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Heat shock protein 90? (HSP90?), a substrate and chaperone of DNA-PK necessary for the apoptotic response.

ABSTRACT: The "apoptotic ring" is characterized by the phosphorylation of histone H2AX at serine 139 (?-H2AX) by DNA-dependent protein kinase (DNA-PK). The ?-H2AX apoptotic ring differs from the nuclear foci patterns observed in response to DNA-damaging agents. It contains phosphorylated DNA damage response proteins including activated Chk2, activated ATM, and activated DNA-PK itself but lacks MDC1 and 53BP1, which are required to initiate DNA repair. Because DNA-PK can phosphorylate heat shock protein 90? (HSP90?) in biochemical assays, we investigated whether HSP90? is involved in the apoptotic ring. Here we show that HSP90? is phosphorylated by DNA-PK on threonines 5 and 7 early during apoptosis and that both phosphorylated HSP90? and DNA-PK colocalize in the apoptotic ring. We also show that DNA-PK is a client of HSP90? and that HSP90? is required for full DNA-PK activation, ?-H2AX formation, DNA fragmentation, and apoptotic body formation. In contrast, HSP90 inhibition by geldanamycin markedly enhances TRAIL-induced DNA-PK and H2AX activation. Together, our results reveal that HSP90? is a substrate and chaperone of DNA-PK in the apoptotic response. The response of phosphorylated HSP90? to TRAIL and its localization to the ?-H2AX ring represent epigenetic features of apoptosis that offer insights for studying and monitoring nuclear apoptosis.

SUBMITTER: Solier S

PROVIDER: S-EPMC3420188 | biostudies-literature | 2012 Aug

REPOSITORIES: biostudies-literature

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Heat shock protein 90α (HSP90α), a substrate and chaperone of DNA-PK necessary for the apoptotic response.

Solier Stéphanie S Kohn Kurt W KW Scroggins Bradley B Xu Wanping W Trepel Jane J Neckers Leonard L Pommier Yves Y

Proceedings of the National Academy of Sciences of the United States of America 20120702 32

The "apoptotic ring" is characterized by the phosphorylation of histone H2AX at serine 139 (γ-H2AX) by DNA-dependent protein kinase (DNA-PK). The γ-H2AX apoptotic ring differs from the nuclear foci patterns observed in response to DNA-damaging agents. It contains phosphorylated DNA damage response proteins including activated Chk2, activated ATM, and activated DNA-PK itself but lacks MDC1 and 53BP1, which are required to initiate DNA repair. Because DNA-PK can phosphorylate heat shock protein 90 ...[more]

PMID: 22753480

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Project description:BackgroundHeat shock proteins (HSPs) are present throughout the brain. They function as molecular chaperones, meaning they help with the folding and unfolding of large protein complexes. These chaperones are vital in the development of neuropathological conditions such as Alzheimer's disease and Lewy body disease, with HSP90, a specific subtype of HSP, playing a key role. Many studies have shown that drugs that inhibit HSP90 activity have beneficial effects in the neurodegenerative diseases. Therefore, HSP90 PET imaging ligand can be used effectively to study HSP90 in neurodegenerative diseases. Among four HSP90 isoforms, two cytosolic isoforms (HSP90α and HSP90β) thought to be involved in the structural homeostasis of the proteins related to the neurodegenerative diseases. Currently, no useful PET imaging ligands selectively targeting the two cytosolic isoforms of HSP90 have been available yet.ResultsIn this study, we developed a novel positron emission tomography (PET) imaging ligand, [11C]BIIB021, by 11C-radiolabeling (a positron emitter with a half-life of 20.4 min) 6-Chloro-9-[(4-methoxy-3,5-dimethylpyridin-2-yl)methyl]-9H-purin-2-amine (BIIB021), an inhibitor with a high affinity for and selectivity to HSP90α and HSP90β. [11C]BIIB021 was synthesized with a high yield, molar activity and radiochemical purity. [11C]BIIB021 showed a high binding affinity for rat brain homogenate as well as human recombinant HSP90α and HSP90β proteins. Radioactivity was well detected in the rat brain (SUV 1.4). It showed clear specific binding in PET imaging of healthy rats and autoradiography of healthy rat and human brain sections. Radiometabolite was detected in the brain, however, total distribution volume was well quantified using dual-input graphical model. Inhibition of p-glycoprotein increased brain radioactivity concentrations. However, total distribution volume values with and without p-glycoprotein inhibition were nearly the same.ConclusionsWe have developed a new PET imaging agent, [11C]BIIB021, specifically targeting HSP90α/β. We have been successful in synthesizing [11C]BIIB021 and in vitro and in vivo imaging HSP90α/β. However, the quantification of HSP90α/β is complicated by the presence of radiometabolites in the brain and the potential to be a substrate for p-glycoprotein. Further efforts are needed to develop radioligand suitable for imaging of HSP90α/β.

Dataset Information

Heat shock protein 90? (HSP90?), a substrate and chaperone of DNA-PK necessary for the apoptotic response.

Publications

Heat shock protein 90α (HSP90α), a substrate and chaperone of DNA-PK necessary for the apoptotic response.

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