BIOSYNTHESIS AND PROCESSING BY PHORBOL ESTER OF THE CELL SURFACE-ASSOCIATED PRECURSOR FORM OF HEPARIN-BINDING EGF-LIKE GROWTH-FACTOR

Human MDA MB 231 cells were found to synthesize mostly the cell surfac e-associated precursor form of heparin-binding EGF-like growth factor (HB-EGF), a 27-kDa protein. Evidence for this form of HB-EGF included increased fluorescence intensity when cells were analyzed by flow cyto metry using anti-HB-EGF antibodies, lack of HB-EGF in conditioned medi um, and sensitivity to diphtheria toxin, for which HB-EGF is the recep tor. Phorbol ester treatment of cells resulted, within 30 minutes, in loss of cell surface 27 kDA HB-EGF, lack of interaction with anti-HB-E GF antibodies, accumulation of active 21 kDa HB-EGF in conditioned med ium, and the acquisition of diphtheria toxin resistance. It was conclu ded that cell surface-associated HB-EGF is the precursor of a bioactiv e growth factor, is biologically active as the receptor for diphtheria toxin, and is susceptible to rapid processing. (C) 1994 Academic Pres s, Inc.