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Obesity is associated with excess lipid deposition in nonadipose tissues, leading to increased oxidative stress and insulin resistance. Very low-density lipoprotein receptor (VLDLR), a member of the LDL receptor family, binds and increases the catabolism of triglyceride-rich lipoproteins. Although VLDLR is highly expressed in the heart, its role in obesity-associated oxidative stress and insulin resistance is unclear. Here, we used lean (wild type), genetically obese leptin-deficient (ob/ob), and leptin-VLDLR double-null (ob/ob-VLDLR−/−) mice to determine the impact of VLDLR deficiency on obesity-induced oxidative stress and insulin resistance in the heart. Although insulin sensitivity and glucose uptake were reduced in the hearts of ob/ob mice, VLDLR expression was upregulated and was associated with increased VLDL uptake and excess lipid deposition. This was accompanied by an upregulation of cardiac NADPH oxidase (Nox) expression and increased production of Nox-dependent superoxides. Silencing the VLDLR in ob/ob mice had reduced VLDL uptake and prevented excess lipid deposition in the heart, in addition to a reduction of superoxide overproduction and the normalization of insulin sensitivity and glucose uptake. In isolated cardiomyocytes, VLDLR deficiency had prevented VLDL-mediated induction of Nox activity and superoxide overproduction while improving insulin sensitivity and glucose uptake. Our findings indicate that VLDLR deficiency prevents excess lipid accumulation and moderates oxidative stress and insulin resistance in the hearts of obese mice. This effect is linked to the active role of VLDLR in VLDL uptake, which triggers a cascade of events leading to increased Nox activity, superoxide overproduction, and insulin resistance. NEW & NOTEWORTHY: Obesity is associated with excess lipid deposition in muscles, which is considered as a leading cause of metabolic dysfunction and oxidative stress. Cellular uptake of lipids is regulated by several membrane receptors, among which is the very low-density lipoprotein receptor (VLDLR). This article provides information on the role of VLDLR in cardiac muscle and how its expression regulates insulin resistance and oxidative stress in the obese mouse model. [ABSTRACT FROM AUTHOR]

Objectives To elucidate the association between genetic variants and the risk of GCA via large-scale genome-wide association studies (GWAS). In addition, to assess the causal effect of a specific molecule by employing the obtained GWAS results as genetic epidemiological tools. Methods We applied additional variant quality control to the publicly available GWAS results from the biobanks of the UK (UKBB) and Finland (FinnGen), which comprised 532 cases vs 408 565 controls and 884 cases vs 332 115 controls, respectively. We further meta-analysed these two sets of results. We performed two-sample Mendelian randomization (MR) to test the causal effect of low-density lipoprotein (LDL) cholesterol on the risk of GCA. Results The MHC class II region showed significant associations in UKBB, FinnGen and the meta-analysis. The VLDLR region was associated with GCA risk in the meta-analysis. The T allele of rs7044155 increased the expression of VLDLR, decreased the LDL cholesterol level and decreased the disease risk. The subsequent MR results indicated that a 1 s. d. increase in LDL cholesterol was associated with an increased risk of GCA (odds ratio 1.21, 95% CI 1.01–1.45; P  = 0.04). Conclusions Our study identified associations between GCA risk and the MHC class II and VLDLR regions. Moreover, LDL cholesterol was suggested to have a causal effect on the risk of developing GCA. [ABSTRACT FROM AUTHOR]

Abstract Background Endoplasmic reticulum (ER) stress-mediated increases in the hepatic levels of the very low-density lipoprotein (VLDL) receptor (VLDLR) promote hepatic steatosis by increasing the delivery of triglyceride-rich lipoproteins to the liver. Here, we examined whether the NAD(+)-dependent deacetylase sirtuin 1 (SIRT1) regulates hepatic lipid accumulation by modulating VLDLR levels and the subsequent uptake of triglyceride-rich lipoproteins. Methods Rats fed with fructose in drinking water, Sirt1 −/− mice, mice treated with the ER stressor tunicamycin with or without a SIRT1 activator, and human Huh-7 hepatoma cells transfected with siRNA or exposed to tunicamycin or different inhibitors were used. Results Hepatic SIRT1 protein levels were reduced, while those of VLDLR were upregulated in the rat model of metabolic dysfunction-associated steatotic liver disease (MASLD) induced by fructose-drinking water. Moreover, Sirt1 −/− mice displayed increased hepatic VLDLR levels that were not associated with ER stress, but were accompanied by an increased expression of hypoxia-inducible factor 1α (HIF-1α)-target genes. The pharmacological inhibition or gene knockdown of SIRT1 upregulated VLDLR protein levels in the human Huh-7 hepatoma cell line, with this increase abolished by the pharmacological inhibition of HIF-1α. Finally, SIRT1 activation prevented the increase in hepatic VLDLR protein levels in mice treated with the ER stressor tunicamycin. Conclusions Overall, these findings suggest that SIRT1 attenuates fatty liver development by modulating hepatic VLDLR levels.

Abstract Background The TGF-β signalling pathway is intricately associated with the progression of glioblastoma (GBM). The objective of this study was to examine the role of circRNAs in the TGF-β signalling pathway. Methods In our research, we used transcriptome analysis to search for circRNAs that were activated by TGF-β. After confirming the expression pattern of the selected circRYK, we carried out in vitro and in vivo cell function assays. The underlying mechanisms were analysed via RNA pull-down, luciferase reporter, and RNA immunoprecipitation assays. Results CircRYK expression was markedly elevated in GBM, and this phenotype was strongly associated with a poor prognosis. Functionally, circRYK promotes epithelial-mesenchymal transition and GSC maintenance in GBM. Mechanistically, circRYK sponges miR-330-5p and promotes the expression of the oncogene VLDLR. In addition, circRYK could enhance the stability of VLDLR mRNA via the RNA-binding protein HuR. Conclusion Our findings show that TGF-β promotes epithelial-mesenchymal transition and GSC maintenance in GBM through the circRYK-VLDLR axis, which may provide a new therapeutic target for the treatment of GBM.

Background: Endoplasmic reticulum (ER) stress-mediated increases in the hepatic levels of the very low-density lipoprotein (VLDL) receptor (VLDLR) promote hepatic steatosis by increasing the delivery of triglyceride-rich lipoproteins to the liver. Here, we examined whether the NAD(+)-dependent deacetylase sirtuin 1 (SIRT1) regulates hepatic lipid accumulation by modulating VLDLR levels and the subsequent uptake of triglyceride-rich lipoproteins. Methods: Rats fed with fructose in drinking water, Sirt1−/− mice, mice treated with the ER stressor tunicamycin with or without a SIRT1 activator, and human Huh-7 hepatoma cells transfected with siRNA or exposed to tunicamycin or different inhibitors were used. Results: Hepatic SIRT1 protein levels were reduced, while those of VLDLR were upregulated in the rat model of metabolic dysfunction-associated steatotic liver disease (MASLD) induced by fructose-drinking water. Moreover, Sirt1−/− mice displayed increased hepatic VLDLR levels that were not associated with ER stress, but were accompanied by an increased expression of hypoxia-inducible factor 1α (HIF-1α)-target genes. The pharmacological inhibition or gene knockdown of SIRT1 upregulated VLDLR protein levels in the human Huh-7 hepatoma cell line, with this increase abolished by the pharmacological inhibition of HIF-1α. Finally, SIRT1 activation prevented the increase in hepatic VLDLR protein levels in mice treated with the ER stressor tunicamycin. Conclusions: Overall, these findings suggest that SIRT1 attenuates fatty liver development by modulating hepatic VLDLR levels. [ABSTRACT FROM AUTHOR]

Background: The TGF-β signalling pathway is intricately associated with the progression of glioblastoma (GBM). The objective of this study was to examine the role of circRNAs in the TGF-β signalling pathway. Methods: In our research, we used transcriptome analysis to search for circRNAs that were activated by TGF-β. After confirming the expression pattern of the selected circRYK, we carried out in vitro and in vivo cell function assays. The underlying mechanisms were analysed via RNA pull-down, luciferase reporter, and RNA immunoprecipitation assays. Results: CircRYK expression was markedly elevated in GBM, and this phenotype was strongly associated with a poor prognosis. Functionally, circRYK promotes epithelial-mesenchymal transition and GSC maintenance in GBM. Mechanistically, circRYK sponges miR-330-5p and promotes the expression of the oncogene VLDLR. In addition, circRYK could enhance the stability of VLDLR mRNA via the RNA-binding protein HuR. Conclusion: Our findings show that TGF-β promotes epithelial-mesenchymal transition and GSC maintenance in GBM through the circRYK-VLDLR axis, which may provide a new therapeutic target for the treatment of GBM. [ABSTRACT FROM AUTHOR]

AbstractIntroductionMaterials and MethodsResultsConclusionsGranule cell dispersion (GCD) is pathognomonic of hippocampal sclerosis seen in the mesial temporal lobe epilepsy (MTLE). Current animal studies indicate deficiency of Reelin is associated with abnormal granule cell migration leading to GCD. The present study aimed to evaluate complete Reelin signalling pathway to assess whether Reelin deficiency is related to MTLE.Hippocampal sclerosis was confirmed by H and E stain. To explore the amount and cellular location of the Reelin cascade molecules, the hippocampal tissues from MTLE surgery and controls (n = 15 each) were studied using Immuno-histochemistry (IHC). Additionally, confocal imaging was used to validate the IHC findings by co-localization of different proteins. Quantification of IHC images was performed using histo-score and confocal images by Image J software.Immune expression of active Reelin was significantly reduced in patients. Reelin receptors were deranged, apolipoprotein E receptor 2 was increased while very low-density lipoprotein receptor was reduced. Disabled-1, a downstream molecule was significantly reduced in MTLE. Its ultimate target, cofilin was thus disinhibited and expressed more in MTLE. Reelin cleaving protease, matrix metalloprotease-9 (MMP-9) and MMP-9 inhibitor, tissue inhibitor of matrix protease-1, showed reduced expression in extracellular matrix. Semi-quantification of immunohistochemistry was done using Histo (H) score. H score of Reelin in diseased patients was 15 against 125 for control patients. These results were validated by confocal fluorescence microscopy.Reelin signalling cascade was deranged in chronic MTLE. Pharmacological manipulation of Reelin cascade can be done at various levels and it may provide novel treatment options for MTLE. [ABSTRACT FROM AUTHOR]

Abstract Lung cancer is a major cause of cancer-related death worldwide. This study investigated the regulatory effects of the microRNA-99a-5p (miR-99a-5)/VLDLR axis on lung cancer cell sensitivity to chemotherapy and its mechanism. miR-99a-5p and VLDLR expression levels were quantified using RT-qPCR and western blotting, respectively. The IC50 value of cisplatin (DDP) was determined using a CCK-8 assay. Lung cancer cell proliferation and apoptosis were measured using the CCK-8 assay and flow cytometry, respectively. The mRNA expression levels of apoptosis-related factors (Bax, Bcl-2, and Caspase-3) were evaluated using RT-qPCR. The direct relationship between miR-99a-5p and VLDLR was validated using dual-luciferase reporter gene and RIP assays. miR-99a-5p was weakly expressed in DDP-resistant lung cancer cells. Overexpression of miR-99a-5p promoted DDP sensitivity, suppressed proliferation and colony formation, and promoted apoptosis of A549/DDP cells in vitro. Mechanistically, miR-99a-5p restrained VLDLR expression by binding to VLDLR 3’UTR, and miR-99a-5p mediated inhibition of VLDLR regulated the DDP sensitivity, proliferation, and apoptosis of A549/ DDP cells. Overexpression of miR-99a-5p inhibited the growth of A549 cells and increased chemosensitivity of A549 cells to DDP in vivo. In conclusion, miR-99a-5p overexpression promotes sensitivity to DDP and cell apoptosis by downregulating VLDLR expression in A549/ DDP cells.

Breast cancer stem cells are responsible for cancer initiation, progression, and drug resistance. However, effective targeting strategies against the cell subpopulation are still limited. Here, we unveil two splice variants of verylow- density lipoprotein receptor, VLDLR-I and -II, which are highly expressed in breast cancer stem cells. In breast cancer cells, VLDLR silencing suppresses sphere formation abilities in vitro and tumor growth in vivo. We find that VLDLR knockdown induces transition from self-renewal to quiescence. Surprisingly, ligand-binding activity is not involved in the cancer-promoting functions of VLDLR-I and -II. Proteomic analysis reveals that citrate cycle and ribosome biogenesis-related proteins are upregulated in VLDLR-I and -II overexpressed cells, suggesting that VLDLR dysregulation is associated with metabolic and anabolic regulation. Moreover, high expression of VLDLR in breast cancer tissues correlates with poor prognosis of patients. Collectively, these findings indicate that VLDLR may be an important therapeutic target for breast cancer treatment. [ABSTRACT FROM AUTHOR]

Very-low-density lipoprotein receptor (VLDLR) involves in ocular neovascularization, a major cause of severe vision loss. However, the underlying molecular mechanisms were not completely clarified. Here, we aimed to investigate roles of circular RNAs (circRNAs) in VLDLR-associated ocular neovascularization. Vldlr knockout (Vldlr -/-, ko), Robo4 knockout (Robo4 -/-, ko) and wild-type (WT) mice were used. Mouse model of oxygen induced retinopathy (OIR) and high-throughput sequence were performed to profile the differential expression of circRNA and transcripts. RNase R treatment, Sanger PCR sequencing and quantitative polymerase chain reaction (qPCR) were used to validate candidate circRNAs and their expression patterns. Choroidal sprouting assay ex vivo and laser induction choroid neovascularization were used to determine the expression and functions of QKI/CircSlc17a5 on choroidal neovascularization. In macrophage and ocular tissues derived from Vldlr (Vldlr-/-,Vldlr ko) or Robo4 (Robo4-/-,Robo4 ko) deficiency as well as wild-type (WT) mice, Quaking (Qki) expression was significantly down-regulated in Vldlr deficiency compared to WT and Robo4 deficiency groups. Ectopic VLDLR expression or Reelin stimulation increased expression of QKI in bEnd.3 cells. Circular RNA sequencing uncovered that VLDLR regulated the biogenesis of certain circular RNAs, including the circSlc17a5. The number of Circular RNAs increased in mice treated with OIR. QKI mediated the biogenesis of circSlc17a5, which was an important regulator of choroidal angiogenesis. CircSlc17a5 regulated by VLDLR/QKI plays important roles in the choroidal angiogenesis. • VLDLR regulates QKI expression. • VLDLR regulates the biogenesis of circular RNAs. • VLDLR regulated circSlc17a5 expression depending on QKI. • CircSlc17a5 inhibits angiogenesis. [ABSTRACT FROM AUTHOR]

In our previous study, microRNA (miR)-199a-3p was found to be the most upregulated miRNA in mammary gland tissue during the non-lactation period compared with the peak-lactation period. However, there have been no reports describing the function of miR-199a-3p in ovine mammary epithelial cells (OMECs) and the biological mechanisms by which the miRNA affects cell proliferation and milk fat synthesis in sheep. In this study, the effect of miR-199a-3p on viability, proliferation, and milk fat synthesis of OMECs was investigated, and the target relationship of the miRNA with very low-density lipoprotein receptor (VLDLR) was also verified. Transfection with a miR-199a-3p mimic increased the viability of OMECs and the number of Edu-labeled positive OMECs. In contrast, a miR-199-3p inhibitor had the opposite effect with the miR-199a-3p mimic. The expression levels of three marker genes were also regulated by both the miR-199a-3p mimic and miR-199-3p inhibitor in OMECs. Together, these results suggest that miR-199a-3p promotes the viability and proliferation of OMECs. A dual luciferase assay confirmed that miR-199a-3p can target VLDLR by binding to the 3′-untranslated regions (3'UTR) of the gene. Further studies found a negative correlation in the expression of miR-199a-3p with VLDLR. The miR-199a-3p mimic decreased the content of triglycerides, as well as the expression levels of six milk fat synthesis marker genes in OMECs, namely, lipoprotein lipase gene (LPL), acetyl-CoA carboxylase alpha gene (ACACA), fatty acid binding protein 3 gene (FABP3), CD36, stearoyl-CoA desaturase gene (SCD), and fatty acid synthase gene (FASN). The inhibition of miR-199a-3p increased the level of triglycerides and the expression of LPL, ACACA, FABP3, SCD, and FASN in OMECs. These findings suggest that miR-199a-3p inhibited milk fat synthesis of OMECs. This is the first study to reveal the molecular mechanisms by which miR-199a-3p regulates the proliferation and milk fat synthesis of OMECs in sheep.

The present study evaluated the effects of natural astaxanthin (ASTA) from Haematococcus pluvialis on the antioxidant capacity, lipid metabolism, and ASTA accumulation in the egg yolk of laying hens. Hy-Line Brown layers (n = 288, 50 wk old) were randomly assigned to 1 of 4 dietary treatment groups. Each group had 6 replicates of 12 hens each. All birds were given a corn-soybean meal–based diet containing 0, 25, 50, or 100 mg/kg ASTA for 6 wk. The results showed that the total antioxidant capacity, superoxide dismutase level, and glutathione peroxidase level in the plasma, livers, and egg yolks were significantly increased in the ASTA groups compared with those of the control group (P

Abstract Background Deficiency of mitochondrial sirtuin 3 (SIRT3), a NAD+-dependent protein deacetylase that maintains redox status and lipid homeostasis, contributes to hepatic steatosis. In this study, we investigated additional mechanisms that might play a role in aggravating hepatic steatosis in Sirt3-deficient mice fed a high-fat diet (HFD). Methods Studies were conducted in wild-type (WT) and Sirt3−/− mice fed a standard diet or a HFD and in SIRT3-knockdown human Huh-7 hepatoma cells. Results Sirt3−/− mice fed a HFD presented exacerbated hepatic steatosis that was accompanied by decreased expression and DNA-binding activity of peroxisome proliferator-activated receptor (PPAR) α and of several of its target genes involved in fatty acid oxidation, compared to WT mice fed the HFD. Interestingly, Sirt3 deficiency in liver and its knockdown in Huh-7 cells resulted in upregulation of the nuclear levels of LIPIN1, a PPARα co-activator, and of the protein that controls its levels and localization, hypoxia-inducible factor 1α (HIF-1α). These changes were prevented by lipid exposure through a mechanism that might involve a decrease in succinate levels. Finally, Sirt3 −/− mice fed the HFD showed increased levels of some proteins involved in lipid uptake, such as CD36 and the VLDL receptor. The upregulation in CD36 was confirmed in Huh-7 cells treated with a SIRT3 inhibitor or transfected with SIRT3 siRNA and incubated with palmitate, an effect that was prevented by the Nrf2 inhibitor ML385. Conclusion These findings demonstrate new mechanisms by which Sirt3 deficiency contributes to hepatic steatosis. Video abstract Graphical abstract

Objectives: Nodakenin (NK) is a coumarin glucoside that is found in the roots of Angelicae gigas. A limited number of studies have been conducted on the pharmacological activities of NK. Although NK is an important natural resource having anti‐inflammatory and antioxidant effects, no investigation has been conducted to examine the effects of NK on obesity and obesity‐induced inflammation. Materials and Methods: The present study investigated the therapeutic effects of NK treatment on obesity and its complications, and its mechanism of action using differentiated 3T3‐L1 adipocytes and high‐fat diet (HFD)‐induced obese mice. Oil red O staining, western blot assay, qRT‐PCR assay, siRNA transfection, enzyme‐linked immunosorbent assay, H&E staining, immunohistochemistry, molecular docking and immunofluorescence staining were utilized. Results: Treatment with NK demonstrated anti‐adipogenesis effects via the regulation of adipogenic transcription factors and genes associated with triglyceride synthesis in differentiated 3T3‐L1 adipocytes. Compared with the control group, the group administered NK showed a suppression in weight gain, dyslipidaemia and the development of fatty liver in HFD‐induced obese mice. In addition, NK administration inhibited adipogenic differentiation and obesity‐induced inflammation and oxidative stress via the suppression of the VLDLR and MEK/ERK1/2 pathways. This is the first study that has documented the interaction between NK and VLDLR structure. Conclusion: These results demonstrate the potential of NK as a natural product‐based therapeutic candidate for the treatment of obesity and its complications by targeting adipogenesis and adipose tissue inflammation‐associated markers. [ABSTRACT FROM AUTHOR]

Loss‐of‐function mutations in the low‐density lipoprotein receptor (LDLR) gene can cause familial hypercholesterolemia (FH), but detailed functional evidence for pathogenicity is limited to a few reported mutations. Here, we investigated the cellular pathogenic mechanisms of three mutations in LDLR causing FH, which are structurally identical to pathogenic mutations in the very low‐density lipoprotein receptor (VLDLR). Similar to the VLDLR mutants, LDLR mutants D482H and C667F were found to be localized to the ER, while D445E, which is a conserved amino acid change, did not affect the trafficking of the receptor to the plasma membrane, as confirmed by the N‐glycosylation profile. Although the ER‐retained mutant proteins were soluble, induction of ER stress was observed as indicated by spliced X‐box binding protein‐1 (XBP‐1) mRNA levels. The mutants were found to associate with ER quality control components, and their stability was enhanced by inhibitors of proteasome. Our results contribute to the growing list of transport‐deficient class II LDLR variants leading to FH and provide evidence for the involvement of endoplasmic reticulum‐associated degradation in their stability.

In the developing neocortex, radially migrating neurons stop migration and form layers beneath the marginal zone (MZ). Reelin plays essential roles in these processes via its receptors, apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (VLDLR). Although we recently reported that reelin causes neuronal aggregation via ApoER2, which is thought to be important for the subsequent layer formation, it remains unknown what effect reelin exerts via the VLDLR. Here, we found that ectopic reelin overexpression in the Vldlr-mutant mouse cortex causes neuronal aggregation, but without an MZ-like cell-sparse central region that is formed when reelin is overexpressed in the normal cortex. We also found that both the early-born and late-born Vldlr-deficient neurons invade the MZ and exhibit impaired dendrite outgrowth from before birth. Rescue experiments indicate that VLDLR suppresses neuronal invasion into the MZ via a cell-autonomous mechanism, possibly mediated by Rap1, integrin and Akt. These results suggest that VLDLR is not a prerequisite for reelin-induced neuronal aggregation and that the major role of VLDLR is to suppress neuronal invasion into the MZ during neocortical development. [ABSTRACT FROM AUTHOR]

It is unknown whether and how very-low density lipoprotein receptors (VLDLRs) impact skeletal homeostasis. Here, we report that maternal and offspring VLDLRs play opposite roles in osteoclastogenesis and bone resorption. VLDLR deletion in the offspring augments osteoclast differentiation by enhancing RANKL signaling, leading to osteoporosis. In contrast, VLDLR deletion in the mother alters milk metabolism, which inhibits osteoclast differentiation and causes osteopetrosis in the offspring. The maternal effects are dominant. VLDLR-null lactating mammary gland exhibits higher mTORC1 signaling and cholesterol biosynthesis. Pharmacological probing reveals that rapamycin, but not statin, treatment of the VLDLR-null mother can prevent both the low bone resorption and our previously described inflammatory fur loss in their offspring. Genetic rescue reveals that maternal mTORC1 attenuation in adipocytes, but not in myeloid cells, prevents offspring osteopetrosis and fur loss. Our studies uncover functions of VLDLR and mTORC1 in lactation and osteoclastogenesis, illuminating key mechanisms and therapeutic insights for bone and metabolic diseases.

Pathological neovascularization of the outer retina is the hallmark of neovascular age-related macular degeneration (nAMD). Building on our previous observations that semaphorin 3F (Sema3f) is expressed in the outer retina and demonstrates anti-angiogenic potential, we have investigated whether Sema3f can be used to protect against subretinal neovascularization in two mouse models. Both in the very low-density lipid-receptor knockout (Vldlr−/−) model of spontaneous subretinal neovascularization as well as in the mouse model of laser-induced choroidal neovascularization (CNV), we found protective effects of Sema3f against the formation of pathologic neovascularization. In the Vldlr−/− model, AAV-induced overexpression of Sema3f reduced the size of pathologic neovascularization by 56%. In the laser-induced CNV model, intravitreally injected Sema3f reduced pathologic neovascularization by 30%. Combined, these results provide the first evidence from two distinct in vivo models for a use of Sema3f in protecting the outer retina against subretinal neovascularization.

Toll-like receptor 2 (TLR2), which recognizes several lipopeptides and transduces inflammatory signaling, promotes the pathogenesis of diet-induced dyslipidemia and obesity. TLR2-deficient mice were shown to have improved insulin sensitivity and reduced diet-induced metabolic syndrome. Previous studies demonstrated that prenatal lipopolysaccharide (LPS) exposure causes dyslipidemia accompanied by increased body weight and insulin resistance in offspring. To determine whether TLRs are involved in this complex abnormal phenotype, we analyzed TLR2 and TLR4 expression levels in adipose tissues from offspring with prenatal LPS-exposure (offspring-pLPS) and compared these levels to those of control offspring with prenatal saline-exposure (offspring-pSaline). TLR2 expression was specifically upregulated in the adipose tissue of offspring-pLPS mice. However, unexpectedly, TLR2-deficient offspring-pLPS mice not only presented with an abnormal phenotype comparable to that of wild-type offspring-pLPS mice but also exhibited significantly more severe hyperlipidemia. Our further analyses revealed a dramatic upregulation of TLR4 expression and overactivation of the TLR4/Myd88 signaling pathway in TLR2-deficient offspring-pLPS adipose tissue. Our finding suggests a compensatory genetic interaction between TLR2 and TLR4 in the context of prenatal inflammatory stimulation, and this interaction likely contributes to the prenatal inflammation-induced hyperlipidemia and lipid overload-induced obesity, thus providing a potential mechanism for the fetal origin of adult metabolic diseases.

The canonical Reelin signaling cascade regulates correct neuronal layering during embryonic brain development. Details of this pathway are still not fully understood since the participating components are highly variable and create a complex mixture of interacting molecules. Reelin is proteolytically processed resulting in five different fragments some of which carrying the binding site for two different but highly homologous receptors, apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (VLDLR). The receptors are expressed in different variants in different areas of the developing brain. Binding of Reelin and its central fragment to the receptors results in phosphorylation of the intracellular adapter disabled-1 (Dab1) in neurons. Here, we studied the changes of the arrangement of the receptors upon Reelin binding and its central fragment at the molecular level in human embryonic kidney 293 (HEK293) cells by time-resolved anisotropy and fluorescence lifetime imaging microscopy (FLIM). In the off-state of the pathway ApoER2 and VLDLR form homo or hetero-di/oligomers. Upon binding of full length Reelin ApoER2 and VLDLR homo-oligomers are rearranged to higher order receptor clusters which leads to Dab1 phosphorylation. When the central fragment of Reelin binds to the receptors the cluster size of homo-oligomers is not affected and Dab1 is not phosphorylated. Hetero-oligomerization, however, can be induced, but does not lead to Dab1 phosphorylation. Cells expressing only ApoER2 or VLDLR change their shape when stimulated with the central fragment. Cells expressing ApoER2 produce filopodia/lamellipodia and cell size increases, whereas VLDLR-expressing cells decrease in size. These findings demonstrate that the primary event in the canonical Reelin pathway is the rearrangement of preformed receptor homo-oligomers to higher order clusters. In addition the possibility of yet another signaling mechanism which is mediated by the central Reelin fragment independent of Dab1 phosphorylation became apparent.

Here we describe methods for investigating alpha-1 antitrypsin (AAT) and very-low-density lipoprotein receptor (VLDLR) interactions with infectious and non-infectious HIV-1 virions. Using silencing RNA to transiently block expression of VLDLR and the receptor-associated protein (RAP) to continuously block VLDLR activity, AAT is demonstrated to participate with VLDLR during internalization and infectivity of HIV-1 virions., (© 2024. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

• CBX is a selective 11β-HSD2 enzyme inhibitor that promotes the direct transfer of maternal corticosteroids (CORT) to the fetus. • Fetal exposure to high levels of maternal CORT acutely increase reln mRNA and protein in the PFC of rat pups at P0, but later decrease at P7-P14. • Maternal CBX treatment during gestation also decreases reelin signaling proteins in the PFC of rat pups as compared to the control. • Early life stress interferes with reelin signaling might have profound effects on cortical development and function later in life. Maternal stress (MS) is associated with various neuropsychiatric disorders and cognitive impairment in the offspring. However, it is unclear how early life stress alters the pup's brain development and how it contributes to the pathology of neuropsychiatric disorders later in life. Reelin is a large extracellular matrix glycoprotein that plays essential roles in early brain development such as neural migration, synaptic development, and maturation. Dysregulation of reelin and its signaling proteins is associated with the emergence of neuropsychiatric disorders in adulthood. This study examined the effect of repeated maternal Carbenoxolone (CBX) injection during late gestation on reelin signaling in the prefrontal cortex (PFC) of rat pups. CBX is a selective 11β-HSD2 enzyme inhibitor that promotes the direct transfer of maternal corticosteroids (CORT) to the fetus. Therefore, treatment with CBX can mimic the animal model of early life exposure to high levels of maternal stress hormone. In this study, pregnant rats were injected daily with either saline or CBX during gestation day (GD) 14–21, and the levels of reelin and its signaling proteins were examined in the PFC of rat pups at different postnatal age from P0-P21. The main result of this study is the repeated maternal CBX injections during GD14-21 acutely increase reln mRNA and protein expression in the PFC of rat pups at birth (P0) and follow by a significant decrease during P7-P14. The treatment also causes long term decreases in the amount of VLDLR and Dab1 which are the downstream signaling proteins for the reelin pathway, at least until P21. Our results indicated that fetal exposure to high levels of maternal CORT interferes with reelin signaling which might have profound effects on cortical development associated with neuropsychiatric disorders later in life. [ABSTRACT FROM AUTHOR]

Loss‐of‐function mutations in the low‐density lipoprotein receptor (LDLR) gene can cause familial hypercholesterolemia (FH), but detailed functional evidence for pathogenicity is limited to a few reported mutations. Here, we investigated the cellular pathogenic mechanisms of three mutations in LDLR causing FH, which are structurally identical to pathogenic mutations in the very low‐density lipoprotein receptor (VLDLR). Similar to the VLDLR mutants, LDLR mutants D482H and C667F were found to be localized to the ER, while D445E, which is a conserved amino acid change, did not affect the trafficking of the receptor to the plasma membrane, as confirmed by the N‐glycosylation profile. Although the ER‐retained mutant proteins were soluble, induction of ER stress was observed as indicated by spliced X‐box binding protein‐1 (XBP‐1) mRNA levels. The mutants were found to associate with ER quality control components, and their stability was enhanced by inhibitors of proteasome. Our results contribute to the growing list of transport‐deficient class II LDLR variants leading to FH and provide evidence for the involvement of endoplasmic reticulum‐associated degradation in their stability. [ABSTRACT FROM AUTHOR]

Emerging evidence suggest that macrophage and osteoclast are two competing differentiation outcomes from myeloid progenitors. In this review, we summarize recent advances in the understanding of the molecular mechanisms controlling the polarization of macrophage and osteoclast. These include nuclear receptors/transcription factors such as peroxisome proliferator-activated receptor γ (PPARγ) and estrogen-related receptor α (ERRα), their transcription cofactor PPARγ coactivator 1-β (PGC-1β), metabolic factors such as mitochondrial complex I (CI) component NADH:ubiquinone oxidoreductase iron-sulfur protein 4 (Ndufs4), as well as transmembrane receptors such as very-low-density-lipoprotein receptor (VLDLR). These molecular rheostats promote osteoclast differentiation but suppress proinflammatory macrophage activation and inflammation, by acting lineage-intrinsically, systemically or cross generation. These findings provide new insights to the understanding of the interactions between innate immunity and bone remodeling, advancing the field of osteoimmunology. [ABSTRACT FROM AUTHOR]

Toll-like receptor 2 (TLR2), which recognizes several lipopeptides and transduces inflammatory signaling, promotes the pathogenesis of diet-induced dyslipidemia and obesity. TLR2-deficient mice were shown to have improved insulin sensitivity and reduced diet-induced metabolic syndrome. Previous studies demonstrated that prenatal lipopolysaccharide (LPS) exposure causes dyslipidemia accompanied by increased body weight and insulin resistance in offspring. To determine whether TLRs are involved in this complex abnormal phenotype, we analyzed TLR2 and TLR4 expression levels in adipose tissues from offspring with prenatal LPS-exposure (offspring-pLPS) and compared these levels to those of control offspring with prenatal saline-exposure (offspring-pSaline). TLR2 expression was specifically upregulated in the adipose tissue of offspring-pLPS mice. However, unexpectedly, TLR2-deficient offspring-pLPS mice not only presented with an abnormal phenotype comparable to that of wild-type offspring-pLPS mice but also exhibited significantly more severe hyperlipidemia. Our further analyses revealed a dramatic upregulation of TLR4 expression and overactivation of the TLR4/Myd88 signaling pathway in TLR2-deficient offspring-pLPS adipose tissue. Our finding suggests a compensatory genetic interaction between TLR2 and TLR4 in the context of prenatal inflammatory stimulation, and this interaction likely contributes to the prenatal inflammation-induced hyperlipidemia and lipid overload-induced obesity, thus providing a potential mechanism for the fetal origin of adult metabolic diseases. [ABSTRACT FROM AUTHOR]

Study Question: Can high resolution array-CGH analysis on a cohort of women showing a primary ovarian insufficiency (POI) phenotype in young age identify copy number variants (CNVs) with a deleterious effect on ovarian function?Summary Answer: This approach has proved effective to clarify the role of CNVs in POI pathogenesis and to better unveil both novel candidate genes and pathogenic mechanisms.What Is Known Already: POI describes the progression toward the cessation of ovarian function before the age of 40 years. Genetic causes are highly heterogeneous and despite several genes being associated with ovarian failure, most of genetic basis of POI still needs to be elucidated.Study Design, Size, Duration: The current study included 67 46,XX patients with early onset POI (<19 years) and 134 control females recruited between 2012 and 2016 at the Medical Cytogenetics and Molecular Genetics Lab, IRCCS Istituto Auxologico Italiano.Participants/materials, Setting, Methods: High resolution array-CGH analysis was carried out on POI patients' DNA. Results of patients and female controls were analyzed to search for rare CNVs. All variants were validated and subjected to a gene content analysis and disease gene prioritization based on the present literature to find out new ovary candidate genes. Case-control study with statistical analysis was carried out to validate our approach and evaluate any ovary CNVs/gene enrichment. Characterization of particular CNVs with molecular and functional studies was performed to assess their pathogenic involvement in POI.Main Results and the Role Of Chance: We identified 37 ovary-related CNVs involving 44 genes with a role in ovary in 32 patients. All except one of the selected CNVs were not observed in the control group. Possible involvement of the CNVs in POI pathogenesis was further corroborated by a case-control analysis that showed a significant enrichment of ovary-related CNVs/genes in patients (P = 0.0132; P = 0.0126). Disease gene prioritization identified both previously reported POI genes (e.g. BMP15, DIAPH2, CPEB1, BNC1) and new candidates supported by transcript and functional studies, such as TP63 with a role in oocyte genomic integrity and VLDLR which is involved in steroidogenesis.Large Scale Data: ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar/); accession numbers SCV000787656 to SCV000787743.Limitations, Reasons For Caution: This is a descriptive analysis for almost all of the CNVs identified. Inheritance studies of CNVs in some non-familial sporadic cases was not performed as the parents' DNA samples were not available. Addionally, RT-qPCR analyses were carried out in few cases as RNA samples were not always available and the genes were not expressed in blood.Wider Implications Of the Findings: Our array-CGH screening turned out to be efficient in identifying different CNVs possibly implicated in disease onset, thus supporting the extremely wide genetic heterogeneity of POI. Since almost 50% of cases are negative rare ovary-related CNVs, array-CGH together with next generation sequencing might represent the most suitable approach to obtain a comprehensive genetic characterization of POI patients.Study Funding/competing Interest(s): Supported by Italian Ministry of Health grants 'Ricerca Corrente' (08C203_2012) and 'Ricerca Finalizzata' (GR-2011-02351636, BIOEFFECT) to IRCCS Istituto Auxologico Italiano. [ABSTRACT FROM AUTHOR]

Very low-density lipoprotein receptor gene (VLDLR) is a part of the low-density lipoprotein receptor (LDLR) family. VLDLR plays important roles in transport egg yolk precursor to the oocyte. This work was conducted to study the effect of VLDLR polymorphism on the productive performance of local Iraqi chickens. In this study, the VLDLR gene was studied using blood samples of 173 pedigreed hens aged 47 weeks representing the third generation selected for high egg production. Genotypic and alleles frequencies in addition to the association between genotypes and egg production, egg weight and egg mass from onset eggs laid to the 80 weeks of age were investigated. The results showed that the genotypic and allelic frequencies of the VLDLR in 173 chickens did not agree with Hardy- Weinberg equilibrium (P<0.0307). The genotypic frequencies were 94.7 and 5.3% for both GG and GT genotypes respectively while, the allele frequency of genes G and T were 97.4 and 2.6%, respectively. The results showed an increase (P<0.0001) in egg production, egg weight and egg of GG genotypes compared to GT genotypes. This finding supports the previous results of VLDLR as a compromising gene. The current results approved that the VLDLR gene can be used as a candidate gene for modulating and improving egg production traits in Iraqi local chickens. [ABSTRACT FROM AUTHOR]

The canonical Reelin signaling cascade regulates correct neuronal layering during embryonic brain development. Details of this pathway are still not fully understood since the participating components are highly variable and create a complex mixture of interacting molecules. Reelin is proteolytically processed resulting in five different fragments some of which carrying the binding site for two different but highly homologous receptors, apolipoprotein E receptor 2 (ApoER2) and very low density lipoprotein receptor (VLDLR). The receptors are expressed in different variants in different areas of the developing brain. Binding of Reelin and its central fragment to the receptors results in phosphorylation of the intracellular adapter disabled-1 (Dab1) in neurons. Here, we studied the changes of the arrangement of the receptors upon Reelin binding and its central fragment at the molecular level in human embryonic kidney 293 (HEK293) cells by time-resolved anisotropy and fluorescence lifetime imaging microscopy (FLIM). In the off-state of the pathway ApoER2 and VLDLR form homo or hetero-di/oligomers. Upon binding of full length Reelin ApoER2 and VLDLR homo-oligomers are rearranged to higher order receptor clusters which leads to Dab1 phosphorylation. When the central fragment of Reelin binds to the receptors the cluster size of homo-oligomers is not affected and Dab1 is not phosphorylated. Hetero-oligomerization, however, can be induced, but does not lead to Dab1 phosphorylation. Cells expressing only ApoER2 or VLDLR change their shape when stimulated with the central fragment. Cells expressing ApoER2 produce filopodia/lamellipodia and cell size increases, whereas VLDLR-expressing cells decrease in size. These findings demonstrate that the primary event in the canonical Reelin pathway is the rearrangement of preformed receptor homo-oligomers to higher order clusters. In addition the possibility of yet another signaling mechanism which is mediated by the central Reelin fragment independent of Dab1 phosphorylation became apparent. [ABSTRACT FROM AUTHOR]

Niemann–Pick disease, type C1, is a cholesterol storage disease where unesterified cholesterol accumulates intracellularly. In the cerebellum this causes neurodegeneration of the Purkinje neurons that die in an anterior-to-posterior and time-dependent manner. This results in cerebellar ataxia as one of the major outcomes of the disease. Proprotein convertase subtilisin/kexin type 9 (PCSK9) plays a significant role in the regulation of serum cholesterol levels by modulating LDL receptor levels on peripheral tissues. In the central nervous system, PCSK9 may have a similar effect on the closely related VLDL and ApoE2 receptors to regulate brain cholesterol. In addition, regulation of VLDLR and ApoER2 by PCSK9 may contribute to neuronal apoptotic pathways through Reelin, the primary ligand of VLDLR and ApoER2. Defects in reelin signaling results in cerebellar dysfunction leading to ataxia as seen in the Reeler mouse. Our recent findings that Pcsk9 is expressed ~8-fold higher in the anterior lobules of the cerebellum compared to the posterior lobule X, which is resistant to neurodegeneration, prompted us to ask whether PCSK9 could play a role in NPC1 disease progression. We addressed this question genetically, by characterizing NPC1 disease in the presence or absence of PCSK9. Analysis of double mutant Pcsk9-/-/Npc1-/- mice by disease severity scoring, motor assessments, lifespan, and cerebellar Purkinje cell staining, showed no obvious difference in NPC1 disease progression with that of Npc1-/- mice. This suggests that PCSK9 does not play an apparent role in NPC1 disease progression.

Cerebellar and hindbrain malformations, such as cerebellar hypoplasia (CH), vermis hypoplasia, and Dandy–Walker malformation, occur in dogs as well as in humans. Neuroimaging is essential for a precise description of these malformations and defining translational animal models. Neuroimaging is increasingly performed in puppies, but there is a lack of data on developmental changes in the caudal fossa, which can impair assessment of caudal fossa size in this age group. The purpose of this study was to validate caudal fossa ratio (CFR) in dogs and to explore CFR in Eurasier dogs with genetic CH. CFR was calculated from midsagittal brain images of 130 dogs as caudal fossa area/total cranial cavity area. In addition, the volume of the caudal fossa was measured in 64 randomly selected dogs from this group. Repeated measurements were used to investigate inter- and intra-rater variability and influence of imaging modality. Furthermore, the influence of age, weight, and breed was explored. The CFR was a reliable parameter with negligible influence from the examiners, imaging modality, and weight of the dog. The midsagittal area of the caudal fossa and the volume of the caudal fossa correlated closely with each other. In this study, we observed a smaller CFR in puppies. The CFR in adult dogs lies within 0.255 and 0.330, while CFR is smaller in puppies up to 4 months of age. Besides age, there was also an effect of breed, which should be explored in larger data sets. Measurements of CFR in Eurasier dogs with genetic CH caused by a mutation in the very-low-density-lipoprotein-receptor gene revealed the presence of two variants, one with an enlarged caudal fossa and one with a normal to small caudal fossa. This observation indicates that there is phenotypic heterogeneity and interaction between the developing cerebellum and the surrounding mesenchyme in this animal model.

Objective The very low-density lipoprotein receptor (VLDLR) plays an important role in the development of hepatic steatosis. In this study, we investigated the role of Peroxisome Proliferator-Activated Receptor (PPAR)β/δ and fibroblast growth factor 21 (FGF21) in hepatic VLDLR regulation. Methods Studies were conducted in wild-type and Pparβ/δ -null mice, primary mouse hepatocytes, human Huh-7 hepatocytes, and liver biopsies from control subjects and patients with moderate and severe hepatic steatosis. Results Increased VLDLR levels were observed in liver of Pparβ/δ -null mice and in Pparβ/δ -knocked down mouse primary hepatocytes through mechanisms involving the heme-regulated eukaryotic translation initiation factor 2α (eIF2α) kinase (HRI), activating transcription factor (ATF) 4 and the oxidative stress-induced nuclear factor (erythroid-derived 2)-like 2 (Nrf2) pathways. Moreover, by using a neutralizing antibody against FGF21, Fgf21 -null mice and by treating mice with recombinant FGF21, we show that FGF21 may protect against hepatic steatosis by attenuating endoplasmic reticulum (ER) stress-induced VLDLR upregulation. Finally, in liver biopsies from patients with moderate and severe hepatic steatosis, we observed an increase in VLDLR levels that was accompanied by a reduction in PPARβ/δ mRNA abundance and DNA-binding activity compared with control subjects. Conclusions Overall, these findings provide new mechanisms by which PPARβ/δ and FGF21 regulate VLDLR levels and influence hepatic steatosis development. [ABSTRACT FROM AUTHOR]

Summary It is unknown whether and how very-low density lipoprotein receptors (VLDLRs) impact skeletal homeostasis. Here, we report that maternal and offspring VLDLRs play opposite roles in osteoclastogenesis and bone resorption. VLDLR deletion in the offspring augments osteoclast differentiation by enhancing RANKL signaling, leading to osteoporosis. In contrast, VLDLR deletion in the mother alters milk metabolism, which inhibits osteoclast differentiation and causes osteopetrosis in the offspring. The maternal effects are dominant. VLDLR-null lactating mammary gland exhibits higher mTORC1 signaling and cholesterol biosynthesis. Pharmacological probing reveals that rapamycin, but not statin, treatment of the VLDLR-null mother can prevent both the low bone resorption and our previously described inflammatory fur loss in their offspring. Genetic rescue reveals that maternal mTORC1 attenuation in adipocytes, but not in myeloid cells, prevents offspring osteopetrosis and fur loss. Our studies uncover functions of VLDLR and mTORC1 in lactation and osteoclastogenesis, illuminating key mechanisms and therapeutic insights for bone and metabolic diseases. [ABSTRACT FROM AUTHOR]

We discovered a hypomorphic reelin (Reln) mutant with abnormal cortical lamination and no cerebellar hypoplasia. This mutant, RelnCTRdel, carries a chemically induced splice-site mutation that truncates the C-terminal region (CTR) domain of RELN protein and displays remarkably distinct phenotypes from reeler. The mutant does not have an inverted cortex, but cortical neurons overmigrate and invade the marginal zone, which are characteristics similar to a phenotype seen in the cerebral cortex of Vldlrnull mice. The dentate gyrus shows a novel phenotype: the infrapyramidal blade is absent, while the suprapyramidal blade is present and laminated. Genetic epistasis analysis showed that RelnCTRdel/Apoer2null double homozygotes have phenotypes akin to those of reeler mutants, while RelnCTRdel/Vldlrnull mice do not. Given that the receptor double knock-out mice resemble reeler mutants, we infer that RelnCTRdel/Apoer2null double homozygotes have both receptor pathways disrupted. This suggests that CTR-truncation disrupts an interaction with VLDLR (very low-density lipoprotein receptor), while the APOER2 signaling pathway remains active, which accounts for the hypomorphic phenotype in RelnCTRdel mice. A RELN-binding assay confirms that CTR truncation significantly decreases RELN binding to VLDLR, but not to APOER2. Together, the in vitro and in vivo results demonstrate that the CTR domain confers receptor-binding specificity of RELN. [ABSTRACT FROM AUTHOR]

Reelin is an extracellular signaling protein synthesized by Cajal-Retius cells in utero and early after birth, its presence being signaled in adult life too. Reelin acts on its receptors, VLDLR and ApoER2, acting on cytoskeleton, controlling migration and subsequently positioning and stabilizing the cortical neurons. We investigated the reelin presence and its receptors, VLDLR and ApoER2, in melanocytic nevi considering the neural crest origin of the nevus cells and their migration into skin during embrionary period. Melanocytic nevi present a strict cellular architecture and an increased malignant transforming capacity. We investigated reelin presence in 32 melanocytic nevi (5 junctional, 27 compound or 14 dysplastic nevi and 18 non dysplastic nevi). The assessment of reelin presence was performed by histological semiquantitative criteria. Results showed the presence of reelin in 29 cases (29/ 32). The presence of reelin was elevated in junctional areas as in dysplastic nevi. VLDLR presented positive values in 16 cases (16/ 32) and ApoER2 was weak positive in 7 cases. Reelin or its receptors was peritumorally absent. Our study showed the presence of reelin in nevus cells from cutaneous melanocytic nevi and, in these cells, only the VLDLR receptor was present in half of the cases. The significance of the reelin presence in cutaneous nevus cells may be hypothetically considered correlated with the position maintenance of the nevus cells or migration of these cells in malignant transforming situation. [ABSTRACT FROM AUTHOR]

Semliki Forest virus (SFV) is an alphavirus that uses the very-low-density lipoprotein receptor (VLDLR) as a receptor during infection of its vertebrate hosts and insect vectors. Herein, we used cryoelectron microscopy to study the structure of SFV in complex with VLDLR. We found that VLDLR binds multiple E1-DIII sites of SFV through its membrane-distal LDLR class A (LA) repeats. Among the LA repeats of the VLDLR, LA3 has the best binding affinity to SFV. The high-resolution structure shows that LA3 binds SFV E1-DIII through a small surface area of 378 Å2, with the main interactions at the interface involving salt bridges. Compared with the binding of single LA3s, consecutive LA repeats around LA3 promote synergistic binding to SFV, during which the LAs undergo a rotation, allowing simultaneous key interactions at multiple E1-DIII sites on the virion and enabling the binding of VLDLRs from divergent host species to SFV. [Display omitted] • The receptor VLDLR binds multiple E1-DIII sites of SFV through its LA repeats • Single LA binds E1-DIII with a small contact surface and a low binding affinity • Multiple LAs promote synergistic binding and a high binding affinity to SFV Semliki Forest virus (SFV) enters host cells by binding to repeat regions of the host cell's very-low-density lipoprotein receptors. The repeat regions enable synergic, multimodal binding with SFV, which is highly tolerant of mutations, allowing SFV to bind efficiently to the receptors of highly divergent species. [ABSTRACT FROM AUTHOR]

Pontocerebellar hypoplasias ( PCH) are characterized by lack of development and/or early neurodegeneration of cerebellum and brainstem. We report five patients referred for PCH, showing atypical clinical and magnetic resonance imaging ( MRI) features suggestive of defects in the Reelin pathway. We screened for mutations in RELN or VLDLR and compared the phenotype of these patients with that of previously reported patients. All patients had profound cerebellar hypoplasia on MRI with peculiar cerebellar morphology, associated with flattened pons and neocortical abnormalities. Patient 1 had profound motor and intellectual disability with moderate lissencephaly suggestive of RELN mutations and was shown to harbor a splicing homozygous RELN mutation. The four other patients had a milder phenotype consistent with CARMQ1 (cerebellar ataxia and mental retardation with or without quadrupedal locomotion). These patients showed mild simplification or thickening of cortical gyration and had VLDLR mutations. Reelin signaling regulates neuronal migration in the developing mammalian brain. VLDLR is a key component of the Reelin pathway. Our patients had a very small and dysplatic cerebellar vermis that should suggest the involvement of these genes. Moreover, differences in clinical severity, involvement of the cerebellar hemispheres, together with the severity of the neocortical defect, enables RELN-mutated patients to be distinguished from VLDLR-mutated patients. [ABSTRACT FROM AUTHOR]

Reelin is a neuronal glycoprotein secreted by the Cajal-Retzius cells in marginal regions of the cerebral cortex and the hippocampus where it plays important roles in the control of neuronal migration and the formation of cellular layers during brain development. This 3461 residue-long protein is composed of a signal peptide, an F-spondin-like domain, eight Reelin repeats (RR1-8), and a positively charged sequence at the C-terminus. Biochemical data indicate that the central region of Reelin binds to the low-density lipoprotein receptors ApoER2 and VLDLR, leading to the phosphorylation of the intracellular adaptor protein Dab1. After secretion, Reelin is rapidly degraded in three major fragments, but the functional significance of this degradation is poorly understood. Probably due to its large mass and the complexity of its architecture, the high-resolution, three-dimensional structure of Reelin has never been determined. However, the crystal structures of some of the reelin repeats have been solved, providing important insights into their fold and the interaction with the ApoER2 receptor. This review discusses the current findings on the structure of Reelin and its binding to the ApoER2 and VLDLR receptors, and we discuss some areas where proteomics and structural biology can help understanding Reelin function in brain development and human health.

Mutations of the transcription factor FOXP2 cause a severe speech and language disorder. In songbirds, FoxP2 is expressed in the medium spiny neurons (MSNs) of the avian basal ganglia song nucleus, Area X, which is crucial for song learning and adult song performance. Experimental downregulation of FoxP2 in Area X affects spine formation, prevents neuronal plasticity induced by social context and impairs song learning. Direct target genes of FoxP2 relevant for song learning and song production are unknown. Here we show that a lentivirally mediated FoxP2 knockdown in Area X of zebra finches downregulates the expression of VLDLR , one of the two reelin receptors. Zebra finch FoxP2 binds to the promoter of VLDLR and activates it, establishing VLDLR as a direct FoxP2 target. Consistent with these findings, VLDLR expression is co-regulated with FoxP2 as a consequence of adult singing and during song learning. We also demonstrate that knockdown of FoxP2 affects glutamatergic transmission at the corticostriatal MSN synapse. These data raise the possibility that the regulatory relationship between FoxP2 and VLDLR guides structural plasticity towards the subset of FoxP2-positive MSNs in an activity dependent manner via the reelin pathway. [ABSTRACT FROM AUTHOR]

Dysequilibrium syndrome (DES) is a non-progressive congenital ataxia characterized by severe intellectual deficit, truncal ataxia and markedly delayed, quadrupedal or absent ambulation. Recessive loss-of-function mutations in the very low density lipoprotein receptor ( VLDLR) gene represent the most common cause of DES. Only two families have been reported harbouring homozygous missense mutations, both with a similarly severe phenotype. We report an Italian girl with very mild DES caused by the novel homozygous VLDLR missense mutation p.(C419Y). This unusually benign phenotype possibly relates to a less disruptive effect of the mutation, falling within a domain (EGF-B) not predicted as crucial for the protein function. [ABSTRACT FROM AUTHOR]

Reelin is a neuronal glycoprotein secreted by the Cajal-Retzius cells in marginal regions of the cerebral cortex and the hippocampus where it plays important roles in the control of neuronal migration and the formation of cellular layers during brain development. This 3461 residue-long protein is composed of a signal peptide, an F-spondin-like domain, eight Reelin repeats (RR1-8), and a positively charged sequence at the C-terminus. Biochemical data indicate that the central region of Reelin binds to the low-density lipoprotein receptors apolipoprotein E receptor 2 (ApoER2) and the very-low-density lipoprotein receptor (VLDLR), leading to the phosphorylation of the intracellular adaptor protein Dab1. After secretion, Reelin is rapidly degraded in three major fragments, but the functional significance of this degradation is poorly understood. Probably due to its large mass and the complexity of its architecture, the high-resolution, three-dimensional structure of Reelin has never been determined. However, the crystal structures of some of the RRs have been solved, providing important insights into their fold and the interaction with the ApoER2 receptor . This review discusses the current findings on the structure of Reelin and its binding to the ApoER2 and VLDLR receptors, and we discuss some areas where proteomics and structural biology can help understanding Reelin function in brain development and human health. [ABSTRACT FROM AUTHOR]

Lipoprotein receptor family members hold multiple roles in the brain, and alterations in lipoprotein receptor expression and function are implicated in neuronal stress, developmental disorders and neurodegenerative diseases, such as Alzheimer's disease. Berberine (BBR), a nutraceutical shown to have both neuroprotective and neurotoxic properties, is suggested to regulate lipoprotein receptor expression. We show that subtoxic concentration of BBR regulates neuronal lipoprotein receptor expression in a receptor- and time-dependent fashion in cerebellar granule neurons (CGN). Similarly to BBR, subtoxic concentrations of neuronal stressors cobalt chloride, thapsigargin and rotenone increased very-low-density lipoprotein receptor (VLDLR) mRNA and protein expression in CGN suggesting a conserved pathway for stress-induced upregulation of VLDLR in neurons. We also show that VLDLR upregulation is accompanied by transiently increased stabilization of hypoxia-induced factor 1 alpha (HIF-1α) and decreased β-catenin levels affecting the Wnt pathway through GSK3β phosphorylation, a crucial player in neurodegenerative processes. Our results indicate that neuronal stress differentially regulates lipoprotein receptor expression in neurons, with VLDLR upregulation as a common element as a modulator of neuronal Wnt signaling. [ABSTRACT FROM AUTHOR]

Various host factors are involved in the cellular entry of hepatitis C virus (HCV). In addition to the factors previously reported, we discovered that the very-low-density lipoprotein receptor (VLDLR) mediates HCV entry independent of CD81. Culturing Huh7.5 cells under hypoxic conditions significantly increased HCV entry as a result of the expression of VLDLR, which was not expressed under normoxic conditions in this cell line. Ectopic VLDLR expression conferred susceptibility to HCV entry of CD81-deficient Huh7.5 cells. Additionally, VLDLR-mediated HCV entry was not affected by the knockdown of cellular factors known to act as HCV receptors or HCV entry factors. Because VLDLR is expressed in primary human hepatocytes, our results suggest that VLDLR functions in vivo as an HCV receptor independent of canonical CD81-mediated HCV entry. [ABSTRACT FROM AUTHOR]

Reelin is an extracellular matrix protein that is defective in reeler mutant mice and plays a key role in the organization of architectonic patterns, particularly in the cerebral cortex. In mammals, a "reelin signal" is activated when reelin, secreted by Cajal-Retzius neurons, binds to receptors of the lipoprotein receptor family on the surface of cortical plate cells, and triggers Dab1 phosphorylation. As reelin is a key component of cortical development in mammals, comparative embryological studies of reelin expression were carried out during cortical development in non-mammalian amniotes (turtles, squamates, birds and crocodiles) in order to assess the putative role of reelin during cortical evolution. The data show that reelin is present in the cortical marginal zone in all amniotes, and suggest that reelin has been implicated in the evolution of the radial organization of the cortical plate in the synapsid lineage leading from stem amniotes to mammals, as well as in the lineage leading to squamates, thus providing an example of homoplastic evolution (evolutionary convergence). The mechanisms by which reelin instructs radial cortical organization in these two lineages seem different: in the synapsid lineage, a drastic amplification of reelin production occurred in Cajal-Retzius cells, whereas in squamates, in addition to reelin-secreting cells in the marginal zone, a second layer of reelin-producing cells developed in the subcortex. Altogether, our results suggest that the reelin-signaling pathway has played a significant role in shaping the evolution of cortical development.