scholarly journals A role of the frontotemporal lobar degeneration risk factor TMEM106B in myelination

Brain ◽  
2020 ◽  
Vol 143 (7) ◽  
pp. 2255-2271 ◽  
Author(s):  
Tuancheng Feng ◽  
Rory R Sheng ◽  
Santiago Solé-Domènech ◽  
Mohammed Ullah ◽  
Xiaolai Zhou ◽  
...  
Keyword(s):  
Risk Factor ◽  
Frontotemporal Lobar Degeneration ◽  
Cathepsin D ◽  
Proteolipid Protein ◽  
Wild Type ◽  
Protein Levels ◽  
Lysosomal Protease ◽  
Precursor Cell Line ◽  
Lysosomal Membrane Protein

Abstract TMEM106B encodes a lysosomal membrane protein and was initially identified as a risk factor for frontotemporal lobar degeneration. Recently, a dominant D252N mutation in TMEM106B was shown to cause hypomyelinating leukodystrophy. However, how TMEM106B regulates myelination is still unclear. Here we show that TMEM106B is expressed and localized to the lysosome compartment in oligodendrocytes. TMEM106B deficiency in mice results in myelination defects with a significant reduction of protein levels of proteolipid protein (PLP) and myelin oligodendrocyte glycoprotein (MOG), the membrane proteins found in the myelin sheath. The levels of many lysosome proteins are significantly decreased in the TMEM106B-deficient Oli-neu oligodendroglial precursor cell line. TMEM106B physically interacts with the lysosomal protease cathepsin D and is required to maintain proper cathepsin D levels in oligodendrocytes. Furthermore, we found that TMEM106B deficiency results in lysosome clustering in the perinuclear region and a decrease in lysosome exocytosis and cell surface PLP levels. Moreover, we found that the D252N mutation abolished lysosome enlargement and lysosome acidification induced by wild-type TMEM106B overexpression. Instead, it stimulates lysosome clustering near the nucleus as seen in TMEM106B-deficient cells. Our results support that TMEM106B regulates myelination through modulation of lysosome function in oligodendrocytes.

scholarly journals Interplay between Pds5 and Rec8 in regulating chromosome axis length and crossover frequency

2021 ◽  
Vol 7 (11) ◽  
pp. eabe7920
Author(s):  
Meihui Song ◽  
Binyuan Zhai ◽  
Xiao Yang ◽  
Taicong Tan ◽  
Ying Wang ◽  
...  
Keyword(s):  
Recombination Frequency ◽  
Crossover Frequency ◽  
Wild Type ◽  
Protein Levels ◽  
Homolog Pairing ◽  
Meiotic Chromosomes ◽  
Homologous Chromosome Pairing ◽  
Axis Length ◽  
Chromosome Axis

Meiotic chromosomes have a loop/axis architecture, with axis length determining crossover frequency. Meiosis-specific Pds5 depletion mutants have shorter chromosome axes and lower homologous chromosome pairing and recombination frequency. However, it is poorly understood how Pds5 coordinately regulates these processes. In this study, we show that only ~20% of wild-type level of Pds5 is required for homolog pairing and that higher levels of Pds5 dosage-dependently regulate axis length and crossover frequency. Moderate changes in Pds5 protein levels do not explicitly impair the basic recombination process. Further investigations show that Pds5 does not regulate chromosome axes by altering Rec8 abundance. Conversely, Rec8 regulates chromosome axis length by modulating Pds5. These findings highlight the important role of Pds5 in regulating meiosis and its relationship with Rec8 to regulate chromosome axis length and crossover frequency with implications for evolutionary adaptation.

scholarly journals The G2385R risk factor for Parkinson's disease enhances CHIP-dependent intracellular degradation of LRRK2

2017 ◽  
Vol 474 (9) ◽  
pp. 1547-1558 ◽  
Author(s):  
Iakov N. Rudenko ◽  
Alice Kaganovich ◽  
Rebekah G. Langston ◽  
Aleksandra Beilina ◽  
Kelechi Ndukwe ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Risk Factor ◽  
Steady State ◽  
Proteasomal Degradation ◽  
Wild Type ◽  
Intracellular Protein ◽  
Protein Levels ◽  
Intracellular Degradation

Autosomal dominant mutations in leucine-rich repeat kinase 2 (LRRK2) are associated with Parkinson's disease (PD). Most pathogenic LRRK2 mutations result in amino acid substitutions in the central ROC (Ras of complex proteins)–C-terminus of ROC–kinase triple domain and affect enzymatic functions of the protein. However, there are several variants in LRRK2, including the risk factor G2385R, that affect PD pathogenesis by unknown mechanisms. Previously, we have shown that G2385R LRRK2 has decreased kinase activity in vitro and altered affinity to LRRK2 interactors. Specifically, we found an increased binding to the chaperone Hsp90 (heat shock protein 90 kDa) that is known to stabilize LRRK2, suggesting that G2385R may have structural effects on LRRK2. In the present study, we further explored the effects of G2385R on LRRK2 in cells. We found that G2385R LRRK2 has lower steady-state intracellular protein levels compared with wild-type LRRK2 due to increased protein turnover of the mutant protein. Mechanistically, this is a consequence of a higher affinity of G2385R compared with the wild-type protein for two proteins involved in proteasomal degradation, Hsc70 and carboxyl-terminus of Hsc70-interacting protein (CHIP). Overexpression of CHIP decreased intracellular protein levels of both G2385R mutant and wild-type LRRK2, while short interfering RNA CHIP knockdown had the opposite effect. We suggest that the G2385R substitution tilts the equilibrium between refolding and proteasomal degradation toward intracellular degradation. The observation of lower steady-state protein levels may explain why G2385R is a risk factor rather than a penetrant variant for inherited PD.

scholarly journals Lin28b-Let-7-PRC1 Axis Guides Developmental Maturation of the Hematopoietic System

Blood ◽  
2021 ◽  
Vol 138 (Supplement 1) ◽  
pp. 21-21
Author(s):  
Mayuri Tanaka-Yano ◽  
Dahai Wang ◽  
Eleanor Meader ◽  
Melissa A. Kinney ◽  
Vivian Morris ◽  
...  
Keyword(s):  
Young Adult ◽  
Developmental Stage ◽  
Conflicts Of Interest ◽  
Fetal Liver ◽  
Polycomb Group ◽  
Wild Type ◽  
Hematopoietic Stem ◽  
Protein Levels ◽  
Developmental Maturation

Abstract Polycomb group (PcG) proteins are a well-studied group of chromatin modifiers belonging to one of two distinct multi-protein complexes: Polycomb repressive complex 1 (PRC1) and PRC2. With definitive hematopoiesis, PRCs contribute to many aspects of fetal and adult blood formation. However, it is largely unknown how many of the age-specific effects of PRCs in hematopoiesis are regulated. Here, we show that the definitive hematopoietic stem and progenitor cell (HSPC) compartment is remodeled from the fetus to the neonate and into young adulthood coordinated with changes in mature blood cell output. This process is in part dependent on the PRC1 component Cbx2, which is regulated by the heterochronic Lin28b/let-7 axis. First, we quantified various population of definitive hematopoietic stem cells (HSCs) and multipotent progenitors (MPPs) using midgestation fetal liver (FL, embryonic day 14.5 (E14.5)), newborn bone marrow (BM, postnatal day 0-1), or young adult (postnatal age 6 to 8 weeks) BM. The lymphoid biased multipotent progenitor 4 (MPP4, ~0.9-fold) declined as the mice matured and aged. We also found erythroid-biased MPP2 diminished (~0.7-fold) while myeloid-biased MPP3 increased (~1.7-fold) with maturation. Using isolated long-term (LT) HSCs from these three stages, we found that E14.5 FL (~8.0-fold) and neonatal LT-HSC (~4.0-fold) showed more rapid B-cell reconstitution compared to young adult LT-HSCs upon transplantation. We found that many of these effects were regulated by Lin28b/let-7. Next, we aimed to determine the downstream mediators of Lin28/let-7's effect on HSPCs maturation. By interrogating gene regulatory subnetworks differentially active across mouse HSPC maturation and mining these subnetworks for predicted let-7 target transcripts, we found Cbx2 enriched in E14.5 FL (P=0.003) and adult HSPCs ectopically expressing LIN28B relative to wild-type adult HSPCs. In cell-based assays, we confirmed that let-7 microRNAs directly regulated CBX2 protein levels. Thus, the Lin28b/let-7 axis governs CBX2 protein levels, leading us to hypothesize that this axis exerts its wide-ranging effects on hematopoietic maturation by regulating PRC1 by controlling Cbx2 levels. As CBX2's developmental stage-specific functions have not been investigated, we generated Cbx2-/-embryos and investigated definitive FL hematopoiesis. We observed skewing of myeloerythorid progenitors to an adult-like myeloid-predominant distribution in Cbx2-/- embryos (P=0.0002), and B-cells in Cbx2-/- neonatal spleens were diminished (P=0.04). We further examined this effect using transplanted Cbx2-/- MPP4 from E14.5 FL which resulted in a decreased donor derived B-lymphoid output compared to wild-type littermates (~0.7-fold). To understand the functional role of Cbx2/PRC1 in juvenile hematopoiesis, we next investigated the role of Cbx2 in maintaining histone H2A monoubiquitinylation (H2AK119Ub) - the histone modification placed by PRC1 - in FL HSPCs. In Cbx2-/- FL HSPCs, the global distribution of H2AK119Ub localization did not change, but several specific H2AK119Ub peaks were altered. We observed differential H2AK119Ub abundance associated with a candidate enhancer within the Erg gene, suggestive of control of Erg expression by Lin28b/let-7/Cbx2. We confirmed that this enhancer activated transcription from a minimal promoter (~8-fold). Erg expression was increased in perinatal spleens of Cbx2-/- mice compared to Cbx2+/+ littermates (~4-fold). Moreover, we found that Cbx2 could repress ERG expression as well as other master HSPC transcription factors. Overall, our findings show that the Lin28b/let-7-axis controls developmental stage-specific hematopoietic output through PRC1-mediated chromatin remodeling. These findings demonstrate a key mechanism by which HSPCs alter their properties during developmental maturation with relevance to age-skewed blood disorders. Disclosures No relevant conflicts of interest to declare.

scholarly journals SMCR8 negatively regulates AKT and MTORC1 signaling to modulate lysosome biogenesis and tissue homeostasis

2018 ◽  
Author(s):  
Yungang Lan ◽  
Peter M. Sullivan ◽  
Fenghua Hu
Keyword(s):  
Frontotemporal Lobar Degeneration ◽  
Physiological Function ◽  
Chromosome Region ◽  
Tissue Homeostasis ◽  
Spine Density ◽  
Protein Levels ◽  
Lysosome Biogenesis ◽  
Mtorc1 Signaling ◽  
Lateral Sclerosis

AbstractThe intronic hexanucleotide expansion in the C9orf72 gene is one of the leading causes of frontotemporal lobar degeneration (FTLD) and amyotrophic lateral sclerosis (ALS), 2 devastating neurodegenerative diseases. C9orf72 forms a heterodimer with SMCR8 (Smith-Magenis syndrome chromosome region, candidate 8) protein. However, the physiological function of SMCR8 remains to be characterized. Here we report that ablation of SMCR8 in mice results in splenomegaly with autoimmune phenotypes similar to that of C9orf72 deficiency. Furthermore, SMCR8 loss leads to a drastic decrease of C9orf72 protein levels. Many proteins involved in the macroautophagy-lysosome pathways are downregulated upon SMCR8 loss due to elevated activation of MTORC1 and AKT, which also leads to increased spine density in the Smcr8 knockout neurons. In summary, our studies demonstrate a key role of SMCR8 in regulating MTORC1 and AKT signaling and tissue homeostasis.

scholarly journals Role of Apolipoprotein E in Anxiety

2007 ◽  
Vol 2007 ◽  
pp. 1-7 ◽  
Author(s):  
Jacob Raber
Keyword(s):  
Risk Factor ◽  
Age At Onset ◽  
Histamine Receptor ◽  
Plasma Corticosterone ◽  
Central Nucleus ◽  
Wild Type ◽  
Adult Mice ◽  
Apoe Isoforms ◽  
Dexamethasone Suppression

Anxiety is most common among Alzheimer's disease (AD) patients with an age at onset under age 65. Apolipoprotein E4 (apoE4) is a risk factor for developing AD at an earlier age and might contribute to this effect. In mice, apoE plays a role in the regulation of anxiety, which might involve histamine receptor-mediated signaling and steroidogenesis in the adrenal gland. In addition, human apoE isoforms have differential effects on anxiety in adult mice lacking apoE and probable AD patients. Compared to wild-type mice, mice lacking apoE and apoE4 mice showed pathological alterations in the central nucleus of the amygdala, which is involved in regulation of anxiety. ApoE4, but not mice lacking apoE, or apoE3 mice showed impaired dexamethasone suppression of plasma corticosterone. Understanding how apoE modulates measures of anxiety might help the developments of therapeutic targets to reduce or even prevent measures of anxiety in health and in dementing illnesses.

scholarly journals The noncanonical role of the protease cathepsin D as a cofilin phosphatase

Cell Research ◽  
2021 ◽  
Author(s):  
Yi-Jun Liu ◽  
Ting Zhang ◽  
Sicong Chen ◽  
Daxiao Cheng ◽  
Cunjin Wu ◽  
...  
Keyword(s):  
Cathepsin D ◽  
Dual Function ◽  
Actin Remodeling ◽  
Actin Organization ◽  
Cellular Processes ◽  
Lysosomal Protease ◽  
Ph Conditions ◽  
Maturation State ◽  
Acidic Compartments

AbstractCathepsin D (cathD) is traditionally regarded as a lysosomal protease that degrades substrates in acidic compartments. Here we report cathD plays an unconventional role as a cofilin phosphatase orchestrating actin remodeling. In neutral pH environments, the cathD precursor directly dephosphorylates and activates the actin-severing protein cofilin independent of its proteolytic activity, whereas mature cathD degrades cofilin in acidic pH conditions. During development, cathD complements the canonical cofilin phosphatase slingshot and regulates the morphogenesis of actin-based structures. Moreover, suppression of cathD phosphatase activity leads to defective actin organization and cytokinesis failure. Our findings identify cathD as a dual-function molecule, whose functional switch is regulated by environmental pH and its maturation state, and reveal a novel regulatory role of cathD in actin-based cellular processes.

scholarly journals Role of the Lysosomal Membrane Protein, CLN3, in the Regulation of Cathepsin D Activity

2017 ◽  
Vol 118 (11) ◽  
pp. 3883-3890 ◽  
Author(s):  
Jaime Cárcel‐Trullols ◽  
Attila D. Kovács ◽  
David A. Pearce
Keyword(s):  
Membrane Protein ◽  
Cathepsin D ◽  
Lysosomal Membrane ◽  
Lysosomal Membrane Protein ◽  
Cathepsin D Activity

scholarly journals Cathepsin D Variants Associated With Neurodegenerative Diseases Show Dysregulated Functionality and Modified α-Synuclein Degradation Properties

2021 ◽  
Vol 9 ◽  
Author(s):  
Josina Bunk ◽  
Susy Prieto Huarcaya ◽  
Alice Drobny ◽  
Jan Philipp Dobert ◽  
Lina Walther ◽  
...  
Keyword(s):  
Enzymatic Activity ◽  
Neurodegenerative Diseases ◽  
Cathepsin D ◽  
Cellular Localization ◽  
Neuronal Ceroid Lipofuscinosis ◽  
Dynamics Simulation ◽  
Disease Development ◽  
Lysosomal Protease ◽  
Enzymatic Function

Cathepsin D (CTSD) is a lysosomal protease important for the degradation of various substrates, including disease-associated proteins like α-synuclein (a-syn), amyloid precursor protein (APP) and tau, all of which tend to aggregate if not efficiently degraded. Hence, it is not surprising that genetic variants within the CTSD gene have been linked to neurodegenerative diseases, like Parkinson’s and Alzheimer’s disease (PD, AD), as well as the lysosomal storage disorder neuronal ceroid lipofuscinosis type-10 (NCL10). Although recent studies have shown the molecular dependence of substrate degradation via CTSD within autophagic pathways, only little is known about the precise role of lysosomal CTSD function in disease development. We here performed biochemical, cellular and structural analyses of eleven disease-causing CTSD point mutations found in genomic sequencing data of patients to understand their role in neurodegeneration. These CTSD variants were analyzed for cellular localization, maturation and enzymatic activity in overexpression analyses. Moreover, for PD-associated mutants, intracellular degradation of a-syn was monitored. In summary, our results suggest that NCL10-associated CTSD variants are significantly impaired in lysosomal maturation and enzymatic activity, whereas the AD- and PD-associated variants seemed rather unaffected, indicating normal maturation, and lysosomal presence. Interestingly, a PD-associated CTSD variant (A239V) exhibited increased enzymatic activity accompanied by enhanced a-syn degradation. By structural analyses of this mutant utilizing molecular dynamics simulation (MDS), we identified a structural change within a loop adjacent to the catalytic center leading to a higher flexibility and potentially accelerated substrate exchange rates. Our data sheds light onto the role of CTSD in disease development and helps to understand the structural regulation of enzymatic function, which could be utilized for targeted CTSD activation. Because of the degradative function of CTSD, this enzyme is especially interesting for therapeutic strategies tackling protein aggregates in neurodegenerative disorders.

scholarly journals An RNA guanine quadruplex regulated pathway to TRAIL-sensitization by DDX21

2019 ◽  
Author(s):  
Ewan K.S. McRae ◽  
Steven J. Dupas ◽  
Evan P. Booy ◽  
Ramanaguru S. Piragasam ◽  
Richard P. Fahlman ◽  
...  
Keyword(s):  
Mrna Levels ◽  
Wild Type ◽  
Biologically Relevant ◽  
Protein Levels ◽  
Guanine Quadruplex ◽  
Repressive Effect ◽  
G Quadruplex ◽  
Different Levels ◽  
In Cells

AbstractDDX21 is a newly discovered RNA G-quadruplex (rG4) binding protein with no known biological rG4 targets. In this study we identified 26 proteins that are expressed at significantly different levels in cells expressing wild type DDX21 relative to an rG4 binding deficient DDX21 (M4). From this list we validate MAGED2 as a protein that is regulated by DDX21 through rG4 in its 5’UTR. MAGED2 protein levels, but not mRNA levels, are reduced by half in cells expressing only DDX21 M4. MAGED2 has a repressive effect on TRAIL-R2 expression that is relieved under these conditions, resulting in elevated TRAIL-R2 mRNA and protein in cells expressing only DDX21 M4, and rendering previously resistant cells sensitive to TRAIL mediated apoptosis. Our work identifies the role of DDX21 in regulation at the translational level through biologically relevant rG4 and shows that MAGED2 protein levels are regulated, at least in part, by a rG4 forming potential in their 5’UTRs.

Abstract 175: The Role of Axl in Accumulation of Immune Cells in Kidney and the Onset of Hypertension

Hypertension ◽  
2012 ◽  
Vol 60 (suppl_1) ◽  
Author(s):  
Sri Nagarjun Batchu ◽  
Angie Hughson ◽  
Janice Gerloff ◽  
Deborah J Fowell ◽  
Vyacheslav A Korshunov
Keyword(s):  
Blood Pressure ◽  
Immune Cells ◽  
Immune Cell ◽  
Kidney Injury ◽  
Wild Type ◽  
Protein Levels ◽  
Immune Cell Subsets ◽  
Early Increase ◽  
Salt Hypertension

Introduction: Gas6/Axl pathway contributes to elevation of blood pressure. Immune cells are implicated in initiation and maintenance of hypertension. In this study we aimed to investigate the role of Axl in immune cells on kidney injury and initiation of hypertension. Methods and Results: Deoxycorticosterone-acetate (DOCA; 75mg, 60days release) and salt hypertension was induced for 1wk or 6wks in four groups of Axl chimeras (n=4-5) that were generated by bone marrow (BM) transplant. Multi parameter flow cytometry was used to quantify five major immune cell subsets in digested kidneys from Axl chimeras. Systolic blood pressure (SBP) increased by 30mmHg in Axl+/+ →Axl+/+, Axl-/- →Axl-/- and Axl+/+ →Axl-/- mice after 1wk of DOCA-salt. However, chimeras that lack Axl in the BM cells (Axl-/- →Axl+/+) showed reduction in early increase in SBP (16+2mmHg). We observed a significant decrease in urine protein levels in Axl-/- →Axl+/+ (0.3+0.1μg/μl) compared to other Axl chimeras (∼0.7μg/μl) after 1wk of DOCA-salt. Kidney glomeruli areas were reduced in Axl-/- →Axl+/+ (4,143+229μm 2 ) compared to other Axl chimeras (∼6,000μm 2 ) after 6wks of DOCA-salt. Kidneys from Axl-/- →Axl-/- showed an increase in total leukocytes (8 vs. 4%), B cells (29 vs. 12%) and decrease in monocytes/macrophages (16 vs. 22%) and dendritic cells (5 vs. 10%) compared to Axl+/+ →Axl+/+. Moreover, Axl-/- →Axl+/+ showed further increase in leukocytes (17%), B (39%) and dendritic (13%) cells in kidneys compared to other Axl chimeras. In addition a small percentage of wild type T cells was increased in the kidneys from Axl-/- →Axl+/+ chimeras. Conclusions: These findings suggest that Axl expression in BM-derived cells is critical for kidney injury in DOCA-salt hypertension. Axl-dependent pathways regulate immune cell populations in the kidneys during initiation of hypertension. This study was supported by HL105623 grant (VAK)

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