[MOSPD2, an inter-organelle connector]

[A lipid exchange market : vectorial cholesterol transport by the protein OSBP]

Cholesterol is synthesized in the endoplasmic reticulum (RE) and then transported to cellular compartments whose functions require high cholesterol levels. Here, we describe the mechanism by which cholesterol is transported from the RE to the trans-Golgi network (TGN) by the protein OSBP (Oxysterol-Binding Protein). OSBP has two complementary activities. First, it tethers the RE to the TGN by forming a contact site where the two membranes are about twenty nanometers away. Then, it exchanges RE cholesterol for a TGN lipid, phosphatidylinositol 4-phosphate (PI4P). Eventually, PI4P is hydrolyzed at the RE, making the exchange cycle irreversible. Thus, OSBP is at the center of a lipid exchange market where a transported cholesterol "costs" a PI4P. Antiviral or anti-cancer molecules target OSBP, suggesting the importance of the OSBP cycle in different physiopathological contexts. The general principles of this cycle are shared by other lipid-transfer proteins.

Identification of Key Genes and the Pathophysiology Associated With Major Depressive Disorder Patients Based on Integrated Bioinformatics Analysis

Background: At present, laboratory blood tests to support major depressive disorder (MDD) diagnosis are not available. This study aimed to screen potential mRNAs for peripheral blood biomarkers and novel pathophysiology of MDD. Methods: The present study utilized public data from two mRNA microarray datasets to analyze the hub genes changes related to MDD. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis of differentially expressed genes (DEGs) were performed. Finally, some potential mRNA quality biomarkers for hub gene expression in blood were identified. Results: A total of 25 significantly co-upregulated DEGs and 98 co-downregulated DEGs were obtained from two datasets. The pathway enrichment analyses showed that co-upregulated genes were significantly enriched in the regulation of cell-matrix adhesion and mitochondrial membrane permeability which were involved in the apoptotic process. Co-downregulated genes were mainly involved in the neutrophil activation which in turn was involved in the immune response, degranulation and cell-mediated immunity, positive regulation of immune response, the Toll-like receptor signaling pathway, and the NOD-like receptor signaling pathway. From the PPI network, 14 hub genes were obtained. Among them, the subnetworks of PLCG1, BCL2A1, TLR8, FADD, and TLR4 screened out from our study have been shown to play a role in immune and inflammation responses. Discussion: The potential molecular mechanisms that have been identified simultaneously include innate immunity, neuroinflammation, and neurotrophic factors for synapse function and development.