Nephronectin Regulates Mesangial Cell Adhesion and Behavior in Glomeruli

J Am Soc Nephrol. 2018 Apr;29(4):1128-1140. doi: 10.1681/ASN.2017070752. Epub 2018 Jan 15.

Abstract

A critical aspect of kidney function occurs at the glomerulus, the capillary network that filters the blood. The glomerular basement membrane (GBM) is a key component of filtration, yet our understanding of GBM interactions with mesangial cells, specialized pericytes that provide structural stability to glomeruli, is limited. We investigated the role of nephronectin (Npnt), a GBM component and known ligand of α8β1 integrin. Immunolocalization and in situ hybridization studies in kidneys of adult mice revealed that nephronectin is produced by podocytes and deposited into the GBM. Conditional deletion of Npnt from nephron progenitors caused a pronounced increase in mesangial cell number and mesangial sclerosis. Nephronectin colocalized with α8β1 integrin to novel, specialized adhesion structures that occurred at sites of mesangial cell protrusion at the base of the capillary loops. Absence of nephronectin disrupted these adhesion structures, leading to mislocalization of α8β1. Podocyte-specific deletion of Npnt also led to mesangial sclerosis in mice. These results demonstrate a novel role for nephronectin and α8β1 integrin in a newly described adhesion complex and begin to uncover the molecular interactions between the GBM and mesangial cells, which govern mesangial cell behavior and may have a role in pathologic states.

Keywords: cell biology and structure; cell-matrix-interactions; glomerular basement membrane; mesangial cells; nephronectin.

Publication types

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

MeSH terms

  • Animals
  • Cell Adhesion / physiology
  • Cell Count
  • Epithelial Cells / metabolism
  • Extracellular Matrix Proteins / biosynthesis
  • Extracellular Matrix Proteins / deficiency
  • Extracellular Matrix Proteins / physiology*
  • Female
  • Focal Adhesions
  • Gene Deletion
  • Glomerular Basement Membrane / physiology*
  • Glomerular Mesangium / abnormalities
  • Glomerular Mesangium / cytology*
  • Integrins / metabolism
  • Kidney Glomerulus / abnormalities
  • Male
  • Mice
  • Mice, Mutant Strains
  • Organ Specificity
  • Pericytes / cytology*
  • Pericytes / metabolism
  • Podocytes / metabolism*

Substances

  • Extracellular Matrix Proteins
  • Integrins
  • Npnt protein, mouse
  • integrin alpha8beta1