Structural studies and cytotoxicity assays of "aggregation-prone" IAPP(8-16) and its non-amyloidogenic variants suggest its important role in fibrillogenesis and cytotoxicity of human amylin.
Amyloid deposits to the islets of Langerhans are responsible for the gradual loss of pancreatic β-cells leading to type II diabetes mellitus. Human mature islet amyloid polypeptide (hIAPP), a 37-residue pancreatic hormone, has been identified as the primary component of amyloid fibrils forming these deposits. Several individual segments along the entire sequence length of hIAPP have been nominated as regions with increased amyloidogenic potential, such as regions 8-20, 20-29, and 30-37. A smaller fragment of the 8-20 region, spanning residues 8-16 of hIAPP has been associated with the formation of early transient α-helical dimers that promote fibrillogenesis and also as a core part of hIAPP amyloid fibrils. Utilizing our aggregation propensity prediction tools AmylPred and AmylPred2, we have identified the high aggregation propensity of the 8-16 segment of hIAPP. A peptide analog corresponding to this segment was chemically synthesized and its amyloidogenic properties were validated using electron microscopy, X-ray fiber diffraction, ATR FT-IR spectroscopy, and polarized microscopy. Additionally, two peptides introducing point mutations L12R and L12P, respectively, to the 8-16 segment, were chemically synthesized. Both mutations disrupt the α-helical properties of the 8-16 region and lower its amyloidogenic potential, which was confirmed experimentally. Finally, cytotoxicity assays indicate that the 8-16 segment of hIAPP shows enhanced cytotoxicity, which is relieved by the L12R mutation but not by the L12P mutation. Our results indicate that the chameleon properties and the high aggregation propensity of the 8-16 region may significantly contribute to the formation of amyloid fibrils and the overall cytotoxic effect of hIAPP.
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Nikolaos N
NN
Louros
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Paraskevi L
PL
Tsiolaki
Department of Pharmacy, University of Patras, Patras, 26504, Greece.
Aikaterini A
AA
Zompra
Department of Pharmacy, University of Patras, Patras, 26504, Greece.
Eleni V
EV
Pappa
Department of Pharmacy, University of Patras, Patras, 26504, Greece.
Vassiliki
V
Magafa
Department of Pharmacy, University of Patras, Patras, 26504, Greece.
George
G
Pairas
Department of Pharmacy, University of Patras, Patras, 26504, Greece.
Paul
P
Cordopatis
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Christina
C
Cheimonidou
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Ioannis P
IP
Trougakos
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Vassiliki A
VA
Iconomidou
Department of Cell Biology and Biophysics, Faculty of Biology, University of Athens, Panepistimiopolis, Athens, 157 01, Greece.
Stavros J
SJ
Hamodrakas
D002460:Cell Line; D003603:Cytotoxins / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D058228:Islet Amyloid Polypeptide / Q000737:chemistry / Q000494:pharmacology; D010455:Peptides / Q000138:chemical synthesis / Q000737:chemistry / Q000494:pharmacology; D066329:Protein Aggregates
D003603:Cytotoxins; D058228:Islet Amyloid Polypeptide; D010455:Peptides; D066329:Protein Aggregates
amylin; amyloid fibrils; cytotoxicity assays; islet amyloid polypeptide (IAPP); peptide analogs; type II diabetes mellitus