UDP-glucose acting at P2Y14 receptors is a mediator of mast cell degranulation

Abstract

UDP-glucose (UDPG), a glycosyl donor in the biosynthesis of carbohydrates, is an endogenous agonist of the G protein-coupled P2Y 14 receptor. RBL-2H3 mast cells endogenously express a P2Y 14 receptor at which UDPG mediates degranulation as indicated by β-hexosaminidase (HEX) release. Both UDPG and a more potent, selective 2-thio-modified UDPG analog, MRS2690 (diphosphoric acid 1-α-D-glucopyranosyl ester 2-(2-thiouridin-5''-yl) ester), caused a substantial calcium transient in RBL-2H3 cells, which was blocked by pertussis toxin, indicating the presence of the G i -coupled P2Y 14 receptor, supported also by quantitative detection of abundant mRNA. Expression of the closely related P2Y 6 receptor was over 100 times lower than the P2Y 14 receptor, and the P2Y 6 agonist 3-phenacyl-UDP was inactive in RBL-2H3 cells. P2Y 14 receptor agonists also induced [ 35 S]GTPγS binding to RBL-2H3 cell membranes, and phosphorylation of ERK1/2, P38 and JNK. UDPG and MRS2690 concentration-dependently enhanced HEX release with EC 50 values of 1150 ± 320 and 103 ± 18 nM, respectively. The enhancement was completely blocked by pertussis toxin and significantly diminished by P2Y 14 receptor-specific siRNA. Thus, mast cells express an endogenous P2Y 14 receptor, which mediates G i -dependent degranulation and is therefore a potential novel therapeutic target for allergic conditions.

UDP-glucose promotes neutrophil recruitment in the lung

“…5). Collectively, these results strongly suggest that UDP-glucose released into CF-like diseased airways acts as a pro-inflammatory mediator, via stimulation of the P2Y 14 R. P2Y 14 R mRNA is expressed in human [45] and murine [46] lungs [17,46] and inflammatory cells [17][18][19][20][21], but the identity of the cell type(s) potentially sensing UDP-glucose in airway surface liquids is not known. We observed no P2Y 14 R mRNA amplification in well-differentiated primary cultures of bronchial epithelial cells (data not shown).…”

“…UDP also is an agonist of this receptor, but ATP, UTP, or other naturally occurring nucleoside 5′-di-or triphosphates have no P2Y 14 R activity [13][14][15][16]. P2Y 14 R mRNA expression has been reported in the brain and several peripheral tissues [13], including the lung, circulating neutrophils, and other immune/inflammatory cells [17][18][19][20][21].…”

Vesicular and conductive mechanisms of nucleotide release

“…P2Y 14 -R is functionally expressed in brain glia and peripheral leucocytes, including neutrophils, lymphocytes, and mast cells [80][81][82][83], suggesting that UDP-sugar release contributes to inflammatory responses. Quantification of endogenous UDP-glucose in extracellular solutions indicated that UDP-glucose release accompanies the release of ATP under resting and stimulated conditions in a number of cells [49,84,85].…”

Purinergic signaling in inflammatory cells: P2 receptor expression, functional effects, and modulation of inflammatory responses

“…Among the P2Y receptors, the presence of P2Y 1 , P2Y 2 , P2Y 11 , P2Y 12 , and P2Y 13 subtypes were shown by RT-PCR on cord blood-derived human mast cells (hMCs) [23]. Recently, the presence of all P2Y receptors in mast cells was reported including P2Y 4 and P2Y 14 receptors as was shown in both murine RBL-2H3 and human LAD2 cell lines, the former being most highly expressed together with the P2Y 11 receptor [215,216].…”

“…Schulman et al confirmed the presence of P2Y 1 and P2Y 2 , but not P2X7 transcript in HLMC's as discussed above. Recent studies indicate that P2Y 13 and P2Y 14 might also be involved in mast cell degranulation, since these receptors induce β-hexosaminidase release in RBL-2H3 rat mast cells [215,221] while P2Y 14 was also reported to potentiate C3a-induced β-hexosaminidase release in human LAD2 cells [216] (Table 1). Triggering of intracellular Ca 2+ signaling in mast cells is also linked to cytokine expression and release.…”