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PNPLA1 is a transacylase essential for the generation of the skin barrier lipid ω-O-acylceramide.

ABSTRACT: Lipids are the primary components of the skin permeability barrier, which is the body's most powerful defensive mechanism against pathogens. Acylceramide (ω-O-acylceramide) is a specialized lipid essential for skin barrier formation. Here, we identify PNPLA1 as the long-sought gene involved in the final step of acylceramide synthesis, esterification of ω-hydroxyceramide with linoleic acid, by cell-based assays. We show that increasing triglyceride levels by overproduction of the diacylglycerol acyltransferase DGAT2 stimulates acylceramide production, suggesting that triglyceride may act as a linoleic acid donor. Indeed, the in vitro analyses confirm that PNPLA1 catalyses acylceramide synthesis using triglyceride as a substrate. Mutant forms of PNPLA1 found in patients with ichthyosis exhibit reduced or no enzyme activity in either cell-based or in vitro assays. Altogether, our results indicate that PNPLA1 is directly involved in acylceramide synthesis as a transacylase, and provide important insights into the molecular mechanisms of skin barrier formation and of ichthyosis pathogenesis.

SUBMITTER: Ohno Y

PROVIDER: S-EPMC5337975 | biostudies-literature |

REPOSITORIES: biostudies-literature

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ABHD5 stimulates PNPLA1-mediated ?-O-acylceramide biosynthesis essential for a functional skin permeability barrier.

Project description:Mutations in the genes coding for patatin-like phospholipase domain-containing 1 (PNPLA1) and ?/?-hydrolase domain-containing 5 (ABHD5), also known as comparative gene identification 58, are causative for ichthyosis, a severe skin barrier disorder. Individuals with mutations in either of these genes show a defect in epidermal ?-O-acylceramide (AcylCer) biosynthesis, suggesting that PNPLA1 and ABHD5 act in the same metabolic pathway. In this report, we identified ABHD5 as a coactivator of PNPLA1 that stimulates the esterification of ?-hydroxy ceramides with linoleic acid for AcylCer biosynthesis. ABHD5 interacts with PNPLA1 and recruits the enzyme to its putative triacylglycerol substrate onto cytosolic lipid droplets. Conversely, alleles of ABHD5 carrying point mutations associated with ichthyosis in humans failed to accelerate PNPLA1-mediated AcylCer biosynthesis. Our findings establish an important biochemical function of ABHD5 in interacting with PNPLA1 to synthesize crucial epidermal lipids, emphasizing the significance of these proteins in the formation of a functional skin permeability barrier.

| S-EPMC6277169 | biostudies-literature

PNPLA1 has a crucial role in skin barrier function by directing acylceramide biosynthesis.

Project description:Mutations in patatin-like phospholipase domain-containing 1 (PNPLA1) cause autosomal recessive congenital ichthyosis, but the mechanism involved remains unclear. Here we show that PNPLA1, an enzyme expressed in differentiated keratinocytes, plays a crucial role in the biosynthesis of ω-O-acylceramide, a lipid component essential for skin barrier. Global or keratinocyte-specific Pnpla1-deficient neonates die due to epidermal permeability barrier defects with severe transepidermal water loss, decreased intercellular lipid lamellae in the stratum corneum, and aberrant keratinocyte differentiation. In Pnpla1-/- epidermis, unique linoleate-containing lipids including acylceramides, acylglucosylceramides and (O-acyl)-ω-hydroxy fatty acids are almost absent with reciprocal increases in their putative precursors, indicating that PNPLA1 catalyses the ω-O-esterification with linoleic acid to form acylceramides. Moreover, acylceramide supplementation partially rescues the altered differentiation of Pnpla1-/- keratinocytes. Our findings provide valuable insight into the skin barrier formation and ichthyosis development, and may contribute to novel therapeutic strategies for treatment of epidermal barrier defects.

| S-EPMC5337976 | biostudies-literature

PNPLA1 has a crucial role in skin barrier function by directing acylceramide biosynthesis

Project description:Mutations in PNPLA1 (patatin-like phospholipase domain containing 1) cause autosomal recessive congenital ichthyosis, but the mechanism involved remains unclear. Here we show that PNPLA1, an enzyme expressed in highly differentiated keratinocytes, plays a crucial role in the biosynthesis of acylceramide, a lipid component essential for skin barrier function. Pnpla1-deficient mice showed neonatal lethality due to epidermal permeability barrier defects with severe transepidermal water loss, decreased intercellular lipid lamellae in the stratum corneum, and impaired terminal differentiation of keratinocytes. In Pnpla1–/– epidermis, three unique linoleate-containing lipids, including acylceramides, acylglucosylceramides and (O-acyl)-ω-hydroxy fatty acids, were almost absent with reciprocal increases in their precursors ω-hydroxy (glucosyl)ceramides and ω-hydroxy fatty acids, indicating that PNPLA1 catalyzes the ω-O-esterification step with linoleic acid to form acylceramides. Our results suggest that PNPLA1 represents the missing piece in the process of acylceramide biosynthesis required for establishment of a permeability barrier.

2016-12-23 | GSE87682 | GEO

Effects of omega-<i>O</i>-acylceramide structures and concentrations in healthy and diseased skin barrier lipid membrane models.

Project description:Ceramides (Cers) with ultralong (∼32-carbon) chains and ω-esterified linoleic acid, composing a subclass called omega-O-acylceramides (acylCers), are indispensable components of the skin barrier. Normal barriers typically contain acylCer concentrations of ∼10 mol%; diminished concentrations, along with altered or missing long periodicity lamellar phase (LPP), and increased permeability accompany an array of skin disorders, including atopic dermatitis, psoriasis, and ichthyoses. We developed model membranes to investigate the effects of the acylCer structure and concentration on skin lipid organization and permeability. The model membrane systems contained six to nine Cer subclasses as well as fatty acids, cholesterol, and cholesterol sulfate; acylCer content-namely, acylCers containing sphingosine (Cer EOS), dihydrosphingosine (Cer EOdS), and phytosphingosine (Cer EOP) ranged from zero to 30 mol%. Systems with normal physiologic concentrations of acylCer mixture mimicked the permeability and nanostructure of human skin lipids (with regard to LPP, chain order, and lateral packing). The models also showed that the sphingoid base in acylCer significantly affects the membrane architecture and permeability and that Cer EOP, notably, is a weaker barrier component than Cer EOS and Cer EOdS. Membranes with diminished or missing acylCers displayed some of the hallmarks of diseased skin lipid barriers (i.e., lack of LPP, less ordered lipids, less orthorhombic chain packing, and increased permeability). These results could inform the rational design of new and improved strategies for the barrier-targeted treatment of skin diseases.

| S-EPMC6997605 | biostudies-literature

PNPLA1-Mediated Acylceramide Biosynthesis and Autosomal Recessive Congenital Ichthyosis.

Project description:The stratum corneum of the epidermis acts as a life-sustaining permeability barrier. Unique heterogeneous ceramides, especially ω-O-acylceramides, are key components for the formation of stable lamellar membrane structures in the stratum corneum and are essential for a vital epidermal permeability barrier. Several enzymes involved in acylceramide synthesis have been demonstrated to be associated with ichthyosis. The function of patatin-like phospholipase domain-containing protein 1 (PNPLA1) was a mystery until the finding that PNPLA1 gene mutations were involved in autosomal-recessive congenital ichthyosis (ARCI) patients, both humans and dogs. PNPLA1 plays an essential role in the biosynthesis of acylceramide as a CoA-independent transacylase. PNPLA1 gene mutations cause decreased acylceramide levels and impaired skin barrier function. More and more mutations in PNPLA1 genes have been identified in recent years. Herein, we describe the structural and functional specificity of PNPLA1, highlight its critical roles in acylceramide synthesis and skin barrier maintenance, and summarize the PNPLA1 mutations currently identified in ARCI patients.

| S-EPMC9332298 | biostudies-literature

Essential role of the cytochrome P450 CYP4F22 in the production of acylceramide, the key lipid for skin permeability barrier formation.

Project description:A skin permeability barrier is essential for terrestrial animals, and its impairment causes several cutaneous disorders such as ichthyosis and atopic dermatitis. Although acylceramide is an important lipid for the skin permeability barrier, details of its production have yet to be determined, leaving the molecular mechanism of skin permeability barrier formation unclear. Here we identified the cytochrome P450 gene CYP4F22 (cytochrome P450, family 4, subfamily F, polypeptide 22) as the long-sought fatty acid ω-hydroxylase gene required for acylceramide production. CYP4F22 has been identified as one of the autosomal recessive congenital ichthyosis-causative genes. Ichthyosis-mutant proteins exhibited reduced enzyme activity, indicating correlation between activity and pathology. Furthermore, lipid analysis of a patient with ichthyosis showed a drastic decrease in acylceramide production. We determined that CYP4F22 was a type I membrane protein that locates in the endoplasmic reticulum (ER), suggesting that the ω-hydroxylation occurs on the cytoplasmic side of the ER. The preferred substrate of the CYP4F22 was fatty acids with a carbon chain length of 28 or more (≥C28). In conclusion, our findings demonstrate that CYP4F22 is an ultra-long-chain fatty acid ω-hydroxylase responsible for acylceramide production and provide important insights into the molecular mechanisms of skin permeability barrier formation. Furthermore, based on the results obtained here, we proposed a detailed reaction series for acylceramide production.

| S-EPMC4485105 | biostudies-other

Lipoxygenases mediate the effect of essential fatty acid in skin barrier formation: a proposed role in releasing omega-hydroxyceramide for construction of the corneocyte lipid envelope.

Project description:A barrier to water loss is vital to maintaining life on dry land. Formation of the mammalian skin barrier requires both the essential fatty acid linoleate and the two lipoxygenases 12R-lipoxygenase (12R-LOX) and epidermal lipoxygenase-3 (eLOX3), although their roles are poorly understood. Linoleate occurs in O-linoleoyl-?-hydroxyceramide, which, after hydrolysis of the linoleate moiety, is covalently attached to protein via the free ?-hydroxyl of the ceramide, forming the corneocyte lipid envelope, a scaffold between lipid and protein that helps seal the barrier. Here we show using HPLC-UV, LC-MS, GC-MS, and (1)H NMR that O-linoleoyl-?-hydroxyceramide is oxygenated in a regio- and stereospecific fashion by the consecutive actions of 12R-LOX and eLOX3 and that these products occur naturally in pig and mouse epidermis. 12R-LOX forms 9R-hydroperoxy-linoleoyl-?-hydroxyceramide, further converted by eLOX3 to specific epoxyalcohol (9R,10R-trans-epoxy-11E-13R-hydroxy) and 9-keto-10E,12Z esters of the ceramide; an epoxy-ketone derivative (9R,10R-trans-epoxy-11E-13-keto) is the most prominent oxidized ceramide in mouse skin. These products are absent in 12R-LOX-deficient mice, which crucially display a near total absence of protein-bound ?-hydroxyceramides and of the corneocyte lipid envelope and die shortly after birth from transepidermal water loss. We conclude that oxygenation of O-linoleoyl-?-hydroxyceramide is required to facilitate the ester hydrolysis and allow bonding of the ?-hydroxyceramide to protein, providing a coherent explanation for the roles of multiple components in epidermal barrier function. Our study uncovers a hitherto unknown biochemical pathway in which the enzymic oxygenation of ceramides is involved in building a crucial structure of the epidermal barrier.

| S-EPMC3129186 | biostudies-literature

Ceramide Is Metabolized to Acylceramide and Stored in Lipid Droplets.

Project description:In an approach aimed at defining interacting partners of ceramide synthases (CerSs), we found that fatty acyl-CoA synthase ACSL5 interacts with all CerSs. We demonstrate that ACSL5-generated FA-CoA was utilized with de novo ceramide for the generation of acylceramides, poorly studied ceramide metabolites. Functionally, inhibition of ceramide channeling to acylceramide enhanced accumulation of de novo ceramide and resulted in augmentation of ceramide-mediated apoptosis. Mechanistically, we show that acylceramide generation is catalyzed by diacylglycerol acyltransferase 2 (DGAT2) on lipid droplets. In summary, this study identifies a metabolic pathway of acylceramide generation and its sequestration in LDs in cells and in livers of mice on a high-fat diet. The study also implicates this pathway in ceramide-mediated apoptosis, and has implications in co-regulation of triglyceride and sphingolipid metabolisms.

| S-EPMC5472424 | biostudies-literature

ZFP750 regulates skin lipid metabolism and cutaneous barrier

Project description:A life-essential function of the epidermis is to provide a physical barrier that prevents the loss of water and electrolytes. Essential mediators of this permeability barrier function include ceramides, cholesterol and very long chain fatty acids. Accordingly, their alteration may lead to distinct human conditions, including psoriasis or atopic dermatitis. Recently, a frameshift mutation in the human ZNF750 gene, that encodes for a zinc finger transcription factor, causing a seborrhea-like dermatitis with psoriasiform element, has brought ZNF750 as a key element for the maintenance of the epidermal tissue homeostasis. To clarify this hypothesis, with its underlying molecular mechanism, we generated a novel mouse knockout by deleting exon 2. Here, we show that genetic deletion of the mouse homolog ZFP750 results in loss of epidermal permeability barrier function. ZFP750-/- mice die shortly after birth, within 12 hours. In the stratum corneum of ZFP750-/- mice levels of ceramides, nonpolar lipids and intercellular lipid lamellae are significantly reduced. The alteration of the epidermal lipid homeostasis is directly linked to the transcriptional activity of ZFP750. Indeed, in addition to epidermal differentiation genes, ZFP750 directly and/or indirectly regulates the expression of nearly 50 crucial enzymes in the biosynthesis of ceramides, such as SPTLC1, DGAT2, SMPD3, ELOVL7 and DEGS2. Overall, our study identifies the transcription factor ZFP750 as a master regulator of lipid biosynthesis and epidermal homeostasis and may contribute to our understanding of the pathogenesis of several human skin diseases.

2023-05-03 | GSE220813 | GEO

Lipid mediator profile in vernix caseosa reflects skin barrier development.

Project description:Vernix caseosa (VC) is a protective layer that covers the skin of most human newborns. This study characterized the VC lipid mediator profile, and examined its relationship to gestational period, gender of the newborn and maternal lifestyle. VC collected at birth from 156 newborns within the ALADDIN birth cohort was analyzed and 3 different groups of lipid mediators (eicosanoids and related oxylipin analogs, endocannabinoids and sphingolipids) were screened using LC-MS/MS. A total of 54 compounds were detected in VC. A number of associations between lipid mediators and the gestational period were observed, including increases in the ceramide to sphingomyelin ratio as well as the endocannabinoids anandamide and 2-arachidonoylglycerol. Gender-specific differences in lipid mediator levels were observed for all 3 lipid classes. In addition, levels of the linoleic acid oxidation products 9(10)-epoxy-12Z-octadecenoic and 12(13)-epoxy-9Z-octadecenoic acid (EpOMEs) as well as 12,13-dihydroxy-9Z-octadecenoic acid (DiHOME) were increased in VC of children from mothers with an anthroposophic lifestyle. Accordingly, VC was found to be rich in multiple classes of bioactive lipid mediators, which evidence lifestyle, gender and gestational week dependencies. Levels of lipid mediators in VC may therefore be useful as early stage non-invasive markers of the development of the skin as a protective barrier.

| S-EPMC4629127 | biostudies-other

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