Both CLIC4 and CLIC5A activate ERM proteins in glomerular endothelium

Am J Physiol Renal Physiol. 2016 Nov 1;311(5):F945-F957. doi: 10.1152/ajprenal.00353.2016. Epub 2016 Aug 31.


The chloride intracellular channel (CLIC) 5A is expressed at very high levels in renal glomeruli, in both endothelial cells (EC) and podocytes. CLIC5A stimulates Rac1- and phosphatidylinositol (4,5)-bisphosphate-dependent ERM (ezrin, radixin, moesin) activation. ERM proteins, in turn, function in lumen formation and in the development of actin-based cellular projections. In mice lacking CLIC5A, ERM phosphorylation is profoundly reduced in podocytes, but preserved in glomerular EC. Since glomerular EC also express CLIC4, we reasoned that, if CLIC4 activates ERM proteins like CLIC5A, then CLIC4 could compensate for the CLIC5A loss in glomerular EC. In glomeruli of CLIC5-deficient mice, CLIC4 expression was upregulated and colocalized with moesin and ezrin in glomerular EC, but not in podocytes. In cultured glomerular EC, CLIC4 silencing reduced ERM phosphorylation and cytoskeletal association, and expression of exogenous CLIC4 or CLIC5A rescued ERM de-phosphorylation due to CLIC4 silencing. In mice lacking either CLIC4 or CLIC5, ERM phosphorylation was retained in glomerular EC, but, in mice lacking both CLIC4 and CLIC5, glomerular EC ERM phosphorylation was profoundly reduced. Although glomerular EC fenestrae developed normally in dual CLIC4/CLIC5-deficient mice, the density of fenestrae declined substantially by 8 mo of age, along with the deposition of subendothelial electron-lucent material. The dual CLIC4/CLIC5-deficient mice developed spontaneous proteinuria, glomerular cell proliferation, and matrix deposition. Thus CLIC4 stimulates ERM activation and can compensate for CLIC5A in glomerular EC. The findings indicate that CLIC4/CLIC5A-mediated ERM activation is required for maintenance of the glomerular capillary architecture.

Keywords: chloride intracellular channel; ezrin; fenestrae; moesin; radixin.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Chloride Channels / genetics
  • Chloride Channels / metabolism*
  • Cytoskeletal Proteins / metabolism*
  • Endothelial Cells / cytology
  • Endothelial Cells / metabolism*
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / metabolism*
  • Membrane Proteins / metabolism*
  • Mice
  • Mice, Knockout
  • Microfilament Proteins / metabolism*
  • Mitochondrial Proteins / genetics
  • Mitochondrial Proteins / metabolism*
  • Phosphorylation
  • Podocytes / metabolism


  • CLIC protein, mouse
  • CLIC5 protein, mouse
  • Chloride Channels
  • Cytoskeletal Proteins
  • Membrane Proteins
  • Microfilament Proteins
  • Mitochondrial Proteins
  • ezrin
  • moesin
  • radixin