31P and 13C solid-state NMR analysis of morphological changes of phospholipid bilayers containing glucagon during fibril formation of glucagon under neutral condition.
 

31P and 13C solid-state NMR analysis of morphological changes of phospholipid bilayers containing glucagon during fibril formation of glucagon under neutral condition.

http://www.bionmr.com//www.ncbi.nlm....PubMedLink.gif Related Articles 31P and 13C solid-state NMR analysis of morphological changes of phospholipid bilayers containing glucagon during fibril formation of glucagon under neutral condition.

Biochim Biophys Acta Biomembr. 2020 07 01;1862(7):183290

Authors: Haya K, Makino Y, Kikuchi-Kinoshita A, Kawamura I, Naito A

Abstract
Glucagon is a 29 amino acid peptide hormone secreted by pancreatic ?-cells that interacts with specific receptors located in various organs. Glucagon tends to form gel-like fibrillar aggregates that are cytotoxic due to their activation of apoptotic signaling pathways. To understand the glucagon-membrane interactions, morphological changes in dimyristoylphosphatidylcholine (DMPC) bilayers containing glucagon in neutral solution were investigated by observing 31P NMR spectra. First, lipid bilayers with a DMPC/glucagon molar ratio of 50/1 were observed. One day after preparing the DMPC/glucagon lipid bilayer sample, lipid bilayers were disrupted below the phase transition temperature (Tc). Membrane disruption was reduced 2*days after preparation due to the reduction of glucagon-DMPC interaction, and subsequently increased by 4*days and was reduced again by 7*days. TEM measurements showed that small ellipsoidal intermediates of glucagon were observed inside the small size of lipid bilayer after 4*days, while fibrils grew inside lipid bilayer after 19*days. These results indicate that morphological changes in DMPC/glucagon lipid bilayers are correlated with the evolution of glucagon aggregate state. Particularly, fibril intermediate shows a strong glucagon lipid bilayer interaction. We further investigated the structure and kinetics of glucagon fibril formation inside the DMPC lipid bilayer in a neutral solution using 13C solid-state NMR spectroscopy. ?-Helical structures were observed around Gly4 and Ala19 in the monomeric form, which changed to ?-sheet structures in the fibril form. The fibrillation process can be explained by a two-step autocatalytic reaction mechanism in which the first step is a homogeneous nuclear formation (k1), and the second step is an autocatalytic heterogeneous fibrillation process (k2).


PMID: 32222378 [PubMed - indexed for MEDLINE]



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