TRKB RECEPTOR MEDIATES BDNF PROTECTION OF ASTROCYTES

J. SABA; D. RAMIREZ; J. TURATI; L. CARNIGLIA; D. DURAND; M. LASAGA; C. CARUSO

Paris

Congreso; 26th ISN-ESN Meeting; 2017

ISN (International Society of Neurochemistry)

Brain-derived neurotrophic factor (BDNF) is a neurotrophin that promotes neuronal survival and inhibits apoptosis. Since little is known about BDNF action on astrocytes, we examine the effect of BDNF on astrocyte viability and the involvement of TrkB isoforms in this action. BDNF treatment for 24 h increase astrocyte viability by reducing apoptosis induced by serum deprivation (SD). BDNF also reduces p53 and active caspase-3 expression induced by SD. Next, we determined TrkB participation by using the selective and potent TrkB antagonist ANA-12 which binds extracellular domain of TrkB thereby antagonizing all TrkB and using K252a which is a potent tyrosine kinase inhibitor of Trks receptors. The presence of both inhibitors blocked the decrease in cell death induced by BDNF, suggesting that TrkB is mediating the protection of astrocytes induced by BDNF. In order to identify which receptor was involved in BDNF protective effect we analyze the mRNA by RT-qPCR which shows that both isoforms TrkB-FL and TrkB-T1 are expressed in astrocytes although TrkB-FL is expressed at lower levels than TrkB-T1. Western Blot of TrkB showed that TrkB-T1 protein levels were high in astrocytes and in the hypothalamus whereas TrkB-FL protein was only detected in the hypothalamus. Thus, although astrocytes expressed mRNA for TrkB-FL this is not translated to detectable protein levels in astrocytes. However, BDNF induced ERK and Akt activation in astrocytes and blocking these pathways abolished BDNF protection on apoptosis induced by SD. These results indicate that TrkB mediates BDNF antiapoptotic effect on astrocytes. Since astrocytes are key players in neuroprotection, understanding BDNF protective mechanisms in these cells may help develop new strategies for treating neurodegeneration.