title: Intersectin-1s regulates the mitochondrial apoptotic pathway in endothelial cells.
abstract: 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.
authors.affiliation: Department of Pharmacology, University of Illinois College of Medicine, Chicago, Illinois 60612, USA. sandap@uic.edu
authors.forename: Sanda A
authors.initials: SA
authors.lastname: Predescu
authors.forename: Dan N
authors.initials: DN
authors.lastname: Predescu
authors.forename: Ivana
authors.initials: I
authors.lastname: Knezevic
authors.forename: Irene K
authors.initials: IK
authors.lastname: Klein
authors.forename: Asrar B
authors.initials: AB
authors.lastname: Malik
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000502:physiology*; D017209:Apoptosis / Q000502:physiology*; D001483:Base Sequence; D002478:Cells, Cultured; D045304:Cytochromes c / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000502:physiology*; D006801:Humans; D020287:In Situ Nick-End Labeling; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000201:enzymology / Q000502:physiology*; D034741:RNA, Small Interfering; D015398:Signal Transduction
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; C485568:ITSN1 protein, human; D034741:RNA, Small Interfering; D045304:Cytochromes c