title: Rab5 mediates caspase-8-promoted cell motility and metastasis.
abstract: Caspase-8 is a key apical sensory protein that governs cell responses to environmental cues, alternatively promoting apoptosis, proliferation, and cell migration. The proteins responsible for integration of these pathways, however, have remained elusive. Here, we reveal that Rab5 regulates caspase-8-dependent signaling from integrins. Integrin ligation leads to Rab5 activation, association with integrins, and activation of Rac, in a caspase-8-dependent manner. Rab5 activation promotes colocalization and coprecipitation of integrins with caspase-8, concomitant with Rab5 recruitment to integrin-rich regions such as focal adhesions and membrane ruffles. Moreover, caspase-8 expression promotes Rab5-mediated internalization and the recycling of beta1 integrins, increasing cell migration independently of caspase catalytic activity. Conversely, Rab5 knockdown prevented caspase-8-mediated integrin signaling for Rac activation, cell migration, and apoptotic signaling, respectively. Similarly, Rab5 was critical for caspase-8-driven cell migration in vivo, because knockdown of Rab5 compromised the ability of caspase-8 to promote metastasis under nonapoptotic conditions. These studies identify Rab5 as a key integrator of caspase-8-mediated signal transduction downstream of integrins, regulating cell survival and migration in vivo and in vitro.
authors.affiliation: Department of Pathology, University of California San Diego, School of Medicine, La Jolla, CA 92093, USA.
authors.forename: Vicente A
authors.initials: VA
authors.lastname: Torres
authors.forename: Ainhoa
authors.initials: A
authors.lastname: Mielgo
authors.forename: Simone
authors.initials: S
authors.lastname: Barbero
authors.forename: Ruth
authors.initials: R
authors.lastname: Hsiao
authors.forename: John A
authors.initials: JA
authors.lastname: Wilkins
authors.forename: Dwayne G
authors.initials: DG
authors.lastname: Stupack
mesh_terms: D000818:Animals; D017209:Apoptosis; D053181:Caspase 8 / Q000378:metabolism*; D002448:Cell Adhesion; D045744:Cell Line, Tumor; D002465:Cell Movement; D002645:Chickens; D004789:Enzyme Activation; D006801:Humans; D019012:Integrin beta1 / Q000378:metabolism; D009362:Neoplasm Metastasis / Q000473:pathology*; D011485:Protein Binding; D021381:Protein Transport; D020696:rab5 GTP-Binding Proteins / Q000378:metabolism*
chemical_list: D019012:Integrin beta1; D053181:Caspase 8; D020696:rab5 GTP-Binding Proteins