Density Lipoprotein Receptor-related Protein Research Articles

Simvastatin induces degradation of the extracellular matrix in human leiomyomata: novel in vitro, in vivo, and patient level evidence of matrix metalloproteinase involvement

ObjectivesTo assess the effect of simvastatin on uterine leiomyoma growth and extracellular matrix (ECM) deposition. DesignLaboratory analysis of human leiomyoma cell culture, xenograft in a mouse model, and patient tissue from a clinical trial. SettingAcademic research center. Patient(s)Tissue culture from human leiomyoma tissue and surgical leiomyoma tissue sections from a placebo-controlled randomized clinical trial. Intervention(s)Simvastatin treatment. Main Outcome Measure(s)Serum concentrations, xenograft volumes, and protein expression. ResultsMice xenografted with 3-dimensional human leiomyoma cultures were divided as follows: 7 untreated controls, 12 treated with activated simvastatin at 10 mg/kg body weight, and 15 at 20 mg/kg body weight. Simvastatin was detected in serum from mice injected at the highest dose. Xenograft volumes were significantly smaller (mean 53% smaller at the highest concentration, p < 0.05). There was dissolution of compact ECM, decreased ECM formation, and lower collagen protein expression in xenografts. Membrane type 1 matrix metalloproteinase (MT1-MMP) was increased in vitro and in vivo. Matrix metalloproteinase 2 (MMP2) and low density lipoprotein receptor related protein 1 (LRP1) were increased in vitro. ConclusionsSimvastatin exhibited antitumoral activity, with extracellular matrix degradation and decreased leiomyoma tumor volume in vivo. Activation of the MMP2/MT1-MMP/LRP1 pathway may explain these findings.

Megalin Facilitates the Regulation of Mitochondrial Function by Extracellular Cues

ABSTRACT Megalin (also known as low density lipoprotein-receptor related protein 2 [LRP2]) is a multi-ligand cell-surface endocytic receptor expressed widely; it is important for the uptake of vitamins, nutrients and hormones. We recently reported the discovery of LRP2/megalin in the mitochondria of many cells and organs. Importantly, megalin traffics the mitochondrial intracrines stanniocalcin-1, TGF-β and angiotensin II from the extracellular milieu to the mitochondria. This transport parallels the retrograde early endosome to Golgi pathway and requires the Rab GTPase Rab32 in the mitochondria, megalin associates with sirtuin family of class III histone deacetylases (Sirt3) and stanniocalcin-1 (Stc1), which are important for anti-oxidant defenses. Deletion of megalin impairs mitochondrial respiration and glycolysis. The interaction between stanniocalcin-1 and megalin is mediated by leucines within the signal peptides of the proteins; and this interaction is essential to the stimulation of mitochondrial respiration and glycolysis by stanniocalcin-1. Our findings suggest that megalin facilitates the regulation of mitochondrial function by extracellular cues.

Development of Vyvgart (Efgartigimod Alfa-Fcab) for Generalized Myasthenia Gravis (gMG) Therapy

Generalized myasthenia gravis (gMG) is a type of myasthenia gravis (MG), a relatively rare neurological disease which would lead to muscle weakness and be life threatening. The pathogenesis of MG is associated with antibodies against acetylcholine receptors, which blocks the neuromuscular transmission. Vyvgart (efgartigimod alfa-fcab) is a recently approved drug for gMG therapy that targets the neonatal Fc receptor (FcRn). By inhibiting the interaction between FcRn and Immunoglobulin G (IgG), efgartigimod promotes the degradation of IgG and autoantibodies, therefore alleviates the symptoms of gMG. Antibodies against the acetylcholine receptor (AChR), muscle-specific kinase (MuSK) or low- density lipoprotein receptor related protein 4 in the postsynaptic muscle membrane would lead to the blocking of the receptors, and block the movement of muscle. Vyvgart (efgartigimod alfa-fcab) is a promising drug, this article contains a brief introduction to the pathogenesis of MG, information about the identification of FcRn as an effective target, and the development as well as advantages of Vyvgart.

Thymosin β4 preserves vascular smooth muscle phenotype in atherosclerosis via regulation of low density lipoprotein related protein 1 (LRP1).

Atherosclerosis is a progressive, degenerative vascular disease and a leading cause of morbidity and mortality. In response to endothelial damage, platelet derived growth factor (PDGF)-BB induced phenotypic modulation of medial smooth muscle cells (VSMCs) promotes atherosclerotic lesion formation and destabilisation of the vessel wall. VSMC sensitivity to PDGF-BB is determined by endocytosis of Low density lipoprotein receptor related protein 1 (LRP1)-PDGFR β complexes to balance receptor recycling with lysosomal degradation. Consequently, LRP1 is implicated in various arterial diseases. Having identified Tβ4 as a regulator of LRP1-mediated endocytosis to protect against aortic aneurysm, we sought to determine whether Tβ4 may additionally function to protect against atherosclerosis, by regulating LRP1-mediated growth factor signalling. By single cell transcriptomic analysis, Tmsb4x, encoding Tβ4, strongly correlated with contractile gene expression and was significantly down-regulated in cells that adopted a modulated phenotype in atherosclerosis. We assessed susceptibility to atherosclerosis of global Tβ4 knockout mice using the ApoE-/- hypercholesterolaemia model. Inflammation, elastin integrity, VSMC phenotype and signalling were analysed in the aortic root and descending aorta. Tβ4KO; ApoE-/- mice develop larger atherosclerotic plaques than control mice, with medial layer degeneration characterised by accelerated VSMC phenotypic modulation. Defects in Tβ4KO; ApoE-/- mice phenocopied those in VSMC-specific LRP1 nulls and, moreover, were underpinned by hyperactivated LRP1-PDGFRβ signalling. We identify an atheroprotective role for endogenous Tβ4 in maintaining differentiated VSMC phenotype via LRP1-mediated PDGFRβ signalling.

MTOR is involved in LRP5-induced osteogenic differentiation of normal and aged periodontal ligament stem cells in vitro.

Periodontal ligament stem cells (PDLSCs) plays an important role in tissue engineering. As the age increased, the cell viability and osteogenic differentiation of PDLSCs all decreased. Low density lipoprotein receptor related protein 5 (LRP5) was found to promote bone marrow mesenchymal stem cells osteogenic differentiation. Therefore, our study explored the effect of LRP5 on normal and aged PDLSCs and relative mechanism. Here, we found that the expression of LRP5 in PDLSCs of 24week-old mice was decreased compared with PDLSCs of 5week-old mice (n = 5). . LRP5 overexpression in PDLSCs increased the intensity of alkaline phosphatase and alizarin red staining, accompanied with upregulated the levels of RUNX family transcription factor 2, collagen type I, and β-Catenin. LRP5 knockdown displayed the opposite results in PDLSCs in vitro.LRP5 overexpression in aged PDLSCs restored part ability of osteogenic differentiation. Meantime, LRP5 increased the protein expression of phosphorylation of mammalian target of rapamycin (p-mTOR) in normal and aged PDLSCs. Immunofluorescence showed that LRP5 increased the accumulation of p-mTOR nucleus. The effect of LRP5 in promoting osteogenic differentiation of PDLSCs can be antagonized by mTOR inhibitor rapamycin. These findings suggest that LRP5 positively regulate osteogenic differentiation of normal and aged PDLSCs and may be a potential target for enlarging the application of PDLSCs in tissue regeneration.

Novel melatonin-trientine conjugate as potential therapeutic agents for Alzheimer’s disease

Researchers continue to explore drug targets to treat the characteristic pathologies of Alzheimer's disease (AD). Some drugs relieve the pathological processes of AD to some extent, but the failed clinical trials indicate that multifunctional agents seem more likely to achieve the therapy goals for this neurodegenerative disease. Herein, a novel compound named melatonin-trientine (TM) has been covalently synthesized with the natural antioxidant compounds melatonin and the metal ion chelator trientine. After toxicological and pharmacokinetic verification, we elucidated the effects of intraperitoneal administration of TM on AD-like pathology in 6-month-old mice that express both the β-amyloid (Aβ) precursor protein and presenilin-1 (APP/PS1). We found that TM significantly decreased Aβ deposition and neuronal degeneration in the brains of the APP/PS1 double transgenic mice. This result may be due to the upregulation of iron regulatory protein-2 (IRP2), insulin degrading enzyme (IDE), and low density lipoprotein receptor related protein 1 (LRP1), which leads to decreases in APP and Aβ levels. Additionally, TM may promote APP non-amyloidogenic processing by activating the melatonin receptor-2 (MT2)-dependent signaling pathways, but not MT1. In addition, TM plays an important role in blocking γ-secretase, tau hyperphosphorylation, neuroinflammation, oxidative stress, and metal ion dyshomeostasis. Our results suggest that TM may effectively maximize the therapeutic efficacy of targeting multiple mechanisms associated with AD pathology.

Interaction between oxidative stress and epigenetics decreases the low density lipoprotein receptor related protein 1 (LRP1) expression on the blood-brain barrier (BBB) in Alzheimer’s disease

Interaction between oxidative stress and epigenetics decreases the low density lipoprotein receptor related protein 1 (LRP1) expression on the blood-brain barrier (BBB) in Alzheimer’s disease

Neural Dynamics of the Primate Attention Network

The objective of this study was to investigate the effects of maternal nutritional restriction on fetal growth and bone metabolism in early pregnancy. Twelve twin-bearing goats (Xiangdong black goats) in second pregnancy, with similar weight (31.2 ± 8.1 kg) and age (2.0 ± 0.3 year) were assigned to two dietary treatments in early gestation (26–65 days): control group (CON, 100% feed) and intake restriction group (IR, 60% of CON intake). The umbilical blood, right femur and liver of the fetuses were sampled on day 65 to determine the bone metabolism indicators and expression of genes involved in bone development. Maternal intake restriction did not affect the growth performance of pregnancies (P > 0.05), increased (P < 0.05) the body weight, body length, thoracic circumference and umbilical circumference of fetal goats, but decreased (P < 0.05) the concentrations of cross-linked N-terminal telopeptides of type I collagen and cross-linked C-terminal telopeptides of type I collagen, which involved in bone metabolic activity, in the fetal umbilical blood of the IR. In fetal femurs, the mRNA expression of bone gamma-carboxyglutamate protein, osteoprotegerin and mothers against decapentaplegic homolog 1 both participating in osteoclast differentiation were increased (P < 0.05), whereas transcript of the low density lipoprotein receptor related protein 5 involved in osteoblast differentiation was decreased (P < 0.05), compared with the fetuses from the CON. These results indicate that nutrition restriction in early pregnancy regulated the fetal growth and promoted formative activity of femur. The molecular mechanism of maternal intake restriction on bone metabolism needs further investigation.

Thymosin β4 protects against aortic aneurysm via endocytic regulation of growth factor signaling.

Vascular stability and tone are maintained by contractile smooth muscle cells (VSMCs). However, injury-induced growth factors stimulate a contractile-synthetic phenotypic modulation which increases susceptibility to abdominal aortic aneurysm (AAA). As a regulator of embryonic VSMC differentiation, we hypothesized that Thymosin β4 (Tβ4) may function to maintain healthy vasculature throughout postnatal life. This was supported by the identification of an interaction with low density lipoprotein receptor related protein 1 (LRP1), an endocytic regulator of platelet-derived growth factor BB (PDGF-BB) signaling and VSMC proliferation. LRP1 variants have been implicated by genome-wide association studies with risk of AAA and other arterial diseases. Tβ4-null mice displayed aortic VSMC and elastin defects that phenocopy those of LRP1 mutants, and their compromised vascular integrity predisposed them to Angiotensin II–induced aneurysm formation. Aneurysmal vessels were characterized by enhanced VSMC phenotypic modulation and augmented PDGFR-β signaling. In vitro, enhanced sensitivity to PDGF-BB upon loss of Tβ4 was associated with dysregulated endocytosis, with increased recycling and reduced lysosomal targeting of LRP1–PDGFR-β. Accordingly, the exacerbated aneurysmal phenotype in Tβ4-null mice was rescued upon treatment with the PDGFR-β antagonist Imatinib. Our study identifies Tβ4 as a key regulator of LRP1 for maintaining vascular health, and provides insights into the mechanisms of growth factor–controlled VSMC phenotypic modulation underlying aortic disease progression.

Theranostic Design of Angiopep-2 Conjugated Hyaluronic Acid Nanoparticles (Thera-ANG-cHANPs) for Dual Targeting and Boosted Imaging of Glioma Cells.

Simple SummaryGlioblastoma multiforme is the most aggressive malignant brain tumor with poor patient prognosis. The presence of the blood-brain barrier and the complex tumor microenvironment impair the efficient accumulation of drugs and contrast agents, causing late diagnosis, inefficient treatment and monitoring. Functionalized theranostic nanoparticles are a valuable tool to modulate biodistribution of active agents, promoting their active delivery and selective accumulation for an earlier diagnosis and effective treatment, and provide simultaneous therapy and imaging for improved evaluation of treatment efficacy. In this work, we developed angiopep-2 functionalized crosslinked hyaluronic acid nanoparticles encapsulating gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and irinotecan (Thera-ANG-cHANPs) that were shown to boost relaxometric properties of Gd-DTPA by the effect of Hydrodenticity, improve the uptake of nanoparticles by the exploitation of angiopep-2 improved transport properties, and accelerate the therapeutic effect of Irinotecan.Glioblastoma multiforme (GBM) has a mean survival of only 15 months. Tumour heterogeneity and blood-brain barrier (BBB) mainly hinder the transport of active agents, leading to late diagnosis, ineffective therapy and inaccurate follow-up. The use of hydrogel nanoparticles, particularly hyaluronic acid as naturally occurring polymer of the extracellular matrix (ECM), has great potential in improving the transport of drug molecules and, furthermore, in facilitatating the early diagnosis by the effect of hydrodenticity enabling the T1 boosting of Gadolinium chelates for MRI. Here, crosslinked hyaluronic acid nanoparticles encapsulating gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and the chemotherapeutic agent irinotecan (Thera-cHANPs) are proposed as theranostic nanovectors, with improved MRI capacities. Irinotecan was selected since currently repurposed as an alternative compound to the poorly effective temozolomide (TMZ), generally approved as the gold standard in GBM clinical care. Also, active crossing and targeting are achieved by theranostic cHANPs decorated with angiopep-2 (Thera-ANG-cHANPs), a dual-targeting peptide interacting with low density lipoprotein receptor related protein-1(LRP-1) receptors overexpressed by both endothelial cells of the BBB and glioma cells. Results showed preserving the hydrodenticity effect in the advanced formulation and internalization by the active peptide-mediated uptake of Thera-cHANPs in U87 and GS-102 cells. Moreover, Thera-ANG-cHANPs proved to reduce ironotecan time response, showing a significant cytotoxic effect in 24 h instead of 48 h.

Low density lipoprotein receptor related protein 6 (LRP6) protects heart against oxidative stress by the crosstalk of HSF1 and GSK3β

Low density lipoprotein receptor-related protein 6 (LRP6), a Wnt co-receptor, induces multiple functions in various organs. We recently reported cardiac specific LRP6 deficiency caused cardiac dysfunction in mice. Whether cardiomyocyte-expressed LRP6 protects hearts against ischemic stress is largely unknown. Here, we investigated the effects of cardiac LRP6 in response to ischemic reperfusion (I/R) injury. Tamoxifen inducible cardiac specific LRP6 overexpression mice were generated to build I/R model by occlusion of the left anterior descending (LAD) coronary artery for 40 min and subsequent release of specific time. Cardiac specific LRP6 overexpression significantly ameliorated myocardial I/R injury as characterized by the improved cardiac function, strain pattern and infarct area at 24 h after reperfusion. I/R induced-apoptosis and endoplasmic reticulum (ER) stress were greatly inhibited by LRP6 overexpression in cardiomyocytes. LRP6 overexpression enhanced the expression of heat shock transcription factor-1(HSF1) and heat shock proteins (HSPs), the level of p-glycogen synthase kinase 3β(GSK3β)(S9) and p-AMPK under I/R. HSF1 inhibitor deteriorated the apoptosis and decreased p-GSK3β(S9) level in LRP6 overexpressed –cardiomyocytes treated with H2O2. Si-HSF1 or overexpression of active GSK3β significantly attenuated the increased expression of HSF1 and p-AMPK, and the inhibition of apoptosis and ER stress induced by LRP6 overexpression in H2O2-treated cardiomyocytes. AMPK inhibitor suppressed the increase in p-GSK3β (S9) level but didn’t alter HSF1 nucleus expression in LRP6 overexpressed-cardiomyocytes treated with H2O2. Active GSK3β, but not AMPK inhibitor, attenuated the inhibition of ubiquitination of HSF1 induced by LRP6-overexpressed-cardiomyocytes treated with H2O2. LRP6 overexpression increased interaction of HSF1 and GSK3β which may be involved in the reciprocal regulation under oxidative stress. In conclusion, cardiac LRP6 overexpression significantly inhibits cardiomyocyte apoptosis and ameliorates myocardial I/R injury by the crosstalk of HSF1 and GSK3β signaling.

Mutation of LRP1 in cardiac neural crest cells causes congenital heart defects by perturbing outflow lengthening

The recent recovery of mutations in vesicular trafficking genes causing congenital heart disease (CHD) revealed an unexpected role for the endocytic pathway. We now show that mice with a C4232R missense mutation in Low density lipoprotein receptor related protein 1 (LRP1) exhibit atrioventricular septal defects with double outlet right ventricle. Lrp1m/m mice exhibit shortened outflow tracts (OFT) and dysmorphic hypocellular cushions with reduced proliferation and increased apoptosis. Lrp1m/m embryonic fibroblasts show decreased cell motility and focal adhesion turnover associated with retention of mutant LRP1 in endoplasmic reticulum and reduced LRP1 expression. Conditional deletion of Lrp1 in cardiac neural crest cells (CNC) replicates the full CHD phenotype. Cushion explants showed defective cell migration, with gene expression analysis indicating perturbation of Wnt and other signaling pathways. Thus, LRP1 function in CNCs is required for normal OFT development with other cell lineages along the CNC migratory path playing a supporting role.

LRP-1 Promotes Colon Cancer Cell Proliferation in 3D Collagen Matrices by Mediating DDR1 Endocytosis.

Low density lipoprotein receptor related protein-1 (LRP-1) is a large ubiquitous endocytic receptor mediating the clearance of various molecules from the extracellular matrix. Several studies have shown that LRP-1 plays crucial roles during tumorigenesis functioning as a main signal pathway regulator, especially by interacting with other cell-surface receptors. Discoïdin Domain Receptors (DDRs), type I collagen receptors with tyrosine kinase activity, have previously been associated with tumor invasion and aggressiveness in diverse tumor environments. Here, we addressed whether it could exist functional interplays between LRP-1 and DDR1 to control colon carcinoma cell behavior in three-dimensional (3D) collagen matrices. We found that LRP-1 established tight molecular connections with DDR1 at the plasma membrane in colon cancer cells. In this tumor context, we provide evidence that LRP-1 regulates by endocytosis the cell surface levels of DDR1 expression. The LRP-1 mediated endocytosis of DDR1 increased cell proliferation by promoting cell cycle progression into S phase and decreasing apoptosis. In this study, we identified a new molecular way that controls the cell-surface expression of DDR1 and consequently the colon carcinoma cell proliferation and apoptosis and highlighted an additional mechanism by which LRP-1 carries out its sensor activity of the tumor microenvironment.

Rituximab in the Treatment of Refractory Myasthenia Gravis: Studying the Outcomes Using MMT Score And Need for Plasmapheresis in Baghdad Teaching Hospital

Introduction: Myasthenia gravis (MG) is an uncommon autoimmune disease that is caused by acetylcholine receptor antibodies (AChRA) at the neuromuscular junction. Its pathogenesis involves complement fixing antibodies directed against acetylcholine receptors, muscle-specific tyrosine kinase or low density lipoprotein receptor–related protein. Method: A descriptive case series study investigating rituximab in refractory MG was conducted in Baghdad teaching hospital .Patients who were included in the study had received a regimen of rituximab that was deemed appropriate by their treating physician. Results: A total of 24 patients with mean disease duration of 6.3 years ±3.6 standard deviation were included in this study. The results showed that the average age of patients was 33.3 ,years ±10.1 SD and 62.5% was females. All twenty four patients showed an obvious improvement in clinical status after finishing the follow-up period. The results demonstrated from all patients that enrolled in our study, only one patient that who was on 14 sessions of plasmapheresis was in need for plasmapheresis after induction of rituximab and this difference was statistically significant. Conclusion: There were a great clinical improvement as shown with MMT score in addition to discontinuation of plasma exchange treatments fallowing treatment with rituximab.

Rituximab in the Treatment of Refractory Myasthenia Gravis : Studying the Outcomes using MMT Score and Need for Plasmapheresis in Baghdad Teaching Hospital

Introduction: Myasthenia gravis (MG) is an uncommon autoimmune disease that is caused by acetylcholine receptor antibodies (AChRA) at the neuromuscular junction. Its pathogenesis involves complement fixing antibodies directed against acetylcholine receptors, muscle-specific tyrosine kinase or low density lipoprotein receptor–related protein. Method: A descriptive case series study investigating rituximab in refractory MG was conducted in Baghdad teaching hospital .Patients who were included in the study had received a regimen of rituximab that was deemed appropriate by their treating physician. Results: A total of 24 patients with mean disease duration of 6.3 years ±3.6 standard deviation were included in this study. The results showed that the average age of patients was 33.3 ,years ±10.1 SD and 62.5% was females. All twenty four patients showed an obvious improvement in clinical status after finishing the follow-up period. The results demonstrated from all patients that enrolled in our study, only one patient that who was on 14 sessions of plasmapheresis was in need for plasmapheresis after induction of rituximab and this difference was statistically significant. Conclusion: There were a great clinical improvement as shown with MMT score in addition to discontinuation of plasma exchange treatments fallowing treatment with rituximab.

Effects of maternal intake restriction during early pregnancy on fetal growth and bone metabolism in goats

• Effect of maternal intake restriction on bone metabolism of goats was investigated. • Maternal intake restriction during early gestation decreased the INTP and CTX-1 in fetal umbilical blood. • Nutritional restriction during early gestion regulated the femur metabolic activity of fetal goats. The objective of this study was to investigate the effects of maternal nutritional restriction on fetal growth and bone metabolism in early pregnancy. Twelve twin-bearing goats (Xiangdong black goats) in second pregnancy, with similar weight (31.2 ± 8.1 kg) and age (2.0 ± 0.3 year) were assigned to two dietary treatments in early gestation (26–65 days): control group (CON, 100% feed) and intake restriction group (IR, 60% of CON intake). The umbilical blood, right femur and liver of the fetuses were sampled on day 65 to determine the bone metabolism indicators and expression of genes involved in bone development. Maternal intake restriction did not affect the growth performance of pregnancies ( P > 0.05), increased ( P < 0.05) the body weight, body length, thoracic circumference and umbilical circumference of fetal goats, but decreased ( P < 0.05) the concentrations of cross-linked N-terminal telopeptides of type I collagen and cross-linked C-terminal telopeptides of type I collagen, which involved in bone metabolic activity, in the fetal umbilical blood of the IR. In fetal femurs, the mRNA expression of bone gamma-carboxyglutamate protein, osteoprotegerin and mothers against decapentaplegic homolog 1 both participating in osteoclast differentiation were increased ( P < 0.05), whereas transcript of the low density lipoprotein receptor related protein 5 involved in osteoblast differentiation was decreased ( P < 0.05), compared with the fetuses from the CON. These results indicate that nutrition restriction in early pregnancy regulated the fetal growth and promoted formative activity of femur. The molecular mechanism of maternal intake restriction on bone metabolism needs further investigation.

Thymosin Β4 Mediates Vascular Protection Via Regulation Of Low Density Lipoprotein Receptor Related Protein 1 (Lrp1)

Abstract Vascular stability and tone are maintained by contractile smooth muscle cells (VSMCs). However, injury-induced growth factors stimulate a contractile-synthetic phenotypic switch which promotes atherosclerosis and susceptibility to abdominal aortic aneurysm (AAA). As a regulator of embryonic VSMC differentiation, we hypothesised that Thymosin β4 (Tβ4) may additionally function to maintain healthy vasculature and protect against disease throughout postnatal life. This was supported by identification of an interaction with Low density lipoprotein receptor related protein 1 (LRP1), an endocytic regulator of PDGF-BB signalling and VSMC proliferation. LRP1 variants have been identified by GWAS as major risk loci for AAA and coronary artery disease. Tβ4-null mice display aortic VSMC and elastin defects, phenocopying LRP1 mutants and suggesting compromised vascular integrity. We confirmed predisposition to disease in models of atherosclerosis and AAA. Diseased vessels and plaques were characterised by accelerated contractile-synthetic VSMC switching and augmented PDGFRβ signalling. In vitro, enhanced sensitivity to PDGF-BB, upon loss of Tβ4, coincided with dysregulated endocytosis, leading to increased recycling of LRP1-PDGFRβ and reduced lysosomal targeting. Our study identifies Tβ4 as a key regulator of LRP1 for maintaining vascular health, providing insight which may reveal useful therapeutic targets for modulation of VSMC phenotypic switching and disease progression.

LRP1-upregulated nanoparticles for efficiently conquering the blood-brain barrier and targetedly suppressing multifocal and infiltrative brain metastases

Brain metastases present mostly multifocal, infiltrative and co-opting growth with the blood-brain barrier (BBB) remaining intact. The BBB, as the barrier of drug delivery to such lesions, is the major cause of the failure of systemic drug therapy and needs to be conquered. Angiopep-2 ligates the low density lipoprotein receptor related protein 1 (LRP1) on brain microvascular endothelial cells (BMECs) to drive transcytosis for BBB crossing. However, besides tight junction, low transcytosis is increasingly deemed to be a crucial factor in restricting BBB permeability. Herein, it is reported that statins-loaded Angiopep-2-anchored nanoparticles (S@A-NPs) can raise LRP1 expression to surmount the low transcytosis of BBB. We demonstrate that S@A-NPs can selectively heighten LRP1 expression on both BMECs and brain metastatic tumor cells, efficiently and self-promotingly penetrate through the BBB and target brain metastases through Angiopep-2 mediated endocytosis and statins induced LRP1 up-regulation. The systemic administration of S@A-NPs loaded with doxorubicin (S@A-NPs/DOX) observably lengthens median survival of mice bearing brain metastases. Due to the efficient BBB passing and brain metastasis targeting, S@A-NPs/DOX may serve as a potential approach for clinical management of brain metastases.

A Role for Low Density Lipoprotein Receptor Related Protein 1 (LRP1) and Hepatocyte Nuclear Factor 4α (HNF4α) in Regulating Lipid Metabolism

IntroductionLiver is essential for maintaining healthy lipid, carbohydrate, and protein levels. The low density lipoprotein receptor related protein 1 (LRP1) is a multifunctional cell surface receptor that is expressed ubiquitously throughout the body on a variety of cell types. In liver, LRP1 is present on stellate cells, Kupffer cells, biliary cells, and hepatocytes (HEPs), where it is known to be one of the most abundant hepatocellular proteins. Among its many roles, LRP1 is believed to participate in lipoprotein metabolism. Recently, we found that aged mice with a conditional knockout (cKO) for hepatocellular LRP1 (LRP1−) are positive for LRP1 in HEPs that surround the periportal region. Further studies determined that a minor population of LRP1+ cells from younger cKO mice likely repopulates the aged livers over time; the number of periportal positive LRP1+ HEPs increases as the animals age. To determine if these LRP1+ and LRP1− HEPs are functionally different, we stained livers from aged animals for several different proteins and found that the hepatocellular transcription factor, HNF4α, a master regulator of hepatic function, was specifically absent in the LRP1− HEPs where lipids are abundant. Upon further investigation, we determined that in WT animals, LRP1 and HNF4α can form a complex that is present in both the nucleus and cytoplasm, leading us to hypothesize that LRP1 is capable of trafficking HNF4α as a means of regulating lipid metabolism. To begin to investigate this hypothesis, we took advantage of the plasminogen activator inhibitor type 1 (PAI‐1) knockout (KO) mouse as PAI‐1 is known to regulate the internalization of LRP1.MethodsTo confirm complex formation, immunoprecipitation (IP) was performed using total cell lysates from livers of PAI‐1 wild type (WT) and KO mice that were fed either normal chow (NC) or high fat diet (HFD). Next, cytoplasmic‐ and nuclear‐enriched extracts were prepared from these livers and probed by western blot to determine if diet affected complex location. Finally, immunohistochemistry (IHC) was used to localize the proteins.ResultsOverall complex formation was increased in the animals on the HFD, regardless of genotype. Similarly, less complex was found in the cytoplasms of animals on HFD, relative to their NC counterparts, regardless of genotype. Finally, localization of HNF4α was found to be regionalized in the PAI‐1 KOs on HFD, but not in their WT counterparts; HNF4α was present in areas of fat deposition in the PAI‐1 WT animals, but absent in the KOs, further implicating LRP1 in HNF4α trafficking.ConclusionThese findings confirm that LRP1 and HNF4α can form a complex, that diet affects quantity and location of the complex, and further indicates that LRP1 has a role in regulating nuclear localization of HNF4α. Further studies will be needed to elucidate the exact function of the complex, as well as its possible implications for lipid regulation and metabolism.Support or Funding InformationSarah Hoskings was supported by an SROPP award from ASIP as well as SURP funding from the family of Dr. William Zeiler.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

In silico studying of the whole protein structure and dynamics of Dickkopf family members showed that N-terminal domain of Dickkopf 2 in contrary to other Dickkopfs facilitates its interaction with low density lipoprotein receptor related protein 5/6

Wnt (Wingless Int) signaling pathway has been known to be dysregulated in several human cancers, especially colorectal cancer (CRC). The Dickkopf (DKK) family which consists of four secreted proteins in vertebrates (DKK 1, 2, 3, 4) is one of the most critical antagonist families for Wnt signaling pathway. They typically antagonize Wnt/β-catenin signaling by binding and inhibiting Wnt co-receptors, LRP5/6 (low density lipoprotein receptor related protein 5/6). However, except for DKK1 (Dickkopf 1), details about structure and function of the members of this family are poorly defined. In this study, main Dickkopf family members were analyzed structurally, using protein structure prediction tools, molecular dynamics (MD), molecular docking and energy analyses. Three dimensional structure of whole DKKs was predicted and their interaction with LRP6 was investigated in detail. The results indicated that in DKK family members, a considerable diversity, in the case of structure, activity and physicochemical properties was seen. This diversity was more profound in DKK3 (Dickkopf3). Interestingly, the interaction mode of DKK2 (Dickkopf2) with its receptor, LRP6, was shown to be substantially different from other Dickkopf family members while N-terminal region of this ligand was also involved in the binding to the LRP6-P3P4. Moreover, the cysteine-rich domain 2 (CRD2) of DKK1 and DKK3 had a higher binding affinity to LRP6 in comparison with the whole protein structures.Communicated by Ramaswamy H. Sarma