The Role And Mechanism Of FKBP51-CREB Signaling Pathway In Corticosterone Mediated Anxiety-like Behavior

Background:Anxiety disorders are common and disabling conditions and mostly affected by multiple factors such as genetic programs and environmental signals.Anxiety disorders constitute the largest group of mental disorders and make a major contribution to the global burden of mental disease.Numerous studies have demonstrated that stress susceptible gene FKBP5 and FKBP5 coded protein FKBP51 were strongly linked to the stress related disorders like anxiety and depression,and contributed to many biological processes including neuroimmune,neuroendocrine and transcriptional regulation.On the other hand,as an important nuclear transcriptional factor,CREB played key roles in regulating multiple stress related signaling pathway that contributed to the pathophysiology of anxiety.However,the effects of FKBP51 on CREB and its downstream signaling,as well as the animal anxiety-like behavior in response to CORT stimulation has not been reported so far.Materials and Methods:We treated the cultured primary cortical neurons from rat embryos and FKBP5 knock out mice with different concentrations of CORT in several time points,with co-immunoprecipitation,immunofluorescence staining,western blot and animal behavioral experiments applied,we explored whether FKBP51 regulate the transcriptional factor CREB and its downstream signaling,as well as the animal anxiety-like behavior in response to CORT stimulation.Results:We demonstrated in vitro and in vivo that:(1)FKBP51/CREB protein complex formation and CREB nuclear translocation were significantly regulated by CORT in a time-and dose-dependent manner.Acute(30 min or 24 h)treatment with CORT led to a significant increase of FKBP51/CREB protein complex formation,as well as the nuclear translocation of CREB;while chronic high dose of CORT(1 ?M CORT for 3 consecutive days)showed an opposite decrease of the FKBP51/CREB protein complex formation and the nuclear translocation of CREB.(2)Next,we identified that FKBP51 is the key factor for the protein complex formation and the CREB nuclear translocation in response to CORT stimulation by using FKBP5 knock out mice.The prominent upregulation of FKBP51/CREB protein complex formation as well as the nuclear translocation of CREB induced by intra-peritoneal injection of 40 mg/kg CORT for 3 h in the prefrontal cortex were observed in wild type mice,which was significantly reversed by FKBP5 knock out.In addition,FKBP5 knock out also sensitized the molecular responses of treatment with 40 mg/kg CORT for 7 consecutive days by down-regulating the FKBP51/CREB protein complex formation as well as the nuclear translocation of CREB.(3)Furthermore,high dose CORT induced a significant reduction of expressions of the CREB mediated downstream proteins that related to neuroimmune in the FKBP5 knock out mice compared with the wild type mice,such as BDNF,TGF?,Arg1 and IL10.(4)Finally,we applied EPM test and MB test to study the effects of FKBP51 and CREB signaling on the animal anxiety-like behavior in response to CORT stimulation.We found that:After 3 hours of a single injection with CORT(4 mg/kg,40 mg/kg),the FKBP5 knock out mice spent less time on the open arm during the EPM test compared with the wild type.Similarly,7 consecutive days of CORT(4 mg/kg,40 mg/kg)treatment also induced significant reductions of the time spent and distance traveled on the open arm in the EPM test,as well as the number of buried marbles in the MB test(40 mg/kg)in the the FKBP5 knock out mice,but not the wild type;furthermore,knocking out of the FKBP5 gene significantly sensitized the animal responses to the 40 mg/kg CORT treatment,significant anxity-like behaviors in the EPM and MB tests were observed in the FKBP5 knock out mice compared with the wild type.Conclusion:We identified a novel signaling pathway involving the nuclear translocation of the transcriptional factor CREB and its downstream neuroimmune related protein expressions such as BDNF?TGF??Argl and IL10,which is regulated by the stress-related protein FKBP51 via formatting an FKBP51/CREB preotein complex during the CORT stimulation.This signaling pathway play a key role in the regulation of animal anxiety-like behaviors.This study provides crucial insight into the cellular responses and molecular mechanisms in FKBP51 induced transcriptional regulation and neuroimmunity during stress hormone CORT stimulation.The results form this study may offer the potential targets for the diagnosis and treatment of anxiety disorders to develop novel anxiolytic drugs,and contribute to the understanding of the pathophysiology of anxiety and other stress-related psychiatric disorders.