CD53 ANTIGEN AND EPIDERMAL GROWTH-FACTOR INDUCE SIMILAR CHANGES IN THE PATTERN OF PHORBOL ESTER BINDING IN A B-CELL LYMPHOMA

The CD53 antigen is a prototype member of the transmembrane-4 superfam ily which includes several tumor antigens. In this report we have stud ied the changes in the cellular binding of phorbol esters after stimul ation with monoclonal antibody (mAb) MRC OX-44 (anti-CD53) and epiderm al growth factor (EGF) using a fluorochrome-phorbol ester binding assa y. Incubation of a rat B cell lymphoma cell Line with this mAb or EGF induces the appearance of high- and low-affinity phorbol ester binding sites and changes the total number of binding sites. Four binding sit es with different characteristics have been detected. The binding data suggest that two structurally different receptors, CD53 antigen and E GF receptor, induce a similar change in the functional protein kinase C expressed in the cell which might be implicated in the responses eli cited after cell stimulation. (C) 1996 Academic Press, Inc