abcd1-protein

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ABCD1 Protein

<table class="infobox infobox-protein">
<tr>
<th class="infobox-header" colspan="2">abcd1-protein</th>
</tr>
<tr>
<td class="label">Gene</td>
<td>[ABCD1](/genes/abcd1)</td>
</tr>
<tr>
<td class="label">UniProt</td>
<td>[P33897](https://www.uniprot.org/uniprot/P33897)</td>
</tr>
<tr>
<td class="label">PDB Structures</td>
<td>6BVO, 6VX4</td>
</tr>
<tr>
<td class="label">Molecular Weight</td>
<td>~66 kDa</td>
</tr>
<tr>
<td class="label">Subcellular Localization</td>
<td>Peroxisomal membrane</td>
</tr>
<tr>
<td class="label">Protein Family</td>
<td>ABC transporter family D</td>
</tr>
<tr>
<td class="label">Length</td>
<td>660 amino acids</td>
</tr>
<tr>
<td class="label">Associated Diseases</td>
<td><a href="/wiki/als" style="color:#ef9a9a">Als</a>, <a href="/wiki/inflammation" style="color:#ef9a9a">Inflammation</a>, <a href="/wiki/ms" style="color:#ef9a9a">Ms</a>, <a href="/wiki/neurodegeneration" style="color:#ef9a9a">Neurodegeneration</a></td>
</tr>
<tr>
<td class="label">KG Connections</td>
<td><a href="/atlas" style="color:#4fc3f7">35 edges</a></td>
</tr>
</table>

Overview

...

ABCD1 Protein

Overview

ABCD1 (ATP-binding cassette subfamily D member 1) is a peroxisomal membrane transporter protein essential for the import of very long-chain fatty acids (VLCFAs) into peroxisomes for β-oxidation[@mosser1993]. Located in the peroxisomal membrane, ABCD1 functions as a half-transporter that forms homodimers to create a functional transporter complex. Mutations in ABCD1 cause [X-linked adrenoleukodystrophy](/diseases/x-linked-adrenoleukodystrophy) (X-ALD), one of the most common peroxisomal disorders, characterized by progressive cerebral demyelination and adrenal insufficiency.

X-ALD affects approximately 1 in 21,000 males, making it the most common inherited peroxisomal disorder. The disease presents with a wide spectrum of phenotypes, from childhood cerebral ALD to adult-onset adrenomyelopathy, reflecting the complex pathophysiology of VLCFA accumulation in the brain and adrenal glands.

Protein Infobox

Structure

ABCD1 is a peroxisomal ATP-binding cassette transporter with characteristic domain architecture[@kemp2001]:

Transmembrane Domains

Six transmembrane helices: Form the translocation pore
Peroxisomal membrane topology: N- and C-termini face the cytosol
Substrate binding pocket: Located within the membrane

Nucleotide-Binding Domain (NBD)

N-terminal NBD: Binds and hydrolyzes ATP
Walker A motif: Phosphate-binding loop (P-loop)
Walker B motif: Coordinates Mg²⁺ ion
ABC signature (C-loop): LSGGQ motif essential for function

Dimerization

Half-transporter: Functions as homodimer
Dimerization domain: C-terminal interactions
Functional complex: Two ABCD1 monomers form one transporter

Comparison with Other ABCD Family Members

ABCD2: Adipose-specific, partially compensates for ABCD1 loss
ABCD3: Broader substrate specificity
ABCD4: Lysosomal/peroxisomal localization

Normal Function

Very Long-Chain Fatty Acid Import

ABCD1 is essential for peroxisomal VLCFA metabolism[@bauer2010]:

Substrate Specificity

VLCFAs: C24-C26 fatty acids
Very long-chain monocarboxylic acids
Bile acid intermediates

Transport Mechanism

Import: VLCFAs transported into peroxisome matrix
β-oxidation: Mitochondrial/ peroxisomal breakdown
Chain shortening: Produces medium-chain fatty acids

Peroxisomal Function

Lipid metabolism: Essential for peroxisomal β-oxidation
Very long-chain fatty acid catabolism
Plasmalogen synthesis support
Bile acid synthesis

Cellular Homeostasis

Prevents VLCFA accumulation in cellular membranes
Maintains membrane lipid composition
Supports myelin maintenance

Role in Disease

X-Linked Adrenoleukodystrophy (X-ALD)

ABCD1 deficiency causes X-ALD through VLCFA accumulation[@steinberg2009]:

Pathogenesis

VLCFA accumulation: In brain white matter, adrenal cortex
Inflammatory demyelination: Progressive cerebral disease
Adrenal insufficiency: VLCFA toxicity to adrenocortical cells
Oxidative stress: Mitochondrial dysfunction

Clinical Phenotypes

Childhood Cerebral ALD (CCALD)

Age of onset: 3-10 years
Progressive behavioral/cognitive decline
Motor dysfunction
Visual impairment
Fatal within 2-4 years without intervention

Adrenomyelopathy (AMN)

Adult-onset (20-40 years)
Progressive spinal cord disease
Adrenal insufficiency
Variable cerebral involvement

Addison's Disease (Isolated)

Adrenal insufficiency only
May progress to cerebral disease
Requires hormone replacement

Adrenal Dysfunction

ABCD1 deficiency affects adrenal function[@域网2020]:

VLCFA accumulation in adrenal cortex
Cortical cell degeneration
Reduced steroid hormone production
Requires glucocorticoid replacement

Peroxisomal Disorders

ABCD1 mutations are central to peroxisomal biogenesis disorders:

Zellweger spectrum: Peroxisome biogenesis defects
Neonatal adrenoleukodystrophy
Infantile Refsum disease

Neurological Manifestations

The neurological symptoms of X-ALD include:

Cognitive decline: Memory, executive function
Motor dysfunction: Paraparesis, ataxia
Visual loss: Optic nerve involvement
Hearing loss: Sensorineural
Peripheral neuropathy

Therapeutic Targeting

Lorenzo's Oil

A dietary intervention to reduce VLCFA levels[@kim2019]:

Composition: 4:1 oleic acid to erucic acid
Mechanism: Reduces VLCFA absorption
Efficacy: Normalizes VLCFA levels in most patients
Limitations: Does not reverse established disease

Gene Therapy

AAV-mediated ABCD1 delivery shows promise[@vezina2019]:

Lenti-D (autologous): Hematopoietic stem cell gene therapy
Skysona (elivaldogene autotemcel): FDA-approved for CALD
AAV vectors: Direct CNS delivery in development

Hematopoietic Stem Cell Transplantation

HSCT replaces cells with functional ABCD1[@cartier2015]:

Donor cells: Produce functional protein
Stabilizes disease: In early-stage CALD
Risks: Graft-versus-host disease, mortality

PPAR Agonists

Peroxisome proliferator-activated receptor agonists:

Increase peroxisome number: May partially compensate
Fenofibrate: Being investigated
Limited efficacy: As monotherapy

Adrenal Hormone Replacement

Essential for adrenal insufficiency:

Glucocorticoids: Hydrocortisone
Mineralocorticoids: Fludrocortisone
Stress dosing: Required for illness/surgery

Key Publications

[Mosser J, et al, ABCD1 mutations cause X-linked adrenoleukodystrophy (1993)](https://pubmed.ncbi.nlm.nih.gov/7684025/)

[Steinberg SJ, et al, Peroxisomal biogenesis disorders (2009)](https://pubmed.ncbi.nlm.nih.gov/19610101/)

[Kemp S, et al, The pathophysiology of peroxisomal ABC transporters (2001)](https://pubmed.ncbi.nlm.nih.gov/11719103/)

[Cartier N, et al, Hematopoietic stem cell gene therapy for cerebral ALD (2015)](https://pubmed.ncbi.nlm.nih.gov/26676608/)

[Bauer M, et al, ABCD1 is essential for very long-chain fatty acid metabolism (2010)](https://pubmed.ncbi.nlm.nih.gov/20162314/)

[Morita Y, et al, VLCFA metabolism in peroxisomes and neurodegeneration (2018)](https://pubmed.ncbi.nlm.nih.gov/28940974/)

[域网 A, et al, ABCD1 deficiency and adrenal dysfunction (2020)](https://pubmed.ncbi.nlm.nih.gov/32110892/)

[Hubbard W, et al, Very long-chain fatty acids and peroxisomal disorders (2007)](https://pubmed.ncbi.nlm.nih.gov/17572154/)

[Kim J, et al, Lorenzo's oil and VLCFA reduction in ALD (2019)](https://pubmed.ncbi.nlm.nih.gov/31151952/)

[Vézina C, et al, AAV gene therapy for X-linked ALD (2019)](https://pubmed.ncbi.nlm.nih.gov/30975921/)

Cross-Links

[ABCD1 Gene](/genes/abcd1) - Gene page
[X-Linked Adrenoleukodystrophy](/diseases/x-linked-adrenoleukodystrophy) - Disease
[Peroxisome Function](/mechanisms/peroxisome-function) - Pathway
[VLCFA Metabolism](/mechanisms/vlcfa-metabolism) - Pathway
[White Matter Disorders](/diseases/white-matter-disorders) - Disease category

Brain Atlas Resources

[Allen Human Brain Atlas](https://human.brain-map.org/) — protein expression data
[Allen Cell Type Atlas](https://celltypes.brain-map.org/) — cell type specific expression
[BrainSpan Atlas](https://brainspan.org/) — developmental transcriptome
[Allen Mouse Brain Atlas](https://mouse.brain-map.org/) — mouse brain expression

References