Extracellular processing of amphoterin generates a peptide active on erythroleukaemia cell differentiation

The release of amphoterin by murine erythroleukaemia cells exposed to the c hemical inducer hexamethylenebisacetamide represents an essential stop for the process of their terminal differentiation. Once exported in the culture medium, amphoterin undergoes limited proteolysis, catalysed by a serine pr oteinase also secreted by stimulated cells. The isolated proteinase is resp onsible for degradation of amphoterin, with the production of a 10-amino-ac id-residue fragment, specifically retaining the cell-differentiation-stimul ating activity of the native protein molecule. This peptide does not expres s other properties of amphoterin, such as protein kinase C-stimulating acti vity or systemic toxicity. These findings define a selective mechanism acco unting for extracellular amphoterin functional maturation.