Disease-causing mutation in α-actinin-4 promotes podocyte detachment through maladaptation to periodic stretch

Proc Natl Acad Sci U S A. 2018 Feb 13;115(7):1517-1522. doi: 10.1073/pnas.1717870115. Epub 2018 Jan 29.

Abstract

α-Actinin-4 (ACTN4) bundles and cross-links actin filaments to confer mechanical resilience to the reconstituted actin network. How this resilience is built and dynamically regulated in the podocyte, and the cause of its failure in ACTN4 mutation-associated focal segmental glomerulosclerosis (FSGS), remains poorly defined. Using primary podocytes isolated from wild-type (WT) and FSGS-causing point mutant Actn4 knockin mice, we report responses to periodic stretch. While WT cells largely maintained their F-actin cytoskeleton and contraction, mutant cells developed extensive and irrecoverable reductions in these same properties. This difference was attributable to both actin material changes and a more spatially correlated intracellular stress in mutant cells. When stretched cells were further challenged using a cell adhesion assay, mutant cells were more likely to detach. Together, these data suggest a mechanism for mutant podocyte dysfunction and loss in FSGS-it is a direct consequence of mechanical responses of a cytoskeleton that is brittle.

Keywords: actin; cytoskeleton; kidney; podocyte; α-actinin-4.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinin / genetics*
  • Actinin / metabolism
  • Animals
  • Cell Adhesion
  • Cytoskeleton / metabolism
  • Female
  • Glomerulosclerosis, Focal Segmental / genetics
  • Glomerulosclerosis, Focal Segmental / pathology
  • Humans
  • Male
  • Mice, Transgenic
  • Podocytes / pathology*
  • Point Mutation*

Substances

  • ACTN4 protein, human
  • Actn4 protein, mouse
  • Actinin