T cell chemotaxis to lysophosphatidylcholine through the G2A receptor

Abstract

G2A is an immunoregulatory G protein-coupled receptor predominantly expressed in lymphocytes and macrophages. Ectopic overexpression studies have implicated G2A as a receptor for the bioactive lysophospholipid, lysophosphatidylcholine (LPC). However, the functional consequences of LPC-G2A interaction at physiological levels of receptor expression, and in a cellular context relevant to its immunological role, remain largely unknown. Here, we show impaired chemotaxis to LPC of a T lymphoid cell line in which G2A expression was chronically down-regulated by RNA interference technology. Rescuing this phenotype by reconstitution of the physiological level of receptor expression further supports a functional connection between LPC-G2A interaction and cellular motility. Overexpression of G2A in the T lymphoid cell line significantly enhanced chemotaxis to LPC. It also modified migration toward the LPC-related molecule, lysophosphatidic acid, indicating the possibility of crosstalk between G2A and endogenous lysophosphatidic acid receptors. The role of G2A in LPCmediated cell migration may be relevant to the autoimmune syndrome associated with genetic inactivation of this G proteincoupled receptor in mice. The experimental system described here can be useful for understanding the structural requirements for LPC recognition by G2A and the signaling pathways regulated by this ligand-receptor pair.

Gi-independent macrophage chemotaxis to lysophosphatidylcholine via the immunoregulatory GPCR G2A

“…17 More recently, siRNA silencing and retroviral overexpression of G2A in the mouse DO11.10 T-cell hybridoma demonstrated the requirement of G2A in LPC-induced T-cell migration. 5 In this report, we show that the chemotaxis of mouse primary and J774A.1 macrophages to LPC is dependent on G2A expression and that the G2A-mediated cell migratory signals are transduced through G i -independent pathways. Taken together, these results demonstrate that G2A is required for LPC-induced chemotaxis of immune cells.…”

“…5 The retroviral expression construct was generated by cloning the open reading frame of mouse G2A cDNA into the MSCV-IRES-GFP vector. The G2A rescue construct was made by cloning the siRNA-resistant form of G2A 5 into a modified pQCXIP vector under the control of the ubiquitin C promoter.…”

“…Expression of G2A siRNA was driven by a human H1 RNA promoter in a retroviral vector as previously reported. 5 Overexpression of G2A was achieved by MSCV-G2A-IRES-GFP retroviral infection (named G2A HIGH J774A.1 cells). In J774A.1 cells transduced with G2A siRNA retrovirus (named G2A siRNA J774A.1 cells), the expression of G2A was stably inhibited by more than 90% (Figure 2A).…”

“…2 The mechanism of lysophospholipid-mediated cell migration recently has been shown to require the expression of specific GPCRs, such as the receptors for sphingosine 1-phosphate (S1P), lysophosphatidic acid (LPA), and LPC. [3][4][5] The immunological importance of these lysophospholipid receptors is illustrated by the profound immunodeficiency observed in mice lacking expression of the S1P 1 receptor in hematopoietic cells. S1P 1 -deficient T cells fail to egress from thymus and therefore are completely absent from the periphery.…”

Functional metagenomic discovery of bacterial effectors in the human microbiome and isolation of commendamide, a GPCR G2A/132 agonist

“…G2A-knockout mice have increased susceptibility to atherosclerosis and develop late-onset autoimmunity (31). These phenotypes are thought to arise from disruption of G2A-dependent modulation of immune cell function including differentiation and chemotaxis (62,(64)(65)(66)(67)(68)(69)(70)(71). This suggests that Bacteroides spp.…”