be released by treatment with a high concentration of salt and is relatively acid stable. Incubation of 125I-labeled salt-extracted proteins with target fibroblasts results in preferential binding of a 34,000-Da protein--i.e., greater than 90% of the cell-bound radioactivity is associated with the 34,000-Da polypeptide. Studies correlating the mitogenic activity with the cell-binding 34,000-Da protein indicate that this protein is the acid-stable, peripherally attached, mitogenically active component of A431 membranes. Available data suggest that this protein may be mitogenically active in the nanomolar concentration range. Some properties of this protein are described.
D000085:Acetates; D019342:Acetic Acid; D002294:Carcinoma, Squamous Cell / Q000032:analysis / Q000473:pathology*; D002450:Cell Communication; D002462:Cell Membrane / Q000502:physiology; D006133:Growth Substances / Q000302:isolation & purification*; D006801:Humans; D008565:Membrane Proteins / Q000302:isolation & purification / Q000502:physiology; D008970:Molecular Weight; D009363:Neoplasm Proteins / Q000502:physiology*; D012492:Salts
D000085:Acetates; D006133:Growth Substances; D008565:Membrane Proteins; D009363:Neoplasm Proteins; D012492:Salts; D019342:Acetic Acid