B Lymphocyte–Specific Loss of Ric-8A Results in a Gα Protein Deficit and Severe Humoral Immunodeficiency

Abstract

Resistance to inhibitors of cholinesterase 8A (Ric-8A) is a highly evolutionarily conserved cytosolic protein initially identified in C. elegans, where it was assigned a regulatory role in asymmetric cell divisions. It functions as a guanine nucleotide exchange factor for Gαi, Gαq, and Gα12/13 and as a molecular chaperone required for the initial association of nascent Gα subunits with cellular membranes in embryonic stem cell lines. To test its role in hematopoiesis and B lymphocytes specifically, we generated ric8fl/flvav1-cre and ric8fl/flmb1-cre mice. The major hematopoietic cell lineages developed in the ric8fl/flvav1-cre mice, notwithstanding severe reduction in Gαi2/3, Gαq, and Gα13 proteins. B lymphocyte specific loss of Ric-8A did not compromise bone marrow B lymphopoiesis, but splenic marginal zone B cell development failed, and B cells underpopulated lymphoid organs. The ric8fl/flmb1-cre B cells exhibited poor responses to chemokines, abnormal trafficking, improper in situ positioning, and loss of polarity components during B cell differentiation. The ric8fl/flmb1-cre mice had a severely disrupted lymphoid architecture and poor primary and secondary antibody responses. In B lymphocytes, Ric-8A is essential for normal Gα protein levels; and is required for B cell differentiation, trafficking, and antibody responses.

The impact of RGS and other G-protein regulatory proteins on Gαi-mediated signaling in immunity

“…These later observations revealed that Ric-8A functioned as a molecular chaperone to target newly synthesized Gα i , Gα q , and Gα 12/13 proteins to cellular membranes. Conditionally targeting ric8 in murine hematopoietic cells using the cre recombinase expressed in either all hematopoietic cells or only in murine B cells also led to severe reductions of Gα proteins with major decreases in Gα i2/i3 , Gα q , and Gα 13 proteins (65). In the hematopoietic cell specific deletion, the mice had a major reduction of platelets, which likely accounted for their shortened lifespan.…”

“…In the hematopoietic cell specific deletion, the mice had a major reduction of platelets, which likely accounted for their shortened lifespan. The B lymphocyte specific deletion did not impact mouse viability, but led to a severe B cell immune phenotype (65). While bone marrow B cell lymphopoiesis was not, splenic marginal zone B cell development was severely compromised.…”

Guanine nucleotide–binding protein G(i)α2 aggravates hepatic ischemia‐reperfusion injury in mice by regulating MLK3 signaling

“…Particularly, guanine nucleotide-binding protein G(i)a2 (GNAI2) has been implicated in numerous pathologic and physiologic processes (9)(10)(11). Indeed, numerous investigations have implicated GNAI2 in neurodevelopmental disorders (12), immunodeficiency (13), tumor (14), and organ I/R injury (15). Furthermore, GNAI2 appears to be an essential modulator in heart and brain I/R injury model, whereas similar contributions to liver I/R injury are unclear.…”

Gαi2 Signaling Regulates Inflammasome Priming and Cytokine Production by Biasing Macrophage Phenotype Determination

“…Rgs19-deficient GFP knock-in (KI) mice were generated by Ozgene. Ric8 2/2 , Rgs10 2/2 , Rgs1 2/2 , and Gpsm1 2/2 mice have been previously described (32)(33)(34)(35). All strains were backcrossed a minimum of 12 times to C57BL/6J and experiments were performed using 6-to 14-wkold mice with littermate controls.…”