P2Y(11) receptor expression by human lymphocytes: evidence for two cAMP-linked purinoceptors

The effects of extracellular ATP, ADP, AMP and adenosine on cAMP accumulati on have been studied in freshly isolated B-lymphocytes from patients with c hronic lymphocytic leukemia. Extracellular ATP and several nucleotide analo gs stimulated cAMP accumulation with the following order of potency: ATP (E C50 = 120 +/- 20 muM) > ADP >> AMP. ADP was less effective than ATP and may be a partial agonist. AMP exhibited variable but generally weak activity. The stable analog of ATP, alpha,beta -methylene ATP (EC50 = 110 +/- 15 muM) also stimulated cAMP accumulation and exhibited similar efficacy to ATP. T he P2Y(2) receptor agonist, UTP had no effect on intracellular cAMP levels. Adenosine and the A(2A)/A(2B) receptor agonist, 5'-N-ethylcarboxamidoadeno sine (NECA) also stimulated cAMP accumulation in CLL lymphocytes. Adenosine deaminase inhibited the cAMP response to adenosine but had no effect on th e ATP-induced cAMP response. On the other hand, the AMP analog, adenosine 5 '-thiomonophosphate, (AMPS; 1.0 mM) inhibited ATP-induced and alpha,beta -m ethylene ATP-induced cAMP production but had no effect on adenosine-induced cAMP production. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed the presence of P2Y(11) receptor as well as A(2A) and A(2 B) receptor mRNA in chronic lymphocytic leukemia lymphocytes. However, A(2B ) receptors would appear to be relatively ineffective because the A(2A) sel ective agonist, CGS-21680 exhibited comparable efficacy to NECA. Furthermor e, the A(2A)-selective antagonist 8-(3-chlorostyryl)-caffeine (CSC) right-s hifted the concentration-response curve for NECA. Taken together, the data indicate that ATP induces cAMP accumulation via the activation of P2Y(11) r eceptors whereas adenosine induces cAMP accumulation via the activation of A(2A) receptors. Coordinate activation of P2Y(11) and A(2A) receptors may i nfluence the developmental fate of normal B-lymphocytes. (C) 2001 Published by Elsevier Science B.V.