title: Expressed isolated integrin beta1 subunit cytodomain induces endothelial cell death secondary to detachment.
abstract: Expression of isolated beta integrin cytoplasmic domains in cultured endothelial cells was reported to induce cell detachment and death. To test whether cell death was the cause or the consequence of cell detachment, we expressed isolated integrin beta1 cytoplasmic and transmembrane domains (CH1) in cultured human umbilical vein endothelial cells (HUVEC), and monitored detachment, viability, caspase activation and signaling. CH1 expression induced dose-dependent cell detachment. At 24 h over 90% of CH1-expressing HUVEC were detached but largely viable (>85%). No evidence of pro-caspase-8,-3, and PARP cleavage or suppression of phosphorylation of ERK, PKB and Ikappa-B was observed. The caspase inhibitor z-VAD did not prevent cell detachment. At 48 h, however, CH1-expressing cells were over 50% dead. As a comparison trypsin-mediated detachment resulted in a time-dependent cell death, paralleled by caspase-3 activation and suppression of ERK, PKB and Ikappa-B phosphoyrylation at 24 h or later after detachment. HUVEC stimulation with agents that strengthen integrin-mediated adhesion (i.e. PMA, the Src inhibitor PP2 and COMP-Ang1) did not prevent CH1-induced detachment. Expression of CH1 in rat carotid artery endothelial cells in vivo caused endothelial cell detachment and increased nuclear DNA fragmentation among detached cells. A construct lacking the integrin cytoplasmic domain (CH2) had no effect on adhesion and cell viability in vitro and in vivo. These results demonstrate that isolated beta1 cytoplasmic domain expression induces caspase-independent detachment of viable endothelial cells and that death is secondary to detachment (i.e. anoikis). They also reveal an essential role for integrins in the adhesion and survival of quiescent endothelial cells in vivo.
authors.affiliation: Centre Pluridisciplinaire d'Oncologie, Swiss Institute for Experimental Cancer Research ISREC, Epalinges, Switzerland.
authors.forename: Meriem
authors.initials: M
authors.lastname: Hasmim
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Vassalli
authors.forename: Gian Carlo
authors.initials: GC
authors.lastname: Alghisi
authors.forename: Jeannine
authors.initials: J
authors.lastname: Bamat
authors.forename: Lionel
authors.initials: L
authors.lastname: Ponsonnet
authors.forename: Grégory
authors.initials: G
authors.lastname: Bieler
authors.forename: Claude
authors.initials: C
authors.lastname: Bonnard
authors.forename: Cécile
authors.initials: C
authors.lastname: Paroz
authors.forename: Delphine
authors.initials: D
authors.lastname: Oguey
authors.forename: Curzio
authors.initials: C
authors.lastname: Rüegg
mesh_terms: D000818:Animals; D023102:Anoikis / Q000502:physiology*; D002339:Carotid Arteries / Q000166:cytology; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D002470:Cell Survival / Q000502:physiology; D002478:Cells, Cultured; D053938:DNA Fragmentation / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology* / Q000502:physiology*; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D015870:Gene Expression / Q000502:physiology; D006801:Humans; D020672:I-kappa B Proteins / Q000378:metabolism; D019012:Integrin beta1 / Q000737:chemistry / Q000235:genetics*; D020935:MAP Kinase Signaling System / Q000502:physiology; D017434:Protein Structure, Tertiary; D021122:Protein Subunits / Q000737:chemistry / Q000235:genetics; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D014471:Umbilical Veins / Q000166:cytology
chemical_list: D020672:I-kappa B Proteins; D019012:Integrin beta1; D021122:Protein Subunits; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; C505407:CASP3 protein, human; C505530:CASP8 protein, human; C505410:Casp3 protein, rat; C505528:Casp8 protein, rat; D053148:Caspase 3; D053181:Caspase 8; D020169:Caspases