Protective Effect of a Hexapeptide Derived from Rotifer-Specific SCO-Spondin Against Beta-Amyloid Toxicity

Abstract

The Rotimer (rotifer-specific biopolymer) like SCO-spondin (R-SSPO/1), predicted as the main component of this biopolymer, is an adequate base for the design of functional small peptides. This macromolecule is interactive and protective against neurotoxic human-type beta-amyloid 1-42 aggregates (agg-Aβ). The current work presents biological investigations and predictable molecular interaction analysis of DSSNDL and PNCRDGSDE peptides that were synthesized based on the sequences of R-SSPO/1. Viability assays (NADH-dependent cellular reduction capacity, intracellular esterase activity, and motility) were performed on differentiated neuro-type cell cultures (SH-SY5Y and PC12) and on Rotimer-depleted rotifers (Euchlanis dilatata and Lecane bulla). A control peptide (STTRPTGTT), not found in Rotimer, was also included in the study. All three peptides are present in both rotifer and human proteomes. Among these small molecules, DSSNDL showed a significant protective effect against the toxicity of agg-Aβ both in vitro and in vivo and presumably interacted with its aggregates. The stagogram analysis of amyloid-peptide complexes and the possible bonding competition of these small molecules against aggregation-specific dyes on agg-Aβ surface suggest that DSSNDL affects the properties of these neurotoxic macromolecules. This effective hexapeptide can serve as a promising candidate for further investigations into the inactivation of beta-amyloid toxicity.

Keywords: SCO-spondin; beta-amyloid; biopolymer; rotifer.

Figure 1

The effect of short peptides derived from rotifer-specific proteins against agg-Aβ-toxicity in differentiated cell cultures (SH-SY5Y and PC12) and biopolymer-depleted rotifers (E. dilatata and L. bulla). In this study, three different procedures were used to monitor viability. The two specific (NADH-dependent cellular reduction capacity and membrane integrity-dependent intracellular esterase activity) and the holistic (motility detection) profile methods are representative of examining the effect of agg-Aβ (simplified version in the figure: Aβ) and short peptides. The error bars represent SEM. One-way ANOVA with Bonferroni post hoc test was used for statistical analysis; the levels of significance are p ** ≤ 0.01, p *** ≤ 0.001, or p **** ≤ 0.0001 (Different number of *, a significant difference from amyloid-treated groups).

Figure 2

Stagogram-based optical imaging and analysis of the interaction between agg-Aβ and short peptides derived from rotifer-specific proteins. The sizes of the particles of the formed crystals (average size, µM) and the area covered by them (covered area, %) were detected. The simplified version of the agg-Aβ in the figure: Aβ. The error bars represent SEM. One-way ANOVA with the Bonferroni post hoc test was used for statistical analysis; the levels of significance are p ** ≤ 0.01, p *** ≤ 0.001 or p **** ≤ 0.0001 (Different number of *, a significant difference from the group with agg-Aβ alone).

Figure 3

Interacting competition between short peptides derived from rotifer-specific proteins and amyloid-specific dyes. The applied reagents: absorbing dyes were Congo Red (CR) and Coomassie Brilliant Blue R 250 (CB-R250); fluorescents dyes were 4,4′-dianilino-1,1′-binaphthyl-5,5′-disulfonic Acid, dipotassium salt (Bis-ANS), and Thioflavin T (ThT). The degree of competition is the reciprocal (in relative units) of the optical (absorbance and fluorescence) values. The simplified version of the agg-Aβ in the figure: Aβ. The error bars represent SEM. One-way ANOVA with Bonferroni post hoc test was used for statistical analysis; the levels of significance are p *** ≤ 0.001 or p **** ≤ 0.0001 (Different number of *, a significant difference from groups with agg-Aβ/CR and agg-Aβ/ThT).