Molecular dynamics simulations of Alzheimer's BACE1 and BACE2 transmembrane domains in neurons: Impact of cholesterol
REVISTA FACULTAD DE INGENIERIA-UNIVERSIDAD DE ANTIOQUIA
Authors: Carlos Cruz-Jimenez, Juan; Mercado-Montoya, Marcela; Eduardo Ostos-Ortiz, Carlos; Mauricio Hernandez-Validivieso, Alher
Abstract
Molecular dynamic (MD) simulation is an approach frequently employed in computational biology for exhaustive sampling of the protein-ligand conformational space. Hence, it is useful for structural analysis and the study of molecular interactions. In this study, we report on a MD simulation protocol to understand the dynamics of beta-secretase 1 (BACE1) and 2 (BACE2), widely known to play a critical role in the etiology of Alzheimer's disease, by a structure change evaluation of their transmembrane domains white inserted in a simulated neural membrane system. We considered two different levels in membrane cholesterol content. Because there is no evidence supporting the capacity of BACE1 and BACE2 to exist as a dimer, single and double (BACE1/BACE1, BACE2/BACE2, BACE1/BACE2) systems, either in parallel or antiparallet orientation, were prepared for each run. Analysis of tridimensional structure of BACE1 and BACE2, after 10ns of MD simulation, revealed a correlation between higher cholesterol levels and both peptide refolding and changes in the secondary structure of both transmembrane domains in single and double systems. Interestingly, our results also indicate a potential interaction in the double system BACE2/BACE2, particularly when the domains had an antiparallel orientation.
A comparison of the Avisoft (v.5.2) and MATLAB Mouse Song Analyzer (v.1.3) vocalization analysis systems in C57BL/6, Fmr1-FVB.129, NS-Pten-FVB, and 129 mice
JOURNAL OF NEUROSCIENCE METHODS
Authors: Binder, Matthew; Nolan, Suzanne O.; Lugo, Joaquin N.
Abstract
Background: Communicative behaviors play a vital role in mammals and are highly relevant to human neurodevelopmental conditions. Mice produce communicative vocalizations that occur in the ultrasonic range, which are commonly analyzed within the Avisoft recording system. Fully automated programs such as the Mouse Song Analyzer in MATLAB, have been developed to analyze USVs in a shorter time period, however, no study has compared the accuracy of MATLAB to Avisoft. New Method: In order to determine MATLAB's accuracy, we used data from four different mouse strains and assessed whether the total number of USVs detected was similar between systems. Results: We found that there was a high correlation between systems for the number of USVs emitted from C57BL/6 and NS-Pten mice however, Avisoft detected significantly more USVs than MATLAB for both strains. For Fmr1-FVB.129 and 129 mice, large correlations were observed between systems and no significant difference was present in the USVs detected. A partial correlation was run to control for the covariates: sex, age, strain, and treatment, and found that only strain substantially influences the relationship between the USVs detected in Avisoft and those detected in MATLAB. Comparison with Existing Method: These findings demonstrate that there is a high degree of agreement between Avisoft and the Mouse Song Analyzer however, Avisoft does detect significantly more USVs depending on the strain assessed. Conclusions: Therefore, there are relative advantages and disadvantages with both systems that vocalization researchers should be aware of when interpreting USV results, and when using either system.