Journal: Journal of the American Society of Nephrology
Article Title: Negative Modulation of B Cell Activation by Melanocortin 1 Receptor Signaling Protects against Membranous Nephropathy
doi: 10.1681/asn.2022050605
Figure Lengend Snippet: Figure 8. Loss of MC1R potentiates B-cell activation and en- hances autologous humoral immune responses in rats with PHN. (A) Animals were treated as elaborated in Figure 1F. Splenocytes derived from WT or KO rats with PHN were pro- cessed for flow cytometry analysis of CD1381 cells. (B) Arbitrary levels of sheep IgG-specific rat IgG in sera collected from WT or KO rats with PHN, as estimated by ELISA of diluted sera; aP,0.05 versus WT rats with PHN (n56). (C) Schematic diagram depicting the working model for negative regulation of B-cell activation by MC1R-mediated melanocortinergic signaling. As a typical G-protein coupled receptor, MC1R is expressed by B lympho- cytes and is able to trigger the cAMP signaling pathway on ac- tivation by diverse melanocortins, such as pan-MCR agonists like ACTH and NDP-MSH, or the selective MC1R agonist MS05. Subsequently, cAMP signaling downstream of MC1R activates MITF, one of the major signaling transducers of MC1R pathway and a critical regulator of a plethora of key cellular processes, including melanogenesis in melanocytes and cellular differenti- ation in nonmelanocytic cells. In B lymphocytes, MITF acts as a repressor of IRF4, a characteristic lymphoid transcription factor essential for B-cell development and maturation. MC1R-medi- ated melanocortinergic signaling suppresses B-cell activation and plasmacytic differentiation and reduces IgG production via the cAMP/MITF/IRF4 pathway, which could be intercepted by SQ22536, an adenylyl cyclase inhibitor. This MC1R-mediated B- cell regulatory signaling is defective in B cells with MC1R KO and could be partially restored by the cAMP mimetic dBcAMP.
Article Snippet: Urinary albumin concentrations were analyzed using a rat albumin enzyme-linked immunosorbent assay (ELISA) quantitation kit (Bethyl Laboratories Inc., Montgomery, TX) or an albumin assay kit (BioAssay System, Hayward, CA).
Techniques: Activation Assay, Derivative Assay, Cytometry, Enzyme-linked Immunosorbent Assay
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