title: The chemokine CXCL12 promotes survival of postmitotic neurons by regulating Rb protein.
abstract: Postmitotic neurons need to keep their cell cycle under control to survive and maintain a differentiated state. This study aims to test the hypothesis that the chemokine CXCL12 regulates neuronal survival and differentiation by promoting Rb function, as suggested by previous studies showing that CXCL12 protects neurons from apoptosis induced by Rb loss. To this end, the effect of CXCL12 on Rb expression and transcriptional activity and the role of Rb in CXCL12-induced neuronal survival were studied. CXCL12 increases Rb protein and RNA levels in rat cortical neurons. The chemokine also stimulates an exogenous Rb promoter expressed in these neurons and counteracts the inhibition of the Rb promoter induced by E2F1 overexpression. Furthermore CXCL12 stimulates Rb activity as a transcription repressor. The effects of CXCL12 are mediated by its specific receptor CXCR4, and do not require the presence of glia. Finally, shRNA studies show that Rb expression is crucial to the neuroprotective activity of CXCL12 as indicated by NMDA-neurotoxicity assays. These findings suggest that proper CXCR4 stimulation in the mature CNS can prevent impairment of the Rb-E2F pathway and support neuronal survival. This is important to maintain CNS integrity in physiological conditions and prevent neuronal injury and loss typical of many neurodegenerative and neuroinflammatory conditions.
authors.affiliation: Department of Pharmacology and Physiology, Drexel University College of Medicine, 245 North 15th Street, Philadelphia, PA 19102, USA.
authors.forename: M Z
authors.initials: MZ
authors.lastname: Khan
authors.forename: R
authors.initials: R
authors.lastname: Brandimarti
authors.forename: S
authors.initials: S
authors.lastname: Shimizu
authors.forename: J
authors.initials: J
authors.lastname: Nicolai
authors.forename: E
authors.initials: E
authors.lastname: Crowe
authors.forename: O
authors.initials: O
authors.lastname: Meucci
mesh_terms: D000818:Animals; D002453:Cell Cycle / Q000502:physiology*; D002454:Cell Differentiation / Q000502:physiology; D002470:Cell Survival / Q000502:physiology*; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000502:physiology; D054377:Chemokine CXCL12 / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D020868:Gene Silencing; D016202:N-Methylaspartate / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D011401:Promoter Regions, Genetic; D051381:Rats; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D016160:Retinoblastoma Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D054377:Chemokine CXCL12; C486264:Cxcr4 protein, rat; D019718:Receptors, CXCR4; D011993:Recombinant Fusion Proteins; D016160:Retinoblastoma Protein; D016202:N-Methylaspartate