Apolipoproteins L1-6 share key cation channel-regulating residues but have different membrane insertion and ion conductance properties

ApoL6 associates with lipid droplets and disrupts Perilipin1-HSL interaction to inhibit lipolysis

Adipose tissue stores triacylglycerol (TAG) in lipid droplets (LD) and release fatty acids upon lipolysis during energy shortage. We identify ApoL6 as a LD-associated protein mainly found in adipose tissue, specifically in adipocytes. ApoL6 expression is low during fasting but induced upon feeding. ApoL6 knockdown results in smaller LD with lower TAG content in adipocytes, while ApoL6 overexpression causes larger LD with higher TAG content. We show that the ApoL6 affects adipocytes through inhibition of lipolysis. While ApoL6, Perilipin 1 (Plin1), and HSL can form a complex on LD, C-terminal ApoL6 directly interacts with N-terminal Plin1 to prevent Plin1 binding to HSL, to inhibit lipolysis. Thus, ApoL6 ablation decreases white adipose tissue mass, protecting mice from diet-induced obesity, while ApoL6 overexpression in adipose brings obesity and insulin resistance, making ApoL6 a potential future target against obesity and diabetes.

Genome-wide SNP analysis provides insights into the XX/XY sex-determination system in silver barb (Barbonymus gonionotus)

Silver barb (Barbonymus gonionotus) is among the most economically important freshwater fish species in Thailand. It ranks fourth in economic value and third in production weight for fisheries and culture in Thailand. An XX/XY sex-determination system based on gynogenesis was previously reported for this fish. In this study, the molecular basis underlying the sex-determination system was further investigated. Genome-wide single-nucleotide polymorphism data were generated for 32 captive-bred silver barb individuals, previously scored by phenotypic sex, to identify sex-linked regions associated with sex determination. Sixty-three male-linked loci, indicating putative XY chromosomes, were identified. Male-specific loci were not observed, which indicates that the putative Y chromosome is young and the sex determination region is cryptic. A homology search revealed that most male-linked loci were homologous to the Mariner/Tc1 and Gypsy transposable elements and are probably the remnants of an initial accumulation of repeats on the Y chromosome from the early stages of sex chromosome differentiation. This research provides convincing insights into the mechanism of sex determination and reveals the potential sex determination regions in silver barb. The study provides the basic data necessary for increasing the commercial value of silver barbs through genetic improvements.

APOL4, a Novel Immune-Related Prognostic Biomarker for Glioma

Glioma is the common, most aggressive and poorest prognostic tumor type in the brain. More and more biomarkers associated with glioma treatment, prognosis, and immunity are being discovered. Here, we aimed to explore the underlying biological functions and prognostic predictive value of Apolipoprotein L4 (APOL4) in glioma. We downloaded the expression data of APOL4 and clinical information from several databases and used R software for preprocessing. The clinical significance of APOL4 in a glioma outcome was explored by the Cox regression analysis and Kaplan–Meier survival analysis. In addition, immune infiltrates and microenvironmental indicators were assessed by CIBERSORT and TIMER. GO and KEGG analyses were used to analyze the potential functions of APOL4 in gliomas. APOL4 expression was increased in glioma specimens compared to normal tissues and correlated dramatically with the WHO grade. A survival analysis showed a shorter overall survival (OS) in glioma patients with APOL4 overexpression, and a Cox regression analysis showed that APOL4 was an independent prognostic factor for the OS of glioma patients. GSEA, GO, and KEGG enrichment analyses showed remarkable enrichment in immune-related pathways. APOL4 expression was positively correlated with immune infiltration (including DC cells, neutrophils, CD8+ T cells, B cells, macrophages, CD4+ T cells, etc.) and microenvironmental parameters (including immune, stromal, and ESTIMATE scores) in gliomas. Glioma patients with a higher expression of APOL4 may be more sensitive to immune checkpoint inhibitors (ICI). In conclusion, these findings suggest that APOL4 is associated with the tumor grade and immune infiltrates; APOL4 may be a new and potential biomarker for therapeutic and prognostic evaluations that may further suggest the therapeutic efficacy of immunotherapy.

Inhibition of endoplasmic reticulum stress signaling rescues cytotoxicity of human apolipoprotein-L1 risk variants in Drosophila

Risk variants of the apolipoprotein-L1 (APOL1) gene are associated with severe kidney disease, putting homozygous carriers at risk. Since APOL1 lacks orthologs in all major model organisms, a wide range of mechanisms frequently in conflict have been described for APOL1-associated nephropathies. The genetic toolkit in Drosophila allows unique in vivo insights into disrupted cellular homeostasis. To perform a mechanistic analysis, we expressed human APOL1 control and gain-of-function kidney risk variants in the podocyte-like garland cells of Drosophila nephrocytes and a wing precursor tissue. Expression of APOL1 risk variants was found to elevate endocytic function of garland cell nephrocytes that simultaneously showed early signs of cell death. Wild-type APOL1 had a significantly milder effect, while a control transgene with deletion of the short BH3 domain showed no overt phenotype. Nephrocyte endo-lysosomal function and slit diaphragm architecture remained unaffected by APOL1 risk variants, but endoplasmic reticulum (ER) swelling, chaperone induction, and expression of the reporter Xbp1-EGFP suggested an ER stress response. Pharmacological inhibition of ER stress diminished APOL1-mediated cell death and direct ER stress induction enhanced nephrocyte endocytic function similar to expression of APOL1 risk variants. We confirmed APOL1-dependent ER stress in the Drosophila wing precursor where silencing the IRE1-dependent branch of ER stress signaling by inhibition with Xbp1-RNAi abrogated cell death, representing the first rescue of APOL1-associated cytotoxicity in vivo. Thus, we uncovered ER stress as an essential consequence of APOL1 risk variant expression in vivo in Drosophila, suggesting a central role of this pathway in the pathogenesis of APOL1-associated nephropathies.

The Roles of Fatty Acids and Apolipoproteins in the Kidneys

The kidneys are organs that require energy from the metabolism of fatty acids and glucose; several studies have shown that the kidneys are metabolically active tissues with an estimated energy requirement similar to that of the heart. The kidneys may regulate the normal and pathological function of circulating lipids in the body, and their glomerular filtration barrier prevents large molecules or large lipoprotein particles from being filtered into pre-urine. Given the permeable nature of the kidneys, renal lipid metabolism plays an important role in affecting the rest of the body and the kidneys. Lipid metabolism in the kidneys is important because of the exchange of free fatty acids and apolipoproteins from the peripheral circulation. Apolipoproteins have important roles in the transport and metabolism of lipids within the glomeruli and renal tubules. Indeed, evidence indicates that apolipoproteins have multiple functions in regulating lipid import, transport, synthesis, storage, oxidation and export, and they are important for normal physiological function. Apolipoproteins are also risk factors for several renal diseases; for example, apolipoprotein L polymorphisms induce kidney diseases. Furthermore, renal apolipoprotein gene expression is substantially regulated under various physiological and disease conditions. This review is aimed at describing recent clinical and basic studies on the major roles and functions of apolipoproteins in the kidneys.

Development of Personalized Signature Based on the Immune Landscape to Predict the Prognosis of Osteosarcoma and the Response to Immunotherapy and Targeted Therapy

As a heterogeneous and aggressive disease, osteosarcoma (OS) faces great challenges to prognosis and individualized treatment. Hence, we explore the role of immune-related genes in predicting prognosis and responsiveness to immunotherapy and targeted therapies in patients with OS based on the immunological landscape of osteosarcoma. Based on the database of the Therapeutical Applicable Research to Generate Effective Treatments (TARGET), single-sample gene set enrichment analysis (ssGSEA) was used to obtain the enrichment scores of 29 immune characteristics. A series of bioinformatics methods were performed to construct the immune-related prognostic signature (IRPS). Gene set enrichment analysis and gene set variation analysis were used to explore the biological functions of IRPS. We also analyzed the relationship between IRPS and tumor microenvironment. Lastly, the reactivity of IRPS to immune checkpoint therapy and targeted drugs was explored. The ssGSEA algorithm was used to define two immune subtypes, namely Immunity_High and Immunity_Low. Immunity_High was associated with a good prognosis and was an independent prognostic factor of OS. The IRPS containing 7 genes was constructed by the least absolute shrinkage and selection operator Cox regression. The IRPS can divide patients into low- and high-risk patients. Compared with high-risk patients, low-risk patients had a better prognosis and were positively correlated with immune cell infiltration and immune function. Low-risk patients benefited more from immunotherapy, and the sensitivity of targeted drugs in high- and low-risk groups was determined. IRPS can be used to predict the prognosis of OS patients, and provide therapeutic responsiveness to immunotherapy and targeted therapy.