scholarly journals The GARP complex is required for cellular sphingolipid homeostasis

eLife ◽  
2015 ◽  
Vol 4 ◽  
Author(s):  
Florian Fröhlich ◽  
Constance Petit ◽  
Nora Kory ◽  
Romain Christiano ◽  
Hans-Kristian Hannibal-Bach ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Therapeutic Strategy ◽  
De Novo ◽  
Cerebral Atrophy ◽  
Eukaryotic Cells ◽  
Disease Pathogenesis ◽  
Complex Mutation ◽  
Membrane Components ◽  
Garp Complex

Sphingolipids are abundant membrane components and important signaling molecules in eukaryotic cells. Their levels and localization are tightly regulated. However, the mechanisms underlying this regulation remain largely unknown. In this study, we identify the Golgi-associated retrograde protein (GARP) complex, which functions in endosome-to-Golgi retrograde vesicular transport, as a critical player in sphingolipid homeostasis. GARP deficiency leads to accumulation of sphingolipid synthesis intermediates, changes in sterol distribution, and lysosomal dysfunction. A GARP complex mutation analogous to a VPS53 allele causing progressive cerebello-cerebral atrophy type 2 (PCCA2) in humans exhibits similar, albeit weaker, phenotypes in yeast, providing mechanistic insights into disease pathogenesis. Inhibition of the first step of de novo sphingolipid synthesis is sufficient to mitigate many of the phenotypes of GARP-deficient yeast or mammalian cells. Together, these data show that GARP is essential for cellular sphingolipid homeostasis and suggest a therapeutic strategy for the treatment of PCCA2.

Dynamics of autophagosome formation: a pulse and a sequence of waves

2014 ◽  
Vol 42 (5) ◽  
pp. 1389-1395 ◽  
Author(s):  
Nicholas T. Ktistakis ◽  
Eleftherios Karanasios ◽  
Maria Manifava
Keyword(s):  
Mammalian Cells ◽  
De Novo ◽  
Stress Conditions ◽  
Present Review ◽  
Eukaryotic Cells ◽  
Current View ◽  
Protein Assemblies ◽  
Autophagosome Formation ◽  
Flat Membrane ◽  
A Current

Autophagosomes form in eukaryotic cells in response to starvation or to other stress conditions brought about by the unwanted presence in the cytosol of pathogens, damaged organelles or aggregated protein assemblies. The uniqueness of autophagosomes is that they form de novo and that they are the only double-membraned vesicles known in cells, having arisen from flat membrane sheets which have expanded and self-closed. The various steps describing their formation as well as most of the protein and lipid components involved have been identified. Furthermore, the hierarchical relationships among the components are well documented, and the mechanistic rationale for some of these hierarchies has been revealed. In the present review, we try to provide a current view of the process of autophagosome formation in mammalian cells, emphasizing along the way gaps in our knowledge that need additional work.

scholarly journals Regulation of NRF1, a master transcription factor of proteasome genes: implications for cancer and neurodegeneration

2020 ◽  
Vol 31 (20) ◽  
pp. 2158-2163 ◽  
Author(s):  
Amy Northrop ◽  
Holly A. Byers ◽  
Senthil K. Radhakrishnan
Keyword(s):  
Endoplasmic Reticulum ◽  
Transcription Factor ◽  
Membrane Protein ◽  
Neurodegenerative Diseases ◽  
Mammalian Cells ◽  
Therapeutic Strategy ◽  
De Novo ◽  
Degradation Pathway ◽  
Special Focus ◽  
Homeostatic Mechanism

The ability to sense proteasome insufficiency and respond by directing the transcriptional synthesis of de novo proteasomes is a trait that is conserved in evolution and is found in organisms ranging from yeast to humans. This homeostatic mechanism in mammalian cells is driven by the transcription factor NRF1. Interestingly, NRF1 is synthesized as an endoplasmic reticulum (ER) membrane protein and when cellular proteasome activity is sufficient, it is retrotranslocated into the cytosol and targeted for destruction by the ER-­associated degradation pathway (ERAD). However, when proteasome capacity is diminished, retrotranslocated NRF1 escapes ERAD and is activated into a mature transcription factor that traverses to the nucleus to induce proteasome genes. In this Perspective, we track the journey of NRF1 from the ER to the nucleus, with a special focus on the various molecular regulators it encounters along its way. Also, using human pathologies such as cancer and neurodegenerative diseases as examples, we explore the notion that modulating the NRF1-proteasome axis could provide the basis for a viable therapeutic strategy in these cases.

Structure of clathrin cages and coats in ice

1986 ◽  
Vol 44 ◽  
pp. 94-97
Author(s):  
G.P.A. Vigers ◽  
R.A. Crowther ◽  
B.M.F. Pearse
Keyword(s):  
Electron Microscopy ◽  
Heavy Chain ◽  
Outer Part ◽  
Coated Vesicles ◽  
Eukaryotic Cells ◽  
Coat Proteins ◽  
Terminal Domain ◽  
Clathrin Heavy Chain ◽  
Membrane Components

Clathrin forms the polyhedral cage of coated vesicles, which mediate the transfer of selected membrane components within eukaryotic cells. Clathrin cages and coated vesicles have been extensively studied by electron microscopy of negatively stained preparations and shadowed specimens. From these studies the gross morphology of the outer part of the polyhedral coat has been established and some features of the packing of clathrin trimers into the coat have also been described. However these previous studies have not revealed any internal details about the position of the terminal domain of the clathrin heavy chain, the location of the 100kd-50kd accessory coat proteins or the interactions of the coat with the enclosed membrane.

scholarly journals Disease course of Neurofibromatosis Type 2; a 30-year follow-up study of 353 patients seen at a single institution

2020 ◽  
Author(s):  
Claire Forde ◽  
Andrew T King ◽  
Scott A Rutherford ◽  
Charlotte Hammerbeck-Ward ◽  
Simon K Lloyd ◽  
...  
Keyword(s):  
De Novo ◽  
Radiation Treatment ◽  
Univariate Analysis ◽  
Age At Onset ◽  
Neurofibromatosis Type ◽  
Neurofibromatosis Type 2 ◽  
Disease Course ◽  
Number Of Patients

Abstract Background Limited data exists on the disease course of Neurofibromatosis Type 2 (NF2) to guide clinical trial design. Methods A prospective database of patients meeting NF2 diagnostic criteria, reviewed between 1990–2020, was evaluated. Follow-up to first vestibular schwannoma (VS) intervention and death was assessed by univariate analysis and stratified by age at onset, era referred and inheritance type. Interventions for NF2-related tumours were assessed. Cox regression was performed to determine the relationship between individual factors from time of diagnosis to NF2-related death. Results Three-hundred-and-fifty-three patients were evaluated. During 4643.1 follow-up years from diagnosis to censoring 60 patients (17.0%) died. The annual mean number of patients undergoing VS surgery or radiotherapy declined, from 4.66 and 1.65 respectively per 100 NF2 patients in 1990-1999 to 2.11 and 1.01 in 2010-2020, as the number receiving bevacizumab increased (2.51 per 100 NF2 patients in 2010-2020). Five patients stopped bevacizumab to remove growing meningioma or spinal schwannoma. 153/353 (43.3%) had at least one neurosurgical intervention/radiation treatment within 5 years of diagnosis. Patients asymptomatic at diagnosis had longer time to intervention and better survival compared to those presenting with symptoms. Those symptomatically presenting <16 and >40 years had poorer overall survival than those presenting at 26-39 years (P=0.03 and P=0.02 respectively) but those presenting between 16-39 had shorter time to VS intervention. Individuals with de novo constitutional variants had worse survival than those with de novo mosaic or inherited disease (P=0.004). Conclusion Understanding disease course improves prognostication, allowing for better informed decisions about care.

Obesity and diabetes: lipids, ‘nowhere to run to'

2008 ◽  
Vol 116 (2) ◽  
pp. 113-123 ◽  
Author(s):  
Margaret J. Hill ◽  
David Metcalfe ◽  
Philip G. McTernan
Keyword(s):  
Short Review ◽  
Therapeutic Strategies ◽  
Cellular Systems ◽  
Ectopic Fat ◽  
Central Adiposity ◽  
Disease Pathogenesis ◽  
Fat Accumulation ◽  
Obesity And Diabetes

Although specific pathogenic entities contributing to diabetic risk, such as central adiposity, ectopic fat accumulation, hyperlipidaemia and inflammation, are well-characterized, the response of cellular systems to such insults are less well understood. This short review highlights the effect of increasing fat mass on ectopic fat accumulation, the role of triacylglycerols (triglycerides) in Type 2 diabetes mellitus and cardiovascular disease pathogenesis, and selected current therapeutic strategies used to ameliorate these risk factors.

scholarly journals CALINCA—A Novel Pipeline for the Identification of lncRNAs in Podocyte Disease

Cells ◽  
2021 ◽  
Vol 10 (3) ◽  
pp. 692
Author(s):  
Sweta Talyan ◽  
Samantha Filipów ◽  
Michael Ignarski ◽  
Magdalena Smieszek ◽  
He Chen ◽  
...  
Keyword(s):  
Cell Biology ◽  
Mammalian Cells ◽  
De Novo ◽  
Depth Information ◽  
Gene Products ◽  
Classical Analysis ◽  
Protein Coding ◽  
Bioinformatic Pipeline ◽  
Non Coding Rnas ◽  
Filtration Unit

Diseases of the renal filtration unit—the glomerulus—are the most common cause of chronic kidney disease. Podocytes are the pivotal cell type for the function of this filter and focal-segmental glomerulosclerosis (FSGS) is a classic example of a podocytopathy leading to proteinuria and glomerular scarring. Currently, no targeted treatment of FSGS is available. This lack of therapeutic strategies is explained by a limited understanding of the defects in podocyte cell biology leading to FSGS. To date, most studies in the field have focused on protein-coding genes and their gene products. However, more than 80% of all transcripts produced by mammalian cells are actually non-coding. Here, long non-coding RNAs (lncRNAs) are a relatively novel class of transcripts and have not been systematically studied in FSGS to date. The appropriate tools to facilitate lncRNA research for the renal scientific community are urgently required due to a row of challenges compared to classical analysis pipelines optimized for coding RNA expression analysis. Here, we present the bioinformatic pipeline CALINCA as a solution for this problem. CALINCA automatically analyzes datasets from murine FSGS models and quantifies both annotated and de novo assembled lncRNAs. In addition, the tool provides in-depth information on podocyte specificity of these lncRNAs, as well as evolutionary conservation and expression in human datasets making this pipeline a crucial basis to lncRNA studies in FSGS.

scholarly journals A Narrative Review on the Role of AMPK on De Novo Lipogenesis in Non-Alcoholic Fatty Liver Disease: Evidence from Human Studies

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1822
Author(s):  
Christian von Loeffelholz ◽  
Sina M. Coldewey ◽  
Andreas L. Birkenfeld
Keyword(s):  
Liver Disease ◽  
Fatty Liver ◽  
Fatty Liver Disease ◽  
Mammalian Cells ◽  
De Novo ◽  
Adenosine Monophosphate ◽  
De Novo Lipogenesis ◽  
Alcoholic Fatty Liver ◽  
Alcoholic Fatty Liver Disease

5′AMP-activated protein kinase (AMPK) is known as metabolic sensor in mammalian cells that becomes activated by an increasing adenosine monophosphate (AMP)/adenosine triphosphate (ATP) ratio. The heterotrimeric AMPK protein comprises three subunits, each of which has multiple phosphorylation sites, playing an important role in the regulation of essential molecular pathways. By phosphorylation of downstream proteins and modulation of gene transcription AMPK functions as a master switch of energy homeostasis in tissues with high metabolic turnover, such as the liver, skeletal muscle, and adipose tissue. Regulation of AMPK under conditions of chronic caloric oversupply emerged as substantial research target to get deeper insight into the pathogenesis of non-alcoholic fatty liver disease (NAFLD). Evidence supporting the role of AMPK in NAFLD is mainly derived from preclinical cell culture and animal studies. Dysbalanced de novo lipogenesis has been identified as one of the key processes in NAFLD pathogenesis. Thus, the scope of this review is to provide an integrative overview of evidence, in particular from clinical studies and human samples, on the role of AMPK in the regulation of primarily de novo lipogenesis in human NAFLD.

mTOR Inhibitors as a New Therapeutic Strategy in Treatment Resistant Epilepsy in Hemimegalencephaly: A Case Report

2018 ◽  
Vol 34 (3) ◽  
pp. 132-138 ◽  
Author(s):  
Qi Xu ◽  
Shimrit Uliel-Sibony ◽  
Christopher Dunham ◽  
Harvey Sarnat ◽  
Laura Flores-Sarnat ◽  
...  
Keyword(s):  
Therapeutic Strategy ◽  
Mtor Inhibitor ◽  
De Novo ◽  
Mtor Inhibitors ◽  
Mtor Pathway ◽  
Definitive Treatment ◽  
Malformations Of Cortical Development ◽  
Treatment Resistant ◽  
Seizure Reduction ◽  
Functional Hemispherectomy

Hemimegalencephaly is a hamartomatous malformation of one hemisphere. Functional hemispherectomy, the definitive treatment, is associated with significant morbidity and mortality in early infancy. Dysregulation of the mTOR pathway can result in malformations of cortical development, and mTOR inhibitors can effectively reduce seizures in tuberous sclerosis complex. We report a 6-day-old female with hemimegalencephaly and frequent seizures despite 9 antiseizure medications. At 3 months of age, while awaiting hemispherectomy, an mTOR inhibitor, rapamycin, was initiated by the neurologist. After 1 week of treatment, there was >50% reduction in seizures and total seizure burden, and after 2 weeks, development improved, resulting in deferral of surgery by 2.5 months with an increased body weight. Pathology demonstrated cortical dysplasia with upregulation of the mTOR pathway. Deep-sequencing of brain tissue demonstrated 16% mosaicism for a pathogenic de novo MTOR gene mutation. This case exemplifies how mTOR inhibitors could be considered for seizure reduction in patients with hemimegalencephaly while awaiting surgery.

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