title: Thrombin activation of PI3K/PDK1/Akt signaling promotes cyclin D1 upregulation and RPE cell proliferation.
abstract: The retinal pigment epithelium (RPE) plays an essential role in the survival and function of the neural retina. RPE uncontrolled proliferation leads to the development of proliferative ocular pathologies, among which proliferative vitreoretinopathy (PVR) is the main cause of retinal surgery failure. Upon the breakdown of the BRB due to trauma or metabolic imbalance the contact of RPE with serum-contained thrombin has been shown to stimulate the proliferation of otherwise quiescent RPE cells. Although the molecular mechanisms involved in this effect are still undetermined, thrombin proteolytic activation of protease-activated G protein coupled receptor-1 (PAR-1) activates PI3K and Akt, known to play an essential role in proliferation. The present study demonstrates that: 1) thrombin stimulates Ser 473 Akt phosphorylation without affecting Thr 308 basal phosphorylation in RPE cells; 2) thrombin-induced Akt stimulation promotes cyclin D1 accumulation through the phosphorylation/ inhibition of GSK-3β, thus preventing Thr 286 cyclin D1 phosphorylation, nuclear export and degradation; 3) Akt signaling requires the upstream activation of PI3K and PLC. Since the pharmacological inhibition of these pathways or the silencing of cyclin expression prevent thrombin-induced RPE cell proliferation, these results contribute relevant evidence for establishing the mechanism involved in the development of proliferative eye diseases.
authors: Universidad Nacional Autonoma de Mexico, Ciudad Universitaria, Mexico.
authors: A
authors: A
authors: Parrales
authors: E
authors: E
authors: López
authors: A M
authors: AM
authors: López-Colomé
mesh_terms: D064413:3-Phosphoinositide-Dependent Protein Kinases; D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D019938:Cyclin D1 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D051058:Oncogene Protein v-akt / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D020318:Rats, Long-Evans; D055213:Retinal Pigment Epithelium / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D015398:Signal Transduction / Q000187:drug effects / Q000235:genetics / Q000502:physiology; D013917:Thrombin / Q000378:metabolism / Q000494:pharmacology* / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000235:genetics
chemical_list: D064413:3-Phosphoinositide-Dependent Protein Kinases; D019938:Cyclin D1; D051058:Oncogene Protein v-akt; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D034741:RNA, Small Interfering; D013917:Thrombin; C578579:Pdpk1 protein, rat