Figure 3 | Scientific Reports

Figure 3

From: VRK3-mediated nuclear localization of HSP70 prevents glutamate excitotoxicity-induced apoptosis and Aβ accumulation via enhancement of ERK phosphatase VHR activity

Figure 3

Glutamate-induced ERK activation stimulates the expression of both HSP70 and VRK3 to suppress its sustained activity that causes cell death.

(a) The protein levels of HSP70 and VRK3 were positively correlated with ERK activity. (b) Blocking ERK phosphorylation using PD98059, a specific MEK/ERK inhibitor, delayed an increase in both HSP70 and VRK3 protein upon glutamate exposure. (c,d) Inhibition of ERK activation delayed mRNA expression of HSP70 (c) and VRK3 (d) following glutamate treatment. The mRNA levels of endogenous genes were detected by quantitative real-time PCR. Values are normalized to RPL32 and shown as mean ± s.d., n = 3. Student’s t-tests, **P < 0.01, ***P < 0.001. (e) Nuclear translocation of active ERK and increased levels of both endogenous HSP70 and VRK3 were observed in glutamate-treated SH-SY5Y cells. (f) HSP70-mediated downregulation of p-ERK prevented glutamate-induced apoptosis. White arrowheads highlight cleaved caspase-3-positive cells. Scale bar, 20 μm. (g) Glutamate-induced apoptosis was suppressed in HSP70-overexpressing SH-SY5Y cells. White arrows show HSP70-overexpressing cells. White arrowheads highlight cleaved caspase-3-positive cells. Scale bar, 20 μm.

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