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

Abstract

Mesangioproliferative glomerulonephritis (MsPGN) is characterized by the proliferation of glomerular mesangial cells (GMCs) and accumulation of extracellular matrix (ECM), followed by glomerulosclerosis and renal failure of patients. Although our previous studies have demonstrated that sublytic C5b‐9 complex formed on the GMC membrane could trigger GMC proliferation and ECM expansion of rat Thy‐1 nephritis (Thy‐1N) as an animal model of MsPGN, their mechanisms are still not fully elucidated. In the present studies, we found that the levels of response gene to complement 32 (RGC‐32), myeloid zinc finger 1 (MZF1), phosphorylated extracellular signal‐regulated kinase 5 (phosphorylated ERK5, p‐ERK5), F‐box only protein 28 (FBXO28) and TNF receptor‐associated factor 6 (TRAF6) were all markedly up‐regulated both in the renal tissues of rats with Thy‐1N (in vivo) and in the GMCs upon sublytic C5b‐9 stimulation (in vitro). Further in vitro experiments revealed that up‐regulated FBXO28 and TRAF6 could form protein complex binding to ERK5 and enhance ERK5 K63‐ubiquitination and subsequent phosphorylation. Subsequently, ERK5 activation contributed to MZF1 expression and MZF1‐dependent RGC‐32 up‐regulation, finally resulting in GMC proliferative response. Furthermore, the MZF1‐binding element within RGC‐32 promoter and the functions of FBXO28 domains were identified. Additionally, knockdown of renal FBXO28, TRAF6, ERK5, MZF1 and RGC‐32 genes respectively markedly reduced GMC proliferation and ECM production in Thy‐1N rats. Together, these findings indicate that sublytic C5b‐9 induces GMC proliferative changes in rat Thy‐1N through ERK5/MZF1/RGC‐32 axis activated by the FBXO28‐TRAF6 complex, which might provide a new insight into MsPGN pathogenesis.

KLF6 Acetylation Promotes Sublytic C5b-9-Induced Production of MCP-1 and RANTES in Experimental Mesangial Proliferative Glomerulonephritis

“…Rat Thy-1N is a wide-spreadly used animal model that recapitulates the main features of human MsPGN 4 . The initial mechanism of this nephritis is the binding of injecting anti-Thy-1 antibody to rat Thy-1 antigen on GMCs membrane, triggering complement system activation, inflammatory response development, and subsequent GMCs injury 30 , 34 , 40 . Our previous experiments have revealed that sublytic C5b-9 complex is the major mediator of renal inflammation and GMCs damage in the rats with Thy-1N 8 , 31 .…”

“…Our previous experiments have revealed that sublytic C5b-9 complex is the major mediator of renal inflammation and GMCs damage in the rats with Thy-1N 8 , 31 . Sublytic C5b-9 induces the release of pro-inflammatory cytokines (IL-6, IL-23, and IL-36a) by GMCs 7 , 8 and GMCs apoptosis 31 or proliferation 30 . In this study, we found that the expression of chemokines MCP-1 and RANTES increased obviously in renal tissue of Thy-1N rats ( in vivo ) and in GMCs stimulated with sublytic C5b-9 ( in vitro ), indicating that the up-regulation of MCP-1 and RANTES may contribute to the recruitment of macrophages into glomeruli in the early stage of Thy-1N.…”

“…Recombinant human C6 was from Sino Biological. Rabbit polyclonal Thy-1 antibody (Ab, 1:640) and normal rabbit serum were prepared in our laboratory according to previous document (30). Ab against KLF6 (sc-365633) was from Santa Cruz Biotechnology.…”

Kaposi’s Sarcoma-Associated Herpesvirus and Host Interaction by the Complement System

“…Furthermore, eukaryotic cells can recover from a MAC attack by removing MAC from the cell surface by shedding or internalizing MAC-containing membrane vesicles after MAC formation. Therefore, the effects of MAC on eukaryotic nucleated cells have been frequently reported to be sublytic, which triggers diverse outcomes through an ion influx, including cell proliferation, inflammatory cytokine release, and the production of growth factors [31,32,34,35]; moreover, all of these may contribute to the pathogenesis of various diseases.…”

Sublytic C5b-9 induces glomerular mesangial cell proliferation via ERK1/2-dependent SOX9 phosphorylation and acetylation by enhancing Cyclin D1 in rat Thy-1 nephritis

“…Rat Thy-1 nephritis (Thy-1N) is an animal model used to study MsPGN 7 – 10 . Our previous reports have demonstrated that sublytic C5b-9 stimulation can induce GMC proliferation 9 , 11 , but the mechanism of sublytic C5b-9‐triggered proliferation in Thy‐1N rats remains unclear.…”