Sam68-like mammalian protein 2, identified by digital differential display as expressed by podocytes, is induced in proteinuria and involved in splice site selection of vascular endothelial growth factor

J Am Soc Nephrol. 2005 Jul;16(7):1958-65. doi: 10.1681/ASN.2005020204. Epub 2005 May 18.

Abstract

Podocytes, the glomerular epithelial cells of the kidney, share important features with neuronal cells. In addition to phenotypical and functional similarities, a number of gene products have been found to be expressed exclusively or predominantly by both cell types. With the hypothesis of a common transcriptome shared by podocytes and neurons, digital differential display was used to identify novel podocyte-expressed gene products. Comparison of brain and kidney cDNA libraries with those of other organs identified Sam68-like mammalian protein 2 (SLM-2), a member of the STAR family of RNA processing proteins, as expressed by podocytes. SLM-2 expression was found to be restricted in the kidney to podocytes. In proteinuric diseases, SLM-2, a known regulator of neuronal mRNA splice site selection, was found significantly upregulated on mRNA and protein levels. Knockdown of SLM-2 by short interfering RNA in podocytes was performed to evaluate its biologic role. RNA splicing of vascular endothelial growth factor (VEGF), a key regulator of the filtration barrier and expressed as functionally distinct splice isoforms, was evaluated. VEGF(165) expression was found to be reduced by 25% after SLM-2 knockdown. In vivo, the glomerular expression of SLM-2 correlated with the mRNA levels of VEGF(165). This study demonstrates the power of digital differential display to predict cell type-specific gene expression by hypothesis-driven analysis of tissue cDNA libraries. SLM-2-dependent VEGF splicing indicates the importance of mRNA splice site selection for glomerular filtration barrier function.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Epithelial Cells / physiology
  • Gene Expression Profiling
  • Gene Library
  • Humans
  • Kidney Glomerulus / cytology
  • Kidney Glomerulus / physiology
  • Mice
  • Proteinuria / metabolism*
  • RNA Splicing
  • RNA, Messenger
  • RNA, Small Interfering
  • RNA-Binding Proteins / biosynthesis*
  • RNA-Binding Proteins / genetics
  • RNA-Binding Proteins / isolation & purification
  • Transfection
  • Vascular Endothelial Growth Factor A / physiology*

Substances

  • Khdrbs3 protein, mouse
  • RNA, Messenger
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • Vascular Endothelial Growth Factor A