THE AGGREGATED FORM OF AN AAMP DERIVED PEPTIDE BEHAVES AS A HEPARIN SENSITIVE CELL-BINDING AGENT

A peptide termed P189, derived from the sequence of a newly discovered protein, AAMP (angio-associated migratory cell protein), contains a m otif that is predicted to bind heparin. It occurs near the amino termi nal end of AAMP. Previous studies have shown that in its solubilized f orm P189 (RRLRRMESESES) binds heparin and melanoma cells. The peptide is bipolar in that it contains positive charges at its amino end and n egative charges at its carboxyl end. It forms strongly aggregated part icles that require exposure to 50% DMSO and 100 degrees C for solubili zation to occur. Now heparin and cell binding (heparin sensitive) are also demonstrated for the peptide in its particulate form. Cell bindin g/clustering to the peptide particles is strong and resists exposure t o various reagents (sugars and inhibitors of glycolysis and protein sy nthesis) except heparin. Tumor cell migration is partially inhibited b y the presence of the peptide. On electron photomicrographs the peptid e is seen in close apposition to cell membranes. Heparin sensitivity o f the cell binding indicates that cell surface glycosaminoglycans are involved. The aggregated peptide binds heparin in a saturable manner w ith a dissociation constant, K-d, of 306 pmol. Cell binding/clustering studies using peptide variants of P189, which have substitutions in e ither the charged and/or nonpolar residues, show that the specific seq uence of P189 optimizes heparin-sensitive cell aggregation. (C) 1997 J ohn Wiley & Sons. Inc.