Paraskevi Tsiolaki

Amylin is a 37-amino acid peptide hormone. It is mainly expressed by the pancreatic islet beta cells [1]. Amylin self-aggregates, forming amyloid fibrils and is related to diabetes type II [2]. Utilizing AMYLPRED [3], a segment of human amylin was identified, with high aggregation potential. Utilizing our tool, several possible, non-amyloidogenic variants of this segment were predicted. Subsequently, the identified ‘aggregation-prone’ peptide and its predicted variants were synthesized and studied experimentally. The peptides were synthesized by the solid phase methodology and Fmoc/tBu chemistry, using 2-chlorotrityl chloride resin as a solid support [4]. The final products were determined to be at least 97% pure by analytical HPLC. Experimental evidence indicates that the predicted ‘aggregation-prone’ peptide-analogue self-assembles into amyloid-like fibrils, but its variants do not. The present work was funded by the SYNERGASIA 2011 PROGRAMME. This Programme is co-funded by the Eu...

Amylin is a 37-amino acid peptide hormone. It is mainly expressed by the pancreatic islet beta cells [1]. Amylin self-aggregates, forming amyloid fibrils and is related to diabetes type II [2]. Utilizing AMYLPRED [3], a segment of human amylin was identified, with high aggregation potential. Utilizing our tool, several possible, non-amyloidogenic variants of this segment were predicted. Subsequently, the identified ‘aggregation-prone’ peptide and its predicted variants were synthesized and studied experimentally. The peptides were synthesized by the solid phase methodology and Fmoc/tBu chemistry, using 2-chlorotrityl chloride resin as a solid support [4]. The final products were determined to be at least 97% pure by analytical HPLC. Experimental evidence indicates that the predicted ‘aggregation-prone’ peptide-analogue self-assembles into amyloid-like fibrils, but its variants do not. The present work was funded by the SYNERGASIA 2011 PROGRAMME. This Programme is co-funded by the Eu...

Amyloidogenic proteins like human Cystatin C (hCC) have been shown to form dimers and oligomers by exchange of subdomains of the monomeric proteins. Normally, the hCC monomer, a low molecular type 2 Cystatin, consists of 120 amino acid residues and functions as an inhibitor of cysteine proteases. The oligomerization of hCC is involved in the pathophysiology of a rare form of amyloidosis namely Icelandic hereditary cerebral amyloid angiopathy, in which an L68Q mutant is deposited as amyloid in brain arteries of young adults. In order to find the shortest stretch responsible to drive the fibril formation of hCC, we have previously demonstrated that the LQVVR peptide forms amyloid fibrils, in vitro (Tsiolaki et al., 2015). Predictions by AMYLPRED, an amyloidogenic determinant prediction algorithm developed in our lab, led us to synthesize and experimentally study two additional predicted peptides derived from hCC. Along with our previous findings, in this work, we reveal that these peptides self-assemble, in a similar way, into amyloid-like fibrils in vitro, as electron microscopy, X-ray fiber diffraction, ATR FT-IR spectroscopy and Congo red staining studies have shown. Further to our experimental results, all three peptides seem to have a fundamental contribution in forming the "aggregation-prone" core of human Cystatin C.

Apolipoprotein A-I (apoA-I) is the major component of high density lipoproteins and plays a vital role in reverse cholesterol transport. Lipid-free apoA-I is the main constituent of amyloid deposits found in atherosclerotic plaques, an acquired type of amyloidosis, whereas its N-terminal fragments have been associated with a hereditary form, known as familial apoA-I amyloidosis. Here, we identified and verified four "aggregation-prone" segments of apoA-I with amyloidogenic properties, utilizing electron microscopy, X-ray fiber diffraction, ATR FT-IR spectroscopy and polarized light microscopy. These segments may act as conformational switches, possibly controlling the transition of the α-helical apoA-I content into the "cross-β" architecture of amyloid fibrils. A structural model illuminating the structure of amyloid fibrils formed by the N-terminal fragments of apoA-I is proposed, indicating that two of the identified chameleon segments may play a vital part in ...

Human cystatin C (HCC) is a low molecular weight member of the cystatin family (type2). HCC consists of 120 amino acids. Normally it is an inhibitor of cysteine proteases, but in pathological conditions it forms amyloid fibrils in brain arteries of young adults. An 'aggregation-prone' pentapeptide ((47)LQVVR(51)) was located within the HCC sequence using AmylPred, an 'aggregation-prone' peptide prediction algorithm developed in our lab. This peptide was synthesized and self-assembled into amyloid-like fibrils in vitro, as electron microscopy, X-ray fiber diffraction, Attenuated Total Reflectance Fourier-Transform Spectroscopy and Congo red staining studies reveal. Thus, the (47)LQVVR(51) peptide seems to have an important role in HCC fibrillization.