Nephrin and CD2AP associate with phosphoinositide 3-OH kinase and stimulate AKT-dependent signaling

Mol Cell Biol. 2003 Jul;23(14):4917-28. doi: 10.1128/mcb.23.14.4917-4928.2003.

Abstract

Mutations of NPHS1 or NPHS2, the genes encoding nephrin and podocin, as well as the targeted disruption of CD2-associated protein (CD2AP), lead to heavy proteinuria, suggesting that all three proteins are essential for the integrity of glomerular podocytes, the visceral glomerular epithelial cells of the kidney. It has been speculated that these proteins participate in common signaling pathways; however, it has remained unclear which signaling proteins are actually recruited by the slit diaphragm protein complex in vivo. We demonstrate that both nephrin and CD2AP interact with the p85 regulatory subunit of phosphoinositide 3-OH kinase (PI3K) in vivo, recruit PI3K to the plasma membrane, and, together with podocin, stimulate PI3K-dependent AKT signaling in podocytes. Using two-dimensional gel analysis in combination with a phosphoserine-specific antiserum, we demonstrate that the nephrin-induced AKT mediates phosphorylation of several target proteins in podocytes. One such target is Bad; its phosphorylation and inactivation by 14-3-3 protects podocytes against detachment-induced cell death, suggesting that the nephrin-CD2AP-mediated AKT activity can regulate complex biological programs. Our findings reveal a novel role for the slit diaphragm proteins nephrin, CD2AP, and podocin and demonstrate that these three proteins, in addition to their structural functions, initiate PI3K/AKT-dependent signal transduction in glomerular podocytes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • 14-3-3 Proteins
  • Adaptor Proteins, Signal Transducing
  • Animals
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism
  • Cell Line
  • Cell Membrane / metabolism
  • Cytoskeletal Proteins
  • Dogs
  • Humans
  • Intracellular Signaling Peptides and Proteins
  • Kidney / cytology
  • Kidney / metabolism
  • Membrane Proteins / genetics
  • Membrane Proteins / metabolism
  • Mice
  • Phosphatidylinositol 3-Kinases / metabolism*
  • Phosphorylation
  • Protein Subunits
  • Protein-Serine-Threonine Kinases*
  • Proteins / genetics
  • Proteins / metabolism*
  • Proto-Oncogene Proteins / genetics
  • Proto-Oncogene Proteins / metabolism*
  • Proto-Oncogene Proteins c-akt
  • Signal Transduction / physiology*
  • Tyrosine 3-Monooxygenase / genetics
  • Tyrosine 3-Monooxygenase / metabolism
  • bcl-Associated Death Protein

Substances

  • 14-3-3 Proteins
  • Adaptor Proteins, Signal Transducing
  • BAD protein, human
  • Bad protein, mouse
  • CD2-associated protein
  • Carrier Proteins
  • Cytoskeletal Proteins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • NPHS2 protein
  • Protein Subunits
  • Proteins
  • Proto-Oncogene Proteins
  • bcl-Associated Death Protein
  • nephrin
  • Tyrosine 3-Monooxygenase
  • Phosphatidylinositol 3-Kinases
  • AKT1 protein, human
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt