Figure 10.

Inhibition of ERK MAPK pathway blocks HQ-induced Hsp27 phosphorylation and focal aggregates formation. A: Abrogation of HQ-induced Hsp27 phosphorylation by PD98059. Confluent serum-starved ARPE-19 cells were pretreated for one hour with 40 μmol/L of ERK inhibitor PD98059 (PD), and then exposed to 100 μmol/L HQ for five minutes. Total Hsp27, p-Hsp27, and GAPDH protein expression was evaluated by Western blot analysis. Top: Western blot from a representative experiment. Numbers on the left represent protein molecular mass in kilodaltons. p-Hsp27 protein expression was normalized to total Hsp27 protein. Bottom: Average densitometry results of three independent experiments run in duplicate. Data are expressed as percentage of control and are means ± SE. *P < 0.01 versus HQ alone; **P < 0.01 versus control. B: Decreased formation of F-actin aggregates showed by staining for F-actin in ARPE-19 cells pretreated for one hour with or without 40 μmol/L of PD and then exposed to 100 μmol/L HQ for six hours. Cells were stained with rhodamine-phalloidin and examined by confocal microscopy by using magnification ×40. Arrows show formation of focal aggregates. C: Quantification of F-acting aggregates from three independent experiments run in duplicate. Data are expressed as percentage of HQ-treated cells and are means ± SE. ***P < 0.001 versus HQ-treated cells.