RGC-32 regulates reactive astrocytosis and extracellular matrix deposition in experimental autoimmune encephalomyelitis

Abstract

Extracellular matrix (ECM) deposition in active demyelinating multiple sclerosis (MS) lesions may impede axonal regeneration and can modify immune reactions. Response gene to complement (RGC)-32 plays an important role in the mediation of TGF-β downstream effects, but its role in gliosis has not been investigated. To gain more insight into the role played by RGC-32 in gliosis, we investigated its involvement in TGF-β-induced ECM expression and the upregulation of the reactive astrocyte markers α-smooth muscle actin (α-SMA) and nestin. In cultured neonatal rat astrocytes, collagens I, IV, and V, fibronectin, α-SMA, and nestin were significantly induced by TGF-β stimulation, and RGC-32 silencing resulted in a significant reduction in their expression. Using astrocytes isolated from RGC-32 knock-out (KO) mice, we found that the expression of TGF-β-induced collagens I, IV, and V, fibronectin, and α-SMA was significantly reduced in RGC-32 KO mice when compared with wild-type (WT) mice. SIS3 inhibition of Smad3 phosphorylation was also associated with a significant reduction in RGC-32 nuclear translocation and TGF-β-induced collagen I expression. In addition, during experimental autoimmune encephalomyelitis (EAE), RGC-32 KO mouse astrocytes displayed an elongated, bipolar phenotype, resembling immature astrocytes and glial progenitors whereas those from WT mice had a reactive, hypertrophied phenotype. Taken together, our data demonstrate that RGC-32 plays an important role in mediating TGF-β-induced reactive astrogliosis in EAE. Therefore, RGC-32 may represent a new target for therapeutic intervention in MS.

TGFB1-Mediated Gliosis in Multiple Sclerosis Spinal Cords Is Favored by the Regionalized Expression of HOXA5 and the Age-Dependent Decline in Androgen Receptor Ligands

“…Also at the transcriptional level, several papers demonstrated the AR-mediated silencing of key genes of the TGFB1 pathway (data supplement 3), including SMAD3 [83]. Since SMAD3 is involved in the progliotic effects of TGFB1 [84,85], one may hypothesize that the hijacking of SMAD3 by AR may support the antigliotic effects exerted by androgens in different in vivo experimental settings [48,49,50,51,67,86]. Finally, since TGFB1 and AR signaling pathways may antagonize each other, any imbalance to the detriment of the AR pathway may also result in a lowered ability of AR ligands in promoting myelin repair and dampening inflammation.…”

RGC-32 Regulates Generation of Reactive Astrocytes in Experimental Autoimmune Encephalomyelitis

“…In vitro studies have shown that RGC-32 is critical for the differentiation of naïve T cells toward the Th17 phenotype ( 23 , 24 ). Moreover, we have found that the expression of collagens type I, IV, and V and fibronectin, together with that of the reactive astrocyte markers nestin and alpha-smooth muscle actin, is decreased in cultured astrocytes after siRNA-mediated RGC-32 silencing and in astrocytes purified from RGC-32-KO mice, suggesting that RGC-32 facilitates the TGF-β-induced expression of these components ( 25 ). These effects are mediated at the molecular level by RGC-32’s interaction with SMAD3 and the nuclear translocation of the two interacting molecules, which plays a central role in the intracellular signaling pathway downstream of the TGF-β receptor ( 25 ).…”

“…Moreover, we have found that the expression of collagens type I, IV, and V and fibronectin, together with that of the reactive astrocyte markers nestin and alpha-smooth muscle actin, is decreased in cultured astrocytes after siRNA-mediated RGC-32 silencing and in astrocytes purified from RGC-32-KO mice, suggesting that RGC-32 facilitates the TGF-β-induced expression of these components ( 25 ). These effects are mediated at the molecular level by RGC-32’s interaction with SMAD3 and the nuclear translocation of the two interacting molecules, which plays a central role in the intracellular signaling pathway downstream of the TGF-β receptor ( 25 ). Interestingly, we have also observed that there are differences in the morphology of spinal cord astrocytes between WT and RGC-32 KO mice with EAE ( 25 ), but whether RGC-32 is involved in regulating astrocyte differentiation in vivo during EAE is not yet known.…”

Sublytic C5b‐9 induces proliferation of glomerular mesangial cells via ERK5/MZF1/RGC‐32 axis activated by FBXO28‐TRAF6 complex

“…As a proliferation-related gene, RGC-32 expression can be induced by sublytic C5b-9 in endothelial cells and smooth muscle cells and contributes to the proliferation of these cells. 15,43,44 For example, Vlaicu et al have reported that RGC-32 expression is increased in the human aortic atherosclerotic wall and related with C5b-9 deposition and atherosclerosis progression. Silencing of RGC-32 expression abolishes C5b-9-induced proliferation of human aortic endothelial cells in vitro.…”