RESUMO
Lowe Syndrome (LS) is a rare X-linked disorder characterized by renal dysfunction, cataracts, and several central nervous system (CNS) anomalies. The mechanisms underlying the neurological dysfunction in LS remain unclear, albeit they share some phenotypic characteristics similar to the deficiency or dysfunction of the Reelin signaling, a relevant pathway with roles in CNS development and neuronal functions. In this study, we investigated the role of OCRL1, an inositol polyphosphate 5-phosphatase encoded by the OCRL gene, mutated in LS, focusing on its impact on endosomal trafficking and receptor recycling in human neuronal cells. Specifically, we tested the effects of OCRL1 deficiency in the trafficking and signaling of ApoER2/LRP8, a receptor for the ligand Reelin. We found that loss of OCRL1 impairs ApoER2 intracellular trafficking, leading to reduced receptor expression and decreased levels at the plasma membrane. Additionally, human neurons deficient in OCRL1 showed impairments in ApoER2/Reelin-induced responses. Our findings highlight the critical role of OCRL1 in regulating ApoER2 endosomal recycling and its impact on the ApoER2/Reelin signaling pathway, providing insights into potential mechanisms underlying the neurological manifestations of LS.
Assuntos
Moléculas de Adesão Celular Neuronais , Endossomos , Proteínas da Matriz Extracelular , Proteínas Relacionadas a Receptor de LDL , Proteínas do Tecido Nervoso , Neurônios , Monoéster Fosfórico Hidrolases , Transporte Proteico , Proteína Reelina , Serina Endopeptidases , Humanos , Monoéster Fosfórico Hidrolases/metabolismo , Monoéster Fosfórico Hidrolases/genética , Monoéster Fosfórico Hidrolases/deficiência , Proteínas do Tecido Nervoso/metabolismo , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/deficiência , Serina Endopeptidases/metabolismo , Serina Endopeptidases/genética , Serina Endopeptidases/deficiência , Moléculas de Adesão Celular Neuronais/metabolismo , Moléculas de Adesão Celular Neuronais/genética , Moléculas de Adesão Celular Neuronais/deficiência , Proteínas da Matriz Extracelular/metabolismo , Proteínas da Matriz Extracelular/genética , Proteínas da Matriz Extracelular/deficiência , Endossomos/metabolismo , Neurônios/metabolismo , Proteínas Relacionadas a Receptor de LDL/metabolismo , Proteínas Relacionadas a Receptor de LDL/genética , Transdução de Sinais , Síndrome Oculocerebrorrenal/genética , Síndrome Oculocerebrorrenal/metabolismoRESUMO
BACKGROUND: Myasthenia gravis (MG) is an autoimmune disease usually caused by antibodies against the acetylcholine receptor (AChR-Abs), muscle-specific tyrosine kinase (MuSK-Abs), or low-density lipoprotein receptor-related protein 4 (LRP4-Abs). However, there are MG patients who do not have these antibodies and are thus said to have triple-seronegative (triple-SN) MG. OBJECTIVE: This study aims to describe the frequency and clinical and epidemiological characteristics of patients with triple-SN MG. METHODS: This was a retrospective cross-sectional study carried out through the analysis of medical records. Descriptive and analytical statistical analysis was performed comparing subgroups of myasthenic patients, classified according to serological profile. RESULTS: The sample population consisted of 93 MG patients: 85 were positive for antibodies, 80 (86%) with AChR-Abs, 5 (5.4%) with MuSK-Abs, and no MG patients with LRP4-Abs. Eight patients (8.6%) had triple-SN MG; they had a median age at disease onset of 30 years (21-45). Their most common initial symptoms were ptosis, diplopia, and generalized weakness. Most patients presented with mild symptoms at their last visit, reflecting a median MG composite scale score of 4 (0-6), and 75% of patients had an adequate response to treatment. CONCLUSION: Our study showed a low frequency of triple-SN MG in Brazilian MG patients. Triple-SN MG was predominant in females, who presented with ptosis, diplopia, and generalized weakness, and most patients had an adequate response to immunosuppressive treatment. There was no significant difference between triple-SN MG and the other subgroups.
ANTECEDENTES: A Miastenia gravis (MG) é uma desordem autoimune geralmente causada por anticorpos antirreceptores de acetilcolina (anti-RACh), tirosina quinase músculo-específica (anti-MuSK) ou proteína 4 relacionada ao receptor de lipoproteína de baixa densidade (anti-LRP4). No entanto, em uma parcela dos pacientes, nenhum destes três anticorpos pôde ser detectado, sendo estes casos denominados "triplo-soronegativos". OBJETIVO: Descrever a frequência, bem como as características clínicas e epidemiológicas dos pacientes com MG triplo-soronegativa. MéTODOS: Consiste em um estudo transversal e restrospectivo, realizado através da análise de prontuários médicos. Foi realizada análise estatística descritiva e analítica entre os subgrupos de pacientes, classificados de acordo com o perfil sorológico. RESULTADOS: A população consistiu de 93 pacientes com MG: 85 pacientes apresentavam positividade para anticorpos, sendo 80 (86%) com anticorpos anti-RACh, cinco (5,4%) com anti-MuSK, e não foram encontrados pacientes com anti-LRP4. Oito (8,6%) eram pacientes triplo-soronegativos, que apresentaram idade média de início da doença de 30 anos (21-45), e com sintomas iniciais mais comuns de ptose, diplopia e fraqueza generalizada. 75% dos pacientes triplo-soronegativos apresentaram resposta adequada ao tratamento. CONCLUSãO: O estudo demonstrou uma baixa frequência da pacientes com MG triplo-soronegativa na população brasileira. A MG triplo-soronegativa foi predominante nas mulheres, que se apresentaram com ptose, diplopia ou fraqueza generalizada, e a maioria dos pacientes apresentou resposta adequada ao tratamento imunossupressor. Não houve diferença significativa entre a MG triplo-soronegativa e os demais subgrupos.
Assuntos
Diplopia , Miastenia Gravis , Feminino , Humanos , Adulto Jovem , Adulto , Pessoa de Meia-Idade , Estudos Retrospectivos , Estudos Transversais , Autoanticorpos , Receptores Proteína Tirosina Quinases , Proteínas Relacionadas a Receptor de LDL , Miastenia Gravis/diagnóstico , Miastenia Gravis/tratamento farmacológico , Miastenia Gravis/epidemiologiaRESUMO
Adaptor protein complex 4 (AP-4) is a heterotetrameric complex that promotes export of selected cargo proteins from the trans-Golgi network. Mutations in each of the AP-4 subunits cause a complicated form of Hereditary Spastic Paraplegia (HSP). Herein, we report that ApoER2, a receptor in the Reelin signaling pathway, is a cargo of the AP-4 complex. We identify the motif ISSF/Y within the ApoER2 cytosolic domain as necessary for interaction with the canonical signal-binding pocket of the µ4 (AP4M1) subunit of AP-4. AP4E1- knock-out (KO) HeLa cells and hippocampal neurons from Ap4e1-KO mice display increased co-localization of ApoER2 with Golgi markers. Furthermore, hippocampal neurons from Ap4e1-KO mice and AP4M1-KO human iPSC-derived cortical i3Neurons exhibit reduced ApoER2 protein expression. Analyses of biosynthetic transport of ApoER2 reveal differential post-Golgi trafficking of the receptor, with lower axonal distribution in KO compared to wild-type neurons, indicating a role of AP-4 and the ISSF/Y motif in the axonal localization of ApoER2. Finally, analyses of Reelin signaling in mouse hippocampal and human cortical KO neurons show that AP4 deficiency causes no changes in Reelin-dependent activation of the AKT pathway and only mild changes in Reelin-induced dendritic arborization, but reduces Reelin-induced ERK phosphorylation, CREB activation, and Golgi deployment. This work thus establishes ApoER2 as a novel cargo of the AP-4 complex, suggesting that defects in the trafficking of this receptor and in the Reelin signaling pathway could contribute to the pathogenesis of HSP caused by mutations in AP-4 subunits.
Assuntos
Complexo 4 de Proteínas Adaptadoras , Proteínas Relacionadas a Receptor de LDL , Paraplegia Espástica Hereditária , Animais , Humanos , Camundongos , Complexo 4 de Proteínas Adaptadoras/genética , Complexo 4 de Proteínas Adaptadoras/metabolismo , Células HeLa , Proteínas Relacionadas a Receptor de LDL/genética , Proteínas Relacionadas a Receptor de LDL/metabolismo , Receptores de Superfície Celular , Paraplegia Espástica Hereditária/genética , Paraplegia Espástica Hereditária/metabolismoRESUMO
Alzheimer's disease (AD) is the most common cause of dementia in the elderly, affecting over 50 million people worldwide in 2020 and this number will triple to 152 million by 2050. Much of the increase will be in developing countries like Colombia. In familial forms, highly penetrant mutations have been identified in three genes, APP, PSEN1, and PSEN2, supporting a role for amyloid-ß peptide. In sporadic forms, more than 30 risk genes involved in the lipid metabolism, the immune system, and synaptic functioning mechanisms. We used whole-exome sequencing (WES) to evaluate a family of 97 members, spanning three generations, with a familiar AD, and without mutations in APP, PSEN1, or PSEN2. We sequenced two affected and one unaffected member with the aim of identifying genetic variants that could explain the presence of the disease in the family and the candidate variants were validated in eleven members. We also built a structural model to try to determine the effect on protein function. WES analysis identified two rare variants in SORL1 and MTHFD1L genes segregating in the family with other potential risk variants in APOE, ABCA7, and CHAT, suggesting an oligogenic inheritance. Additionally, the structural 3D models of SORL1 and MTHFD1L variants shows that these variants produce polarity changes that favor hydrophobic interactions, resulting in local structural changes that could affect the protein function and may contribute to the development of the disease in this family.
Assuntos
Doença de Alzheimer , Idoso , Humanos , Doença de Alzheimer/genética , Precursor de Proteína beta-Amiloide/genética , Colômbia , Sequenciamento do Exoma , Predisposição Genética para Doença , Proteínas Relacionadas a Receptor de LDL/genética , Proteínas de Membrana Transportadoras/genética , Mutação , Presenilina-1/genéticaRESUMO
The present study evaluated the risk effect of 12 Single Nucleotide Polymorphisms in the SORL1 gene in the Mexican population using Late-Onset Alzheimer's Disease (LOAD) and control subjects. Considering APOE as the strongest genetic risk factor for LOAD, we conducted interaction analyses between single nucleotide polymorphisms (SNPs) and the APOE genotype. METHODS: Patients were interviewed during their scheduled visits at neurologic and geriatric clinics from different institutions. The LOAD diagnosis included neurological, geriatric, and psychiatric examinations, as well as the medical history and neuroimaging. Polymorphisms in SORL1 were genotyped by real-time PCR in 156 subjects with LOAD and 221 controls. APOE genotype was determined in each study subject. Allelic, genotypic, and haplotypic frequencies were analyzed; an ancestry analysis was also performed. RESULTS: The A/A genotype in rs1784933 might be associated with an increased LOAD risk. Two blocks with high degree linkage disequilibrium (LD) were identified. The first block composed by the genetic variants rs668387, rs689021 and rs641120 showed a positive interaction (mainly the rs689021) with rs1784933 polymorphism. Moreover, we found a significant association between the APOE ε4 allele carriers and the variant rs2070045 located in the second LD block. CONCLUSION: The rs1784933 polymorphism is associated with LOAD in Mexican patients. In addition, the presence of APOE ε4 allele and SORL1 variants could represent a genetic interaction effect that favors LOAD risk in the Mexican population. SNPs have been proposed as genetic markers associated with the development of LOAD that can support the clinical diagnosis. Future molecular studies could help understand sporadic Alzheimer's Disease (AD) among the Mexican population, where currently there is a sub-estimate number in terms of disease frequency and incidence.
Assuntos
Doença de Alzheimer , Idoso , Doença de Alzheimer/epidemiologia , Doença de Alzheimer/genética , Apolipoproteína E4/genética , Humanos , Proteínas Relacionadas a Receptor de LDL/genética , Proteínas de Membrana Transportadoras/genética , México , Polimorfismo de Nucleotídeo ÚnicoRESUMO
Abstract Background: Sizeable proportion of patients have discordant low-density lipoprotein cholesterol (LDL-C) and non-high density lipoprotein cholesterol (NHDL-C). It has been shown that discordance of LDL-C and NHDL-C either underestimates or overestimates coronary risk. Objectıve: We assessed whether this discordance has an impact on GRACE and TIMI risk scores in patients with acute myocardial infarction (AMI). Methods: We retrospectively evaluated the data of 198 consecutive patients with AMI. Fasting serum lipid profiles were recorded, GRACE and TIMI scores were calculated. Patients were divided into 3 groups according to LDL-C and NHDL-C percentiles: Discordant group: LDL-C<NHDL-C (n=38), concordant group: LDL-C=NHDL-C (n=112) and discordant group LDL-C>NHDL-C (n=48). GRACE and TIMI scores, mortality and cardiovascular events (heart failure, non-fatal myocardial infarction and angina) at sixth month were compared between these three groups. Differences between these groups were analyzed with One-way ANOVA or Kruskal-Wallis rank test, and with chi-square for percentages. Also, post hoc LSD or Conover-Iman's non-parametric multiple comparison test were used. A p value <0.05 was accepted as statistically significant. Results: TIMI risk score didn't differ between discordant or concordant groups. Mean GRACE (death) and GRACE (death and MI) scores were higher in group with LDL-C<NHDL-C than with LDL-C=NHDL-C and LDL-C>NHDL-C (p=0.029 and 0.008, respectively). Cardiovascular events and mortality at sixth month were not different among groups (p=0.473 and p=0.176, respectively). Conclusion: GRACE score was higher in discordant group with LDL-C<NHDL-C, but there is no difference regarding TIMI scores between discordant and concordant groups in AMI patients.
Assuntos
Humanos , Feminino , Pessoa de Meia-Idade , Idoso , Proteínas Relacionadas a Receptor de LDL , Lipoproteínas LDL , Infarto do Miocárdio/sangue , Triglicerídeos , Estudos Retrospectivos , Síndrome Coronariana Aguda , Fatores de Risco de Doenças Cardíacas , Infarto do Miocárdio/diagnósticoRESUMO
For proper cholesterol metabolism, normal expression and function of scavenger receptor class B type I (SR-BI), a high-density lipoprotein (HDL) receptor, is required. Among the factors that regulate overall cholesterol homeostasis and HDL metabolism, the nuclear farnesoid X receptor plays an important role. Guggulsterone, a bioactive compound present in the natural product gugulipid, is an antagonist of this receptor. This natural product is widely used globally as a natural lipid-lowering agent, although its anti-atherogenic cardiovascular benefit in animal models or humans is unknown. The aim of this study was to determine the effects of gugulipid on cholesterol homeostasis and development of mild and severe atherosclerosis in male mice. For this purpose, we evaluated the impact of gugulipid treatment on liver histology, plasma lipoprotein cholesterol, endothelial function, and development of atherosclerosis and/or ischemic heart disease in wild-type mice; apolipoprotein E knockout mice, a model of atherosclerosis without ischemic complications; and SR-B1 knockout and atherogenic-diet-fed apolipoprotein E hypomorphic (SR-BI KO/ApoER61h/h) mice, a model of lethal ischemic heart disease due to severe atherosclerosis. Gugulipid administration was associated with histological abnormalities in liver, increased alanine aminotransferase levels, lower hepatic SR-BI content, hypercholesterolemia due to increased HDL cholesterol levels, endothelial dysfunction, enhanced atherosclerosis, and accelerated death in animals with severe ischemic heart disease. In conclusion, our data show important adverse effects of gugulipid intake on HDL metabolism and atherosclerosis in male mice, suggesting potential and unknown deleterious effects on cardiovascular health in humans. In addition, these findings reemphasize the need for rigorous preclinical and clinical studies to provide guidance on the consumption of natural products and regulation of their use in the general population.
Assuntos
Aterosclerose/metabolismo , Endotélio Vascular/metabolismo , Hipercolesterolemia/metabolismo , Isquemia Miocárdica/metabolismo , Extratos Vegetais/toxicidade , Gomas Vegetais/toxicidade , Animais , Aterosclerose/induzido quimicamente , Aterosclerose/genética , Aterosclerose/patologia , Commiphora , Endotélio Vascular/patologia , Hipercolesterolemia/induzido quimicamente , Hipercolesterolemia/genética , Hipercolesterolemia/patologia , Proteínas Relacionadas a Receptor de LDL/deficiência , Masculino , Camundongos , Camundongos Knockout , Isquemia Miocárdica/induzido quimicamente , Isquemia Miocárdica/genética , Isquemia Miocárdica/patologia , Receptores Depuradores Classe B/deficiênciaRESUMO
Reelin, an extracellular glycoprotein secreted in embryonic and adult brain, participates in neuronal migration and neuronal plasticity. Extensive evidence shows that reelin via activation of the ApoER2 and VLDLR receptors promotes dendrite and spine formation during early development. Further evidence suggests that reelin signaling is needed to maintain a stable architecture in mature neurons, but, direct evidence is lacking. During activity-dependent maturation of the neuronal circuitry, the synaptic protein PSD95 is inserted into the postsynaptic membrane to induce structural refinement and stability of spines and dendrites. Given that ApoER2 interacts with PSD95, we tested if reelin signaling interference in adult neurons reactivates the dendritic architecture. Unlike findings in developing cultures, the presently obtained in vitro and in vivo data show, for the first time, that reelin signaling interference robustly increase dendritogenesis and reduce spine density in mature hippocampal neurons. In particular, the expression of a mutant ApoER2 form (ApoER2-tailless), which is unable to interact with PSD95 and hence cannot transduce reelin signaling, resulted in robust dendritogenesis in mature hippocampal neurons in vitro. These results indicate that reelin/ApoER2/PSD95 signaling is important for neuronal structure maintenance in mature neurons. Mechanistically, obtained immunofluorescent data indicate that reelin signaling impairment reduced synaptic PSD95 levels, consequently leading to synaptic re-insertion of NR2B-NMDARs. Our findings underscore the importance of reelin in maintaining adult network stability and reveal a new mode for reactivating dendritogenesis in neurological disorders where dendritic arbor complexity is limited, such as in depression, Alzheimer's disease, and stroke. J. Cell. Physiol. 232: 1187-1199, 2017. © 2016 Wiley Periodicals, Inc.
Assuntos
Moléculas de Adesão Celular Neuronais/metabolismo , Diferenciação Celular , Dendritos/metabolismo , Proteínas da Matriz Extracelular/metabolismo , Hipocampo/citologia , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Relacionadas a Receptor de LDL/metabolismo , Proteínas de Membrana/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurogênese , Serina Endopeptidases/metabolismo , Transdução de Sinais , Animais , Proteínas de Transporte/metabolismo , Espinhas Dendríticas/metabolismo , Giro Denteado/metabolismo , Proteína 4 Homóloga a Disks-Large , Genes Dominantes , Glutationa Transferase/metabolismo , Camundongos Endogâmicos C57BL , Plasticidade Neuronal , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/metabolismo , Proteínas Recombinantes de Fusão/metabolismo , Proteína ReelinaRESUMO
ApoER2 and its ligand Reelin participate in neuronal migration during development. Upon receptor binding, Reelin induces the proteolytic processing of ApoER2 as well as the activation of signaling pathway, including small Rho GTPases. Besides its presence in the central nervous system (CNS), Reelin is also secreted by Schwann cells (SCs), the glial cells of the peripheral nervous system (PNS). Reelin deficient mice (reeler) show decreased axonal regeneration in the PNS; however neither the presence of ApoER2 nor the role of the Reelin signaling pathway in the PNS have been evaluated. Interestingly SC migration occurs during PNS development and during injury-induced regeneration and involves activation of small Rho GTPases. Thus, Reelin-ApoER2 might regulate SC migration during axon regeneration in the PNS. Here we demonstrate the presence of ApoER2 in PNS. After sciatic nerve injury Reelin was induced and its receptor ApoER2 was proteolytically processed. In vitro, SCs express both Reelin and ApoER2 and Reelin induces SC migration. To elucidate the molecular mechanism underlying Reelin-dependent SC migration, we examined the involvement of Rac1, a conspicuous small GTPase family member. FRET experiments revealed that Reelin activates Rac1 at the leading edge of SCs. In addition, Tiam1, a major Rac1-specific GEF was required for Reelin-induced SC migration. Moreover, Reelin-induced SC migration was decreased after suppression of the polarity protein PAR3, consistent with its association to Tiam1. Even more interesting, we demonstrated that PAR3 binds preferentially to the full-length cytoplasmic tail of ApoER2 corresponding to the splice-variant containing the exon 19 that encodes a proline-rich insert and that ApoER2 was required for SC migration. Our study reveals a novel function for Reelin/ApoER2 in PNS, inducing cell migration of SCs, a process relevant for PNS development and regeneration.
Assuntos
Moléculas de Adesão Celular Neuronais/metabolismo , Movimento Celular/fisiologia , Proteínas da Matriz Extracelular/metabolismo , Proteínas Relacionadas a Receptor de LDL/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Neurogênese/fisiologia , Células de Schwann/citologia , Serina Endopeptidases/metabolismo , Proteínas rac1 de Ligação ao GTP/metabolismo , Animais , Células Cultivadas , Camundongos Endogâmicos C57BL , Neurônios/metabolismo , Ligação Proteica/fisiologia , Proteína Reelina , Transdução de Sinais/fisiologiaRESUMO
PURPOSE: This study aimed to evaluate the association of age-related macular degeneration (AMD) with apolipoprotein E (APOE) variants and serum lipid profiles, including levels and fractions of total serum cholesterol (TC), low-density lipoprotein cholesterol (LDLc), and high-density lipoprotein cholesterol (HDLc), and triglycerides (TG). METHODS: Genotyping of APOE-HhaI was performed in 134 patients (study group, SG) and 164 individuals without AMD (control group, CG), aged 50-89 years. Lipid profiles were analyzed in a subgroup of 30 subjects of both groups, matched according to age and sex. The significance level was set at P<0.05. RESULTS: APOE E3/E3 was more prevalent (SG=74.6%; CG=77.4%), with no difference between both groups (P=0.667). The same result was observed for risk genotypes (APOE E -/2: SG=7.4%; CG=10.3%, P=0.624). Serum levels of TC, LDLc, and TG revealed similar median values between SG (193.5, 116, and 155 mg/dL, respectively) and CG (207.5, 120, and 123.5 mg/dL, respectively; P >0.05). For HDLc, a higher median value was observed in SG (53.3 mg/dL) versus CG (42.5 mg/dL; P=0.016). Logistic regression analysis showed the same value, and the HDLc/TC ratio was -11.423 (P=0.014), as also confirmed by an increase in HDLc in SG. The association between lipid profiles and apolipoprotein E genotypes was similar in both groups (P>0.05). CONCLUSION: APOE-HhaI is not associated with AMD. However, an increase in serum HDLc level appears to exert a protective effect against the disease, irrespective of the genetic variants of apoE.