The Effects Of GABA_B Receptor On PI3K/Akt Signaling Pathway In Breast Cancer Cells

Gamma-aminobutyric acid (GABA) is the major inhibitory neurotransmitter and it iswidely distributed in the mammalian central nervous system.However, GABA also exists invarious tissues outside the central nervous system. The receptors for GABA include twotypes,GABAAand GABACreceptors are ionotropic, GABA_Breceptor is metabotropic andbelongs to the G-protein coupled receptors (GPCR)family. Interestingly,as aneurotransmitter receptor, GABA_Breceptor can regulate a variety of tumor cellproliferation and migration, but the mechanism is not clear.PI3K/Akt signaling pathwayplays an important role in tumor development. PI3Ks(phosphatidylinositol3-kinases) aredivided into three categories (class Ⅰ, Ⅱ and Ⅲ) based on the structure and function.Class IAPI3Ks can be activated by tyrosine kinases, Class IB PI3Ks can be activated by Gprotein-coupled receptors, IA class PI3Ks include the catalytic subunit and differentregulatory subunits, p110α, p110β, p110γ, p110δ are catalytic subunits,p85α, p85β,p55γ areregulatory subunits. PI3K/Akt signaling pathway can promote cell growth, proliferation andsurvival, which is abnormally activated in tumor cells. It has been revealed that someGPCR can activate PI3K/Akt signaling pathway, but there is no report regarding theregulation of PI3K/Akt signaling pathway by GABA_Breceptor in tumor cells.In this study, activation of PI3K/Akt pathway inuced by GABA_Breceptor in humanbreast cancer cell lines MCF-7and MDA-MB-231was investigated. GABA_Breceptorspecific allosteric modulator CGP7930was used to treat breast cancer cells for a short time,and the result showed that Akt was transiently activated by GABA_Breceptors. Aktphosphorylation reached the highest level at the time point of30minutes,and thendecreased gradually.However,whether GABA_Breceptor can directly through PI3Kscatalytic subunit p110α or p110γ work or through transactivion of RTK and then activateAkt by p110α, p110β, p110δ is not clear, To exam whether p110α is involved in the activation of Akt induced by GABA_Breceptor, stable breast cancer cell lines expressingp110α were established. In the three cell lines, high expression p110α, silent expressionp110α and normal expression p110α, I use CGP7930treatment with breast cancer cells in ashort time. I found that as the increased expression levels of p110α,Akt phosphorylationlevels gradually increased, at the same time, I use MTT method and Transwell to detect cellproliferation and migration. Baclofen for the proliferation of MCF-7cells had nosignificant inhibited，But can be significantly inhibited MDA-MB-231cell proliferation.However, high concentrations of CGP7930have toxic effects on cells, the effect on cellproliferation is caused by its toxic effect on the GABA_Breceptor, or due to the drugs affectthe downstream signaling molecules are not very clear. As for the migration of the twocells,Baclofen can increase the migration of MDA-MB-231, The results provided somebasis for depth study of GABA_Breceptor activation of Akt by coupling p110α molecularmechanisms of some research basis. which can provides a new theoretical basis and modelfor GABA_BR-p110-conjugated anti-tumor drug screening.