title: Implication of PI3K-dependent HSP27 and p53 expression in mild heat shock-triggered switch of metabolic stress-induced necrosis to apoptosis in A549 cells.
abstract: Previously, we showed that mild heat shock modulates patterns of cell death in response to glucose deprivation (GD), a common characteristic of the tumor microenvironment, by switching necrosis to apoptosis through ERK-dependent suppression of reactive oxygen species production in A549 cells. In the present study, we further examined the molecular mechanism underlying mild heat shock-induced necrosis-to-apoptosis switch. We examined the possible implication of p53 and heat shock proteins (HSPs) in the mechanism. Inhibition of p53 by pifithrin-alpha or p53 siRNA markedly suppressed apoptosis induced by heat shock/GD. On the other hand, silencing of HSP27, but not of HSP70, reversed heat shock/GD-induced apoptosis to necrosis, and HSP27 overexpression suppressed GD-induced necrosis. We further demonstrate that mild heat shock activated AKT and ERK1/2 through phosphorylation. Prevention of PI3K by LY294002 blocked heat shock/GD-induced apoptosis without reversing the cell death mode to necrosis, while inhibition of MEK1/2 by U0126 reversed heat shock/GD-induced apoptosis to necrosis, indicating a different role(s) of PI3K and ERK1/2 in heat shock/GD-induced cell death mode determination. We also found that mild heat shock increased HSP27 and p53 protein levels dependent on PI3K and suppressed the GD-induced increase in RIPA-insoluble HSP27 and p53 protein levels dependent on PI3K and ERK1/2. In conclusion, these results indicate that PI3K-dependent HSP27 and p53 induction and PI3K- and ERK1/2-dependent inhibition of the GD-induced increase in RIPA-insoluble HSP27 and p53 protein levels by heat play a key role(s) in heat shock-mediated switch of GD-induced necrosis to apoptosis.
authors.affiliation: Research Center for Resistant Cells, Department of Pathology, College of Medicine, Chosun University, Gwangju 501-759, Korea.
authors.forename: Sung-Chul
authors.initials: SC
authors.lastname: Lim
authors.forename: Hong-Quan
authors.initials: HQ
authors.lastname: Duong
authors.forename: Jeong Eun
authors.initials: JE
authors.lastname: Choi
authors.forename: Keshab Raj
authors.initials: KR
authors.lastname: Parajuli
authors.forename: Ho Sung
authors.initials: HS
authors.lastname: Kang
authors.forename: Song Iy
authors.initials: SI
authors.lastname: Han
mesh_terms: D017209:Apoptosis / Q000502:physiology*; D002460:Cell Line; D005947:Glucose / Q000172:deficiency; D006801:Humans; D015151:Immunoblotting; D047908:Intracellular Signaling Peptides and Proteins; D009336:Necrosis / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis*; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological / Q000502:physiology; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis*; D000099190:MAP-Kinase-Activated Kinase 2
chemical_list: D005947:Glucose; D047908:Intracellular Signaling Peptides and Proteins; D019869:Phosphatidylinositol 3-Kinases; D017346:Protein Serine-Threonine Kinases; D016159:Tumor Suppressor Protein p53; D000099190:MAP-Kinase-Activated Kinase 2