Adenosine triphosphate-induced shedding of CD23 and L-selectin (CD62L) from lymphocytes is mediated by the same receptor but different metalloproteases.
CD23 is a transmembrane protein expressed on the surface of B-lymphocytes that binds IgE, CD21, CD11b, and CD11c. High concentrations of soluble CD23 and L-selectin are found in the serum of patients with B-chronic lymphocytic leukemia (B-CLL). Because extracellular adenosine triphosphate (ATP) causes shedding of L-selectin via activation of P2Z/P2X7 receptors expressed on B-CLL lymphocytes, we studied the effect of ATP on shedding of CD23. ATP-induced shedding of CD23 at an initial rate of 12% of that for L-selectin, whereas the EC50 for ATP was identical (35 micromol/L) for shedding of both molecules. Furthermore, benzoylbenzoyl ATP also produced shedding of CD23 and L-selectin with the same agonist EC50 values for both (10 micromol/L). Inactivation of the P2Z/P2X7 receptor by preincubation with oxidized ATP abolished ATP-induced shedding of both molecules. Moreover, KN-62, the most potent inhibitor for the P2Z/P2X7 receptor, inhibited ATP-induced shedding of both CD23 and L-selectin with the same IC50 (12 nmol/L). Ro 31-9790, a membrane permeant zinc chelator that inhibits the phorbol-ester-stimulated shedding of L-selectin, also inhibited shedding of CD23 from B-CLL lymphocytes. However, the IC50 for this inhibition by Ro31-9790 was different for L-selectin and CD23 (83 v 6 micromol/L, respectively). Although L-selectin was completely shed by incubation of cells with phorbol-ester, CD23 was not lost under these conditions. The data show that extracellular ATP induces shedding of L-selectin and CD23 from B-CLL lymphocytes by an action mediated by the P2Z/P2X7 receptor. However, different membrane metalloproteases seem to mediate the shedding of L-selectin and CD23.
Sydney University Department of Medicine, Nepean Hospital, Penrith, Australia.
B
B
Gu
L J
LJ
Bendall
J S
JS
Wiley
D000255:Adenosine Triphosphate / Q000031:analogs & derivatives / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000187:drug effects* / Q000378:metabolism; D014408:Biomarkers, Tumor / Q000378:metabolism*; D002118:Calcium / Q000494:pharmacology; D006801:Humans; D006877:Hydroxamic Acids; D019041:L-Selectin / Q000378:metabolism*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000473:pathology*; D008666:Metalloendopeptidases / Q000502:physiology*; D009363:Neoplasm Proteins / Q000378:metabolism*; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000378:metabolism; D011480:Protease Inhibitors / Q000494:pharmacology; D017455:Receptors, IgE / Q000378:metabolism*; D018048:Receptors, Purinergic P2 / Q000502:physiology*; D058486:Receptors, Purinergic P2X7; D012995:Solubility; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
D014408:Biomarkers, Tumor; D006877:Hydroxamic Acids; D009363:Neoplasm Proteins; C546468:P2RX7 protein, human; D011480:Protease Inhibitors; D017455:Receptors, IgE; D018048:Receptors, Purinergic P2; D058486:Receptors, Purinergic P2X7; C097661:Ro 31-9790; D019041:L-Selectin; C033901:3'-O-(4-benzoyl)benzoyladenosine 5'-triphosphate; C017199:2',3'-dialdehyde ATP; D000255:Adenosine Triphosphate; D008666:Metalloendopeptidases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium