Abstract: SA-PO232

CLIC5A Protects Renal Glomeruli from Diabetes-Induced Damage

Session Information

  • Glomerular: Cell Biology
    November 04, 2017 | Location: Hall H, Morial Convention Center
    Abstract Time: 10:00 AM - 10:00 AM

Category: Glomerular

  • 1003 Glomerular: Cell Biology

Authors

  • Wang, Xin, University of Alberta, Edmonton, Alberta, Canada
  • Li, Laiji, University of Alberta, Edmonton, Alberta, Canada
  • Ballermann, Barbara J., University of Alberta, Edmonton, Alberta, Canada
Background

Podocyte injury, including foot process (FP) effacement, is a critical early step in the development of diabetic nephropathy. Activated ezrin, podocalyxin and CLIC5A form a complex at the apical plasma membrane of FPs, coupling podocalyxin to actin. Disruption of this complex leads to FP effacement. We have shown that CLIC5A stimulates ezrin activation through Rac1-dependent PI(4,5)P2 accumulation (J Cell Sci 127:5164; 2014 & Kidney Int 89:833; 2016). Here, we studied the role of CLIC5A in FP formation and diabetic nephropathy.

Methods

Conditionally immortalized mouse podocytes were differentiated for 14 days and infected with adenovirus-CLIC5A or vector. Cdc42 and Rac1 activity were determined by GTPase pull-down. Podocyte morphology was assessed by scanning electron microscopy (SEM) and confocal actin immunofluorescence (IF). Diabetes was induced with streptozotocin (50 mg/kg, IP X 5 days) in wild-type (WT) or CLIC5A deficient (KO) mice. Controls were given buffer IP. Histology was evaluated on Masson-Trichrome stained sections (n= 3-6 mice/group).

Results

In differentiated podocytes, CLIC5A raised active GTP-Cdc42 and Rac1 levels, it activated ezrin, and induced FP-like projections, observed by SEM and actin IF. In glomerular lysates of WT diabetic mice, CLIC5A, active ezrin and podocalyxin levels were reduced compared to nondiabetic WT mice. GTP-Cdc42/Rac1 complexes from renal cortex lysates of WT mice contained both, CLIC5A and the PI(4,5)P2 generating enzyme PI4P5Kα (n=6). Notably, PI4P5Kα was absent from GTP-Cdc42/Rac1 pulldowns of KO mice (n=6). Diabetes strongly activated Cdc42 and Rac1 in WT and KO mice (n=3 each), but active ezrin was profoundly reduced in lysates and GTP-Cdc42/Rac1 complexes from KO compared to WT diabetic mice. Albuminuria, segmental glomerular sclerosis and interstitial fibrosis were significantly greater in CLIC5A KO diabetic mice than in WT diabetic mice.

Conclusion

In podocytes, CLIC5A activates Rac1 and Cdc42 and stimulates FP formation. The findings in mice that CLIC5A is necessary for the association of PI4P5Kα with GTP-Rac1/Cdc42, and that ezrin activation is profoundly reduced in diabetic CLIC5A deficient mice despite Rac1/Cdc42 activation, indicate that CLIC5A forms the critical link between the active GTPase(s) and PI4P5Kα which leads to PI(4,5)P2-dependent ezrin activation. Inhibition of this novel mechanism contributes to diabetic nephropathy.

Funding

  • Private Foundation Support