scholarly journals A Specific Structural Requirement for Ergosterol in Long-chain Fatty Acid Synthesis Mutants Important for Maintaining Raft Domains in Yeast

2002 ◽  
Vol 13 (12) ◽  
pp. 4414-4428 ◽  
Author(s):  
Marlis Eisenkolb ◽  
Christoph Zenzmaier ◽  
Erich Leitner ◽  
Roger Schneiter
Keyword(s):  
Plasma Membrane ◽  
Fatty Acid ◽  
Double Mutant ◽  
Chain Fatty Acid ◽  
Long Chain Fatty Acid ◽  
Structural Requirement ◽  
Fatty Acid Elongase ◽  
Synthetically Lethal ◽  
Raft Domains ◽  
Long Chain

Fungal sphingolipids contain ceramide with a very-long-chain fatty acid (C26). To investigate the physiological significance of the C26-substitution on this lipid, we performed a screen for mutants that are synthetically lethal with ELO3. Elo3p is a component of the ER-associated fatty acid elongase and is required for the final elongation cycle to produce C26 from C22/C24 fatty acids.elo3Δ mutant cells thus contain C22/C24- instead of the natural C26-substituted ceramide. We now report that under these conditions, an otherwise nonessential, but also fungal-specific, structural modification of the major sterol of yeast, ergosterol, becomes essential, because mutations in ELO3 are synthetically lethal with mutations in ERG6. Erg6p catalyzes the methylation of carbon atom 24 in the aliphatic side chain of sterol. The lethality of an elo3Δ erg6Δ double mutant is rescued by supplementation with ergosterol but not with cholesterol, indicating a vital structural requirement for the ergosterol-specific methyl group. To characterize this structural requirement in more detail, we generated a strain that is temperature sensitive for the function of Erg6p in an elo3Δ mutant background. Examination of raft association of the GPI-anchored Gas1p and plasma membrane ATPase, Pma1p, in the conditional elo3Δ erg6 ts double mutant, revealed a specific defect of the mutant to maintain raft association of preexisting Pma1p. Interestingly, in an elo3Δ mutant at 37°C, newly synthesized Pma1p failed to enter raft domains early in the biosynthetic pathway, and upon arrival at the plasma membrane was rerouted to the vacuole for degradation. These observations indicate that the C26 fatty acid substitution on lipids is important for establishing raft association of Pma1p and stabilizing the protein at the cell surface. Analysis of raft lipids in the conditional mutant strain revealed a selective enrichment of ergosterol in detergent-resistant membrane domains, indicating that specific structural determinants on both sterols and sphingolipids are required for their association into raft domains.

scholarly journals Two Italian Patients with ELOVL4-Related Neuro-Ichthyosis:  Expanding the Genotypic and Phenotypic Spectrum and Ultrastructural Characterization

Genes ◽  
2021 ◽  
Vol 12 (3) ◽  
pp. 343
Author(s):  
Andrea Diociaiuti ◽  
Diego Martinelli ◽  
Francesco Nicita ◽  
Claudia Cesario ◽  
Elisa Pisaneschi ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Chain Fatty Acid ◽  
Spinocerebellar Ataxia Type ◽  
Facial Dysmorphism ◽  
Macular Dystrophy ◽  
Compound Heterozygous ◽  
Long Chain Fatty Acid ◽  
Fatty Acid Elongase ◽  
Spastic Quadriplegia ◽  
Long Chain

Elongation of Very Long Chain Fatty Acid-4 (ELOVL4) is a fatty acid elongase responsible for very long-chain fatty acid biosynthesis in the brain, retina, and skin. Heterozygous mutations in ELOVL4 gene cause Stargardt-like macular dystrophy and spinocerebellar ataxia type-34, while different homozygous mutations have been associated with ichthyosis, spastic quadriplegia, and mental retardation syndrome in three kindred. We report the first two Italian children affected with neuro-ichthyosis due to the previously undescribed ELOVL4 homozygous frameshift variant c.435dupT (p.Ile146TyrfsTer29), and compound heterozygous variants c.208C>T (p.Arg70Ter) and c.487T>C (p.Cys163Arg), respectively. Both patients were born with collodion membrane followed by development of diffuse mild hyperkeratosis and scaling, localized erythema, and palmoplantar keratoderma. One infant displayed mild facial dysmorphism. They suffered from failure to thrive, and severe gastro-esophageal reflux with pulmonary aspiration. The patients presented axial hypotonia, hypertonia of limbs, and absent head control with poor eye contact from infancy. Visual evoked potentials showed markedly increased latency and poor morphological definition, indicative of alteration of the retro-retinal visual pathways in both patients. Ultrastructural skin examination revealed abnormalities of lamellar bodies with altered release in the epidermal granular and horny layer intracellular spaces. Our findings contribute to expanding the phenotypic and genotypic features of ELOVL4-related neuro-ichthyosis.

High-Fat Diet Elevates Liver Docosahexaenoic Acid Possibly through Over-Expression of Very Long-Chain Fatty Acid Elongase 2 in C57BL/6J Mice

2019 ◽  
Vol 89 (1-2) ◽  
pp. 62-72
Author(s):  
Mooli Raja Gopal Reddy ◽  
Gundluri Venkata Asha ◽  
Sravan Kumar Manchiryala ◽  
Uday Kumar Putcha ◽  
Ayyalasomayajula Vajreswari ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Lipid Metabolism ◽  
High Fat Diet ◽  
Chain Fatty Acid ◽  
High Fat ◽  
Long Chain Fatty Acid ◽  
Fatty Acid Elongase ◽  
Over Expression ◽  
Long Chain

Abstract. The liver is the main site of lipid metabolism and vitamin A storage. Dietary factors are known to affect liver function, thereby leading to metabolic abnormalities. Here, we assessed the impact of long-term feeding of a high-fat diet on hepatic vitamin A status and lipid metabolism. For this purpose, 14 male and 14 female 35-day-old mice (strain C57BL/6J) were each divided into 2 groups of 7 animals and fed either a stock diet or a high-fat (HF) diet for 26 weeks. In addition to increased body weight/weight gain, the HF diet induced hypertriglyceridemia in both (p < 0.01). However, liver triglyceride levels were comparable among groups, which could be partly explained by unaltered expression of various lipogenic pathway proteins such as sterol regulatory element binding protein 1 (SREBP1), fatty acid synthase (FAS), microsomal triglyceride transfer protein (MTTP), and glycerol 3-phosphate acyl transferase (GPAT). On the other hand, hepatic retinol stores increased significantly in both sexes, whereas males displayed elevated circulatory retinol levels. Notably, long-term feeding of a HF diet elevated n-3 polyunsaturated fatty acid (PUFA) and docosahexaenoic acid (DHA, C22:6) levels in the liver (p ≤ 0.001), which is in line with the over-expression of very long-chain fatty acid elongase 2 (ELOVL2) protein in both sexes of mice (p < 0.01). In conclusion, very long-term feeding of a HF diet increased hepatic retinol stores and induced hypertriglyceridemia. However, it had no effect on hepatic triglyceride accumulation, possibly due to increased DHA levels arising from the ELOVL2-mediated elongation pathway.

scholarly journals A long-chain fatty acid elongase Elovl6 regulates mechanical damage–induced keratinocyte death and skin inflammation

2018 ◽  
Author(s):  
Yoshiyuki Nakamura ◽  
Takashi Matsuzaka ◽  
Satoko Tahara-Hanaoka ◽  
Kazuko Shibuya ◽  
Hitoshi Shimano ◽  
...  
Keyword(s):  
Fatty Acid ◽  
Skin Diseases ◽  
Vaccenic Acid ◽  
Mechanical Damage ◽  
Skin Inflammation ◽  
Chain Fatty Acid ◽  
Tape Stripping ◽  
Long Chain Fatty Acid ◽  
Fatty Acid Elongase ◽  
Long Chain

AbstractMechanical damage on the skin not only affect the barrier function but also induce various immune responses, which trigger or exacerbate the inflammation in healthy individuals and patients with inflammatory skin diseases. However, how mechanical damage-induced skin inflammation is regulated remains largely unknown. Here, we show that mechanical damage due to tape stripping triggered keratinocyte death and release of danger-associated molecular patterns (DAMPs) such as high-mobility group box 1 protein (HMGB-1) and IL-1α, which induced production of proinflammatory cytokines and chemokines IL-1β and CXCL-1 by keratinocytes in mice. We also show that a long-chain fatty acid elongase Elovl6 is expressed in keratinocytes. Mice deficient in Elovl6 had increased epidermal levels of cis-vaccenic acid (CVA); this accelerated keratinocyte death triggered by tape stripping and release of DAMPs and exacerbated skin inflammation. Our results demonstrate that Elovl6 regulates mechanical damage–triggered keratinocyte death and skin inflammation.

scholarly journals The effect of intracellular pH on long-chain fatty acid uptake in 3T3-L1 adipocytes: evidence that uptake involves the passive diffusion of protonated long-chain fatty acids across the plasma membrane

1996 ◽  
Vol 313 (2) ◽  
pp. 487-494 ◽  
Author(s):  
Bernardo L. TRIGATTI ◽  
Gerhard E. GERBER
Keyword(s):  
Fatty Acids ◽  
Plasma Membrane ◽  
Fatty Acid ◽  
Chain Fatty Acid ◽  
Long Chain Fatty Acids ◽  
Cytoplasmic Ph ◽  
Long Chain Fatty Acid ◽  
Intact Cells ◽  
Fatty Acid Binding ◽  
Long Chain

To understand the mechanism of long-chain fatty acid permeation of the plasma membrane in mammalian cells, the effects of changes in the cytoplasmic pH on the internalization of physiologically relevant, submicromolar concentrations of uncomplexed long-chain fatty acids were investigated in 3T3-L1 adipocytes. The acidification of the cytoplasm upon NH4Cl prepulsing of intact cells was accompanied by a rapid reduction of cellular long-chain fatty acid uptake (measured as the total accumulation of [9,10-3H]oleate). This was followed by a slow recovery to normal levels of uptake as the cytoplasmic pH recovered. Conventional filtration assays do not distinguish between fatty acid movement across the plasma membrane and intracellular steps, such as binding to cytoplasmic fatty acid-binding proteins or metabolism. While the in vitro binding of a photoreactive fatty acid, 11-m-diazirinophenoxy[11-3H]undecanoate, to a cytoplasmic fatty acid-binding protein was insensitive to changes in pH from pH 7.5 to 5.5, the in vitro conversion of oleate into oleoyl-CoA by cellular acyl-CoA synthetase decreased dramatically. Therefore, the labelling of the 15 kDa cytoplasmic fatty acid-binding protein in intact cells by the photoreactive fatty acid was used as a more direct measure of the permeation of the probe across the plasma membrane. Acidification of the cytoplasm resulted in an immediate reduction in the labelling of this protein in intact adipocytes. Its photolabelling recovered, however, upon the recovery of the cytoplasmic pH to normal levels. This was due to effects of the cytoplasmic pH on the permeation of the photoreactive fatty acid across the plasma membrane rather than its binding to the 15 kDa protein or metabolism in vivo. This is the first demonstration that the movement of physiologically relevant, submicromolar concentrations of uncomplexed long-chain fatty acids across the plasma membrane of intact cells is coupled to the cytoplasmic pH and suggests that it occurs by the diffusion of the protonated long-chain fatty acid through the lipid bilayer.

Sign in / Sign up

Export Citation Format

Share Document