4-Hydroxynonenal-modified amyloid-beta peptide inhibits the proteasome: possible importance in Alzheimer's disease

The amyloid β-peptide (Aβ) is a 4-kDa species derived from the amyloid precursor protein, which accumulates in the brains of patients with Alzheimer’s disease. Although we lack full understanding of the etiology and pathogenesis of selective neuron death, considerable data do imply roles for both the toxic Aβ and increased oxidative stress. Another significant observation is the accumulation of abnormal, ubiquitin-conjugated proteins in affected neurons, suggesting dysfunction of the proteasome proteolytic system in these cells. Recent reports have indicated that Aβ can bind and inhibit the proteasome, the major cytoslic protease for degrading damaged and ubiquitin-conjugated proteins. Earlier results from our laboratory showed that moderately oxidized proteins are preferentially recognized and degraded by the proteasome; however, severely oxidized proteins cannot be easily degraded and, instead, inhibit the proteasome. We hypothesized that oxidatively modified Aβ might have a stronger (or weaker) inhibitory effect on the proteasome than does native Aβ. We therefore also investigated the proteasome inhibitory action of Aβ _1–40 (a peptide comprising the first 40 residues of Aβ) modified by the intracellular oxidant hydrogen peroxide, and by the lipid peroxidation product 4-hydroxynonenal (HNE). H₂O₂ modification of Aβ _1–40 generates a progressively poorer inhibitor of the purified human 20S proteasome. In contrast, HNE modification of Aβ _1–40 generates a progressively more selective and efficient inhibitor of the degradation of fluorogenic peptides and oxidized protein substrates by human 20S proteasome. This interaction may contribute to certain pathological manifestations of Alzheimer’s disease Received 26 September 2000; accepted 26 September 2000     

Bericht über die 4. Tagung für Elektronen-mikroskopie des Schweizer Komitees für Optik

Ohne Zusammenfassung     

<Emphasis Type="Italic">LAPTM4A</Emphasis> interacts with <Emphasis Type="Italic">hOCT2</Emphasis> and regulates its endocytotic recruitment

Human organic cation transporter 2 (hOCT2) is involved in the transport of endogenous and exogenous organic cations mainly in cells of the kidney and the brain. Here, we focus on the regulation of hOCT2 by direct protein–protein interaction. Screening within a mating-based split-ubiquitin-yeast-two-hybrid system (mBSUS) revealed the lysosomal-associated protein transmembrane 4 alpha (LAPTM4A) as a potential interacting protein. Interaction of LAPTM4A and hOCT2 was confirmed by pulldown assays, FRET microscopy analysis and immunofluorescence microscopy. Functionally, overexpression of LAPTM4A significantly decreased ASP⁺ uptake in HEK293 cells stably transfected with hOCT2, suggesting a negative regulation of hOCT2-mediated transport. Furthermore, overexpression of LAPTM4A leads to a significantly decreased hOCT2 plasma membrane expression in surface biotinylation experiments. In addition, significant expression of LAPTM4A in human kidney was demonstrated by immunoblotting and immunofluorescence.     

上市公司经营活动状况对金融资产规模影响探究

越来越多的非金融业上市公司开始参与金融投资.通过实证研究来探索非金融业上市公司经营状况对其金融资产投资规模的影响,发现上市公司的金融资产有显著规模效应,同一行业内经营活动状况较好的上市公司有较少的金融投资,经营活动收入稳定增长的上市公司有较少的金融投资.