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 superfamily which includes several tumor antigens. In this report we have studied the changes in the cellular binding of phorbol esters after stimulation with monoclonal antibody (mAb) MRC OX-44 (anti-CD53) and epidermal growth factor (EGF) using a fluorochrome–phorbol ester binding assay. 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 sites with different characteristics have been detected. The binding data suggest that two structurally different receptors, CD53 antigen and EGF receptor, induce a similar change in the functional protein kinase C expressed in the cell which might be implicated in the responses elicited after cell stimulation.