Affinage

PNPLA1

Omega-hydroxyceramide transacylase · UniProt Q8N8W4

Length
532 aa
Mass
57.9 kDa
Annotated
2026-04-28
28 papers in source corpus 11 papers cited in narrative 11 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

PNPLA1 is a lipid droplet-associated transacylase essential for epidermal permeability barrier formation through its catalysis of the terminal step in ω-O-acylceramide biosynthesis. It transfers linoleic acid (and γ-linolenic acid) from triglyceride donors to ω-hydroxyceramide, ω-hydroxy glucosylceramide, and ω-hydroxy fatty acid acceptors in a CoA-independent reaction, with ~3:1 selectivity for linoleate over oleate, accounting for the linoleic acid enrichment of skin barrier lipids (PMID:28248318, PMID:37087101, PMID:38340658). Its catalytic activity and localization to lipid droplets require the coactivator ABHD5 (CGI-58), which physically interacts with PNPLA1 and recruits it to the lipid droplet surface where its triglyceride substrate resides; co-localization alone is sufficient to restore full enzymatic activity (PMID:30361410, PMID:40818613). Loss-of-function mutations in PNPLA1 cause autosomal recessive congenital ichthyosis in humans and dogs, and Pnpla1 knockout mice die neonatally from transepidermal water loss due to complete absence of acylceramides and disorganized extracellular lipid lamellae (PMID:22246504, PMID:28248300, PMID:28369476).

Mechanistic history

Synthesis pass · year-by-year structured walk · 8 steps
  1. 2012 High

    The genetic basis of PNPLA1 in skin barrier function was established when loss-of-function mutations in its catalytic domain were identified as the cause of autosomal recessive congenital ichthyosis across species, revealing that this uncharacterized PNPLA family member is essential for epidermal lipid barrier formation.

    Evidence Genome-wide association in golden retriever dogs plus mutation screening in human ARCI families

    PMID:22246504

    Open questions at the time
    • Enzymatic activity unknown
    • Substrate and product not identified
    • Mechanism by which PNPLA1 contributes to barrier lipids unresolved
  2. 2017 High

    The enzymatic function of PNPLA1 was defined: it acts as a transacylase catalyzing ω-O-esterification of ω-hydroxyceramide with linoleic acid donated by triglyceride to produce acylceramides, and knockout mice confirmed this is essential for neonatal survival by demonstrating lethal barrier defects with absent acylceramides and accumulation of precursors.

    Evidence In vitro enzyme reconstitution with recombinant PNPLA1, cell-based acylceramide assays, global and keratinocyte-specific Pnpla1 KO mice with lipidomic analysis, and electron microscopy of cornified envelope in KO mice and human patient skin

    PMID:28248300 PMID:28248318 PMID:28369476

    Open questions at the time
    • Mechanism of PNPLA1 activation and localization to its substrate unknown
    • Structural basis of substrate selectivity not determined
    • Whether PNPLA1 requires cofactors in vivo not established
  3. 2018 High

    The regulatory mechanism was identified: ABHD5 (CGI-58) physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets, stimulating acylceramide biosynthesis; ichthyosis-associated ABHD5 mutations and Chanarin-Dorfman syndrome mutations disrupt this activation, unifying two ichthyosis gene products in a single pathway.

    Evidence Co-immunoprecipitation, immunofluorescence showing ABHD5-dependent relocalization of PNPLA1 to lipid droplets, immunoelectron microscopy, cell-based functional assays with disease mutants

    PMID:30361410 PMID:30527376

    Open questions at the time
    • Whether ABHD5 activates PNPLA1 allosterically or solely through co-localization not resolved
    • Structural details of the ABHD5–PNPLA1 interaction unknown
    • Role of perilipins in modulating the ABHD5–PNPLA1 axis in keratinocytes not tested
  4. 2018 Low

    A potential connection to lipophagy was reported: patient-derived PNPLA1 mutant fibroblasts showed impaired lipid droplet degradation via autophagy with reduced LC3 and decreased co-localization of lipid droplets with autophagosomes.

    Evidence BODIPY staining and LC3 immunostaining in patient fibroblasts with PNPLA1 mutations

    PMID:30655104

    Open questions at the time
    • Lipophagy role not independently confirmed
    • Whether lipid droplet accumulation is a direct PNPLA1 function or secondary to acylceramide loss not distinguished
    • No rescue experiment performed
  5. 2022 High

    Systematic genotype–phenotype mapping of 16 ichthyosis-associated PNPLA1 missense mutations revealed that nearly all abolish transacylase activity, while residual activity (C216R) correlates with milder disease; mutations were classified into four functional groups based on enzyme activity and ABHD5-dependent lipid droplet localization.

    Evidence Cell-based acylceramide production assay and immunofluorescence of patient mutation panel

    PMID:35970721

    Open questions at the time
    • No crystal structure to rationalize mutation effects
    • Whether any mutations affect ABHD5 binding directly versus protein folding not determined
  6. 2023 High

    In vitro reconstitution with purified recombinant PNPLA1 established its substrate scope — accepting trilinolein, dilinolein, ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid — and quantified a 3:1 selectivity for linoleate over oleate transfer, explaining the in vivo fatty acid composition of skin barrier lipids.

    Evidence Recombinant truncated PNPLA1 from E. coli, HPLC-UV and LC-MS product analysis

    PMID:37087101

    Open questions at the time
    • Full-length enzyme not purified
    • ABHD5-dependent activation not reconstituted in vitro with purified components
    • Kinetic parameters not fully reported
  7. 2024 Medium

    PNPLA1 was shown to esterify γ-linolenic acid in addition to linoleic acid onto acylceramide subspecies in human keratinocytes, expanding its known substrate range, and its knockdown decreased involucrin expression linking it to keratinocyte terminal differentiation.

    Evidence siRNA knockdown in differentiating normal human keratinocytes with LC-MS lipidomics

    PMID:38340658

    Open questions at the time
    • Whether GLA esterification is physiologically significant in vivo not tested
    • Mechanism linking PNPLA1 loss to involucrin downregulation not addressed
  8. 2025 High

    The mechanism of ABHD5-mediated PNPLA1 regulation was resolved into two separable functions — direct PNPLA1 binding and perilipin-dependent lipid droplet association — and proteoliposome reconstitution demonstrated that co-localization of ABHD5 with PNPLA1 is sufficient to fully rescue enzyme activity, establishing a co-localization-driven rather than allosteric activation model.

    Evidence Proteoliposome reconstitution with seven disease-associated ABHD5 missense mutants, enzyme activity measurement, imaging

    PMID:40818613

    Open questions at the time
    • No structural model of the ABHD5–PNPLA1 complex
    • Whether perilipins modulate PNPLA1 activity in intact keratinocytes not tested in this system
    • How PNPLA1 accesses ω-hydroxyceramide acceptors at the lipid droplet surface remains unresolved

Open questions

Synthesis pass · forward-looking unresolved questions
  • A high-resolution structure of PNPLA1 — alone or in complex with ABHD5 — is lacking, leaving open the structural basis for linoleate selectivity, the precise ABHD5 binding interface, and the mechanism by which the enzyme simultaneously engages triglyceride donor and ω-hydroxyceramide acceptor at the lipid droplet surface.
  • No crystal or cryo-EM structure available
  • Kinetic mechanism (ping-pong vs. ternary complex) not determined
  • In vivo regulation by perilipins and other lipid droplet proteins in keratinocytes untested

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0016740 transferase activity 3 GO:0008289 lipid binding 2
Localization
GO:0005811 lipid droplet 4 GO:0005829 cytosol 1
Pathway
R-HSA-1430728 Metabolism 4
Partners
ABHD5

Evidence

Reading pass · 11 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2012 PNPLA1 is expressed in epidermis and is essential for formation of the epidermal lipid barrier; loss-of-function mutations (premature stop codon in dogs; missense and nonsense mutations in humans) in the catalytic domain of PNPLA1 cause autosomal recessive congenital ichthyosis, establishing its role in skin barrier lipid biosynthesis. Genome-wide association study, mutation identification, and localization experiments in golden retriever dogs and human ARCI patients Nature genetics High 22246504
2017 PNPLA1 acts as a transacylase that catalyzes the final step of acylceramide (ω-O-acylceramide) synthesis by esterifying ω-hydroxyceramide with linoleic acid using triglyceride as the linoleic acid donor; ichthyosis patient-derived mutant forms of PNPLA1 show reduced or absent enzyme activity in both cell-based and in vitro assays. Cell-based acylceramide production assay, in vitro enzyme assay with recombinant PNPLA1 and triglyceride substrate, active-site mutant analysis Nature communications High 28248318
2017 Global or keratinocyte-specific Pnpla1 knockout mice die neonatally from epidermal permeability barrier defects with severe transepidermal water loss, absent acylceramides, acylglucosylceramides and (O-acyl)-ω-hydroxy fatty acids in epidermis, and reciprocal accumulation of their precursors, confirming that PNPLA1 catalyses ω-O-esterification with linoleic acid to form acylceramides; acylceramide supplementation partially rescues the differentiation defect of Pnpla1-/- keratinocytes. Conditional and global knockout mouse model, lipidomic analysis, acylceramide rescue experiment Nature communications High 28248300
2017 Pnpla1 knockout mice show loss of ω-O-acylceramides in stratum corneum with accumulation of precursors, defective lipid coverage of the cornified envelope, and disorganized extracellular lipid matrix; these defects are recapitulated in stratum corneum of PNPLA1-mutated human patients. Pnpla1 KO mouse model, ceramide species quantification by lipidomics, electron microscopy of cornified envelope Human molecular genetics High 28369476
2018 ABHD5 (CGI-58) acts as a coactivator of PNPLA1: it physically interacts with PNPLA1 and recruits it to cytosolic lipid droplets where its triglyceride substrate resides, thereby stimulating PNPLA1-mediated ω-O-acylceramide biosynthesis; ichthyosis-associated ABHD5 point mutations fail to stimulate PNPLA1 activity. Co-immunoprecipitation, cell-based acylceramide production assay, immunofluorescence microscopy showing PNPLA1 relocalization to lipid droplets upon ABHD5 co-expression Journal of lipid research High 30361410
2018 ABHD5 enhances PNPLA1-catalyzed acylceramide production and causes PNPLA1 to relocalize from dispersed cytosolic distribution to lipid droplet membranes or periphery; at high expression levels, lipid droplets disappear, morphing into vesicles or becoming incorporated into the ER; ABHD5 mutations found in Chanarin-Dorfman syndrome patients reduce ABHD5's ability to promote PNPLA1-dependent acylceramide production. Cell-based acylceramide production assay, indirect immunofluorescence microscopy, immunoelectron microscopy Journal of dermatological science High 30527376
2022 Of 16 PNPLA1 missense mutations from ichthyosis patients, 15 cause complete loss of acylceramide-producing activity, while C216R only weakly affects activity (correlating with milder disease); mutants differ in their ability to localize to lipid droplets in an ABHD5-dependent manner, classifying them into four groups by activity and localization. Cell-based acylceramide production assay, indirect immunofluorescence microscopy, structure-function analysis of patient mutations Journal of dermatological science High 35970721
2023 Recombinant truncated PNPLA1 (expressed in E. coli) catalyzes acyl transfer from trilinolein and dilinolein donors to ω-hydroxy ceramide, ω-hydroxy glucosylceramide, and ω-hydroxy acid acceptors to form acylceramide, glucosyl-acylceramide, and acyl acid respectively; PNPLA1 shows 3:1 selectivity for transferring linoleate over oleate, explaining the linoleic acid enrichment of these skin barrier lipids in vivo. In vitro enzyme reconstitution with recombinant PNPLA1, HPLC-UV and LC-MS product analysis, substrate selectivity comparison Journal of lipid research High 37087101
2024 PNPLA1 is responsible for esterification of γ-linolenic acid (GLA), in addition to linoleic acid, to ω-hydroxy fatty acids of ceramide 1 (acylceramide) subspecies in terminally differentiated human keratinocytes; siRNA knockdown of PNPLA1 causes accumulation of non-esterified ω-hydroxy ceramide precursors and decreases involucrin expression. siRNA knockdown in normal human keratinocytes, LC-MS lipidomics of ceramide subspecies, differentiation marker analysis Biochemical and biophysical research communications Medium 38340658
2018 Mutations in PNPLA1 in patient fibroblasts (p.Y245del and p.D172N) impair lipophagy-mediated degradation of lipid droplets: affected cells show abnormal lipid droplet accumulation, decreased LC3 expression, reduced autophagosome number, and decreased co-localization of lipid droplets with autophagosomes and lysosomes, indicating a role for PNPLA1 in lipid droplet regulation via lipophagy. BODIPY staining of lipid droplets in patient fibroblasts, siRNA knockdown, immunocytochemistry and immunoblotting for LC3 and PNPLA1, autophagosome/lysosome co-localization Journal of dermatological science Low 30655104
2025 ABHD5 regulates PNPLA1 by two mechanisms: (i) direct interaction through a PNPLA1-binding region on ABHD5 that recruits PNPLA1 to lipid droplets, and (ii) association of ABHD5 with lipid droplets via perilipin-binding domains; restoring co-localization of ABHD5 mutants with PNPLA1 in proteoliposomes is sufficient to rescue full PNPLA1 enzyme activity, establishing a co-localization-driven model of PNPLA1 regulation. Analysis of seven disease-associated ABHD5 missense mutations, proteoliposome reconstitution assay, enzyme activity measurement, imaging of PNPLA1 localization Journal of lipid research High 40818613

Source papers

Stage 0 corpus · 28 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2012 PNPLA1 mutations cause autosomal recessive congenital ichthyosis in golden retriever dogs and humans. Nature genetics 195 22246504
2017 PNPLA1 has a crucial role in skin barrier function by directing acylceramide biosynthesis. Nature communications 111 28248300
2017 PNPLA1 is a transacylase essential for the generation of the skin barrier lipid ω-O-acylceramide. Nature communications 105 28248318
2018 The role of PNPLA1 in ω-O-acylceramide synthesis and skin barrier function. Biochimica et biophysica acta. Molecular and cell biology of lipids 45 30290227
2018 ABHD5 stimulates PNPLA1-mediated ω-O-acylceramide biosynthesis essential for a functional skin permeability barrier. Journal of lipid research 45 30361410
2018 Molecular mechanism of the ichthyosis pathology of Chanarin-Dorfman syndrome: Stimulation of PNPLA1-catalyzed ω-O-acylceramide production by ABHD5. Journal of dermatological science 45 30527376
2017 PNPLA1 defects in patients with autosomal recessive congenital ichthyosis and KO mice sustain PNPLA1 irreplaceable function in epidermal omega-O-acylceramide synthesis and skin permeability barrier. Human molecular genetics 42 28369476
2016 Gene-Targeted Next Generation Sequencing Identifies PNPLA1 Mutations in Patients with a Phenotypic Spectrum of Autosomal Recessive Congenital Ichthyosis: The Impact of Consanguinity. The Journal of investigative dermatology 31 27884779
2017 Sixteen novel mutations in PNPLA1 in patients with autosomal recessive congenital ichthyosis reveal the importance of an extended patatin domain in PNPLA1 that is essential for proper human skin barrier function. The British journal of dermatology 28 28093717
2018 Impairment of lipophagy by PNPLA1 mutations causes lipid droplet accumulation in primary fibroblasts of Autosomal Recessive Congenital Ichthyosis patients. Journal of dermatological science 12 30655104
2023 Recombinant PNPLA1 catalyzes the synthesis of acylceramides and acyl acids with selective incorporation of linoleic acid. Journal of lipid research 8 37087101
2019 Novel and Recurrent PNPLA1 Mutations in Spanish Patients with Autosomal Recessive Congenital Ichthyosis; Evidence of a Founder Effect. Acta dermato-venereologica 7 31120544
2016 Autosomal recessive congenital ichthyosis due to PNPLA1 mutation in a golden retriever-poodle cross-bred dog and the effect of topical therapy. Veterinary dermatology 7 27237723
2021 Variants in the PNPLA1 Gene in Families with Autosomal Recessive Congenital Ichthyosis Reveal Clinical Significance. Molecular syndromology 6 34899144
2018 Prevalence of PNPLA1 Gene Mutation in 48 Breeding Golden Retriever Dogs. Veterinary sciences 6 29738490
2017 Identification of two novel PNPLA1 mutations in Turkish families with autosomal recessive congenital ichthyosis. The Turkish journal of pediatrics 6 29624231
2022 Impaired production of skin barrier lipid acylceramides and abnormal localization of PNPLA1 due to ichthyosis-causing mutations in PNPLA1. Journal of dermatological science 5 35970721
2019 Targeted regions sequencing identified four novel PNPLA1 mutations in two Chinese families with autosomal recessive congenital ichthyosis. Molecular genetics & genomic medicine 5 31833240
2022 PNPLA1-Mediated Acylceramide Biosynthesis and Autosomal Recessive Congenital Ichthyosis. Metabolites 4 35893253
2025 Defective targeting of PNPLA1 to lipid droplets causes ichthyosis in ABHD5-syndromic epidermal differentiation disorder. Journal of lipid research 3 40818613
2022 Novel Pathogenic Mutation of PNPLA1 Identified in Autosomal Recessive Congenital Ichthyosis: A Case Report. Chinese medical sciences journal = Chung-kuo i hsueh k'o hsueh tsa chih 3 36647593
2025 Intragenic PNPLA1 duplication in Labrador retrievers with nonepidermolytic ichthyosis. Veterinary dermatology 2 40150930
2025 The First Reported Japanese Case of PNPLA1-Nonsyndromic Epidermal Differentiation Disorder (PNPLA1-nEDD) Associated With an Unreported 92-Base-Pair Duplication Variant. Experimental dermatology 2 40545863
2024 PNPLA1 knockdown inhibits esterification of γ-linolenic acid to ceramide 1 in differentiated keratinocytes. Biochemical and biophysical research communications 2 38340658
2026 Progressive symmetrical erythrokeratoderma associated with biallelic PNPLA1 variants. The British journal of dermatology 1 41530952
2020 [Analysis of PNPLA1 gene mutation in a child with ichthyosis]. Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 1 32924119
2026 Genome-wide identification of the phospholipase gene family in Panax notoginseng and functional analysis of PnPLA1-8 response to Fusarium oxysporum infection. Plant physiology and biochemistry : PPB 0 41655508
2026 Mutation Analysis in Ten Cases With PNPLA1-Nonsyndromic Epidermal Differentiation Disorder: Evidence of a Founder Effect. The Journal of dermatology 0 41964248