Stage-specific expression of P2Y receptors, ecto-apyrase, and ecto-5'-nucleotidase in myeloid leukocytes

Abstract

The expression of P2 purinergic receptor subtypes in leukocytes varies with both lineage and developmental stage. Given the recent identification and cloning of at least seven distinct G protein-coupled ATP receptor subtypes (P2Y family), we investigated P2Y receptor subtype expression during myeloid cell differentiation. We observed that KG-1 myeloblasts express P2Y1 but not P2Y2 receptors (previously termed P2U receptors), whereas later myeloid progenitors, including HL-60 promyelocytes and THP-1 monocytes, expressed P2Y2 but not P2Y1 receptors. In KG-1 cells, significant activation of Ca2+ mobilization by P2Y1 receptors was only observed after preincubation with potato apyrase, an exogenous ATPase. This indicated that P2Y1 receptors are desensitized in KG-1 cells by autocrine mechanisms that may involve enhanced release of endogenous nucleotides and/or decreased expression of cell-surface ecto-nucleotidases. We compared the levels of ecto-apyrase activity and expression in KG-1 myeloblasts and HL-60 promyelocytes. Extracellular ATP was rapidly metabolized by HL-60 but not by KG-1 cells. Reverse transcription-polymerase chain reaction analysis indicated that mRNA for CD39 (cluster of differentiation), an identified ecto-apyrase, was present in HL-60 but not KG-1 cells. Ecto-apyrase activity was modestly increased with differentiation of myeloid progenitors with either phorbol 12-myristate 13-acetate (PMA) or dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP). Differentiation of HL-60 cells with PMA, but not DBcAMP, strongly induced ecto-5'-nucleotidase activity and CD73 mRNA expression. These observations indicate that signal transduction by extracellular ATP in myeloid leukocytes can be regulated by developmentally programmed changes in the expression of P2Y receptor subtypes and multiple ecto-nucleotidases.

Innate Response to Focal Necrotic Injury Inside the Blood-Brain Barrier

“…Although leukocytes can also use ATP as a signaling molecule (33,39,40), it is not clear whether ATP is used in the leukocyte response in the meninges. The meninges are an important site for infections by viruses and bacteria so understanding this response will be important.…”

Regulation of Endothelial CD73 by Adenosine: Paracrine Pathway for Enhanced Endothelial Barrier Function

“…For instance, original studies suggested that CD73 promoter constructs lacking the consensus CRE were still functional and that CD73 production in myeloid cell lines was not influenced by agents that elevate intracellular cAMP (12). It has been reported, however, that agents that activate protein kinase C (i.e., PMA) strongly induce CD73 mRNA and activity in myeloid leukocytes (HL-60 cells) (24). Similarly, in Jurkat T cells, PMA induces CD73 gel shift using oligonucleotides corresponding to the CRE site (25).…”

Modulation of P2X7 nucleotide receptor expression by pro- and anti-inflammatory stimuli in THP-1 monocytes

“…This is an important consideration because ecto-nucleotidases will rapidly degrade this ATP and thus minimize the maintenance of high extracellular ATP concentrations in the local vicinity of the macrophage. Indeed, we have recently characterized the expression of both the CD39 ectoATPase and the CD73 ecto-5Ј nucleotidase in human monocyte/ macrophage cell types [42]. The recent discovery that ICE/ caspase-1 also processes IFN-␥-inducing factor (IGIF or IL-18) to its active form raises an additional possibility that T cell-mediated IFN-␥ production can also be indirectly regulated by ATP-activated macrophages [43].…”