Variations in Gnai2 and Rgs1 expression affect chemokine receptor signaling and the organization of secondary lymphoid organs

Abstract

Ligand bound chemoattractant receptors activate the heterotrimeric G protein Gi to stimulate downstream signaling pathways to properly position lymphocytes in lymphoid organs. Here we show how variations the expression of a chemokine receptor and in two components in the signaling pathway, Gαi2 and RGS1, affects the output fidelity of the signaling pathway. Examination of B cells from mice with varying numbers of intact alleles of Ccr7, Rgs1, Gnai2, and Gnai3 provided the basis for these results. Loss of a single allele of either Gnai2 or Rgs1 affected CCL19 triggered chemotaxis, while loss of a single allele of Ccr7, which encodes the cognate CCL19 receptor, had little effect. Emphasizing the importance of Gnai2, B cells lacking Gnai3 expression responded to chemokines better than did wild type B cells. At an organismal level, variations in Rgs1 and Gnai2 expression affected marginal zone B cell development, splenic architecture, lymphoid follicle size, and germinal center morphology. Gnai2 expression was also needed for the proper alignment of MOMA-1+ macrophages and MAdCAM-1+ endothelial cells along marginal zone sinuses in the spleen. These data indicate that chemoattractant receptors, heterotrimeric G-proteins, and RGS protein expression levels have a complex inter-relationship that affects the responses to chemoattractant exposure.

Regulation of Chemokine Signal Integration by Activator of G-Protein Signaling 4 (AGS4)

“…5B) suggests that AGS4 may play an important role in modulating cellular responses at higher levels of receptor activation. Similar observations were noted for regulator of G-protein signaling 1 (RGS1), another accessory protein important for chemokine-regulated G-protein signal processing (Han et al, 2006;Hwang et al, 2010). Furthermore, our data indicate that AGS4-null neutrophils have a defect in chemoattractant-mediated migration ex vivo, which manifests in a defect in neutrophil recruitment to sites of inflammation in vivo (Fig.…”

Lymph node B lymphocyte trafficking is constrained by anatomy and highly dependent upon chemoattractant desensitization

“…Together these results indicate that receptor desensitization mediated by either receptor G-protein uncoupling or RGS protein induction had occurred. [31][32][33] Suggesting RGS protein involvement, RT-PCR documented increases in Rgs1, Rgs3S, and Rgs16 mRNA in the CD62L antibody-treated group relative to control, whereas Gnai2 and Gnai3 expression levels remained constant. The differences in Rgs gene expression could not be accounted for by contaminating T cells or germinal center B cells (Figure 5E-F).…”

An Essential Role for RGS Protein/Gαi2 Interactions in B Lymphocyte–Directed Cell Migration and Trafficking

“…Yet the loss of one Gnai2 allele decreases B lymphocyte chemotaxis to CXCL12, CXCL13, and CCL19, particularly so, at low ligand concentrations. The loss of both Gnai2 alleles profoundly reduces chemotaxis while the loss of both Gnai3 alleles has a minimal effect (1, 14). Whether Gα i2 plasma membrane levels undergo physiologically relevant regulation is unknown, however suggesting that they may, Gα i2 is subject to ubiquitination and proteasomal degradation (15).…”