Characterization of anticoagulant heparinoids by immunoprofiling

Heparinoids are used in the clinic as anticoagulants. A specific pentasaccharide in heparinoids activates antithrombin III, resulting in inactivation of factor Xa and–when additional saccharides are present–inactivation of factor IIa. Structural and functional analysis of the heterogeneous heparinoids generally requires advanced equipment, is time consuming, and needs (extensive) sample preparation. In this study, a novel and fast method for the characterization of heparinoids is introduced based on reactivity with nine unique anti-heparin antibodies. Eight heparinoids were biochemically analyzed by electrophoresis and their reactivity with domain-specific anti-heparin antibodies was established by ELISA. Each heparinoid displayed a distinct immunoprofile matching its structural characteristics. The immunoprofile could also be linked to biological characteristics, such as the anti-Xa/anti-IIa ratio, which was reflected by reactivity of the heparinoids with antibodies HS4C3 (indicative for 3-O-sulfates) and HS4E4 (indicative for domains allowing anti-factor IIa activity). In addition, the immunoprofile could be indicative for heparinoid-induced side-effects, such as heparin-induced thrombocytopenia, as illustrated by reactivity with antibody NS4F5, which defines a very high sulfated domain. In conclusion, immunoprofiling provides a novel, fast, and simple methodology for the characterization of heparinoids, and allows high-throughput screening of (new) heparinoids for defined structural and biological characteristics

Tau/MAPT disease-associated variant A152T alters tau function and toxicity via impaired retrograde axonal transport

Mutations in the microtubule-associated protein tau (MAPT) underlie multiple neurodegenerative disorders, yet the pathophysiological mechanisms are unclear. A novel variant in MAPT resulting in an alanine to threonine substitution at position 152 (A152T tau) has recently been described as a significant risk factor for both frontotemporal lobar degeneration and Alzheimer's disease. Here we use complementary computational, biochemical, molecular, genetic and imaging approaches in Caenorhabditis elegans and mouse models to interrogate the effects of the A152T variant on tau function. In silico analysis suggests that a threonine at position 152 of tau confers a new phosphorylation site. This finding is borne out by mass spectrometric survey of A152T tau phosphorylation in C. elegans and mouse. Optical pulse-chase experiments of Dendra2-tau demonstrate that A152T tau and phosphomimetic A152E tau exhibit increased diffusion kinetics and the ability to traverse across the axon initial segment more efficiently than wild-type (WT) tau. A C. elegans model of tauopathy reveals that A152T and A152E tau confer patterns of developmental toxicity distinct from WT tau, likely due to differential effects on retrograde axonal transport. These data support a role for phosphorylation of the variant threonine in A152T tau toxicity and suggest a mechanism involving impaired retrograde axonal transport contributing to human neurodegenerative disease

Synthesis of Lithocholic Acid Derivatives as Proteasome Regulators

[Image: see text] Accumulation of aberrant protein aggregates, such as amyloid β peptide (Aβ), due to decreased proteasome activities, might contribute to the neurodegeneration in Alzheimer's disease. In this study, lithocholic acid derivatives 3α-O-pimeloyl-lithocholic acid methyl ester (2) and its isosteric isomer (6) were found to activate the chymotrypsin-like activity of the proteasome at an EC(50) of 7.8 and 4.3 μM, respectively. Replacing the C24 methyl ester in 2 with methylamide resulted in a complete devoid of proteasome activating activity. Epimerizing the C3 substituent from an α to β orientation transformed the activator into a proteasome inhibitor. Unlike the cellular proteasome activator PA28, proteasome activated by 2 was not inhibited by Aβ. Furthermore, 2 potently antagonized the inhibitory effect of Aβ on the proteasome. In summary, compound 2 represents a novel class of small molecules that not only activates the proteasome but also antagonizes the inhibitory effect of Aβ on the proteasome