title: Thrombin promotes the expression of Ccnd1 gene in RPE cells through the activation of converging signaling pathways.
abstract: The breakdown of the blood-retina barrier exposes retinal pigment epithelium (RPE) to serum components, thrombin among them. In addition to coagulation, thrombin acting through Protease-Activated Receptors (PARs 1-4) participates in a number of processes including cell proliferation, transformation, and migration. The purpose of this study was to identify interacting signaling pathways by which the activation of PAR1 by thrombin triggers cyclin D1 gene (Ccnd1) expression and the proliferation of RPE cells, characteristic of proliferative vitreoretinopathy (PVR). Our results demonstrate that thrombin induces the expression of the c-fos gene (c-fos), the activation of the (fos/jun) AP-1 site and the expression of Ccnd1, in precise correlation with the activation of CREB. Although the expression of both, c-fos and Ccnd1 requires the activation of conventional PKC isoforms and PI3K, downstream signaling from PI3K differs for both genes. Whereas the expression of c-fos requires PI3K-induced PDK1/Akt activity, that of Ccnd1 is mediated by PDK1-independent PKCζ signaling. Additionally, CREB activation may contribute to the induction of Ccnd1 expression through binding to the Ca/CRE element in the Ccnd1 gene promoter. Since cyclin D1 is a key regulator of cell cycle G1/S phase progression essential for proliferation, these findings further strengthen the critical involvement of thrombin in the development of proliferative retinopathies and may provide pharmacologic targets for the prevention or treatment of these diseases.
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D. F., Mexico.
authors.forename: Irene
authors.initials: I
authors.lastname: Lee-Rivera
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D. F., Mexico.
authors.forename: Edith
authors.initials: E
authors.lastname: López
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D. F., Mexico.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Parrales
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D. F., Mexico.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Alvarez-Arce
authors.affiliation: Instituto de Fisiología Celular, Universidad Nacional Autónoma de México, México, D. F., Mexico. Electronic address: acolome@ifc.unam.mx.
authors.forename: Ana María
authors.initials: AM
authors.lastname: López-Colomé
mesh_terms: D001813:Blood-Retinal Barrier / Q000187:drug effects; D015153:Blotting, Western; D049109:Cell Proliferation; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000096:biosynthesis / Q000235:genetics*; D006490:Hemostatics / Q000494:pharmacology; D006801:Humans; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000235:genetics*; D055213:Retinal Pigment Epithelium / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction; D013917:Thrombin / Q000494:pharmacology; D015854:Up-Regulation; D018630:Vitreoretinopathy, Proliferative / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism
chemical_list: C530104:CCND1 protein, human; D006490:Hemostatics; D012333:RNA, Messenger; D019938:Cyclin D1; D013917:Thrombin
keywords: Cell-cycle regulation; Proliferation; Retina; Signal transduction; c-Fos