ABSTRACT
OBJECTIVE: To explore the mechanism of ubiquitin-proteasome pathway(UPP) in the degradation of hyperphosphorylated tau protein in aluminum-induced mouse neuroblastoma N2 a cells. METHODS: N2 a cells in logarithmic growth period were randomly divided into control group and MG132 group. Cells in control group were exposed to concentrations of 0 or 1 mmol/L aluminum chloride for 24 hours. Cells in MG132 group were pretreated with MG132 at a concentration of 5 μmol/L for 6 hours, then exposed to concentrations of 0 or 1 mmol/L aluminum chloride for 24 hours. After exposure, the cells were collected. Western blotting was used to detect the relative expression of tau-5, P-tau181, P-tau231, P-tau262, P-tau396, heat shock protein 70(Hsp70) and carboxyl terminus of the Hsp70-interacting protein(CHIP). The ubiquitin relative expression was detected by enzyme-linked immunosorbent assay. RESULTS: The results of factorial analysis showed that the relative expression of tau-5, P-tau231, P-tau262, P-tau396, CHIP, Hsp70 and ubiquitin in N2 a cells were statistically significant in the main effect and interaction effect of aluminum chloride and MG132 treatment(P<0.05). Both in the control group and MG132 group, the relative expression of tau-5, P-tau231, P-tau262, P-tau396, CHIP, Hsp70 and ubiquitin in N2 a cells exposed to 1 mmol/L aluminum chloride increased(P<0.05) when compared with the N2 a cells without exposed to aluminum chloride. No matter aluminum chloride exposed or not, the relative expression of tau-5, P-tau231, P-tau262, P-tau396, CHIP, Hsp70 and ubiquitin in N2 a cells of MG132 group was higher than that of control group(P<0.05). CONCLUSION: UPP is involved in the regulation of hyperphosphorylated tau protein by proteasome degradation in aluminum-induced N2 a cells. UPP mainly regulates P-tau231, P-tau262, and P-tau396 sites. CHIP and Hsp70 played an important role in the UPP pathway.
ABSTRACT
Carboxyl terminus of the HSP70-interacting protein (CHIP) is a co-chaperone of HSPs as well as an E3 ubiquitin ligase, and it is the connexin between heat shock proteins and ubiquitin-proteasome system. Recent research discovered that CHIP also possesses an intrinsic chaperone activity that enables it to recognize and bind nonnative proteins independently. CHIP regulates the HSPs expression and activity, and facilitates the client proteins ubiquitination and subsequent proteasome-dependent degradation. CHIP also inhibits apoptosis through MAPKs signaling pathways, and affects eNOS specific activity by means of the effects on Akt. Moreover, CHIP plays an important role in mitochondrial oxidative stress protection. With these above points, this paper reviews the function of CHIP in myocardial ischemia/reperfusion injury.
ABSTRACT
Objective To explore the influence of proteasome inhibitor, MG-132 (N-benz0y1oxycarbonyl(Z)-Leu-Leuleucina1) on the expressions of carboxyl terminus of the Hsc70-interacting protein (CHIP) and heat shock protein 70 (HSP70) in ischemia reperfusion (I/R) rats and investigate the underlying mechanism of myocardial protection by the inhibitor. Methods Totally 54 adult SD rats were randomly divided into 3 groups, sham group (n=6), I/R group (n=24) and treatment group (I/R+T, n=24). The later 2 groups were further equally divided into 3 subgroups according different time of reperfusion. Left anterior descending (LAD) coronary artery was ligated for 30 min and then released for 2 h or 24 h or 7 d in different subgroups. Five minutes before reperfusion, MG-132 at dose of 0.75 mg/kg was given intravenously in I/R+T group,but I/R group and sham group were given the same volume of normal saline. The levels of CHIP and HSP70 at mRNA and protein level were detected by real-time PCR and Western blotting respectively. The correlation between CHIP and HSP70 expression was analyzed. Results Compared with I/R groups, the mRNA levels of CHIP and HSP70 were significantly increased in I/R+T groups (P