RESUMO
The broad tissue distribution and evolutionary conservation of the glycosylphosphatidylinositol (GPI)-anchored prion protein (PrP, also known as PRNP) suggests that it plays a role in cellular homeostasis. Given that integrin adhesion determines cell behavior, the proposed role of PrP in cell adhesion might underlie the various in vitro and in vivo effects associated with PrP loss-of-function, including the immune phenotypes described in PrP(-/-) mice. Here, we investigated the role of PrP in the adhesion and (transendothelial) migration of human (pro)monocytes. We found that PrP regulates ß1-integrin-mediated adhesion of monocytes. Additionally, PrP controls the cell morphology and migratory behavior of monocytes: PrP-silenced cells show deficient uropod formation on immobilized VCAM and display bleb-like protrusions on the endothelium. Our data further show that PrP regulates ligand-induced integrin activation. Finally, we found that PrP controls the activation of several proteins involved in cell adhesion and migration, including RhoA and its effector cofilin, as well as proteins of the ERM family. We propose that PrP modulates ß1 integrin adhesion and migration of monocytes through RhoA-induced actin remodeling mediated by cofilin, and through the regulation of ERM-mediated membrane-cytoskeleton linkage.
Assuntos
Adesão Celular/genética , Integrina beta1/genética , Príons/genética , Proteína rhoA de Ligação ao GTP/metabolismo , Actinas , Animais , Movimento Celular/genética , Cofilina 1/genética , Citoesqueleto/genética , Citoesqueleto/metabolismo , Humanos , Integrina beta1/metabolismo , Camundongos , Proteínas dos Microfilamentos , Monócitos/metabolismo , Proteínas Priônicas , Príons/metabolismo , Transdução de Sinais , Proteína rhoA de Ligação ao GTP/genéticaRESUMO
Leukocyte traffic out of the blood stream is crucial for an adequate immune response. Leukocyte extravasation is critically dependent on the binding of leukocyte integrins to their endothelial counterreceptors. This interaction enables the firm adhesion of leukocytes to the luminal side of the vascular wall and allows for leukocyte polarization, crawling and diapedesis. Leukocyte adhesion, polarization and migration requires the orchestrated regulation of integrin adhesion/de-adhesion dynamics and actin cytoskeleton rearrangements. Adhesion strength depends on conformational changes of integrin molecules (affinity) as well as the number of integrin molecules engaged at adhesion sites (valency). These two processes can be independently regulated and several molecules modulate either one or both processes. Cholesterol-rich membrane domains (lipid rafts) participate in integrin regulation and play an important role in leukocyte adhesion, polarization and motility. In particular, lipid raft-resident glycosyl-phosphatidyl-inositol-anchored proteins (GPI-APs) have been reported to regulate leukocyte adhesion, polarization and motility in both integrin-dependent and independent manners. Here, we present our recent discovery concerning the novel role of the GPI-AP prion protein (PrP) in the regulation of ß1 integrin-mediated monocyte adhesion, migration and shape polarization in the context of existing literature on GPI-AP-dependent regulation of integrins.