The Effect Of Early Growth Response 1 On The Level Of A?40

BackgroundThe gene of Early Growth Response 1, named for its quickly expression, exist in various kinds of animals and human cells. It belongs to immediate early gene family, more than 30 members of the family contain the zinc-binding domain and there genetic structure are highly homologous and conservative regions. The signal pathway of EGR1 is a highly complex process that is involved in a wide variety of reaction factors and essential cellular processes in living cells. EGR1 having various biological function that might be related to cell growth regulation, celluar material transportation and other physiology activity which play an important role in providing nutrition for cells. Studies have shown that EGR1 not only aid in improving long-term memory and learning-memory abilities, but also accelerate the processes of aging with the help of p53 gene and participate in the pathogenesis of Alzheimer's disease. Numerous theories exist regarding the mechanism of Alzheimer's disease, that mainly include the ?-amyloid cascade hypothesis and Tau hypothesis,futhermore, there are also other theories such as the vascular nerve hypothesis and the cholinergic hypothesis and so on. The ?-amyloid cascade hypothesis and Tau hypothesis have attracted extensive attentions and studies because of closing association with histopathology. A?, which is the small molecular peptides posed by 39-43 amino acid protein.Normally, the ?-secretase activity on APP can't generate A? peptides, but generate a neuroprotection peptide which is named s APP?. Under some condition, ?-secretase will activity on APP to generate APP-?CTF and s APP? in the pathway of pathologic metabolism, and ?-secretase will activity on the APP-?CTF then to generate A? peptides. There are three degradation pathways of A? in the brain: phagocytic of gliocyte hyperplasia in the brain; degradation in peripheral blood circulation; through out the blood-brain barrier. The reason of the A? deposition is the balance of A? formation and elimination overcharging. Enzymes called ?-secretase and ?-secretase play a critical role in the process of abnormal metabolism of amyloid precursor protein. The tetrameric structure of ?-secretase consists of four subunits: PS1, APH1, PSEN2, NCT, the PS1 is the catalytic subunit which is essential in reaction. Recent some studies reveal that EGR1 has a relationship with the ?-amyloid cascade hypothesis and Tau hypothesis in the mechanism of Alzheimer's disease. ObjectiveTo research the effect of Early Growth Response 1 on the level of Beta amyloid protein40 expression in vitro. MethodsTo construct overexpression plasmid of CMV-EGFP-EGR1-Kanamycin and transfect U87 MG cells as the experimental group; the control group cells were transfected by the plasmids of CMV-EGFP-Kanamycin. The fluorescence microscopy was used to observe transfection efficiency of plasmids after 6 hours. The m RNA expression of EGR1 was detected by q RT-PCR. To collected culture media and detect A?40 with ELISA technology; to extract the total proteins and measure BACE1 and PS1 in Western blot assay. ResultsThe experimental group and the control group were transfected by plasmids successfully. The result of q RT-PCR revealed that in the experimental group the expression of m RNA increased significantly, compared with the control group(t=18.755; P<0.001). Average concetration of A?40 was significantly higher in the experimental group(0.365mg/L)than the control group(0.191mg/L)(t=-22.839; P<0.001). There was a significant increase of BACE1 protein level in the experimental group than the control group(t=212.781; P<0.001); there was no significant difference in PS1 Protein level between the two groups(t=0.91; P=0.367). Conclusion1. Over-expression of EGR1 can increase the protein of A?40 in vitro, that may associate with up-regulated the expression of BACE1 protein;2. Over-expression of EGR1 may not up-regulate the expression of PS1 protein in vitro, but the reason of A?40 was significantly higher in the experimental group cannot rule out the effect of ?-secretase and Tau to A?.