Intersectin-1s regulates the mitochondrial apoptotic pathway in endothelial cells

J Biol Chem. 2007 Jun 8;282(23):17166-78. doi: 10.1074/jbc.M608996200. Epub 2007 Apr 3.


Intersectins (ITSNs) are multidomain adaptor proteins implicated in endocytosis, regulation of actin polymerization, and Ras/MAPK signaling. We have previously shown that ITSN-1s is required for caveolae fission and internalization in endothelial cells (ECs). In the present study, using small interfering RNA to knock down ITSN-1s protein expression, we demonstrate a novel role of ITSN-1s as a key antiapoptotic protein. Knockdown of ITSN-1s in ECs activated the mitochondrial pathway of apoptosis as determined by genomic DNA fragmentation, extensive mitochondrial fission, activation of the proapoptotic proteins BAK and BAX, and cytochrome c efflux from mitochondria. ITSN-1 knockdown acts as a proapoptotic signal that causes mitochondrial outer membrane permeabilization, dissipation of the mitochondrial membrane potential, and generation of reactive oxygen species. These effects were secondary to decreased activation of Erk1/2 and its direct activator MEK. Bcl-X(L) overexpression prevented BAX activation and the apoptotic ECs death induced by suppression of ITSN-1s. Our findings demonstrate a novel role of ITSN-1s as a negative regulator of the mitochondrial pathway-dependent apoptosis secondary to activation of the Erk1/2 survival signaling pathway.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Adaptor Proteins, Vesicular Transport / physiology*
  • Apoptosis / physiology*
  • Base Sequence
  • Cells, Cultured
  • Cytochromes c / metabolism
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / physiology*
  • Humans
  • In Situ Nick-End Labeling
  • Microscopy, Electron
  • Microscopy, Fluorescence
  • Mitochondria / enzymology
  • Mitochondria / physiology*
  • RNA, Small Interfering
  • Signal Transduction


  • Adaptor Proteins, Vesicular Transport
  • ITSN1 protein, human
  • RNA, Small Interfering
  • Cytochromes c