Def-6, a novel regulator of small GTPases in podocytes, acts downstream of atypical protein kinase C (aPKC) λ/ι

Am J Pathol. 2013 Dec;183(6):1945-1959. doi: 10.1016/j.ajpath.2013.08.026. Epub 2013 Oct 3.


The atypical protein kinase C (aPKC) isotypes PKCλ/ι and PKCζ are both expressed in podocytes; however, little is known about differences in their function. Previous studies in mice have demonstrated that podocyte-specific loss of PKCλ/ι leads to a severe glomerular phenotype, whereas mice deficient in PKCζ develop no renal phenotype. We analyzed various effects caused by PKCλ/ι and PKCζ deficiency in cultured murine podocytes. In contrast to PKCζ-deficient podocytes, PKCλ/ι-deficient podocytes exhibited a severe actin cytoskeletal phenotype, reduced cell size, decreased number of focal adhesions, and increased activation of small GTPases. Comparative microarray analysis revealed that the guanine nucleotide exchange factor Def-6 was specifically up-regulated in PKCλ/ι-deficient podocytes. In vivo Def-6 expression is significantly increased in podocytes of PKCλ/ι-deficient mice. Cultured PKCλ/ι-deficient podocytes exhibited an enhanced membrane association of Def-6, indicating enhanced activation. Overexpression of aPKCλ/ι in PKCλ/ι-deficient podocytes could reduce the membrane-associated expression of Def-6 and rescue the actin phenotype. In the present study, PKCλ/ι was identified as an important factor for actin cytoskeletal regulation in podocytes and Def-6 as a specific downstream target of PKCλ/ι that regulates the activity of small GTPases and subsequently the actin cytoskeleton of podocytes.

Publication types

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

MeSH terms

  • Actin Cytoskeleton / genetics
  • Actin Cytoskeleton / metabolism*
  • Animals
  • Cell Membrane / genetics
  • Cell Membrane / metabolism*
  • Cells, Cultured
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • GTP Phosphohydrolases / genetics
  • GTP Phosphohydrolases / metabolism
  • Gene Expression Regulation / physiology*
  • Guanine Nucleotide Exchange Factors
  • Isoenzymes / genetics
  • Isoenzymes / metabolism*
  • Mice
  • Mice, Knockout
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Podocytes / cytology
  • Podocytes / metabolism*
  • Protein Kinase C / genetics
  • Protein Kinase C / metabolism*
  • Protein Kinase C-epsilon / genetics
  • Protein Kinase C-epsilon / metabolism


  • DNA-Binding Proteins
  • Guanine Nucleotide Exchange Factors
  • Isoenzymes
  • Nuclear Proteins
  • SLAT protein, mouse
  • Protein Kinase C
  • Protein Kinase C-epsilon
  • protein kinase C lambda
  • GTP Phosphohydrolases