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K562 leukemia cells express P2T (adenosine diphosphate) purinergic receptors

A J Murgo1, F D Sistare

  • 1Division of Research and Testing, Food and Drug Administration, Washington, DC.

The Journal of Pharmacology and Experimental Therapeutics
|May 1, 1992
PubMed

Insights

The P2T purinergic receptor for ADP was identified in K562 leukemia cells, responding to ADP by increasing intracellular calcium. This suggests P2T receptors are early markers for megakaryocytic differentiation.

Area of Science:

  • Biochemistry
  • Cell Biology
  • Pharmacology

Background:

  • The P2T purinergic receptor for adenosine diphosphate (ADP) was previously identified exclusively in platelets.
  • K562 leukemia cells possess potential for megakaryocytic differentiation, a process involving platelet precursor cells.

Purpose of the Study:

  • To investigate the effect of ADP on intracellular free calcium ([Ca++]i) concentration in K562 leukemia cells.
  • To determine if K562 cells express functional P2T purinergic receptors.
  • To explore the signal transduction pathways mediating the ADP response in these cells.

Main Methods:

  • K562 leukemia cells were loaded with fura-2 to measure intracellular calcium levels.
  • Cells were exposed to varying concentrations of ADP to assess dose-dependent responses.
  • Experiments were conducted with and without extracellular calcium to differentiate between store mobilization and influx.
  • Protein kinase C (PKC) activators and inhibitors were used to probe signaling pathways.

Main Results:

  • ADP induced a rapid, transient increase in [Ca++]i in K562 cells, peaking within 5-10 seconds (EC50 = 0.4 microM).
  • A significant portion of the calcium increase originated from intracellular stores, indicating partial mobilization.
  • Cells exhibited desensitization to subsequent ADP exposure.
  • Phorbol 12-myristate 13-acetate (PKC activator) blocked the ADP response, an effect reversed by staurosporine (PKC inhibitor).
  • Adenosine triphosphate (ATP) did not elicit a calcium response but antagonized ADP's effect.

Conclusions:

  • K562 cells express functional P2T purinergic receptors for ADP, mediating calcium release from intracellular stores.
  • The P2T receptor in K562 cells may serve as an early indicator of megakaryocytic differentiation.
  • This cell line provides a valuable model for studying ADP signal transduction pathways relevant to megakaryopoiesis.

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