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Gallo CM, Kistler SA, Natrakul A, Labadorf AT, Beffert U, Ho A. APOER2 splicing repertoire in Alzheimer's disease: Insights from long-read RNA sequencing. PLoS Genet 2024; 20:e1011348. [PMID: 39038048 PMCID: PMC11293713 DOI: 10.1371/journal.pgen.1011348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2024] [Revised: 08/01/2024] [Accepted: 06/21/2024] [Indexed: 07/24/2024] Open
Abstract
Disrupted alternative splicing plays a determinative role in neurological diseases, either as a direct cause or as a driver in disease susceptibility. Transcriptomic profiling of aged human postmortem brain samples has uncovered hundreds of aberrant mRNA splicing events in Alzheimer's disease (AD) brains, associating dysregulated RNA splicing with disease. We previously identified a complex array of alternative splicing combinations across apolipoprotein E receptor 2 (APOER2), a transmembrane receptor that interacts with both the neuroprotective ligand Reelin and the AD-associated risk factor, APOE. Many of the human APOER2 isoforms, predominantly featuring cassette splicing events within functionally important domains, are critical for the receptor's function and ligand interaction. However, a comprehensive repertoire and the functional implications of APOER2 isoforms under both physiological and AD conditions are not fully understood. Here, we present an in-depth analysis of the splicing landscape of human APOER2 isoforms in normal and AD states. Using single-molecule, long-read sequencing, we profiled the entire APOER2 transcript from the parietal cortex and hippocampus of Braak stage IV AD brain tissues along with age-matched controls and investigated several functional properties of APOER2 isoforms. Our findings reveal diverse patterns of cassette exon skipping for APOER2 isoforms, with some showing region-specific expression and others unique to AD-affected brains. Notably, exon 15 of APOER2, which encodes the glycosylation domain, showed less inclusion in AD compared to control in the parietal cortex of females with an APOE ɛ3/ɛ3 genotype. Also, some of these APOER2 isoforms demonstrated changes in cell surface expression, APOE-mediated receptor processing, and synaptic number. These variations are likely critical in inducing synaptic alterations and may contribute to the neuronal dysfunction underlying AD pathogenesis.
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Affiliation(s)
- Christina M. Gallo
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, United States of America
| | - Sabrina A. Kistler
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, United States of America
| | - Anna Natrakul
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Adam T. Labadorf
- Bioinformatics Program, Boston University, Boston, Massachusetts, United States of America
- Department of Neurology, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, United States of America
| | - Uwe Beffert
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
| | - Angela Ho
- Department of Biology, Boston University, Boston, Massachusetts, United States of America
- Department of Pharmacology, Physiology & Biophysics, Boston University Chobanian & Avedisian School of Medicine, Boston, Massachusetts, United States of America
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Kang J, Zhang C, Wang Y, Peng J, Berger B, Perrimon N, Shen J. Lipophorin receptors genetically modulate neurodegeneration caused by reduction of Psn expression in the aging Drosophila brain. Genetics 2024; 226:iyad202. [PMID: 37996068 PMCID: PMC10763532 DOI: 10.1093/genetics/iyad202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Revised: 11/01/2023] [Accepted: 11/12/2023] [Indexed: 11/25/2023] Open
Abstract
Mutations in the Presenilin (PSEN) genes are the most common cause of early-onset familial Alzheimer's disease (FAD). Studies in cell culture, in vitro biochemical systems, and knockin mice showed that PSEN mutations are loss-of-function mutations, impairing γ-secretase activity. Mouse genetic analysis highlighted the importance of Presenilin (PS) in learning and memory, synaptic plasticity and neurotransmitter release, and neuronal survival, and Drosophila studies further demonstrated an evolutionarily conserved role of PS in neuronal survival during aging. However, molecular pathways that interact with PS in neuronal survival remain unclear. To identify genetic modifiers that modulate PS-dependent neuronal survival, we developed a new DrosophilaPsn model that exhibits age-dependent neurodegeneration and increases of apoptosis. Following a bioinformatic analysis, we tested top ranked candidate genes by selective knockdown (KD) of each gene in neurons using two independent RNAi lines in Psn KD models. Interestingly, 4 of the 9 genes enhancing neurodegeneration in Psn KD flies are involved in lipid transport and metabolism. Specifically, neuron-specific KD of lipophorin receptors, lpr1 and lpr2, dramatically worsens neurodegeneration in Psn KD flies, and overexpression of lpr1 or lpr2 does not alleviate Psn KD-induced neurodegeneration. Furthermore, lpr1 or lpr2 KD alone also leads to neurodegeneration, increased apoptosis, climbing defects, and shortened lifespan. Lastly, heterozygotic deletions of lpr1 and lpr2 or homozygotic deletions of lpr1 or lpr2 similarly lead to age-dependent neurodegeneration and further exacerbate neurodegeneration in Psn KD flies. These findings show that LpRs modulate Psn-dependent neuronal survival and are critically important for neuronal integrity in the aging brain.
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Affiliation(s)
- Jongkyun Kang
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Chen Zhang
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Yuhao Wang
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Jian Peng
- Department of Computer Science, University of Illinois at Urbana-Champaign, Champaign, IL 61801, USA
| | - Bonnie Berger
- Computer Science and Artificial Intelligence Laboratory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
- Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | - Norbert Perrimon
- Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Howard Hughes Medical Institute, Boston, MA 02115, USA
| | - Jie Shen
- Department of Neurology, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA
- Program in Neuroscience, Harvard Medical School, Boston, MA 02115, USA
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Mizuno A, Toyama T, Ichikawa A, Sakai N, Yoshioka Y, Nishito Y, Toga R, Amesaka H, Kaneko T, Arisawa K, Tsutsumi R, Mita Y, Tanaka SI, Noguchi N, Saito Y. An efficient selenium transport pathway of selenoprotein P utilizing a high-affinity ApoER2 receptor variant and being independent of selenocysteine lyase. J Biol Chem 2023; 299:105009. [PMID: 37406814 PMCID: PMC10407282 DOI: 10.1016/j.jbc.2023.105009] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/07/2023] Open
Abstract
Selenoprotein P (SeP, encoded by the SELENOP gene) is a plasma protein that contains selenium in the form of selenocysteine residues (Sec, a cysteine analog containing selenium instead of sulfur). SeP functions for the transport of selenium to specific tissues in a receptor-dependent manner. Apolipoprotein E receptor 2 (ApoER2) has been identified as a SeP receptor. However, diverse variants of ApoER2 have been reported, and the details of its tissue specificity and the molecular mechanism of its efficiency remain unclear. In the present study, we found that human T lymphoma Jurkat cells have a high ability to utilize selenium via SeP, while this ability was low in human rhabdomyosarcoma cells. We identified an ApoER2 variant with a high affinity for SeP in Jurkat cells. This variant had a dissociation constant value of 0.67 nM and a highly glycosylated O-linked sugar domain. Moreover, the acidification of intracellular vesicles was necessary for selenium transport via SeP in both cell types. In rhabdomyosarcoma cells, SeP underwent proteolytic degradation in lysosomes and transported selenium in a Sec lyase-dependent manner. However, in Jurkat cells, SeP transported selenium in Sec lyase-independent manner. These findings indicate a preferential selenium transport pathway involving SeP and high-affinity ApoER2 in a Sec lyase-independent manner. Herein, we provide a novel dynamic transport pathway for selenium via SeP.
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Affiliation(s)
- Ayako Mizuno
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Takashi Toyama
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Atsuya Ichikawa
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Naoko Sakai
- The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan
| | - Yuya Yoshioka
- The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan
| | - Yukina Nishito
- The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan
| | - Renya Toga
- Laboratory of Biostructural Chemistry, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Hiroshi Amesaka
- Laboratory of Biostructural Chemistry, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan
| | - Takayuki Kaneko
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Kotoko Arisawa
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Ryouhei Tsutsumi
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan
| | - Yuichiro Mita
- The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan
| | - Shun-Ichi Tanaka
- Laboratory of Biostructural Chemistry, Graduate School of Life and Environmental Sciences, Kyoto Prefectural University, Kyoto, Japan; Department of Biotechnology, College of Life Sciences, Ritsumeikan University, Shiga, Japan
| | - Noriko Noguchi
- The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan
| | - Yoshiro Saito
- Laboratory of Molecular Biology and Metabolism, Graduate School of Pharmaceutical Sciences, Tohoku University, Sendai, Japan; The Systems Life Sciences Laboratory, Department of Medical Life Systems, Faculty of Life and Medical Sciences, Doshisha University, Kyotanabe, Japan.
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Omuro KC, Gallo CM, Scrandis L, Ho A, Beffert U. Human APOER2 Isoforms Have Differential Cleavage Events and Synaptic Properties. J Neurosci 2022; 42:4054-4068. [PMID: 35414534 PMCID: PMC9121830 DOI: 10.1523/jneurosci.1800-21.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Revised: 03/24/2022] [Accepted: 04/06/2022] [Indexed: 11/21/2022] Open
Abstract
Human apolipoprotein E receptor 2 (APOER2) is a type I transmembrane protein with a large extracellular domain (ECD) and a short cytoplasmic tail. APOER2-ECD contains several ligand-binding domains (LBDs) that are organized into exons with aligning phase junctions, which allows for in-frame exon cassette splicing events. We have identified 25 human APOER2 isoforms from cerebral cortex using gene-specific APOER2 primers, where the majority are exon-skipping events within the N-terminal LBD regions compared with six identified in the heart. APOER2 undergoes proteolytic cleavage in response to ligand binding that releases a C-terminal fragment (CTF) and transcriptionally active intracellular domain (ICD). We tested whether the diversity of human brain-specific APOER2 variants affects APOER2 cleavage. We found isoforms with differing numbers of ligand-binding repeats generated different amounts of CTFs compared with full-length APOER2 (APOER2-FL). Specifically, APOER2 isoforms lacking exons 5-8 (Δex5-8) and lacking exons 4-6 (Δex4-6) generated the highest and lowest amounts of CTF generation, respectively, in response to APOE peptide compared with APOER2-FL. The differential CTF generation of Δex5-8 and Δex4-6 coincides with the proteolytic release of the ICD, which mediates transcriptional activation facilitated by the Mint1 adaptor protein. Functionally, we demonstrated loss of mouse Apoer2 decreased miniature event frequency in excitatory synapses, which may be because of a decrease in the total number of synapses and/or VAMP2 positive neurons. Lentiviral infection with human APOER2-FL or Δex4-6 isoform in Apoer2 knockout neurons restored the miniature event frequency but not Δex5-8 isoform. These results suggest that human APOER2 isoforms have differential cleavage events and synaptic properties.SIGNIFICANCE STATEMENT Humans and mice share virtually the same number of protein-coding genes. However, humans have greater complexity of any higher eukaryotic organisms by encoding multiple protein forms through alternative splicing modifications. Alternative splicing allows pre-mRNAs transcribed from genes to be spliced in different arrangements, producing structurally and functionally distinct protein variants that increase proteomic diversity and are particularly prevalent in the human brain. Here, we identified 25 distinct human APOER2 splice variants from the cerebral cortex using gene-specific APOER2 primers, where the majority are exon-skipping events that exclude N-terminal ligand-binding regions of APOER2. We show that some of the APOER2 variants have differential proteolytic properties in response to APOE ligand and exhibit distinct synaptic properties.
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Affiliation(s)
| | | | - Lauren Scrandis
- Department of Biology, Boston University, Boston, Massachusetts 02215
| | - Angela Ho
- Department of Biology, Boston University, Boston, Massachusetts 02215
| | - Uwe Beffert
- Department of Biology, Boston University, Boston, Massachusetts 02215
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From the low-density lipoprotein receptor-related protein 1 to neuropathic pain: a potentially novel target. Pain Rep 2021; 6:e898. [PMID: 33981930 PMCID: PMC8108589 DOI: 10.1097/pr9.0000000000000898] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2020] [Revised: 12/21/2020] [Accepted: 12/25/2020] [Indexed: 12/12/2022] Open
Abstract
The low-density lipoprotein receptor–related protein 1 plays a major role in the regulation of neuroinflammation, neurodegeneration, neuroregeneration, neuropathic pain, and deficient cognitive functions. This review describes the roles of the low-density lipoprotein receptor–related protein 1 (LRP-1) in inflammatory pathways, nerve nerve degeneration and -regeneration and in neuropathic pain. Induction of LRP-1 is able to reduce the activation of the proinflammatory NFκB-mediated pathway and the mitogen-activated protein kinase (MAPK) c-Jun N-terminal kinase and p38 signaling pathways, in turn decreasing the production of inflammatory mediators. Low-density lipoprotein receptor-related protein 1 activation also decreases reactive astrogliosis and polarizes microglial cells and macrophages from a proinflammatory phenotype (M1) to an anti-inflammatory phenotype (M2), attenuating the neuroinflammatory environment. Low-density lipoprotein receptor-related protein 1 can also modulate the permeability of the blood–brain barrier and the blood–nerve barrier, thus regulating the infiltration of systemic insults and cells into the central and the peripheral nervous system, respectively. Furthermore, LRP-1 is involved in the maturation of oligodendrocytes and in the activation, migration, and repair phenotype of Schwann cells, therefore suggesting a major role in restoring the myelin sheaths upon injury. Low-density lipoprotein receptor-related protein 1 activation can indirectly decrease neurodegeneration and neuropathic pain by attenuation of the inflammatory environment. Moreover, LRP-1 agonists can directly promote neural cell survival and neurite sprouting, decrease cell death, and attenuate pain and neurological disorders by the inhibition of MAPK c-Jun N-terminal kinase and p38-pathway and activation of MAPK extracellular signal–regulated kinase pathway. In addition, activation of LRP-1 resulted in better outcomes for neuropathies such as Alzheimer disease, nerve injury, or diabetic peripheral neuropathy, attenuating neuropathic pain and improving cognitive functions. To summarize, LRP-1 plays an important role in the development of different experimental diseases of the nervous system, and it is emerging as a very interesting therapeutic target.
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6
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Güner G, Lichtenthaler SF. The substrate repertoire of γ-secretase/presenilin. Semin Cell Dev Biol 2020; 105:27-42. [PMID: 32616437 DOI: 10.1016/j.semcdb.2020.05.019] [Citation(s) in RCA: 101] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2020] [Revised: 05/17/2020] [Accepted: 05/25/2020] [Indexed: 12/09/2022]
Abstract
The intramembrane protease γ-secretase is a hetero-tetrameric protein complex with presenilin as the catalytic subunit and cleaves its membrane protein substrates within their single transmembrane domains. γ-Secretase is well known for its role in Notch signalling and in Alzheimer's disease, where it catalyzes the formation of the pathogenic amyloid β (Aβ) peptide. However, in the 21 years since its discovery many more substrates and substrate candidates of γ-secretase were identified. Although the physiological relevance of the cleavage of many substrates remains to be studied in more detail, the substrates demonstrate a broad role for γ-secretase in embryonic development, adult tissue homeostasis, signal transduction and protein degradation. Consequently, chronic γ-secretase inhibition may cause significant side effects due to inhibition of cleavage of multiple substrates. This review provides a list of 149 γ-secretase substrates identified to date and highlights by which expeirmental approach substrate cleavage was validated. Additionally, the review lists the cleavage sites where they are known and discusses the functional implications of γ-secretase cleavage with a focus on substrates identified in the recent past, such as CHL1, TREM2 and TNFR1. A comparative analysis demonstrates that γ-secretase substrates mostly have a long extracellular domain and require ectodomain shedding before γ-secretase cleavage, but that γ-secretase is also able to cleave naturally short substrates, such as the B cell maturation antigen. Taken together, the list of substrates provides a resource that may help in the future development of drugs inhibiting or modulating γ-secretase activity in a substrate-specific manner.
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Affiliation(s)
- Gökhan Güner
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Neuroproteomics, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, 81675, Munich, Germany
| | - Stefan F Lichtenthaler
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany; Neuroproteomics, School of Medicine, Klinikum rechts der Isar, Technical University of Munich, 81675, Munich, Germany; Munich Cluster for Systems Neurology (SyNergy), Munich, Germany.
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Lee YJ, Ch'ng TH. RIP at the Synapse and the Role of Intracellular Domains in Neurons. Neuromolecular Med 2019; 22:1-24. [PMID: 31346933 DOI: 10.1007/s12017-019-08556-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2019] [Accepted: 07/12/2019] [Indexed: 12/18/2022]
Abstract
Regulated intramembrane proteolysis (RIP) occurs in a cell when transmembrane proteins are cleaved by intramembrane proteases such as secretases to generate soluble protein fragments in the extracellular environment and the cytosol. In the cytosol, these soluble intracellular domains (ICDs) have local functions near the site of cleavage or in many cases, translocate to the nucleus to modulate gene expression. While the mechanism of RIP is relatively well studied, the fate and function of ICDs for most substrate proteins remain poorly characterized. In neurons, RIP occurs in various subcellular compartments including at the synapse. In this review, we summarize current research on RIP in neurons, focusing specifically on synaptic proteins where the presence and function of the ICDs have been reported. We also briefly discuss activity-driven processing of RIP substrates at the synapse and the cellular machinery that support long-distance transport of ICDs from the synapse to the nucleus. Finally, we describe future challenges in this field of research in the context of understanding the contribution of ICDs in neuronal function.
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Affiliation(s)
- Yan Jun Lee
- Lee Kong Chian School of Medicine, Nanyang Technological University, Clinical Science Building, 11 Mandalay Road, 10-01-01 M, Singapore, 308232, Singapore.,Interdisciplinary Graduate School (IGS), Nanyang Technological University, Singapore, Singapore
| | - Toh Hean Ch'ng
- Lee Kong Chian School of Medicine, Nanyang Technological University, Clinical Science Building, 11 Mandalay Road, 10-01-01 M, Singapore, 308232, Singapore. .,School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
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Dlugosz P, Tresky R, Nimpf J. Differential Action of Reelin on Oligomerization of ApoER2 and VLDL Receptor in HEK293 Cells Assessed by Time-Resolved Anisotropy and Fluorescence Lifetime Imaging Microscopy. Front Mol Neurosci 2019; 12:53. [PMID: 30873003 PMCID: PMC6403468 DOI: 10.3389/fnmol.2019.00053] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2018] [Accepted: 02/12/2019] [Indexed: 01/12/2023] Open
Abstract
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.
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Affiliation(s)
- Paula Dlugosz
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University Vienna, Vienna, Austria
| | - Roland Tresky
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University Vienna, Vienna, Austria
| | - Johannes Nimpf
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University Vienna, Vienna, Austria
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Lopez-Font I, Iborra-Lazaro G, Sánchez-Valle R, Molinuevo JL, Cuchillo-Ibañez I, Sáez-Valero J. CSF-ApoER2 fragments as a read-out of reelin signaling: Distinct patterns in sporadic and autosomal-dominant Alzheimer disease. Clin Chim Acta 2018; 490:6-11. [PMID: 30552869 DOI: 10.1016/j.cca.2018.12.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Accepted: 12/11/2018] [Indexed: 01/06/2023]
Abstract
Reelin is a glycoprotein associated with synaptic plasticity and neurotransmission. The malfunctioning of reelin signaling in the brain is likely to contribute to the pathogenesis of Alzheimer's disease (AD). Reelin binding to Apolipoprotein E receptor 2 (ApoER2) activates downstream signaling and induces the proteolytic cleavage of ApoER2, resulting in the generation of soluble fragments. To evaluate the efficiency of reelin signaling in AD, we have quantified the levels of reelin and soluble ectodomain fragments of ApoER2 (ectoApoER2) in the cerebrospinal fluid (CSF). CSF from sporadic AD patients (sAD; n = 14, age 54-83 years) had lower levels of ecto-ApoER2 (~31% reduction; p = .005) compared to those in the age-matched controls (n = 10, age 61-80), and a higher reelin/ecto-ApoER2 ratio. In contrast, autosomal dominant AD patients, carriers of PSEN1 mutations (ADAD; n = 7, age 31-49 years) had higher ecto-ApoER2 levels (~109% increment; p = .001) and a lower reelin/ecto-ApoER2 ratio than the non-mutation carriers from the same families (n = 7, age 25-47 years). Our data suggest that the levels of ecto-ApoER2 in CSF could be a suitable read-out of an impaired reelin signaling in AD, but also indicate differences between sAD and ADAD.
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Affiliation(s)
- Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Guillermo Iborra-Lazaro
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Raquel Sánchez-Valle
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036 Barcelona, Spain
| | - José-Luis Molinuevo
- Alzheimer's Disease and Other Cognitive Disorders Unit, Neurology Service, Hospital Clinic, 08036 Barcelona, Spain
| | - Inmaculada Cuchillo-Ibañez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, 03550 Sant Joan d'Alacant, Spain; Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain.
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10
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The Reelin Receptors Apolipoprotein E receptor 2 (ApoER2) and VLDL Receptor. Int J Mol Sci 2018; 19:ijms19103090. [PMID: 30304853 PMCID: PMC6213145 DOI: 10.3390/ijms19103090] [Citation(s) in RCA: 48] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2018] [Revised: 10/03/2018] [Accepted: 10/03/2018] [Indexed: 01/28/2023] Open
Abstract
Apolipoprotein E receptor 2 (ApoER2) and VLDL receptor belong to the low density lipoprotein receptor family and bind apolipoprotein E. These receptors interact with the clathrin machinery to mediate endocytosis of macromolecules but also interact with other adapter proteins to perform as signal transduction receptors. The best characterized signaling pathway in which ApoER2 and VLDL receptor (VLDLR) are involved is the Reelin pathway. This pathway plays a pivotal role in the development of laminated structures of the brain and in synaptic plasticity of the adult brain. Since Reelin and apolipoprotein E, are ligands of ApoER2 and VLDLR, these receptors are of interest with respect to Alzheimer’s disease. We will focus this review on the complex structure of ApoER2 and VLDLR and a recently characterized ligand, namely clusterin.
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Mata‐Balaguer T, Cuchillo‐Ibañez I, Calero M, Ferrer I, Sáez‐Valero J. Decreased generation of C‐terminal fragments of ApoER2 and increased reelin expression in Alzheimer's disease. FASEB J 2018; 32:3536-3546. [DOI: 10.1096/fj.201700736rr] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Trinidad Mata‐Balaguer
- Instituto de Neurociencias de AlicanteUniversidad Miguel Hernández‐Consejo Superior de Investigaciones Cientificas (CSIC)Sant Joan d'AlacantAlicanteSpain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)MadridSpain
| | - Inmaculada Cuchillo‐Ibañez
- Instituto de Neurociencias de AlicanteUniversidad Miguel Hernández‐Consejo Superior de Investigaciones Cientificas (CSIC)Sant Joan d'AlacantAlicanteSpain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)MadridSpain
| | - Miguel Calero
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)MadridSpain
- Alzheimer Disease Research UnitCentro Nacional de Investigación en Enfermedades Neurológicas (CIEN) FoundationQueen Sofia Foundation Alzheimer CenterMadridSpain
- Chronic Disease ProgrammeCarlos III Institute of HealthMadridSpain
| | - Isidro Ferrer
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)MadridSpain
- Instituto de NeuropatologíaHospital Universitario de BellvitgeUniversidad de BarcelonaHospitalet de LlobregatBarcelonaSpain
| | - Javier Sáez‐Valero
- Instituto de Neurociencias de AlicanteUniversidad Miguel Hernández‐Consejo Superior de Investigaciones Cientificas (CSIC)Sant Joan d'AlacantAlicanteSpain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED)MadridSpain
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12
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Regulated intramembrane proteolysis: emergent role in cell signalling pathways. Biochem Soc Trans 2017; 45:1185-1202. [PMID: 29079648 DOI: 10.1042/bst20170002] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2017] [Revised: 08/27/2017] [Accepted: 08/29/2017] [Indexed: 12/12/2022]
Abstract
Receptor signalling events including those initiated following activation of cytokine and growth factor receptors and the well-characterised death receptors (tumour necrosis factor receptor, type 1, FasR and TRAIL-R1/2) are initiated at the cell surface through the recruitment and formation of intracellular multiprotein signalling complexes that activate divergent signalling pathways. Over the past decade, research studies reveal that many of these receptor-initiated signalling events involve the sequential proteolysis of specific receptors by membrane-bound proteases and the γ-secretase protease complexes. Proteolysis enables the liberation of soluble receptor ectodomains and the generation of intracellular receptor cytoplasmic domain fragments. The combined and sequential enzymatic activity has been defined as regulated intramembrane proteolysis and is now a fundamental signal transduction process involved in the termination or propagation of receptor signalling events. In this review, we discuss emerging evidence for a role of the γ-secretase protease complexes and regulated intramembrane proteolysis in cell- and immune-signalling pathways.
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13
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Tien WS, Chen JH, Wu KP. SheddomeDB: the ectodomain shedding database for membrane-bound shed markers. BMC Bioinformatics 2017; 18:42. [PMID: 28361715 PMCID: PMC5374707 DOI: 10.1186/s12859-017-1465-7] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
BACKGROUND A number of membrane-anchored proteins are known to be released from cell surface via ectodomain shedding. The cleavage and release of membrane proteins has been shown to modulate various cellular processes and disease pathologies. Numerous studies revealed that cell membrane molecules of diverse functional groups are subjected to proteolytic cleavage, and the released soluble form of proteins may modulate various signaling processes. Therefore, in addition to the secreted protein markers that undergo secretion through the secretory pathway, the shed membrane proteins may comprise an additional resource of noninvasive and accessible biomarkers. In this context, identifying the membrane-bound proteins that will be shed has become important in the discovery of clinically noninvasive biomarkers. Nevertheless, a data repository for biological and clinical researchers to review the shedding information, which is experimentally validated, for membrane-bound protein shed markers is still lacking. RESULTS In this study, the database SheddomeDB was developed to integrate publicly available data of the shed membrane proteins. A comprehensive literature survey was performed to collect the membrane proteins that were verified to be cleaved or released in the supernatant by immunological-based validation experiments. From 436 studies on shedding, 401 validated shed membrane proteins were included, among which 199 shed membrane proteins have not been annotated or validated yet by existing cleavage databases. SheddomeDB attempted to provide a comprehensive shedding report, including the regulation of shedding machinery and the related function or diseases involved in the shedding events. In addition, our published tool ShedP was embedded into SheddomeDB to support researchers for predicting the shedding event on unknown or unrecorded membrane proteins. CONCLUSIONS To the best of our knowledge, SheddomeDB is the first database for the identification of experimentally validated shed membrane proteins and currently may provide the most number of membrane proteins for reviewing the shedding information. The database included membrane-bound shed markers associated with numerous cellular processes and diseases, and some of these markers are potential novel markers because they are not annotated or validated yet in other databases. SheddomeDB may provide a useful resource for discovering membrane-bound shed markers. The interactive web of SheddomeDB is publicly available at http://bal.ym.edu.tw/SheddomeDB/ .
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Affiliation(s)
- Wei-Sheng Tien
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.,Bioinformatics Program, Taiwan International Graduate Program, Academia Sinica, Taipei, 115, Taiwan
| | - Jun-Hong Chen
- Department of Computer Science, National Taipei University of Education, Taipei, 106, Taiwan
| | - Kun-Pin Wu
- Institute of Biomedical Informatics, National Yang Ming University, Taipei, 112, Taiwan.
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14
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Pohlkamp T, Wasser CR, Herz J. Functional Roles of the Interaction of APP and Lipoprotein Receptors. Front Mol Neurosci 2017; 10:54. [PMID: 28298885 PMCID: PMC5331069 DOI: 10.3389/fnmol.2017.00054] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Accepted: 02/16/2017] [Indexed: 11/24/2022] Open
Abstract
The biological fates of the key initiator of Alzheimer’s disease (AD), the amyloid precursor protein (APP), and a family of lipoprotein receptors, the low-density lipoprotein (LDL) receptor-related proteins (LRPs) and their molecular roles in the neurodegenerative disease process are inseparably interwoven. Not only does APP bind tightly to the extracellular domains (ECDs) of several members of the LRP group, their intracellular portions are also connected through scaffolds like the one established by FE65 proteins and through interactions with adaptor proteins such as X11/Mint and Dab1. Moreover, the ECDs of APP and LRPs share common ligands, most notably Reelin, a regulator of neuronal migration during embryonic development and modulator of synaptic transmission in the adult brain, and Agrin, another signaling protein which is essential for the formation and maintenance of the neuromuscular junction (NMJ) and which likely also has critical, though at this time less well defined, roles for the regulation of central synapses. Furthermore, the major independent risk factors for AD, Apolipoprotein (Apo) E and ApoJ/Clusterin, are lipoprotein ligands for LRPs. Receptors and ligands mutually influence their intracellular trafficking and thereby the functions and abilities of neurons and the blood-brain-barrier to turn over and remove the pathological product of APP, the amyloid-β peptide. This article will review and summarize the molecular mechanisms that are shared by APP and LRPs and discuss their relative contributions to AD.
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Affiliation(s)
- Theresa Pohlkamp
- Department of Molecular Genetics, UT Southwestern Medical CenterDallas, TX, USA; Center for Translational Neurodegeneration Research, UT Southwestern Medical CenterDallas, TX, USA
| | - Catherine R Wasser
- Department of Molecular Genetics, UT Southwestern Medical CenterDallas, TX, USA; Center for Translational Neurodegeneration Research, UT Southwestern Medical CenterDallas, TX, USA
| | - Joachim Herz
- Department of Molecular Genetics, UT Southwestern Medical CenterDallas, TX, USA; Center for Translational Neurodegeneration Research, UT Southwestern Medical CenterDallas, TX, USA; Department of Neuroscience, UT Southwestern Medical CenterDallas, TX, USA; Department of Neurology and Neurotherapeutics, UT Southwestern Medical CenterDallas, TX, USA
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15
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Wang W, Moerman-Herzog AM, Slaton A, Barger SW. Presenilin 1 mutations influence processing and trafficking of the ApoE receptor apoER2. Neurobiol Aging 2016; 49:145-153. [PMID: 27810638 DOI: 10.1016/j.neurobiolaging.2016.10.005] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Revised: 09/29/2016] [Accepted: 10/01/2016] [Indexed: 12/15/2022]
Abstract
Presenilin (PS)-1 is an intramembrane protease serving as the catalytic component of γ-secretase. Mutations in the PS1 gene are the most common cause of familial Alzheimer's disease (FAD). The low-density lipoprotein (LDL)-receptor family member apoER2 is a γ-secretase substrate that has been associated with AD in several ways, including acting as a receptor for apolipoprotein E (ApoE). ApoER2 is processed by γ-secretase into a C-terminal fragment (γ-CTF) that appears to regulate gene expression. FAD PS1 mutations were tested for effects on apoER2. PS1 mutation R278I showed impaired γ-secretase activity for apoER2 in the basal state or after exposure to Reelin. PS1 M146V mutation permitted accumulation of apoER2 CTFs after Reelin treatment, whereas no difference was seen between wild-type (WT) and M146V in the basal state. PS1 L282V mutation, combined with the γ-secretase inhibitor N-(N-[3,5-Difluorophenacetyl]-L-alanyl)-S-phenylglycine t-butyl ester, greatly reduced the cell-surface levels of apoER2 without affecting total apoER2 levels, suggesting a defect in receptor trafficking. These findings indicate that impaired processing or localization of apoER2 may contribute to the pathogenic effects of FAD mutations in PS1.
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Affiliation(s)
- Wei Wang
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | | | - Arthur Slaton
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Steven W Barger
- Department of Geriatrics, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Department of Neurobiology & Developmental Sciences, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Geriatrics Research, Education and Clinical Center, Central Arkansas Veterans Healthcare System, Little Rock, AR, USA.
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16
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Cuchillo-Ibañez I, Mata-Balaguer T, Balmaceda V, Arranz JJ, Nimpf J, Sáez-Valero J. The β-amyloid peptide compromises Reelin signaling in Alzheimer's disease. Sci Rep 2016; 6:31646. [PMID: 27531658 PMCID: PMC4987719 DOI: 10.1038/srep31646] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2016] [Accepted: 07/21/2016] [Indexed: 12/13/2022] Open
Abstract
Reelin is a signaling protein that plays a crucial role in synaptic function, which expression is influenced by β-amyloid (Aβ). We show that Reelin and Aβ oligomers co-immunoprecipitated in human brain extracts and were present in the same size-exclusion chromatography fractions. Aβ treatment of cells led to increase expression of Reelin, but secreted Reelin results trapped together with Aβ aggregates. In frontal cortex extracts an increase in Reelin mRNA, and in soluble and insoluble (guanidine-extractable) Reelin protein, was associated with late Braak stages of Alzheimer's disease (AD), while expression of its receptor, ApoER2, did not change. However, Reelin-dependent induction of Dab1 phosphorylation appeared reduced in AD. In cells, Aβ reduced the capacity of Reelin to induce internalization of biotinylated ApoER2 and ApoER2 processing. Soluble proteolytic fragments of ApoER2 generated after Reelin binding can be detected in cerebrospinal fluid (CSF). Quantification of these soluble fragments in CSF could be a tool to evaluate the efficiency of Reelin signaling in the brain. These CSF-ApoER2 fragments correlated with Reelin levels only in control subjects, not in AD, where these fragments diminished. We conclude that while Reelin expression is enhanced in the Alzheimer's brain, the interaction of Reelin with Aβ hinders its biological activity.
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Affiliation(s)
- Inmaculada Cuchillo-Ibañez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, E-03550, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Trinidad Mata-Balaguer
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, E-03550, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Valeria Balmaceda
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, E-03550, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Juan José Arranz
- Departamento Producción Animal, Universidad de León, León, Spain
| | - Johannes Nimpf
- Department of Medical Biochemistry, Max F. Perutz Laboratories, Medical University of Vienna, 1030 Vienna, Austria
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, E-03550, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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17
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Bock HH, May P. Canonical and Non-canonical Reelin Signaling. Front Cell Neurosci 2016; 10:166. [PMID: 27445693 PMCID: PMC4928174 DOI: 10.3389/fncel.2016.00166] [Citation(s) in RCA: 71] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2016] [Accepted: 06/08/2016] [Indexed: 12/11/2022] Open
Abstract
Reelin is a large secreted glycoprotein that is essential for correct neuronal positioning during neurodevelopment and is important for synaptic plasticity in the mature brain. Moreover, Reelin is expressed in many extraneuronal tissues; yet the roles of peripheral Reelin are largely unknown. In the brain, many of Reelin's functions are mediated by a molecular signaling cascade that involves two lipoprotein receptors, apolipoprotein E receptor-2 (Apoer2) and very low density-lipoprotein receptor (Vldlr), the neuronal phosphoprotein Disabled-1 (Dab1), and members of the Src family of protein tyrosine kinases as crucial elements. This core signaling pathway in turn modulates the activity of adaptor proteins and downstream protein kinase cascades, many of which target the neuronal cytoskeleton. However, additional Reelin-binding receptors have been postulated or described, either as coreceptors that are essential for the activation of the "canonical" Reelin signaling cascade involving Apoer2/Vldlr and Dab1, or as receptors that activate alternative or additional signaling pathways. Here we will give an overview of canonical and alternative Reelin signaling pathways, molecular mechanisms involved, and their potential physiological roles in the context of different biological settings.
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Affiliation(s)
- Hans H Bock
- Clinic of Gastroenterology and Hepatology, Heinrich-Heine-University Düsseldorf Düsseldorf, Germany
| | - Petra May
- Clinic of Gastroenterology and Hepatology, Heinrich-Heine-University Düsseldorf Düsseldorf, Germany
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18
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Cuchillo-Ibañez I, Balmaceda V, Mata-Balaguer T, Lopez-Font I, Sáez-Valero J. Reelin in Alzheimer’s Disease, Increased Levels but Impaired Signaling: When More is Less. J Alzheimers Dis 2016; 52:403-16. [DOI: 10.3233/jad-151193] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Inmaculada Cuchillo-Ibañez
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Valeria Balmaceda
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Trinidad Mata-Balaguer
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Inmaculada Lopez-Font
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
| | - Javier Sáez-Valero
- Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Sant Joan d’Alacant, Spain
- Centro de Investigación Biomédica en Red sobre Enfermedades Neurodegenerativas (CIBERNED), Spain
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19
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Honda T, Nakajima K. Proper Level of Cytosolic Disabled-1, Which Is Regulated by Dual Nuclear Translocation Pathways, Is Important for Cortical Neuronal Migration. Cereb Cortex 2015. [PMID: 26209842 DOI: 10.1093/cercor/bhv162] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
Abstract
Disabled-1 (Dab1) is an essential intracellular protein in the Reelin pathway. It has a nuclear localization signal (NLS; hereafter referred to as "NLS1") and 2 nuclear export signals, and shuttles between the nucleus and the cytoplasm. In this study, we found that Dab1 has an additional unidentified NLS, and that the Dab1 NLS1 mutant could translocate to the nucleus in an unconventional ATP/temperature-dependent and cytoplasmic factor/RanGTP gradient-independent manner. Additional mutations in the NLS1 mutant revealed that K(67) and K(69) are important for the nuclear transport. Furthermore, an excess of the intracellular domain of the Reelin receptors inhibited the nuclear translocation of Dab1. An in utero electroporation study showed that a large amount of Dab1 in the cytoplasm in migrating neurons inhibited the migration, and that forced transport of Dab1 into the nucleus attenuated this inhibitory effect. In addition, rescue experiments using yotari, an autosomal recessive mutant of dab1, revealed that cells expressing Dab1 NLS1 mutant tend to distribute at more superficial positions than those expressing wild-type Dab1. Taken together, these findings suggest that Dab1 has at least 2 NLSs, and that the regulation of the subcellular localization of Dab1 is important for the proper migration of excitatory neurons.
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Affiliation(s)
- Takao Honda
- Department of Anatomy, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
| | - Kazunori Nakajima
- Department of Anatomy, Keio University School of Medicine, Shinjuku-ku, Tokyo 160-8582, Japan
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20
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Telese F, Ma Q, Perez PM, Notani D, Oh S, Li W, Comoletti D, Ohgi KA, Taylor H, Rosenfeld MG. LRP8-Reelin-Regulated Neuronal Enhancer Signature Underlying Learning and Memory Formation. Neuron 2015; 86:696-710. [PMID: 25892301 DOI: 10.1016/j.neuron.2015.03.033] [Citation(s) in RCA: 108] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2014] [Revised: 02/11/2015] [Accepted: 03/13/2015] [Indexed: 11/16/2022]
Abstract
One of the exceptional properties of the brain is its ability to acquire new knowledge through learning and to store that information through memory. The epigenetic mechanisms linking changes in neuronal transcriptional programs to behavioral plasticity remain largely unknown. Here, we identify the epigenetic signature of the neuronal enhancers required for transcriptional regulation of synaptic plasticity genes during memory formation, linking this to Reelin signaling. The binding of Reelin to its receptor, LRP8, triggers activation of this cohort of LRP8-Reelin-regulated neuronal (LRN) enhancers that serve as the ultimate convergence point of a novel synapse-to-nucleus pathway. Reelin simultaneously regulates NMDA-receptor transmission, which reciprocally permits the required γ-secretase-dependent cleavage of LRP8, revealing an unprecedented role for its intracellular domain in the regulation of synaptically generated signals. These results uncover an in vivo enhancer code serving as a critical molecular component of cognition and relevant to psychiatric disorders linked to defects in Reelin signaling.
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Affiliation(s)
- Francesca Telese
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Qi Ma
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Bioinformatis and System Biology Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Patricia Montilla Perez
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Dimple Notani
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Soohwan Oh
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA; Biology Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Wenbo Li
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Davide Comoletti
- Child Health Institute of New Jersey and Department of Neuroscience and Cell Biology, Robert Wood Johnson Medical School, Rutgers University, New Brunswick, NJ 08901, USA
| | - Kenneth A Ohgi
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Havilah Taylor
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA
| | - Michael G Rosenfeld
- Howard Hughes Medical Institute, Department of Medicine, School of Medicine, University of California, San Diego, La Jolla, CA 92093, USA.
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21
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Bachmeier C, Shackleton B, Ojo J, Paris D, Mullan M, Crawford F. Apolipoprotein E isoform-specific effects on lipoprotein receptor processing. Neuromolecular Med 2014; 16:686-96. [PMID: 25015123 PMCID: PMC4280344 DOI: 10.1007/s12017-014-8318-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2014] [Accepted: 07/01/2014] [Indexed: 01/24/2023]
Abstract
Recent findings indicate an isoform-specific role for apolipoprotein E (apoE) in the elimination of beta-amyloid (Aβ) from the brain. ApoE is closely associated with various lipoprotein receptors, which contribute to Aβ brain removal via metabolic clearance or transit across the blood–brain barrier (BBB). These receptors are subject to ectodomain shedding at the cell surface, which alters endocytic transport and mitigates Aβ elimination. To further understand the manner in which apoE influences Aβ brain clearance, these studies investigated the effect of apoE on lipoprotein receptor shedding. Consistent with prior reports, we observed an increased shedding of the low-density lipoprotein receptor (LDLR) and the LDLR-related protein 1 (LRP1) following Aβ exposure in human brain endothelial cells. When Aβ was co-treated with each apoE isoform, there was a reduction in Aβ-induced shedding with apoE2 and apoE3, while lipoprotein receptor shedding in the presence of apoE4 remained increased. Likewise, intracranial administration of Aβ to apoE-targeted replacement mice (expressing the human apoE isoforms) resulted in an isoform-dependent effect on lipoprotein receptor shedding in the brain (apoE4 > apoE3 > apoE2). Moreover, these results show a strong inverse correlation with our prior work in apoE transgenic mice in which apoE4 animals showed reduced Aβ clearance across the BBB compared to apoE3 animals. Based on these results, apoE4 appears less efficient than other apoE isoforms in regulating lipoprotein receptor shedding, which may explain the differential effects of these isoforms in removing Aβ from the brain.
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Affiliation(s)
- Corbin Bachmeier
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
| | - Ben Shackleton
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
| | - Joseph Ojo
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
| | - Daniel Paris
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
| | - Michael Mullan
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
| | - Fiona Crawford
- The Roskamp Institute, 2040 Whitfield Avenue, Sarasota, Florida 34243, USA
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22
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Wasser CR, Masiulis I, Durakoglugil MS, Lane-Donovan C, Xian X, Beffert U, Agarwala A, Hammer RE, Herz J. Differential splicing and glycosylation of Apoer2 alters synaptic plasticity and fear learning. Sci Signal 2014; 7:ra113. [PMID: 25429077 DOI: 10.1126/scisignal.2005438] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Apoer2 is an essential receptor in the central nervous system that binds to the apolipoprotein ApoE. Various splice variants of Apoer2 are produced. We showed that Apoer2 lacking exon 16, which encodes the O-linked sugar (OLS) domain, altered the proteolytic processing and abundance of Apoer2 in cells and synapse number and function in mice. In cultured cells expressing this splice variant, extracellular cleavage of OLS-deficient Apoer2 was reduced, consequently preventing γ-secretase-dependent release of the intracellular domain of Apoer2. Mice expressing Apoer2 lacking the OLS domain had increased Apoer2 abundance in the brain, hippocampal spine density, and glutamate receptor abundance, but decreased synaptic efficacy. Mice expressing a form of Apoer2 lacking the OLS domain and containing an alternatively spliced cytoplasmic tail region that promotes glutamate receptor signaling showed enhanced hippocampal long-term potentiation (LTP), a phenomenon associated with learning and memory. However, these mice did not display enhanced spatial learning in the Morris water maze, and cued fear conditioning was reduced. Reducing the expression of the mutant Apoer2 allele so that the abundance of the protein was similar to that of Apoer2 in wild-type mice normalized spine density, hippocampal LTP, and cued fear learning. These findings demonstrated a role for ApoE receptors as regulators of synaptic glutamate receptor activity and established differential receptor glycosylation as a potential regulator of synaptic function and memory.
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Affiliation(s)
- Catherine R Wasser
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
| | - Irene Masiulis
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Murat S Durakoglugil
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Courtney Lane-Donovan
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Xunde Xian
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Uwe Beffert
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Anandita Agarwala
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Robert E Hammer
- Department of Biochemistry, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA
| | - Joachim Herz
- Center for Translational Neurodegeneration Research, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Neurology and Neurotherapeutics, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA. Department of Neuroscience, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
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23
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Larios JA, Jausoro I, Benitez ML, Bronfman FC, Marzolo MP. Neurotrophins regulate ApoER2 proteolysis through activation of the Trk signaling pathway. BMC Neurosci 2014; 15:108. [PMID: 25233900 PMCID: PMC4177048 DOI: 10.1186/1471-2202-15-108] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2014] [Accepted: 09/15/2014] [Indexed: 12/27/2022] Open
Abstract
Background ApoER2 and the neurotrophin receptors Trk and p75NTR are expressed in the CNS and regulate key functional aspects of neurons, including development, survival, and neuronal function. It is known that both ApoER2 and p75NTR are processed by metalloproteinases, followed by regulated intramembrane proteolysis. TrkA activation by nerve growth factor (NGF) increases the proteolytic processing of p75NTR mediated by ADAM17. Reelin induces the sheeding of ApoER2 ectodomain depending on metalloproteinase activity. However, it is not known if there is a common regulation mechanism for processing these receptors. Results We found that TrkA activation by NGF in PC12 cells induced ApoER2 processing, which was dependent on TrkA activation and metalloproteinases. NGF-induced ApoER2 proteolysis was independent of mitogen activated protein kinase activity and of phosphatidylinositol-3 kinase activity. In contrast, the basal proteolysis of ApoER2 increased when both kinases were pharmacologically inhibited. The ApoER2 ligand reelin regulated the proteolytic processing of its own receptor but not of p75NTR. Finally, in primary cortical neurons, which express both ApoER2 and TrkB, we found that the proteolysis of ApoER2 was also regulated by brain-derived growth factor (BDNF). Conclusions Our results highlight a novel relationship between neurotrophins and the reelin-ApoER2 system, suggesting that these two pathways might be linked to regulate brain development, neuronal survival, and some pathological conditions.
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Affiliation(s)
| | | | | | | | - Maria-Paz Marzolo
- Departamento de Biología Celular y Molecular, Laboratorio de Tráfico Intracelular y Señalización, Facultad de Ciencias Biológicas, Pontificia Universidad Católica, Alameda 340, Santiago 8320000, Chile.
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Sotelo P, Farfán P, Benitez ML, Bu G, Marzolo MP. Sorting nexin 17 regulates ApoER2 recycling and reelin signaling. PLoS One 2014; 9:e93672. [PMID: 24705369 PMCID: PMC3976305 DOI: 10.1371/journal.pone.0093672] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Accepted: 03/10/2014] [Indexed: 11/30/2022] Open
Abstract
ApoER2 is a member of the low density-lipoprotein receptor (LDL-R) family. As a receptor for reelin, ApoER2 participates in neuronal migration during development as well as synaptic plasticity and survival in the adult brain. A previous yeast two-hybrid screen showed that ApoER2 is a binding partner of sorting nexin 17 (SNX17) - a cytosolic adaptor protein that regulates the trafficking of several membrane proteins in the endosomal pathway, including LRP1, P-selectin and integrins. However, no further studies have been performed to investigate the role of SNX17 in ApoER2 trafficking and function. In this study, we present evidence based on GST pull-down and inmunoprecipitation assays that the cytoplasmic NPxY endocytosis motif of ApoER2 interacts with the FERM domain of SNX17. SNX17 stimulates ApoER2 recycling in different cell lines including neurons without affecting its endocytic rate and also facilitates the transport of ApoER2 from the early endosomes to the recycling endosomes. The reduction of SNX17 was associated with accumulation of an ApoER2 carboxy-terminal fragment (CTF). In addition, in SNX17 knockdown cells, constitutive ApoER2 degradation was not modified, whereas reelin-induced ApoER2 degradation was increased, implying that SNX17 is a regulator of the receptor's half-life. Finally, in SNX17 silenced hippocampal and cortical neurons, we underscored a positive role of this endosomal protein in the development of the dendritic tree and reelin signaling. Overall, these results establish the role of SNX17 in ApoER2 trafficking and function and aid in identifying new links between endocytic trafficking and receptor signaling.
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Affiliation(s)
- Pablo Sotelo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pamela Farfán
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - María Luisa Benitez
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Guojun Bu
- Department of Neuroscience, Mayo Clinic, Jacksonville, Florida, United States of America
| | - María-Paz Marzolo
- Departamento de Biología Celular y Molecular, Facultad de Ciencias Biológicas, Millenium Nucleus for Renerative Biology (MINREB), Pontificia Universidad Católica de Chile, Santiago, Chile
- * E-mail:
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Balmaceda V, Cuchillo-Ibáñez I, Pujadas L, García-Ayllón MS, Saura CA, Nimpf J, Soriano E, Sáez-Valero J. ApoER2 processing by presenilin-1 modulates reelin expression. FASEB J 2013; 28:1543-54. [PMID: 24344333 DOI: 10.1096/fj.13-239350] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The reelin signaling protein and its downstream components have been associated with synaptic plasticity and neurotransmission. The reelin signaling pathway begins with the binding of reelin to the transmembrane lipoprotein receptor apolipoprotein E receptor 2 (ApoER2), which in turns induces the sequential cleavage of ApoER2 by the sequential action of α- and γ-secretases. Using conditional-knockout mice of the catalytic component of the γ-secretase complex, presenilin 1 (PS1), we demonstrated increased brain ApoER2 and reelin protein and transcript levels, with no changes in the number of reelin-positive cells. Using the human SH-SY5Y neuroblastoma cell line, we showed that ApoER2 processing occurs in the presence of PS1, producing an intracellular ApoER2 C-terminal fragment. In addition, the pharmacologic inhibition of γ-secretase in SH-SY5Y cells led to increased reelin levels. Overexpression of ApoER2 decreased reelin mRNA levels in these cells. A luciferase reporter gene assay and nuclear fractionation confirmed that increased amounts of intracellular fragment of ApoER2 suppressed reelin expression at a transcriptional level. Chromatin immunoprecipitation experiments corroborated that the intracellular fragment of ApoER2 bound to the RELN promoter region. Our study suggests that PS1/γ-secretase-dependent processing of the reelin receptor ApoER2 inhibits reelin expression and may regulate its signaling.
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Affiliation(s)
- Valeria Balmaceda
- 1Instituto de Neurociencias de Alicante, Universidad Miguel Hernández-CSIC, Av. Ramón y Cajal s/n, E-03550 Sant Joan d'Alacant, Spain.
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Smolarkiewicz M, Skrzypczak T, Wojtaszek P. The very many faces of presenilins and the γ-secretase complex. PROTOPLASMA 2013; 250:997-1011. [PMID: 23504135 PMCID: PMC3788181 DOI: 10.1007/s00709-013-0494-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 03/01/2013] [Indexed: 05/02/2023]
Abstract
Presenilin is a central, catalytic component of the γ-secretase complex which conducts intramembrane cleavage of various protein substrates. Although identified and mainly studied through its role in the development of amyloid plaques in Alzheimer disease, γ-secretase has many other important functions. The complex seems to be evolutionary conserved throughout the Metazoa, but recent findings in plants and Dictyostelium discoideum as well as in archeons suggest that its evolution and functions might be much more diversified than previously expected. In this review, a selective survey of the multitude of functions of presenilins and the γ-secretase complex is presented. Following a brief overview of γ-secretase structure, assembly and maturation, three functional aspects are analyzed: (1) the role of γ-secretase in autophagy and phagocytosis; (2) involvement of the complex in signaling related to endocytosis; and (3) control of calcium fluxes by presenilins.
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Affiliation(s)
- Michalina Smolarkiewicz
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Tomasz Skrzypczak
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Przemysław Wojtaszek
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
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Wagner T, Dieckmann M, Jaeger S, Weggen S, Pietrzik CU. Stx5 is a novel interactor of VLDL-R to affect its intracellular trafficking and processing. Exp Cell Res 2013; 319:1956-1972. [DOI: 10.1016/j.yexcr.2013.05.010] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2012] [Revised: 04/10/2013] [Accepted: 05/13/2013] [Indexed: 11/30/2022]
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Abstract
The Alzheimer's disease (AD)-associated amyloid-β protein precursor (AβPP) is cleaved by α-, β-, and presenilin (PS)/γ-secretases through sequential regulated proteolysis. These proteolytic events control the generation of the pathogenic amyloid-β (Aβ) peptide, which excessively accumulates in the brains of individuals afflicted by AD. A growing number of additional proteins cleaved by PS/γ-secretase continue to be discovered. Similarly to AβPP, most of these proteins are type-I transmembrane proteins involved in vital signaling functions regulating cell fate, adhesion, migration, neurite outgrowth, or synaptogenesis. All the identified proteins share common structural features, which are typical for their proteolysis. The consequences of the PS/γ-secretase-mediated cleavage on the function of many of these proteins are largely unknown. Here, we review the current literature on the proteolytic processing mediated by the versatile PS/γ-secretase complex. We begin by discussing the steps of AβPP processing and PS/γ-secretase complex composition and localization, which give clues to how and where the processing of other PS/γ-secretase substrates may take place. Then we summarize the typical features of PS/γ-secretase-mediated protein processing. Finally, we recapitulate the current knowledge on the possible physiological function of PS/γ-secretase-mediated cleavage of specific substrate proteins.
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Affiliation(s)
- Annakaisa Haapasalo
- Institute of Clinical Medicine-Neurology, University of Eastern Finland, Kuopio, Finland.
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Dumanis SB, Chamberlain KA, Jin Sohn Y, Jin Lee Y, Guénette SY, Suzuki T, Mathews PM, Pak DT, Rebeck GW, Suh YH, Park HS, Hoe HS. FE65 as a link between VLDLR and APP to regulate their trafficking and processing. Mol Neurodegener 2012; 7:9. [PMID: 22429478 PMCID: PMC3379943 DOI: 10.1186/1750-1326-7-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Accepted: 03/19/2012] [Indexed: 11/17/2022] Open
Abstract
Background Several studies found that FE65, a cytoplasmic adaptor protein, interacts with APP and LRP1, altering the trafficking and processing of APP. We have previously shown that FE65 interacts with the ApoE receptor, ApoER2, altering its trafficking and processing. Interestingly, it has been shown that FE65 can act as a linker between APP and LRP1 or ApoER2. In the present study, we tested whether FE65 can interact with another ApoE receptor, VLDLR, thereby altering its trafficking and processing, and whether FE65 can serve as a linker between APP and VLDLR. Results We found that FE65 interacted with VLDLR using GST pull-down and co-immunoprecipitation assays in COS7 cells and in brain lysates. This interaction occurs via the PTB1 domain of FE65. Co-transfection with FE65 and full length VLDLR increased secreted VLDLR (sVLDLR); however, the levels of VLDLR C-terminal fragment (CTF) were undetectable as a result of proteasomal degradation. Additionally, FE65 increased cell surface levels of VLDLR. Moreover, we identified a novel complex between VLDLR and APP, which altered trafficking and processing of both proteins. Furthermore, immunoprecipitation results demonstrated that the presence of FE65 increased the interaction between APP and VLDLR in vitro and in vivo. Conclusions These data suggest that FE65 can regulate VLDLR trafficking and processing. Additionally, the interaction between VLDLR and APP altered both protein's trafficking and processing. Finally, our data suggest that FE65 serves as a link between VLDLR and APP. This novel interaction adds to a growing body of literature indicating trimeric complexes with various ApoE Receptors and APP.
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Affiliation(s)
- Sonya B Dumanis
- Department of Neuroscience, Georgetown University Medical Center, 3970 Reservoir Road NW, Washington, DC 20057-1464, USA
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Novel aspects of the apolipoprotein-E receptor family: regulation and functional role of their proteolytic processing. ACTA ACUST UNITED AC 2012. [DOI: 10.1007/s11515-011-1186-7] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Purow B. Notch inhibition as a promising new approach to cancer therapy. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 727:305-19. [PMID: 22399357 DOI: 10.1007/978-1-4614-0899-4_23] [Citation(s) in RCA: 111] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The Notch pathway powerfully influences stem cell maintenance, development and cell fate and is increasingly recognized for the key roles it plays in cancer. Notch promotes cell survival, angiogenesis and treatment resistance in numerous cancers, making it a promising target for cancer therapy. It also crosstalks with other critical oncogenes, providing a means to affect numerous signaling pathways with one intervention. While the gamma-secretase inhibitors are the only form of Notch inhibitors in clinical trials, other forms of Notch inhibition have been developed or are theoretically feasible. In this chapter we review the rationales for Notch inhibition in cancer and then discuss in detail the various modalities for Notch inhibition, both current and speculative.
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Affiliation(s)
- Benjamin Purow
- Neurology Department, University of Virginia, Charlottesville, VA, USA.
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Pardossi-Piquard R, Checler F. The physiology of the β-amyloid precursor protein intracellular domain AICD. J Neurochem 2011; 120 Suppl 1:109-124. [PMID: 22122663 DOI: 10.1111/j.1471-4159.2011.07475.x] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
The amyloid-β precursor protein (βAPP) undergoes several cleavages by enzymatic activities called secretases. Numerous studies aimed at studying the biogenesis and catabolic fate of Aβ peptides, the proteinaceous component of the senile plaques that accumulate in Alzheimer's disease-affected brains. Relatively recently, another secretase-mediated β-APP-derived catabolite called APP IntraCellular Domain (AICD) entered the game. Whether AICD corresponded to a biologically inert by-pass product of βAPP processing or whether it could harbor its own function remained questionable. In this study, we review the mechanisms by which AICD is generated and how its production is regulated. Furthermore, we discuss the degradation mechanism underlying its rapid catabolic fate. Finally, we review putative AICD-related functions and more particularly, the numerous studies indicating that AICD could translocate to the nucleus and control at a transcriptional level, the expression of a series of proteins involved in various functions including the control of cell death and Aβ degradation.
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Affiliation(s)
- Raphaëlle Pardossi-Piquard
- Université de Nice Sophia-Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire UMR6097 CNRS, Equipe labellisée Fondation pour la Recherche Médicale, Sophia-Antipolis, Valbonne, France
| | - Frédéric Checler
- Université de Nice Sophia-Antipolis, Institut de Pharmacologie Moléculaire et Cellulaire UMR6097 CNRS, Equipe labellisée Fondation pour la Recherche Médicale, Sophia-Antipolis, Valbonne, France
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Abstract
The cellular and molecular mechanisms responsible for the development of inner retinal circuitry are poorly understood. Reelin and apolipoprotein E (apoE), ligands of apoE receptor 2 (ApoER2), are involved in retinal development and degeneration, respectively. Here we describe the function of ApoER2 in the developing and adult retina. ApoER2 expression was highest during postnatal inner retinal synaptic development and was considerably lower in the mature retina. Both during development and in the adult, ApoER2 was expressed by A-II amacrine cells. ApoER2 knock-out (KO) mice had rod bipolar morphogenic defects, altered A-II amacrine dendritic development, and impaired rod-driven retinal responses. The presence of an intact ApoER2 NPxY motif, necessary for binding Disabled-1 and transducing the Reelin signal, was also necessary for development of the rod bipolar pathway, while the alternatively spliced exon 19 was not. Mice deficient in another Reelin receptor, very low-density lipoprotein receptor (VLDLR), had normal rod bipolar morphology but altered A-II amacrine dendritic development. VLDLR KO mice also had reductions in oscillatory potentials and delayed synaptic response intervals. Interestingly, age-related reductions in rod and cone function were observed in both ApoER2 and VLDLR KOs. These results support a pivotal role for ApoER2 in the establishment and maintenance of normal retinal synaptic connectivity.
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The role of lipoprotein receptors on the physiological function of APP. Exp Brain Res 2011; 217:377-87. [PMID: 21947084 DOI: 10.1007/s00221-011-2876-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2011] [Accepted: 09/09/2011] [Indexed: 12/26/2022]
Abstract
In this review, we will primarily focus on the role of members of the low-density lipoprotein receptor (LDL-R) family that are involved in trafficking and processing of the amyloid precursor protein (APP). We will discuss the role of the LDL-receptor family members, low-density lipoprotein receptor-related protein 1 (LRP1), LRP1b, apolipoprotein E receptor 2, sortilin-related receptor (SorLA/LR11) and megalin/LRP2 on the physiological function of APP and its cellular localization. Additionally, we will focus on adaptor proteins that have been shown to influence the physiological function of LDL-R family members in combination with APP processing. The results in this review emphasize that the physiological function of APP cannot be explained by the focus on the APP protein alone but rather in combination with various direct or indirect interaction partners within the cellular environment.
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Perman JC, Boström P, Lindbom M, Lidberg U, StÅhlman M, Hägg D, Lindskog H, Scharin Täng M, Omerovic E, Mattsson Hultén L, Jeppsson A, Petursson P, Herlitz J, Olivecrona G, Strickland DK, Ekroos K, Olofsson SO, Borén J. The VLDL receptor promotes lipotoxicity and increases mortality in mice following an acute myocardial infarction. J Clin Invest 2011; 121:2625-40. [PMID: 21670500 DOI: 10.1172/jci43068] [Citation(s) in RCA: 112] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2010] [Accepted: 04/20/2011] [Indexed: 12/18/2022] Open
Abstract
Impaired cardiac function is associated with myocardial triglyceride accumulation, but it is not clear how the lipids accumulate or whether this accumulation is detrimental. Here we show that hypoxia/ischemia-induced accumulation of lipids in HL-1 cardiomyocytes and mouse hearts is dependent on expression of the VLDL receptor (VLDLR). Hypoxia-induced VLDLR expression in HL-1 cells was dependent on HIF-1α through its interaction with a hypoxia-responsive element in the Vldlr promoter, and VLDLR promoted the endocytosis of lipoproteins. Furthermore, VLDLR expression was higher in ischemic compared with nonischemic left ventricles from human hearts and was correlated with the total lipid droplet area in the cardiomyocytes. Importantly, Vldlr-/- mice showed improved survival and decreased infarct area following an induced myocardial infarction. ER stress, which leads to apoptosis, is known to be involved in ischemic heart disease. We found that ischemia-induced ER stress and apoptosis in mouse hearts were reduced in Vldlr-/- mice and in mice treated with antibodies specific for VLDLR. These findings suggest that VLDLR-induced lipid accumulation in the ischemic heart worsens survival by increasing ER stress and apoptosis.
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Affiliation(s)
- Jeanna C Perman
- Sahlgrenska Center for Cardiovascular and Metabolic Research, Wallenberg Laboratory, Sahlgrenska University Hospital, Göteborg, Sweden
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Reddy SS, Connor TE, Weeber EJ, Rebeck W. Similarities and differences in structure, expression, and functions of VLDLR and ApoER2. Mol Neurodegener 2011; 6:30. [PMID: 21554715 PMCID: PMC3113299 DOI: 10.1186/1750-1326-6-30] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2011] [Accepted: 05/09/2011] [Indexed: 11/29/2022] Open
Abstract
Very Low Density Lipoprotein Receptor (VLDLR) and Apolipoprotein E Receptor 2 (ApoER2) are important receptors in the brain for mediating the signaling effects of the extracellular matrix protein Reelin, affecting neuronal function in development and in the adult brain. VLDLR and ApoER2 are members of the low density lipoprotein family, which also mediates the effects of numerous other extracellular ligands, including apolipoprotein E. Although VLDLR and ApoER2 are highly homologous, they differ in a number of ways, including structural differences, expression patterns, alternative splicing, and binding of extracellular and intracellular proteins. This review aims to summarize important aspects of VLDLR and ApoER2 that may account for interesting recent findings that highlight the unique functions of each receptor.
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Affiliation(s)
- Sunil S Reddy
- Department of Neuroscience; Georgetown University Medical Center, 3970 Reservoir Rd, NW, Washington, DC, 20007, USA.
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ApoE receptor 2 regulates synapse and dendritic spine formation. PLoS One 2011; 6:e17203. [PMID: 21347244 PMCID: PMC3039666 DOI: 10.1371/journal.pone.0017203] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2010] [Accepted: 01/25/2011] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Apolipoprotein E receptor 2 (ApoEr2) is a postsynaptic protein involved in long-term potentiation (LTP), learning, and memory through unknown mechanisms. We examined the biological effects of ApoEr2 on synapse and dendritic spine formation-processes critical for learning and memory. METHODOLOGY/PRINCIPAL FINDINGS In a heterologous co-culture synapse assay, overexpression of ApoEr2 in COS7 cells significantly increased colocalization with synaptophysin in primary hippocampal neurons, suggesting that ApoEr2 promotes interaction with presynaptic structures. In primary neuronal cultures, overexpression of ApoEr2 increased dendritic spine density. Consistent with our in vitro findings, ApoEr2 knockout mice had decreased dendritic spine density in cortical layers II/III at 1 month of age. We also tested whether the interaction between ApoEr2 and its cytoplasmic adaptor proteins, specifically X11α and PSD-95, affected synapse and dendritic spine formation. X11α decreased cell surface levels of ApoEr2 along with synapse and dendritic spine density. In contrast, PSD-95 increased cell surface levels of ApoEr2 as well as synapse and dendritic spine density. CONCLUSIONS/SIGNIFICANCE These results suggest that ApoEr2 plays important roles in structure and function of CNS synapses and dendritic spines, and that these roles are modulated by cytoplasmic adaptor proteins X11α and PSD-95.
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Bellocci M, Sala GL, Callegari F, Rossini GP. Azaspiracid-1 Inhibits Endocytosis of Plasma Membrane Proteins in Epithelial Cells. Toxicol Sci 2010; 117:109-21. [DOI: 10.1093/toxsci/kfq172] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Minami SS, Cordova A, Cirrito JR, Tesoriero JA, Babus LW, Davis GC, Dakshanamurthy S, Turner RS, Pak DT, Rebeck GW, Paige M, Hoe HS. ApoE mimetic peptide decreases Abeta production in vitro and in vivo. Mol Neurodegener 2010; 5:16. [PMID: 20406479 PMCID: PMC2890633 DOI: 10.1186/1750-1326-5-16] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2010] [Accepted: 04/20/2010] [Indexed: 12/03/2022] Open
Abstract
Background Apolipoprotein E (apoE) is postulated to affect brain Aβ levels through multiple mechanisms--by altering amyloid precursor protein (APP) processing, Aβ degradation, and Aβ clearance. We previously showed that an apoE-derived peptide containing a double repeat of the receptor-binding region was similarly effective in increasing APP processing in vivo. Here, we further examined whether peptides containing tandem repeats of the apoE receptor-binding region (amino acids 141-149) affected APP trafficking, APP processing, and Aβ production. Results We found that peptides containing a double or triple tandem repeat of the apoE receptor-binding region, LRKLRKRLL, increased cell surface APP and decreased Aβ levels in PS1-overexpressing PS70 cells and in primary neurons. This effect was potentiated by a sequential increase in the number of apoE receptor-binding domain repeats (trimer > dimer > monomer). We previously showed that the apoE dimer increased APP CTF in vivo; to determine whether the dimer also affected secreted APP or Aβ levels, we performed a single hippocampal injection of the apoE dimer in wild-type mice and analyzed its effect on APP processing. We found increased sAPPα and decreased Aβ levels at 24 hrs after treatment, suggesting that the apoE dimer may increase α-secretase cleavage. Conclusions These data suggest that small peptides consisting of tandem repeats of the apoE receptor-binding region are sufficient to alter APP trafficking and processing. The potency of these peptides increased with increasing repeats of the receptor binding domain of apoE. In addition, in vivo administration of the apoE peptide (dimer) increased sAPPα and decreased Aβ levels in wild-type mice. Overall, these findings contribute to our understanding of the effects of apoE on APP processing and Aβ production both in vitro and in vivo.
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Affiliation(s)
- S Sakura Minami
- Department of Neuroscience, Georgetown University, 3970 Reservoir Rd, NW, Washington, DC 20057, USA.
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Beagle B, Mi K, Johnson GVW. Phosphorylation of PPP(S/T)P motif of the free LRP6 intracellular domain is not required to activate the Wnt/beta-catenin pathway and attenuate GSK3beta activity. J Cell Biochem 2010; 108:886-95. [PMID: 19711366 DOI: 10.1002/jcb.22318] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The canonical Wnt/beta-catenin signaling pathway plays a critical role in numerous physiological and pathological processes. LRP6 is an essential co-receptor for Wnt/beta-catenin signaling; as transduction of the Wnt signal is strongly dependent upon GSK3beta-mediated phosphorylation of multiple PPP(S/T)P motifs within the membrane-anchored LRP6 intracellular domain. Previously, we showed that the free LRP6 intracellular domain (LRP6-ICD) can activate the Wnt/beta-catenin pathway in a beta-catenin and TCF/LEF-1 dependent manner, as well as interact with and attenuate GSK3beta activity. However, it is unknown if the ability of LRP6-ICD to attenuate GSK3beta activity and modulate activation of the Wnt/beta-catenin pathway requires phosphorylation of the LRP6-ICD PPP(S/T)P motifs, in a manner similar to the membrane-anchored LRP6 intracellular domain. Here we provide evidence that the LRP6-ICD does not have to be phosphorylated at its PPP(S/T)P motif by GSK3beta to stabilize endogenous cytosolic beta-catenin resulting in activation of TCF/LEF-1 and the Wnt/beta-catenin pathway. LRP6-ICD and a mutant in which all 5 PPP(S/T)P motifs were changed to PPP(A)P motifs equivalently interacted with and attenuated GSK3beta activity in vitro, and both constructs inhibited the in situ GSK3beta-mediated phosphorylation of beta-catenin and tau to the same extent. These data indicate that the LRP6-ICD attenuates GSK3beta activity similar to other GSK3beta binding proteins, and is not a result of it being a GSK3beta substrate. Our findings suggest the functional and regulatory mechanisms governing the free LRP6-ICD may be distinct from membrane-anchored LRP6, and that release of the LRP6-ICD may provide a complimentary signaling cascade capable of modulating Wnt-dependent gene expression.
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Affiliation(s)
- Brandon Beagle
- Department of Anesthesiology, University of Rochester, Rochester, New York 14642, USA
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41
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Krishnaswamy S, Verdile G, Groth D, Kanyenda L, Martins RN. The structure and function of Alzheimer’s gamma secretase enzyme complex. Crit Rev Clin Lab Sci 2009; 46:282-301. [DOI: 10.3109/10408360903335821] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
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42
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Duit S, Mayer H, Blake SM, Schneider WJ, Nimpf J. Differential functions of ApoER2 and very low density lipoprotein receptor in Reelin signaling depend on differential sorting of the receptors. J Biol Chem 2009; 285:4896-908. [PMID: 19948739 DOI: 10.1074/jbc.m109.025973] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
ApoER2 and very low density lipoprotein (VLDL) receptor transmit the Reelin signal into target cells of the central nervous system. To a certain extent, both receptors can compensate for each other, and only the loss of both receptors results in the reeler phenotype, which is characterized by a gross defect in the architecture of laminated brain structures. Nevertheless, both receptors also have specific distinct functions, as corroborated by analyses of the subtle phenotypes displayed in mice lacking either ApoER2 or VLDL receptor. The differences in their function(s), however, have not been defined at the cellular level. Here, using a panel of chimeric receptors, we demonstrate that endocytosis of Reelin and the fate of the individual receptors upon stimulation are linked to their specific sorting to raft versus non-raft domains of the plasma membrane. VLDL receptor residing in the non-raft domain endocytoses and destines Reelin for degradation via the clathrin-coated pit/clathrin-coated vesicle/endosome pathway without being degraded to a significant extent. Binding of Reelin to ApoER2, a resident of rafts, leads to the production of specific receptor fragments with specific functions of their own and to degradation of ApoER2 via lysosomes. These features contribute to a receptor-specific fine tuning of the Reelin signal, leading to a novel model that emphasizes negative feedback loops specifically mediated by ApoER2 and VLDL receptor, respectively.
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Affiliation(s)
- Sarah Duit
- Max F. Perutz Laboratories, Vienna Biocenter, Department of Medical Biochemistry, Medical University of Vienna, Dr. Bohrgasse 9/2, A-1030 Vienna, Austria
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43
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Minami SS, Sung YM, Dumanis SB, Chi SH, Burns MP, Ann EJ, Suzuki T, Turner RS, Park HS, Pak DTS, Rebeck GW, Hoe HS. The cytoplasmic adaptor protein X11alpha and extracellular matrix protein Reelin regulate ApoE receptor 2 trafficking and cell movement. FASEB J 2009; 24:58-69. [PMID: 19720620 DOI: 10.1096/fj.09-138123] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The goal of this study was to determine the effect of X11alpha on ApoE receptor 2 (ApoEr2) trafficking and the functional significance of this interaction on cell movement in MCF 10A epithelial cells. We found that X11alpha increased surface levels of ApoEr2 by 64% compared to vector control, as determined by surface protein biotinylation. To examine the functional significance of this effect, we tested whether ApoEr2 played a novel role in cell movement in a wound-healing assay. We found that overexpression of ApoEr2 in MCF 10A cells increased cell migration velocity by 87% (P<0.01, n=4) compared to GFP control. Cotransfection of X11alpha had an additive effect on average velocity compared to ApoEr2 alone (13%; P<0.05, n=4). In addition, we tested whether ApoEr2 ligands altered the effect of ApoEr2 on cell movement. We found that treatment with concentrated medium containing the extracellular matrix protein Reelin, but not control medium, further increased the velocity of ApoEr2- but not APP-transfected cells (20%; P<0.001, n=4). Similarly, Reelin treatment increased cell velocity in the presence of ApoEr2 and X11alpha (10%; P<0.05, n=4). In the present study, we are the first to demonstrate that ApoEr2 regulates cell movement, and both X11alpha and Reelin enhance this effect.
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Affiliation(s)
- S Sakura Minami
- Department of Neurology, Georgetown University, 4000 Reservoir Road NW, Washington, DC 20057, USA
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Abstract
The development of the hippocampal dentate gyrus is a complex process in which several signaling pathways are involved and likely interact with each other. The extracellular matrix molecule Reelin is necessary both for normal development of the dentate gyrus radial glia and neuronal migration. In Reelin-deficient Reeler mice, the hippocampal radial glial scaffold fails to form, and granule cells are dispersed throughout the dentate gyrus. Here, we show that both formation of the radial glia scaffold and lamination of the dentate gyrus depend on intact Notch signaling. Inhibition of Notch signaling in organotypic hippocampal slice cultures induced a phenotype reminiscent of the Reelin-deficient hippocampus, i.e., a reduced density of radial glia fibers and granule cell dispersion. Moreover, a Reelin-dependent rescue of the Reeler phenotype was blocked by inhibition of Notch activation. In the Reeler dentate gyrus, we found reduced Notch1 signaling; the activated Notch intracellular domain as well as the transcriptional targets, brain lipid-binding protein, and Hes5 are decreased. Disabled1, a component of the Reelin-signaling pathway colocalizes with Notch1, thus indicating a direct interaction between the Reelin- and Notch1-signaling pathways. These results suggest that Reelin enhances Notch1 signaling, thereby contributing to the formation of the radial glial scaffold and the normal development of the dentate gyrus.
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45
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Pocivavsek A, Mikhailenko I, Strickland DK, Rebeck GW. Microglial low-density lipoprotein receptor-related protein 1 modulates c-Jun N-terminal kinase activation. J Neuroimmunol 2009; 214:25-32. [PMID: 19586665 DOI: 10.1016/j.jneuroim.2009.06.010] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2009] [Revised: 06/14/2009] [Accepted: 06/15/2009] [Indexed: 01/23/2023]
Abstract
Apolipoprotein E (apoE)-induced activation of low-density lipoprotein receptor (LDL) family members reduces inflammatory responses by suppressing c-Jun N-terminal kinase (JNK) activation. We aimed to identify which specific receptor family member mediates the effect of apoE on inflammation in primary cultures of microglia. Low-density lipoprotein receptor-related protein 1 (LRP1)-deficient (LRP1-/-) microglia were derived from mice using tissue-specific loxP/Cre recombination. Using a peptide formed from the receptor-binding region of apoE (EP), we found that LRP1 mediates the effects of apoE on microglial inflammation. Microglial LRP1 was also essential for EP to suppress JNK activation induced by lipopolysaccharide.
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Affiliation(s)
- Ana Pocivavsek
- Department of Neuroscience, Georgetown University, Washington, DC 20057-1464, USA
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46
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Purow B. Notch inhibitors as a new tool in the war on cancer: a pathway to watch. Curr Pharm Biotechnol 2009; 10:154-60. [PMID: 19199947 DOI: 10.2174/138920109787315060] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Notch was first recognized as an important developmental pathway in Drosophila in the first half of the 20th century. Many decades later, this pathway has been found to play central roles in humans in stem cell maintenance, cell fate decisions, and in cancer as well. Notch family members are being revealed as oncogenes in an ever-increasing number of cancers. Though significant progress has been made in dissecting the complex workings of this signaling pathway, there are very limited options available for Notch inhibitors. However, the pioneering class of Notch inhibitors is already in clinical trials for two cancer types. This review will address the current state-of-the-art, agents in the pipeline, and potential strategies for future Notch inhibitors. Successful development of Notch inhibitors in the clinic holds great promise as a new anti-cancer strategy.
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Affiliation(s)
- Benjamin Purow
- Neuro-Oncology Division, Neurology Department, University of Virginia, Charlottesville, VA, USA.
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47
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Kosacka J, Gericke M, Nowicki M, Kacza J, Borlak J, Spanel-Borowski K. Apolipoproteins D and E3 exert neurotrophic and synaptogenic effects in dorsal root ganglion cell cultures. Neuroscience 2009; 162:282-91. [PMID: 19414061 DOI: 10.1016/j.neuroscience.2009.04.073] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2009] [Revised: 04/27/2009] [Accepted: 04/29/2009] [Indexed: 11/17/2022]
Abstract
Co-cultures of 3T3-L1 adipocytes with neurons from the rat dorsal root ganglia (DRG) showed enhanced neuritogenesis and synaptogenesis. Microarray analysis for upregulated genes in adipocyte/DRG co-cultures currently points to apolipoproteins D and E (ApoD, ApoE) as influential proteins. We therefore tested adipocyte-secreted cholesterol and the carrier proteins ApoD and ApoE3. Cholesterol, ApoD, and ApoE3 each increased neurite outgrowth and upregulated the expression of presynaptic synaptophysin and synaptotagmin, as well as the postsynaptic density protein 95. The neurotrophic effects of ApoD and ApoE3 were associated with an increased expression of the low-density lipoprotein receptor and apolipoprotein E receptor 2. Simultaneous treatment with receptor-associated protein, an apolipoprotein receptor antagonist, inhibited the neurotrophic function of both apolipoproteins. The application of ApoD, ApoE3, and cholesterol to DRG cell cultures corresponded with increased expression of the chemokine stromal cell-derived factor 1 and its receptor CXC chemokine receptor 4 (CXCR4). Surprisingly, the inhibition of CXCR4 by the antagonistic drug AMD3100 decreased the apolipoprotein/cholesterol dependent neurotrophic effects. We thus assume that apolipoprotein-induced neuritogenesis in DRG cells interferes with CXCR4 signaling, and that adipocyte-derived apolipoproteins might be helpful in nerve repair.
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Affiliation(s)
- J Kosacka
- Institute of Anatomy, University of Leipzig, Liebigstrabetae 13, D-04103 Leipzig, Germany.
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48
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Abstract
The low-density lipoprotein receptor family consists of a large number of single transmembrane proteins that are involved both in endocytosis of extracellular ligands and in intracellular signaling processes. New evidence ties these receptors to the transactivation of Trk receptors. Thus, this single receptor family demonstrates several distinct mechanisms for transducing information across the plasma membrane.
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Affiliation(s)
- G William Rebeck
- Department of Neuroscience, Georgetown University, Washington, DC 20007, USA.
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Sakai K, Tiebel O, Ljungberg MC, Sullivan M, Lee HJ, Terashima T, Li R, Kobayashi K, Lu HC, Chan L, Oka K. A neuronal VLDLR variant lacking the third complement-type repeat exhibits high capacity binding of apoE containing lipoproteins. Brain Res 2009; 1276:11-21. [PMID: 19393635 DOI: 10.1016/j.brainres.2009.04.030] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2009] [Revised: 03/30/2009] [Accepted: 04/12/2009] [Indexed: 12/31/2022]
Abstract
Very-low-density lipoprotein receptor (VLDLR) is a multi ligand apolipoprotein E (apoE) receptor and is involved in brain development through Reelin signaling. Different forms of VLDLR can be generated by alternative splicing. VLDLR-I contains all exons. VLDLR-II lacks an O-linked sugar domain encoded by exon 16, while VLDLR-III lacks the third complement-type repeat in the ligand binding domain encoded by exon 4. We quantitatively compared lipoprotein binding to human VLDLR variants and analyzed their mRNA expression in both human cerebellum and mouse brain. VLDLR-III exhibited the highest capacity in binding to apoE enriched beta-VLDL in vitro and was more effective in removing apoE containing lipoproteins from the circulation than other variants in vivo. In human cerebellum, the major species was VLDLR-II, while the second most abundant species was a newly identified VLDLR-IV which lacks both exon 4 and 16. VLDLR-I was present at low levels. In adult mice, exon 4 skipping varied between 30 and 47% in different brain regions, while exon 16 skipping ranged by 51-76%. Significantly higher levels of VLDLR proteins were found in mouse cerebellum and cerebral cortex than other regions. The deletions of exon 4 and exon 16 frequently occurred in primary neurons, indicating that newly identified variant VLDLR-IV is abundant in neurons. In contrast, VLDLR mRNA lacking exon 4 was not detectable in primary astrocytes. Such cell type-specific splicing patterns were found in both mouse cerebellum and cerebral cortex. These results suggest that a VLDLR variant lacking the third complement-type repeat is generated by neuron-specific alternative splicing. Such differential splicing may result in different lipid uptake in neurons and astrocytes.
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Affiliation(s)
- Keiko Sakai
- Department of Neurology, Baylor College of Medicine, Houston, TX 77030, USA
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50
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Liu Z, Li H, Li Y, Wang Y, Zong Y, Feng Y, Feng Z, Deng Y, Qu S. Up-regulation of VLDL receptor expression and its signaling pathway induced by VLDL and beta-VLDL. ACTA ACUST UNITED AC 2009; 29:1-7. [PMID: 19224153 DOI: 10.1007/s11596-009-0101-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2008] [Indexed: 11/26/2022]
Abstract
Very low density lipoprotein receptor (VLDLR) is thought to participate in the pathogenesis of atherosclerosis induced by VLDL and beta-VLDL. The present study was undertaken to elucidate the effects of VLDL and beta-VLDL on VLDLR expression and its signaling pathway. RAW264.7 cells were incubated with VLDL and beta-VLDL. The expression of VLDLR mRNA was detected by RT-PCR. The transcriptional activity of VLDLR gene was detected in recombinant plasmid pGL4.2VR-luciferase transfected RAW264.7. Western blot assay was used to detect the changes of phosphorylated ERK1/2 protein. Inhibitors or activators were used to observe the signal pathway involving VLDLR expression regulation. The results showed that VLDL and beta-VLDL stimulated ERK1/2 activity in a PKC-dependent manner. VLDL or beta-VLDL-induced VLDLR expression on macrophages was extremely abolished by inhibitors ERK1/2 or PKC. Our findings revealed that VLDL or beta-VLDL-induced VLDLR expression via PKC/ERK cascades and the effect was linked to the transcriptional activation of VLDLR gene promoter.
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Affiliation(s)
- Zhiguo Liu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China.
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