Effect And Mechanism Of KCTD12 In Chronic Social Defeat Stress-induced Depression-like Behaviors Of Mice

Part I The role of KCTD12 in depression-like behavior in mice induced by chronic social defeat stressObjective: KCTD12(potassium channel tetramerization domain-containing 12)is a member of the KCTD family,which is an auxiliary subunit of the GABAB receptor.It has been reported that KCTD12 is involved in the regulation of mental disorders such as fear memory and bipolar disorder.However,the role of KCTD12 in the major depression disorder is not clear.Thus,we will clarify the effect of KCTD12 on depressive behavior induced by chronic social defeat stress in mice.Methods: the depressive behaviors of mice were induced by chronic social defeat stress(CSDS),then the social interaction test(SIT)and the sucrose preference test(SPT)were used to access the depressive behaviors;quantitative real-time PCR(q RT-PCR)was operated to determine the levels of KCTD12 m RNA in a series of brain areas;Western blotting(WB)was used to detect the protein expression;Immunofluorescence(IF)was used to detect the expression of KCTD12 in the cells;sh RNA-mediated RNA interference techniques were used to study the effects of KCTD12 knockdown in DG of hippocampus on depressive-like behavior in mice.Results:(1)After chronic social defeat stress,the susceptible mice displayed depressive behaviors,the ratio of social interaction and sucrose preference ratio were significantly reduced in the susceptible mice(p < 0.001).(2)Compared with control group,the gene expression of KCTD12 was not altered in the brain of the susceptible mice.(3)The KCTD12 protein level was obviously elevated in the DG of hippocampus in susceptible mice,but it was markedly decreased in the CA3 of hippocampus(p < 0.001;CA3: p < 0.05).(4)Tissue and cellular immunofluorescence showed that KCTD12 was located in both glial cells and neurons,and that in the DG of hippocampal was significantly higher in susceptible mice than that in normal controls.(5)The knockdown of KCTD12 of DG of hippocampal produced antidepressant-like effects(p < 0.001).Conclusion: Chronic social defeat stress can induce the depressive behaviors of mice,the protein expression of KCTD12 is obviously increased in the DG of hippocampus in susceptible mice,and the knockdown of KCTD12 of DG of hippocampal can recovery the depressive behaviors.Part II The mechanism of KCTD12 in depressive behavior of mice induced chronic social defeat stressObjective: KCTD12 binds to GB2 as a part of GABAB receptor,but it is not clear that the combination between KCTD12 and GB2 is changed and KCTD12 regulates the depressive behaviors through the GABAB receptor signaling pathway.Besides,fluoxetine has a wide range of targets and KCTD12 maybe one of them.Thus,we research the mechanism of KCTD12 in the chronic social defeat stress.Methods: Western blotting was performed to determine the key proteins in the GABAB receptor signaling pathway;The selective GABAB receptor antagonists and antidepressant drug were used to determine their effect on social interaction test(SIT)and tail suspension test(TST).Results:(1)The western blotting results showed that the protein level of GB2 was significantly elevated in the DG of hippocampus(p < 0.01).(2)The fluorescence results showed that the expression of KCTD12 and GB2 were both increased in DG of hippocampus.(3)Intraperitoneal injection of the selective GABABR antagonists increased the ratio of social interaction(p < 0.001)and decreased the immobility time of tail suspension test(p < 0.001).(4)Intraperitoneal injection of the selective GABABR antagonists reversed the protein level of KCTD12 and GB2 in DG of hippocampus in susceptible mice(KCTD12: p < 0.001;GB2: p < 0.01).(5)Intraperitoneal injection of fluoxetine produced antidepressant effects in mice in the social interaction test(p < 0.001)and tail suspension test(p < 0.001).(6)the protein level of KCTD12 and GB2 in DG of hippocampus in susceptible mice were reversed after intraperitoneal injection of fluoxetine(p < 0.001;GB2: p < 0.01).Conclusion: Compared with control group,the protein levels of GB2 and KCTD12 were significantly elevated in susceptible mice,suggesting that the GABAB receptor signaling pathway was upregulated in susceptible mice.The depressive behavior and the protein level of GB2 and KCTD12 were recovered in susceptible mice after intraperitoneal injection of selective GABABR antagonists or fluoxetine,which implied that KCTD12 was involved in GABAB receptor signaling pathway and KCTD12 was a potential target of fluoxetine.