Abstract
15-deoxy-Δ12,14-prostaglandin J2 (15d-PGJ2) is one of factors contributed to the neurotoxicity of amyloid β (Aβ), a causative protein of Alzheimer's disease. Type 2 receptor for prostaglandin D2 (DP2) and peroxysome-proliferator activated receptorγ (PPARγ) are identified as the membrane receptor and the nuclear receptor for 15d-PGJ2, respectively. Previously, we reported that the cytotoxicity of 15d-PGJ2 was independent of DP2 and PPARγ, and suggested that 15d-PGJ2 induced apoptosis through the novel specific binding sites of 15d-PGJ2 different from DP2 and PPARγ. To relate the cytotoxicity of 15d-PGJ2 to amyloidoses, we performed binding assay [3H]15d-PGJ2 and specified targets for 15d-PGJ2 associated with cytotoxicity. In the various cell lines, there was a close correlation between the susceptibilities to 15d-PGJ2 and fibrillar Aβ. Specific binding sites of [3H]15d-PGJ2 were detected in rat cortical neurons and human bronchial smooth muscle cells. When the binding assay was performed in subcellular fractions of neurons, the specific binding sites of [3H]15d-PGJ2 were detected in plasma membrane, nuclear and cytosol, but not in microsome. A proteomic approach was used to identify protein targets for 15d-PGJ2 in the plasma membrane. By using biotinylated 15d-PGJ2, eleven proteins were identified as biotin-positive spots and classified into three different functional proteins: glycolytic enzymes (Enolase2, pyruvate kinase M1 (PKM1) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH)), molecular chaperones (heat shock protein 8 and T-complex protein 1 subunit α), cytoskeletal proteins (Actin β, F-actin-capping protein, Tubulin β and Internexin α). GAPDH, PKM1 and Tubulin β are Aβ-interacting proteins. Thus, the present study suggested that 15d-PGJ2 plays an important role in amyloidoses not only in the central nervous system but also in the peripheral tissues.
Highlights
Eicosanoids are divided into two groups, according to their mechanism of action: the conventional eicosanoids, e.g., prostaglandin D2 (PGD2) and the cyclopentenone-type PGs, e.g., 15-deoxyD12,14-prostaglandin J2 (PGJ2) (15d-PGJ2)
bronchial smooth muscle cells (BSMC), hepatocytes and dermal fibroblasts were exposed to fAb or vehicle for 48 h, and their viability was quantified by the MTT-reducing activity
The specific binding sites of [3H]15d-PGJ2 were detected in the neuronal subcellular fractions of nuclear, cytosol and plasma membrane, but not in the microsomal fraction. 15dPGJ2 binds to the nuclear receptor, peroxysome-proliferator activated receptorc (PPARc) [9] and the cytosolic protein, Ras [23]
Summary
Eicosanoids are divided into two groups, according to their mechanism of action: the conventional eicosanoids, e.g., prostaglandin D2 (PGD2) and the cyclopentenone-type PGs, e.g., 15-deoxyD12,14-PGJ2 (15d-PGJ2). Amyloid b (Ab) generated PGD2 from cortical neurons before inflammation [3]. The toxicity of PGD2 via its GTP-binding protein-coupled PGD2 receptors does not occur. Little mRNA of the PGD2 receptor is observed in the rat [5] and human [6] cerebral cortex. Few binding sites of [3H]PGD2 were detected in the plasma membranes from rat cortices [4]. The extent of specific [3H]PGD2 in total biding is much lower (30–40%) than that of [3H]15d-PGJ2 (.80%), binding sites of PGD2 have been reported in synaptosomes of rat [7] and human brains [6]. PGD2 appeared to mediate inflammation via 15d-PGJ2 in the amyloidoses
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