Anti-RGS13 monoclonal antibody Made to order

Regulators of G-protein signaling (RGS) proteins are scaffolds that control diverse signaling pathways by modulating signalosome formation and by accelerating the GTPase activity of heterotrimeric G proteins. Although expression of many RGS proteins is relatively low in quiescent cells, transcriptional and post-translational responses to environmental cues regulate both their abundance and activity. We found previously that RGS13, one of the smallest RGS proteins in the family, inhibited cyclic AMP-dependent protein kinase (PKA)-induced gene expression through interactions with the transcription factor cAMP-response element-binding (CREB) protein. Here, we show that PKA activation also leads to increased steady-state RGS13 expression through RGS13 phosphorylation, which inhibits RGS13 protein degradation. RGS13 turnover was significantly reduced in cells stimulated with cAMP, which was reversed by expression of the PKA-specific inhibitory peptide PKI. RGS13 phosphorylation was diminished by mutation of an N-terminal Thr residue (T41) identified as a phosphorylation site by mass spectrometry. Mutation of Thr41 in RGS13 to Ala (T41A) reduced steady-state RGS13 levels and its ability to inhibit M2 muscarinic receptor-mediated Erk phosphorylation compared with wild-type RGS13 by attenuating the protective effect of cAMP on RGS13 degradation. RGS13 underwent ubiquitylation, indicating that it is a likely target of the proteasome. These studies are the first to demonstrate post-translational mechanisms controlling the expression of RGS13. Stabilization of RGS13 through PKA-mediated phosphorylation could enhance RGS13 functions, providing negative feedback regulation that promotes cellular desensitization.

Background: Childhood asthma is classified into allergic asthma (AA) and nonallergic asthma (NA), yet both are treated identically, with only partial success. Objective: We sought to identify novel immune phenotypes for childhood AA and NA. Methods: The Clinical Asthma Research Association cohort study includes 275 steroid-naive 4-to 15-year-old German children (healthy control subjects [HCs], patients with AA, and patients with NA). In PBMCs both quantitative and functional analysis of regulatory T (Treg) and T(H)17 cells (flow cytometry/Treg cell suppression) before/after anti-CD3/CD28, lipid A, and peptidoglycan stimulation were performed. Cytokines and gene expression, as assessed by using Luminex or transcriptomics/quantitative real-time RT-PCR, were analyzed by means of regression analysis. Linear discriminant analysis was applied to discriminate between phenotypes. Results: The 3 phenotypes were immunologically well discriminated by means of microarray and protein analysis with linear discriminant analysis. Patients with AA were characterized by increased Treg cells compared with those in HCs but not those in patients with NA. Treg cells from patients with AA, but not patients with NA, significantly suppressed IL5, IL-13, and IFN-gamma secretion. Patients with AA had decreased expression of chloride intracellular channel 4 (CLIC4) and tuberous sclerosis 1 (TSC1), important innate immunity regulators. Patients with NA were characterized by increased proinflammatory IL-1 beta levels, neutrophil counts, and IL-17-shifted immunity. In parallel, expressions of anti-inflammatory IL37, proline-serine-threonine phosphatase-interacting protein 2 (PSTPIP2), and the neutrophil-associated genes CD93, triggering receptor expressed on myeloid cells 1 (TREM1), and regulator of G-protein signaling 13 (RGS13) were increased in patients with NA. A shared T(H)2 immunity was present in both asthma phenotypes. Conclusion: Novel immune-regulatory mechanisms in childhood asthma identified increased Treg cells in patients with AA compared with those in HCs but not those in NA and decreased innate immunity genes for patients with AA, the first potentially indicating a counterregulatory mechanism to suppress cytokines yet not sufficient to control allergic inflammation. Very distinctly, patients with NA showed an IL-17-shifted proinflammatory immunity, promoting neutrophil inflammation and less functional Treg cells. Identification of these unique pathways provides a profound basis for future strategies for individualized prediction of asthma development, disease course, and prevention.