Human Immature Monocyte-Derived Dendritic Cells Express the G Protein-Coupled Receptor GPR105 (KIAA0001, P2Y14) and Increase Intracellular Calcium in Response to its Agonist, Uridine Diphosphoglucose

Abstract

Dendritic cells (DC) are essential to the initiation of an immune response due to their unique ability to take-up and process Ag, translocate to lymph nodes, and present processed Ag to naive T cells. Many chemokines, chemokine receptors and other G protein-coupled receptors (GPCRs) are implicated in these various aspects of DC biology. Through microarray analysis, we compared expression levels of chemokines, their cognate receptors, and selected GPCRs in human monocytes and in vitro monocyte-derived immature and mature DC. Hierarchical clustering of gene expression clearly distinguishes the three cell types, most notably highlighting exceptional levels of expression of the GPCR GPR105 within the immature monocyte-derived DC (MDDC) gene cluster. Little or no expression was observed within the monocyte and mature MDDC cluster. Putative functionality of the GPR105 receptor was demonstrated by an observed calcium flux in immature MDDC treated with the potent GPR105 agonist, uridine 5′-diphosphoglucose (UDP-glucose), while no response to the nucleotide sugar was seen in monocytes and mature MDDC. This UDP-glucose-induced calcium response was, at least in part, pertussis toxin-sensitive. Moreover, immature MDDC from some donors treated with UDP-glucose exhibit an increase in expression of the costimulatory molecule CD86, which correlates with the intensity of the UDP-glucose-induced calcium flux. Together, these data demonstrate differential expression of GPR105 on immature and mature MDDC and suggest a role for the receptor and its agonist ligand in DC activation.

The inflammatory effects of UDP-glucose in N9 microglia are not mediated by P2Y14 receptor activation

“…However, because the pro-inflammatory effects of microbial-derived UDPG on NO production were not blocked by PTX, it is likely that these stimulatory effects in microglia do not involve P2Y14 receptors. Although the function of P2Y14 in any cell type remains unclear, in immature dendritic cells, activation of P2Y14 receptors increases expression of CD86, suggesting their involvement in dendritic cell maturation [13]. Also, proinflammatory stimuli such as LPS [8] and interferon-γ (JMC and JJW, unpublished observations) increase the expression levels of GPR105 in glial cells and in N9 microglia, respectively, supporting the idea that this receptor plays a role in the microglial response to proinflammatory stimuli.…”

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].…”

Endoplasmic Reticulum/Golgi Nucleotide Sugar Transporters Contribute to the Cellular Release of UDP-sugar Signaling Molecules

“…P2Y 14 receptor transcripts are expressed in several human tissues, including placenta, stomach, intestine, adipose, brain, lung, spleen, heart, and circulating leukocytes (3,(5)(6)(7). UDPsugar-promoted signaling has been reported in astrocytes and microglial cells (8,9), lung epithelial cells (10), bone marrow hematopoietic stem cells (11), and multiple types of peripheral immune cells, including neutrophils, lymphocytes, and dendritic cells (6,7,12,13). These observations suggest that UDPsugars, high energy donor substrates in biosynthetic reactions, potentially are released from cells in a regulated fashion to perform autocrine/paracrine signaling.…”

“…P2Y receptors belong to the superfamily of G protein-coupled receptors. At least eight human P2Y receptor species have been identified, seven of which (P2Y 1 , P2Y 2 , P2Y 4 , P2Y 6 , P2Y 11 , P2Y 12 , and P2Y 13 ) are activated by adenine and/or uridine nucleoside di-and triphosphates (2). The P2Y 14 receptor was identified as the eighth member of the P2Y family (3,4).…”