An increasing number of human diseases has been shown to be linked to aggregation and amyloid formation by intrinsically disordered proteins (IDPs). Amylin, amyloid-β, and α-synuclein are, indeed, involved in type-II diabetes, Alzheimer’s, and Parkinson’s, respectively. Despite the correlation of the toxicity of these proteins at early aggregation stages with membrane damage, the molecular events underlying the process is quite complex to understand. In this study, we demonstrate the crucial role of free lipids in the formation of lipid–protein complex, which enables an easy membrane insertion for amylin, amyloid-β, and α-synuclein. Experimental results from a variety of biophysical methods and molecular dynamics results reveal that this common molecular pathway in membrane poration is shared by amyloidogenic (amylin, amyloid-β, and α-synuclein) and nonamyloidogenic (rat IAPP, β-synuclein) proteins. Based on these results, we propose a “lipid-chaperone” hypothesis as a unifying framework for protein–membrane poration.

Appetite for ubiquitin: a gushy travel companion in the intracellular journey of the amyloid β peptide.

Alzheimer's disease (AD) is linked to the abnormal accumulation of amyloid β peptide (Aβ) aggregates in the brain. Silybin B, a natural compound extracted from milk thistle (Silybum marianum), has been shown to significantly inhibit Aβ aggregation in vitro and to exert neuroprotective properties in vivo. However, further explorations of silybin B's clinical potential are currently limited by three main factors: (a) poor solubility, (b) instability in blood serum, and (c) only partial knowledge of silybin's mechanism of action. Here, we address these three limitations. We demonstrate that conjugation of a trehalose moiety to silybin significantly increases both water solubility and stability in blood serum without significantly compromising its antiaggregation properties. Furthermore, using a combination of biophysical techniques with different spatial resolution, that is, TEM, ThT fluorescence, CD, and NMR spectroscopy, we profile the interactions of the trehalose conjugate with both Aβ monomers and oligomers and evidence that silybin may shield the "toxic" surfaces formed by the N-terminal and central hydrophobic regions of Aβ. Finally, comparative analysis with silybin A, a less active diastereoisomer of silybin B, revealed how even subtle differences in chemical structure may entail different effects on amyloid inhibition. The resulting insight on the mechanism of action of silybins as aggregation inhibitors is anticipated to facilitate the future investigation of silybin's therapeutic potential.

Mature microRNAs are short non-coding RNA sequences which upon incorporation into the RISC ribonucleoprotein complex, play a crucial role in regulation of gene expression. However, miRNAs can exist within the cell also as free molecules fulfilling their biological activity. Therefore, it is emerging that in addition to sequence even the structure adopted by mature miRNAs might play an important role to reach the target. Indeed, we analysed by several spectroscopic techniques the secondary structures of two artificial miRNAs selected by computational tool (miR-Synth) as best candidates to silence c-MET and EGFR genes and of two endogenous miRNAs (miR-15a and miR-15b) having the same seed region, but different biological activity. Our results demonstrate that both endogenous and artificial miRNAs can arrange in several 3D-structures which affect their activity and selectivity toward the targets.MicroRNAs (miRNAs) are a class of highly conserved, short (18-24 nucleotides) and non-coding single-stranded RNA, with a crucial role in different cellular and metabolic pathways 1-4 . They act as key post-transcriptional regulators of gene expression in development 3,5 , immunity 6 and peptide bond formation 7 . The normal expression of miRNAs is important in physiological processes, while the aberrant expression of miRNAs is often associated to the initiation and development of human diseases like cancer, genetic disorders and altered immune system functions 1,8,9 . Since the early 2000s, a systematic profiling of several human cancer samples showed that changes in miRNA concentration, as consequence of up-or down-regulation in their biogenesis, are correlated with the development and differentiation of cancer cells, thus providing good diagnostic biomarkers for a great variety of cancers 10-12 . The discovery of cancer-promoting miRNAs has been accompanied also by the identification of many cancer-suppressing miRNAs, such as miR-15a and miR-16-1, which are able to inhibit tumorigenesis driven by the Bcl2 oncogene [13][14][15][16][17][18][19] .So far, over 2000 miRNAs have been identified in humans, and they target most of human protein coding genes. Mature miRNAs are obtained through a series of steps starting from 1-3 Kb long RNA precursors called pri-miRNAs 4 . These are transcribed in the nucleus by RNA polymerase II and processed by the RNase III enzyme Drosha and the double-stranded RNA-binding protein (dsRNAbd) to produce hairpin-shaped secondary precursors called pre-miRNAs (~60-100 nucleotides) 20-22 . Next, pre-miRNAs are transported by Exportin-5 to the cytoplasm where they are further cleaved by the RNase III Dicer to give the mature double stranded miRNAs (~18-24 nucleobases) 23,24 . Following the separation of the two strands, the strand known as "guide strand" is then incorporated into the RISC ribonucleoprotein complex (miRNA-Induced Silencing Complex) which binds and silences the complementary target mRNA, whereas the other strand, known as the "passenger strand", is degraded or involved in the regulation ...