Moon, I. S. | bioRxiv Science

bioRxiv2019

Natural LXRβ agonist stigmasterol confers protection against excitotoxicity after hypoxia-reoxygenation (H/R) injury via regulation of mitophagy in primary hippocampal neurons

Ischemic brain injury represents insufficient oxygen supply to the brain and further damage occurs upon reoxygenation due to elevated intracellular levels excitatory neurotransmitter glutamate and subsequent production of reactive oxygen species (ROS) which has long been related to neuronal cell death of hippocampus brain region. Previously, using cell biological assay and transcriptomics analysis we reported that naturally occurring phytosterol Stigmasterol (ST) promotes brain development and function through the enhancement of neuronal cytoarchitectural complexity and functional maturation in rat hippocampal neurons by induction of immediate early genes (IEGs). In the present study we investigated the STs role in neuroprotection and found that ST also dose-dependently increased the neuronal viability in hypoxia reoxygenation (H/R) induced injury at hippocampal culture. ST, at an optimal concentration of 20 M, significantly reduced the transport of vesicular glutamate (VGULT1), synaptic vesicle pool size, expression of GluN2B, rate of ROS formation (DCFDA) but restore mitochondrial membrane potential (JC1) and DNA fragmentation (H2AX) against H/R induced injury. More interestingly, ST also significantly induces the expression of autophagy marker protein LC3BII and the adaptor protein P62 but not HSC70 which indicates STs capability of induction of chaperon independent autophagy at H/R treated cultures. Furthermore densitometric analysis reveals ST also significantly increases PINK1 (PTEN induced protein kinase 1) expression therefore, indicates its role in mitophagy. In addition, molecular dynamic simulations study indicates that ST bind to LXR{beta} and forms hydrogen bonds with ASN239, GLU281, ARG319, THR316, SER278, ASN239 and SER278 residues at high occupancy with GLU281(20.21%) and ARG319 (21.04%,) residues, which is necessary for sterol binding to the LXR{beta}. Taken together these findings suggest that neuroprotective effect of ST might be associated with anti-excitatory and anti-oxidative actions on CNS neurons and could be a promising drug candidate for the treatment or prevention of ischemic stroke related neurological disorders.

neuroscience↗

bioRxiv2019

Mechanistic insights into the deleterious role of nasu-hakola disease associated TREM2 variants

Recently, critical roles of genetic variants in Triggering Receptor Expressed on Myeloid cells 2 (TREM2) for myeloid cells to Alzhimers disease have been aggressively highlighted. However, little studies focused to the deleterious role of Nasu-Hakola disease (NHD) associated TREM2 variants. In order to get insights into the contributions of these variants in neurodegeneration, we investigated the influences of three well-known NHD associated TREM2 mutations (Y38C, T66M and V126G) on the loss-of-function by using conventional molecular dynamics simulation. Compared to the wild type, the mutants produced substantial differences in the collective motions in the loop regions, which not only promotes structural remodelling in complementarity-determining region 2 (CDR2) loop but also in CDR1 loop, through changing the inter and intra-loop hydrogen bonding network. In addition, the structural studies from free energy landscape showed that Y38, T66 and V126 are crucial for maintaining structural features of CDR1 and CDR2 loops, while their mutation at this position produced steric clash and thus contributes to the structural impact and loss of ligand binding. These results revealed that the presence of the mutations in TREM2 ectodomain induced flexibility and promotes structural alterations. Dynamical scenarios, which are provided by the present study, may be critical to our understanding of the role of the three TREM2 mutations in neurodegenerative diseases.

biochemistry↗