TY - JOUR T1 - Astrogliosis Induced by Brain Injury Is Regulated by Sema4B Phosphorylation JF - eneuro JO - eneuro DO - 10.1523/ENEURO.0078-14.2015 VL - 2 IS - 3 SP - ENEURO.0078-14.2015 AU - Liat Ben-Gigi AU - Sahar Sweetat AU - Elazar Besser AU - Yakov Fellig AU - Thorsten Wiederhold AU - Roberto D. Polakiewicz AU - Oded Behar Y1 - 2015/05/01 UR - http://www.eneuro.org/content/2/3/ENEURO.0078-14.2015.abstract N2 - Injury to the CNS induces astrogliosis, an astrocyte-mediated response that has both beneficial and detrimental impacts on surrounding neural and non-neural cells. The precise signaling events underlying astrogliosis are not fully characterized. Here, we show that astrocyte activation was altered and proliferation was reduced in Semaphorin 4B (Sema4B)-deficient mice following injury. Proliferation of cultured Sema4B−/− astrocytes was also significantly reduced. In contrast to its expected role as a ligand, the Sema4B ectodomain was not able to rescue Sema4B−/− astrocyte proliferation but instead acted as an antagonist against Sema4B+/− astrocytes. Furthermore, the effects of Sema4B on astrocyte proliferation were dependent on phosphorylation of the intracellular domain at Ser825. Our results suggest that Sema4B functions as an astrocyte receptor, defining a novel signaling pathway that regulates astrogliosis after CNS injury. ER -