Probing the Structure–Function relationship and amyloidogenic propensities in natural variants of apolipoprotein A-I

Abstract

Background Apolipoprotein A-I (apoA-I) protects against atherosclerosis and participates in the removal of excess cellular cholesterol from peripheral organs. Several naturally occurring apoA-I mutations are associated with familial systemic amyloidosis, with deposition of amyloid aggregates in peripheral organs, resulting in multiple organ failure. Systematic studies on naturally occurring variants are needed to delineate their roles and involvement in pathogenesis. Methods We performed a comparative structure–function analysis of five naturally occurring apoA-I variants and the wild-type protein. Circular dichroism, Fourier-transform infrared spectroscopy, thioflavin T and congo red fluorescence assays, thermal, chemical, and proteolytic stability assays, and 1,2-Dimyristoyl- sn -glycero-3-phosphocholine clearance analyses were used to assess the effects of mutations on the structure, function, stability, aggregation, and proteolytic susceptibility of the proteins to explore the mechanisms underlying amyloidosis and hypercholesterolemia. Results We observed structural changes in the mutants independent of fibril formation, suggesting the influence of the surrounding environment. The mutants were involved in aggregate formation to varying degree; L170P, R173P, and V156E showed an increased propensity to aggregate under different physiological conditions. β sheet formation indicates that L170P and R173P participate in amyloid formation. Compared to WT, V156E and L170P exhibited higher capacity for lipid clearance. Conclusions The selected point mutations, including those outside the hot spot regions of apoA-I structure, perturb the physiochemical and conformational behavior of the protein, influencing its function. General significance The study provides insights into the structure–function relationships of naturally occurring apoA-I variants outside the hot spot mutation sites.

Antiglycation potential of plant based TiO2 nanoparticle in D‐ribose glycated BSA in vitro

“…The delocalization of amide I band is tabulated in Table 2 and its respective line graph in Figure 6A. In the same context, percent transmittance is also observed, might be due the progressive proteins tendency towards aggregated state 26 . Such alteration in BSA structure due to the vibrational shift in amide‐I band of d ‐Rib‐BSA were significantly regained by treatment of TNP.…”

“…Under continuous N 2 purging, the spectra were taken over the range of 400–4000 cm −1 . The spectra for all the protein reaction are the averages of the three determinations 26 …”

“…Conformational changes in the BSA tertiary confirmation and its hydrophobic moiety of the protein surface including N‐BSA, glycated BSA as well as TNP and AG treated glycated BSA were analyzed by ANS binding assay. As described previously, the respective emission fluorescence spectra of the ANS (blank) and the BSA‐ANS reaction mixture were recorded over a wavelength range 500–600 nm, with excitation at 380 nm 26 …”

Physicochemical Characterization of In Vitro LDL Glycation and Its Inhibition by Ellagic Acid (EA): An In Vivo Approach to Inhibit Diabetes in Experimental Animals

“…The excitation wavelength and emission wavelength range for AGE detection were 370 nm and 400-600 nm, respectively. To detect EA effect upon aromatic amino acid environment that gives intrinsic fluorescence, the samples were excited at 295 nm and the emission was observed in the range between 310 and 450 nm wavelength [ 27 ].…”

Pathogenic D76N Variant of β2-Microglobulin: Synergy of Diverse Effects in Both the Native and Amyloid States

“…Amyloid fibrils can deposit as amyloid plaques in various tissues throughout the body, resulting in a wide range of pathological conditions [ 3 ]. Point mutations of amyloidogenic proteins (Aβ [ 4 ], transthyretin [ 5 ], apolipoprotein [ 6 ], gelsolin [ 7 ], and synuclein [ 8 ]) are known to be responsible for several familial amyloid disorders. These mutations can provoke protein aggregation by changing the protein’s physico-chemical properties or the stability of the native structure via changes in charge network, hydrophobicity, and propensity to form an intermolecular β-sheet structure [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ].…”