Mouse anti-Human RGS13 monoclonal antibody, clone 2E6

G protein-coupled receptors (GPCRs) have important functions in both innate and adaptive immunity, with the capacity to bridge interactions between the two arms of the host responses to pathogens through direct recognition of secreted microbial products or the by-products of host cells damaged by pathogen exposure. In the mid-1990s, a large group of intracellular proteins was discovered, the regulator of G protein signaling (RGS) family, whose main, but not exclusive, function appears to be to constrain the intensity and duration of GPCR signaling. The R4/B subfamily-the focus of this review-includes RGS1-5, 8, 13, 16, 18, and 21, which are the smallest RGS proteins in size, with the exception of RGS3. Prominent roles in the trafficking of B and T lymphocytes and macrophages have been described for RGS1, RGS13, and RGS16, while RGS18 appears to control platelet and osteoclast functions. Additional G protein independent functions of RGS13 have been uncovered in gene expression in B lymphocytes and mast cell-mediated allergic reactions. In this review, we discuss potential physiological roles of this RGS protein subfamily, primarily in leukocytes having central roles in immune and inflammatory responses. We also discuss approaches to target RGS proteins therapeutically, which represents a virtually untapped strategy to combat exaggerated immune responses leading to inflammation.

BACKGROUND & AIMS: We aimed to identify biomarkers that might be used to predict responses of patients with inflammatory bowel diseases (IBD) to vedolizumab therapy. METHODS: We obtained biopsies from inflamed colon of patients with IBD who began treatment with vedolizumab (n = 31) or tumor necrosis factor (TNF) antagonists (n = 20) and performed RNA-sequencing analyses. We compared gene expression patterns between patients who did and did not enter endoscopic remission (absence of ulcerations at month 6 for patients with Crohn's disease or Mayo endoscopic subscore <= 1at week 14 for patients with ulcerative colitis) and performed pathway analysis and cell deconvolution for training (n = 20) and validation (n = 11) datasets. Colon biopsies were also analyzed by immunohistochemistry. We validated a baseline gene expression pattern associated with endoscopic remission after vedolizumab therapy using 3 independent datasets (n = 66). RESULTS: We identified significant differences in expression levels of 44 genes between patients who entered remission after vedolizumab and those who did not; we found significant increases in leukocyte migration in colon tissues from patients who did not enter remission (P < .006). Deconvolution methods identified a significant enrichment of monocytes (P = .005), M1-macrophages (P = .05), and CD4+ T cells (P = .008) in colon tissues from patients who did not enter remission, whereas colon tissues from patients in remission had higher numbers of naive B cells before treatment (P = .05). Baseline expression levels of PIWIL1, MAATS1, RGS13, and DCHS2 identified patients who did vs did not enter remission with 80% accuracy in the training set and 100% accuracy in validation dataset 1. We validated these findings in the 3 independent datasets by microarray, RNA sequencing and quantitative PCR analysis (P = .003). Expression levels of these 4 genes did not associate with response to anti-TNF agents. We confirmed the presence of proteins encoded by mRNAs using immunohistochemistry. CONCLUSIONS: We identified 4 genes whose baseline expression levels in colon tissues of patients with IBD associate with endoscopic remission after vedolizumab, but not anti-TNF, treatment. We validated this signature in 4 independent datasets and also at the protein level. Studies of these genes might provide insights into the mechanisms of action of vedolizumab.