Palmitoylation of CD44 interferes with CD3-mediated signaling in human T lymphocytes

We studied the interactions between CD44 and four differentmonoclonal antl-CD44 antibodies. All four monoclonal anti-CD44antibodies studied (P3H9, Bu52, IM.7, and GKW.A3) act in synergywith human anti-CD2 antibodies in stimulating normal human peripheralblood lymphocytes to proliferate. GKW.A3 and IM.7 but not P3H9or Bu52 Inhibited the proliferation of normal human peripheralblood lymphocytes stimulated by antl-CD3. Interestingly, onlyGKW.A3 and IM.7 stimulated the incorporation of [3H]palmltlcacid and palmitoylation of CD44 molecules by normal human peripheralblood lymphocytes. The two monoclonal antl-CD44 antibodies (P3H9and Bu52) that failed to inhibit antl-CD3 induced proliferationalso failed to induce the incorporation of [³H]palmltlc acid.More Importantly, the inhibitory effects of GKW.A3 were reversedin the presence of cerulenln, an inhibitor of protein palmitoylation.Therefore, palmitoylation of CD44 may interfere with antl-CD3mediated signaling pathways. These data support the hypothesisthat palmitoylation of cell surface receptors may play an activerole in receptor and receptor interactions and signal transductlonin normal human T lymphocytes.