RGMb protects against acute kidney injury by inhibiting tubular cell necroptosis via an MLKL-dependent mechanism

Abstract

Tubular cell necrosis is a key histological feature of acute kidney injury (AKI). Necroptosis is a type of programed necrosis, which is executed by mixed lineage kinase domain-like protein (MLKL) upon its binding to the plasma membrane. Emerging evidence indicates that necroptosis plays a critical role in the development of AKI. However, it is unclear whether renal tubular cells undergo necroptosis in vivo and how the necroptotic pathway is regulated during AKI. Repulsive guidance molecule (RGM)-b is a member of the RGM family. Our previous study demonstrated that RGMb is highly expressed in kidney tubular epithelial cells, but its biological role in the kidney has not been well characterized. In the present study, we found that RGMb reduced membrane-associated MLKL levels and inhibited necroptosis in cultured cells. During ischemia/reperfusion injury (IRI) or oxalate nephropathy, MLKL was induced to express on the apical membrane of proximal tubular (PT) cells. Specific knockout of Rgmb in tubular cells (Rgmb cKO) increased MLKL expression at the apical membrane of PT cells and induced more tubular cell death and more severe renal dysfunction compared with wild-type mice. Treatment with the necroptosis inhibitor Necrostatin-1 or GSK'963 reduced MLKL expression on the apical membrane of PT cells and ameliorated renal function impairment after IRI in both wild-type and Rgmb cKO mice. Taken together, our results suggest that proximal tubular cell necroptosis plays an important role in AKI, and that RGMb protects against AKI by inhibiting MLKL membrane association and necroptosis in proximal tubular cells.

Necroptosis in Acute Kidney Injury

“…As global RGMb -deficient mice die in the early postnatal stage, only heterozygous mice or tubular cell-specific knockout mice are used to study AKI. Employing the latter approach, Liu et al [25] demonstrated an aggravation of post-ischemic AKI or acute oxalate nephropathy, which confirms RGMb as an endogenous inhibitor of tubular injury (Table 1). Elegant in vitro studies demonstrate that lack of RGMb enhances MLKL deposition in tubular cell membranes and the execution of renal cell death.…”

“…RGMb has diverse biological functions that relate to its modulatory effect on IL-6 expression and neurite outgrowth but it was recently described as an inhibitor of MLKL homotrimer binding to the plasma membrane, and hence as another endogenous necroptosis inhibitor [25]. Interestingly, RGMb is highly expressed in tubular epithelial cells.…”

Molecular Insights into the Mechanism of Necroptosis: The Necrosome as a Potential Therapeutic Target

“…Necroptosis is also involved in kidney diseases. RIPK3 and MLKL are activated during acute kidney injury, where MLKL is expressed on the apical membrane of proximal tubules [85]. Thus, this suggests that the necrosome is an active mediator of kidney injury.…”

hsa‐miR‐500a‐3P alleviates kidney injury by targeting MLKL‐mediated necroptosis in renal epithelial cells

“…A recent study showed that conditional knockout of repulsive guidance molecule (RGM)b, a member of the RGM family, induced MLKL expression at the apical membrane and increased renal dysfunction. These findings indicate that RGMb prevents AKI by inhibiting MLKL membrane association and necroptosis in tubular epithelial cells (17,19). However, the regulatory mechanism of MLKL signaling is unknown, and targeted therapy is lacking.…”