Monosialoganglioside-GM1 triggers binding of the amyloid-protein salmon calcitonin to a Langmuir membrane model mimicking the occurrence of lipid-rafts

Abstract

GM1 ganglioside is known to be involved in the amyloid-associated diseases and it is a crucial factor for the assembly of amyloid proteins on lipid-rafts, which are lipid structures located on the synaptic plasma membranes. Due to its slow aggregation rate, we employed salmon calcitonin (sCT) as a suitable probe representative of amyloid proteins, to study the interaction between this class of proteins and a membrane model. Here, we prepared a neuronal membrane model by depositing onto mica two Langmuir-Blodgett films in liquid-condensed phase: the outer monolayer was characterized by high content of GM1 (50%) and minority parts of cholesterol and POPC (25–25%), while the inner one by plain POPC. To deeply investigate the interaction of sCT with this model and the role-played by GM1, we prepared the outer leaflet adding sCT at a concentration such that the number of proteins equals that of GM1. Atomic Force Microscopy revealed the occurrence of two distinct kinds of flat surfaces, with globular aggregates localized exclusively on top of the highest one. To unravel the nature of the interaction, we studied by ζ-potential technique liposomes composed as the outer leaflet of the model. Results demonstrated that an electrostatic interaction sCT-GM1 occurred. Finally, to investigate the interaction thermodynamics between sCT and the outer leaflet, Langmuir films as the outer monolayer and containing increasing content of sCT were studied by compression isotherms and Brewster Angle Microscopy experiments. Based on the all body of results we propose an interaction model where GM1 plays a pivotal role.

The Interaction between Amyloid Prefibrillar Oligomers of Salmon Calcitonin and a Lipid-Raft Model: Molecular Mechanisms Leading to Membrane Damage, Ca2+-Influx and Neurotoxicity

“…Working with cell lines we found that the neurotoxicity of aggregated and unfractionated sCT samples was similar if not greater than that of Aβ and correlated to the abundance of "lipid-rafts" in the cells [46]. Thus, to investigate this outcome we performed biophysical studies on the interaction of sCT with model membranes mimicking the presence of "lipid-rafts" confirming the GM1 pivotal role [47]. Recently, we fractionated the sCT aggregates and demonstrated that PFOs was the species able to induce neurotoxicity in primary hippocampal neurons and mouse brain slices [5,20].…”

Anomalous interaction of tri-acyl ester derivatives of uridine nucleoside with al-α-dimyristoylphosphatidylcholine biomembrane model: a differential scanning calorimetry study

“…Although very simplified compared to the complexity of biological cell membranes, lipid bilayers and monolayers can be employed as useful models. The biomembrane models permitted to investigate the nature of the interaction between phospholipids and drugs or compounds with biological activity . The l ‐α‐dimyristoylphosphatidylcholine (DMPC) is a saturated phospholipid that is found in high quantities as component of healthy and tumour cell membranes of mammalian.…”

“…The procedure for the formation of liposomes is relativity simple and allows to use phospholipids of several types as biomembrane models. Moreover, this method is trustworthy in revealing details of the diverse types of interactions of drugs, prodrugs and biologically active substances of different polarity with diverse phases of MLV; therefore, offering information about the miscibility and distribution of the compounds analysed over the phospholipid structures …”

“…The biomembrane models permitted to investigate the nature of the interaction between phospholipids and drugs or compounds with biological activity. [24][25][26] The L-a-dimyristoylphosphatidylcholine (DMPC) is a saturated phospholipid that is found in high quantities as component of healthy and tumour cell membranes of mammalian. It easily builds phospholipid structures as monolayer and liposomes, and the main transitions are under of 37°C, which is the human corporal temperature; therefore, the DMPC is widely used as phospholipid for the biomembrane models.…”

“…Moreover, this method is trustworthy in revealing details of the diverse types of interactions of drugs, prodrugs and biologically active substances of different polarity with diverse phases of MLV; therefore, offering information about the miscibility and distribution of the compounds analysed over the phospholipid structures. [20,24,25] Here, we prepared DMPC-MLV as a simplified model of biomembrane and we studied, by DSC, the interactions between uridine and the nucleoside derivatives and the phospholipid bilayers.…”