scholarly journals Microtubule-dependent and independent roles of spastin in lipid droplet dispersion and biogenesis

2020 ◽  
Vol 3 (6) ◽  
pp. e202000715
Author(s):  
Nimesha Tadepalle ◽  
Lennart Robers ◽  
Matteo Veronese ◽  
Peter Zentis ◽  
Felix Babatz ◽  
...  
Keyword(s):  
Hereditary Spastic Paraplegia ◽  
Mammalian Cells ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Plastic Behavior ◽  
Glucose Starvation ◽  
Spastic Paraplegia ◽  
Microtubule Severing ◽  
Tag Accumulation

Lipid droplets (LDs) are metabolic organelles that store neutral lipids and dynamically respond to changes in energy availability by accumulating or mobilizing triacylglycerols (TAGs). How the plastic behavior of LDs is regulated is poorly understood. Hereditary spastic paraplegia is a central motor axonopathy predominantly caused by mutations in SPAST, encoding the microtubule-severing protein spastin. The spastin-M1 isoform localizes to nascent LDs in mammalian cells; however, the mechanistic significance of this targeting is not fully explained. Here, we show that tightly controlled levels of spastin-M1 are required to inhibit LD biogenesis and TAG accumulation. Spastin-M1 maintains the morphogenesis of the ER when TAG synthesis is prevented, independent from microtubule binding. Moreover, spastin plays a microtubule-dependent role in mediating the dispersion of LDs from the ER upon glucose starvation. Our results reveal a dual role of spastin to shape ER tubules and to regulate LD movement along microtubules, opening new perspectives for the pathogenesis of hereditary spastic paraplegia.

scholarly journals Mouse models for hereditary spastic paraplegia uncover a role of PI4K2A in autophagic lysosome reformation

Autophagy ◽  
2021 ◽  
pp. 1-17
Author(s):  
Mukhran Khundadze ◽  
Federico Ribaudo ◽  
Adeela Hussain ◽  
Henry Stahlberg ◽  
Nahal Brocke-Ahmadinejad ◽  
...  
Keyword(s):  
Mouse Models ◽  
Hereditary Spastic Paraplegia ◽  
Spastic Paraplegia

scholarly journals Current Knowledge of Endolysosomal and Autophagy Defects in Hereditary Spastic Paraplegia

Cells ◽  
2021 ◽  
Vol 10 (7) ◽  
pp. 1678
Author(s):  
Liriopé Toupenet Marchesi ◽  
Marion Leblanc ◽  
Giovanni Stevanin
Keyword(s):  
Nervous System ◽  
Motor Neurons ◽  
Neurological Disorders ◽  
Hereditary Spastic Paraplegia ◽  
Current Knowledge ◽  
Spastic Paraplegia ◽  
Functional Convergence ◽  
The Common ◽  
Hsp Genes

Hereditary spastic paraplegia (HSP) refers to a group of neurological disorders involving the degeneration of motor neurons. Due to their clinical and genetic heterogeneity, finding common effective therapeutics is difficult. Therefore, a better understanding of the common pathological mechanisms is necessary. The role of several HSP genes/proteins is linked to the endolysosomal and autophagic pathways, suggesting a functional convergence. Furthermore, impairment of these pathways is particularly interesting since it has been linked to other neurodegenerative diseases, which would suggest that the nervous system is particularly sensitive to the disruption of the endolysosomal and autophagic systems. In this review, we will summarize the involvement of HSP proteins in the endolysosomal and autophagic pathways in order to clarify their functioning and decipher some of the pathological mechanisms leading to HSP.

scholarly journals Direct lysosome-based autophagy of lipid droplets in hepatocytes

2020 ◽  
Vol 117 (51) ◽  
pp. 32443-32452
Author(s):  
Ryan J. Schulze ◽  
Eugene W. Krueger ◽  
Shaun G. Weller ◽  
Katherine M. Johnson ◽  
Carol A. Casey ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Lipid Droplets ◽  
Critical Role ◽  
Specific Protein ◽  
Lipid Homeostasis ◽  
Dynamic Interactions ◽  
Double Membrane ◽  
Live Cell Microscopy ◽  
Cell Microscopy

Hepatocytes metabolize energy-rich cytoplasmic lipid droplets (LDs) in the lysosome-directed process of autophagy. An organelle-selective form of this process (macrolipophagy) results in the engulfment of LDs within double-membrane delimited structures (autophagosomes) before lysosomal fusion. Whether this is an exclusive autophagic mechanism used by hepatocytes to catabolize LDs is unclear. It is also unknown whether lysosomes alone might be sufficient to mediate LD turnover in the absence of an autophagosomal intermediate. We performed live-cell microscopy of hepatocytes to monitor the dynamic interactions between lysosomes and LDs in real-time. We additionally used a fluorescent variant of the LD-specific protein (PLIN2) that exhibits altered fluorescence in response to LD interactions with the lysosome. We find that mammalian lysosomes and LDs undergo interactions during which proteins and lipids can be transferred from LDs directly into lysosomes. Electron microscopy (EM) of primary hepatocytes or hepatocyte-derived cell lines supports the existence of these interactions. It reveals a dramatic process whereby the lipid contents of the LD can be “extruded” directly into the lysosomal lumen under nutrient-limited conditions. Significantly, these interactions are not affected by perturbations to crucial components of the canonical macroautophagy machinery and can occur in the absence of double-membrane lipoautophagosomes. These findings implicate the existence of an autophagic mechanism used by mammalian cells for the direct transfer of LD components into the lysosome for breakdown. This process further emphasizes the critical role of lysosomes in hepatic LD catabolism and provides insights into the mechanisms underlying lipid homeostasis in the liver.

scholarly journals Lecithin:Retinol Acyl Transferase (LRAT) induces the formation of lipid droplets

2019 ◽  
Author(s):  
Martijn R. Molenaar ◽  
Tsjerk A. Wassenaar ◽  
Kamlesh K. Yadav ◽  
Alexandre Toulmay ◽  
Muriel C. Mari ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Yeast Cells ◽  
Acyl Transferase ◽  
Hydrophobic Core ◽  
Retinyl Ester ◽  
Steryl Esters ◽  
Retinyl Esters

AbstractLipid droplets are unique and nearly ubiquitous organelles that store neutral lipids in a hydrophobic core, surrounded by a monolayer of phospholipids. The primary neutral lipids are triacylglycerols and steryl esters. It is not known whether other classes of neutral lipids can form lipid droplets by themselves. Here we show that production of retinyl esters by lecithin:retinol acyl transferase (LRAT) in yeast cells, incapable of producing triacylglycerols and steryl esters, causes the formation of lipid droplets. By electron microscopy, these lipid droplets are morphologically indistinguishable from those in wild-type cells. In silico and in vitro experiments confirmed the propensity of retinyl esters to segregate from membranes and to form lipid droplets. The hydrophobic N-terminus of LRAT displays preferential interactions with retinyl esters in membranes and promotes the formation of large retinyl ester-containing lipid droplets in mammalian cells. Our combined data indicate that the molecular design of LRAT is optimally suited to allow the formation of characteristic large lipid droplets in retinyl ester-storing cells.

Lipid droplets are dysregulated in the adult dentate gyrus during seizure

2021 ◽  
Vol 156 (Supplement_1) ◽  
pp. S88-S88
Author(s):  
A Ahamad ◽  
S Ge
Keyword(s):  
Lipid Metabolism ◽  
Dentate Gyrus ◽  
Lipid Droplets ◽  
Neutral Lipids ◽  
Continuous Production ◽  
Mesial Temporal Lobe Epilepsy ◽  
Inhibitory Neurons ◽  
Specific Marker ◽  
Time Points

Abstract Introduction/Objective Dentate gyrus (DG), a neurogenic niche, is a metabolically dense subregion of the hippocampus. Continuous production and integration of new neurons in the existing circuit and harmonious relationship between excitatory and inhibitory neurons accompanied by neuron-glia coupling is essential to maintain hippocampal homeostasis throughout adulthood. Imbalance in the neuronal activity generates seizures and can result in mesial temporal lobe epilepsy (MTLE). MTLE affects 50 million people across the globe and impairs the overall hippocampal network and its associated functions such as memory and cognition. Although altered lipid metabolism has been associated with status epilepticus, the role of lipid droplets (LDs), the minuscule metabolically active organelle known to provide a substrate for cellular energy, has not been explored in DG during seizure. LDs are composed of neutral lipids and surrounded by phospholipid monolayer, which is studded with a structural Perilipin family of proteins 1-5, reported to be involved in lipid metabolism. Methods/Case Report To study LDs in the brain, we used a novel approach by injecting Bodipy, a lipid dye in the tail vein of mice, and successfully labeled LDs in the DG. We used the pilocarpine-induced seizure model. After Bodipy injection followed by seizure induction, mice were sacrificed at four time-points 0.5, 1-, 3- and 18 hours. Results (if a Case Study enter NA) We found a significant increase in Bodipy signal and Perilipin 4, LDs specific marker expression at four time-points post-seizure than in the control cohort. To elucidate the role of neuron-glia metabolic coupling in DG, we measured LDs in microglia and astrocytes and found a significant increase in LDs in seizure mice than control groups suggesting the role of glia in lipid regulation in DG. Conclusion Overall, this novel study will highlight the undiscovered role of LDs in dentate gyrus during seizure and, in the future, can be used as a therapeutic target to alleviate the MTLE phenotype.

Intracellular communication between lipid droplets and peroxisomes: the Janus face of PEX19

2018 ◽  
Vol 399 (7) ◽  
pp. 741-749 ◽  
Author(s):  
Bianca Schrul ◽  
Wolfgang Schliebs
Keyword(s):  
Metabolic Pathways ◽  
Lipid Droplets ◽  
Environmental Changes ◽  
Neutral Lipids ◽  
Nutrient Supply ◽  
Metabolic Energy ◽  
Central Question ◽  
And Function ◽  
Metabolic Output

Abstract In order to adapt to environmental changes, such as nutrient availability, cells have to orchestrate multiple metabolic pathways, which are catalyzed in distinct specialized organelles. Lipid droplets (LDs) and peroxisomes are both endoplasmic reticulum (ER)-derived organelles that fulfill complementary functions in lipid metabolism: Upon nutrient supply, LDs store metabolic energy in the form of neutral lipids and, when energy is needed, supply fatty acids for oxidation in peroxisomes and mitochondria. How these organelles communicate with each other for a concerted metabolic output remains a central question. Here, we summarize recent insights into the biogenesis and function of LDs and peroxisomes with emphasis on the role of PEX19 in these processes.

scholarly journals A Novel SPAST/SPG4 Splice-Site Variant in a Family with Dominant Hereditary Spastic Paraplegia

2020 ◽  
Vol 2020 ◽  
pp. 1-3
Author(s):  
Nathaniel M. Robbins ◽  
Jillian R. Ozmore ◽  
Thomas L. Winder ◽  
Pedro Gonzalez-Alegre ◽  
Tanya M. Bardakjian
Keyword(s):  
Splice Site ◽  
Hereditary Spastic Paraplegia ◽  
Spastic Paraparesis ◽  
Spastic Paraplegia ◽  
Novel Variant ◽  
Consensus Splice Site ◽  
Diagnostic Work ◽  
Next Generation Sequencing Ngs ◽  
Work Up

Some causes of spastic paraplegia are treatable and many are not. Diagnostic work-up to determine the etiology can be costly and invasive. Here we report the case of a man with slowly progressive spastic paraparesis. Using a multigene next-generation sequencing (NGS) panel, we identified a novel variant in the consensus splice site of the SPAST gene (exon 13, c.1536G>A, heterozygous), affecting codon 512 of the SPAST mRNA. The observed variant segregated with the disease in four tested family members. In this case, genetic confirmation obviated the need for additional testing such as MRI and lumbar puncture and helped the patient and his family understand his condition and prognosis. We conclude with a brief discussion of the SPG4/SPAST gene and the role of multigene panels in the diagnosis and management of hereditary spastic paraplegia.

Systematic Analysis of Brain MRI Findings in Adaptor Protein Complex 4–Associated Hereditary Spastic Paraplegia

Neurology ◽  
2021 ◽  
pp. 10.1212/WNL.0000000000012836
Author(s):  
Darius Ebrahimi-Fakhari ◽  
Julian E Alecu ◽  
Marvin Ziegler ◽  
Gregory Geisel ◽  
Catherine Jordan ◽  
...  
Keyword(s):  
White Matter ◽  
Corpus Callosum ◽  
Brain Development ◽  
Hereditary Spastic Paraplegia ◽  
Anterior Commissure ◽  
Brain Mri ◽  
Adaptor Protein ◽  
Spastic Paraplegia ◽  
Mri Findings

Background and Objectives:AP-4-associated hereditary spastic paraplegia (AP-4-HSP: SPG47, SPG50, SPG51, SPG52) is an emerging cause of childhood-onset hereditary spastic paraplegia and mimic of cerebral palsy. This study aims to define the spectrum of brain MRI findings in AP-4-HSP and to investigate radio-clinical correlations.Methods:A systematic qualitative and quantitative analysis of 107 brain MRI studies from 76 individuals with genetically-confirmed AP-4-HSP and correlation with clinical findings including surrogates of disease severity.Results:We define AP-4-HSP as a disorder of gray and white matter and demonstrate that abnormal myelination is common and that metrics of reduced white matter volume correlate with severity of motor symptoms. We identify a common diagnostic imaging signature consisting of (1) a thin splenium of the corpus callosum, (2) an absent or thin anterior commissure, (3) characteristic signal abnormalities of the forceps minor (“ears of the grizzly sign”), and (4) periventricular white matter abnormalities. The presence of two or more of these findings has a sensitivity of ∼99% for detecting AP-4-HSP, while the combination of all four is found in ∼45% of cases. Compared to other HSP with a thin corpus callosum, the absent anterior commissure appears to be specific to AP-4-HSP. Our analysis further identified a subset of AP-4-HSP patients with polymicrogyria, underscoring the role of AP-4 in early brain development. Of clinical importance, these patients displayed a higher prevalence of seizures and status epilepticus, many at a young age.Discussion:Our findings define the MRI spectrum of AP-4-HSP providing opportunities for early diagnosis, identification of individuals at risk for complications, and a window into the role of the AP-4 complex in brain development and neurodegeneration.

The role of hereditary spastic paraplegia related genes in multiple sclerosis

2007 ◽  
Vol 254 (9) ◽  
pp. 1221-1226 ◽  
Author(s):  
G. C. DeLuca ◽  
S. V. Ramagopalan ◽  
M. Z. Cader ◽  
D. A. Dyment ◽  
B. M. Herrera ◽  
...  
Keyword(s):  
Multiple Sclerosis ◽  
Hereditary Spastic Paraplegia ◽  
Spastic Paraplegia
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