Seroatlas · Human Serome Atlas

CX3CL1

Fractalkine

Also known as: ABCD-3, C3Xkine, CXC3, CXC3C, NTN, SCYD1, X3CL1_HUMAN

Cross-references: UniProt · Ensembl · Human Protein Atlas · GeneCards · NCBI Gene

Protein identityUniProt · HPA

UniProt accession
P78423
Gene
CX3CL1
Ensembl
ENSG00000006210
Chromosome
16
Canonical length
397 aa
Protein class
Plasma proteins, Predicted membrane proteins, Predicted secreted proteins
Subcellular location
Plasma membrane
Secretome location
Secreted to blood

OverviewNCBI Gene

This gene belongs to the CX3C subgroup of chemokines, characterized by the number of amino acids located between the conserved cysteine residues. This is the only member of the CX3C subgroup, which contains three amino acids between cysteine residues, resulting in a Cys-X-X-X-Cys configuration. The encoded protein contains an extended mucin-like stalk with a chemokine domain on top, and exists in both a membrane-anchored form where it acts as a binding molecule, or, in soluble form, as a chemotactic cytokine. The mature form of this protein can be cleaved at the cell surface, yielding different soluble forms that can interact with the G-protein coupled receptor, C-X3-C motif chemokine receptor 1 gene product. This gene plays a role in a wide range of diseases, including cancer, vasculitis, neuropathies, atherosclerosis, inflammatory diseases, and in human immunodeficiency virus infections. [provided by RefSeq, Sep 2017]

Canonical amino-acid sequenceUniProt

397 residues, UniProt reviewed canonical sequence.

>P78423|CX3CL1
     1  MAPISLSWLL RLATFCHLTV LLAGQHHGVT KCNITCSKMT SKIPVALLIH YQQNQASCGK
    61  RAIILETRQH RLFCADPKEQ WVKDAMQHLD RQAAALTRNG GTFEKQIGEV KPRTTPAAGG
   121  MDESVVLEPE ATGESSSLEP TPSSQEAQRA LGTSPELPTG VTGSSGTRLP PTPKAQDGGP
   181  VGTELFRVPP VSTAATWQSS APHQPGPSLW AEAKTSEAPS TQDPSTQAST ASSPAPEENA
   241  PSEGQRVWGQ GQSPRPENSL EREEMGPVPA HTDAFQDWGP GSMAHVSVVP VSSEGTPSRE
   301  PVASGSWTPK AEEPIHATMD PQRLGVLITP VPDAQAATRR QAVGLLAFLG LLFCLGVAMF
   361  TYQSLQGCPR KMAGEMAEGL RYIPRSCGSN SYVLVPV

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against CX3CL1 can act on the native protein depends on physical access: surface and secreted proteins are reachable by circulating antibodies, intracellular proteins usually are not.

Antibody reachability
Cell surface
Secreted
No
Transmembrane segments
1
Mean surface accessibility (rSASA)
0.61
Highest tissue expression
101 nTPM

Expression across tissuesHPA

Tissue

  • breast: 101 nTPM
  • lung: 94 nTPM
  • salivary gland: 70 nTPM
  • blood vessel: 69 nTPM
  • adipose tissue: 65 nTPM
  • cerebral cortex: 58 nTPM

Single-cell type

  • breast secretory cells: 133 nCPM
  • vascular endothelial cells: 93 nCPM
  • pancreatic duct cells: 78 nCPM
  • salivary duct cells: 71 nCPM
  • epididymal clear cells: 69 nCPM
  • submucosal glandular cells: 65 nCPM

Immune cell

  • basophil: 0.2 nTPM
  • neutrophil: 0.1 nTPM
  • classical monocyte: 0 nTPM
  • eosinophil: 0 nTPM
  • gdT-cell: 0 nTPM
  • intermediate monocyte: 0 nTPM

Brain region

  • hippocampal formation: 96 nTPM
  • cerebral cortex: 91 nTPM
  • basal ganglia: 77 nTPM
  • amygdala: 68 nTPM
  • thalamus: 63 nTPM
  • white matter: 62 nTPM

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about CX3CL1.

Disease | ImmuneIEDB

Conditions an epitope on CX3CL1 was assayed in.

Genetic constraint and essentialitygnomAD · DepMap

Does the body need this protein intact? Low LOEUF or a strong DepMap dependency means loss or blockade of the protein is likely to be felt.

gnomAD LOEUF (loss-of-function intolerance)
0.55
gnomAD pLI
0.61
gnomAD missense Z
0.84
DepMap mean gene effect
-0.01
DepMap dependency class
none

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 3% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

Molecular functions

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads CX3CL1 as an antibody target. Whether an autoantibody or antibody against CX3CL1 could matter depends on whether native CX3CL1 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

CX3CL1 is annotated at the cell surface, where native CX3CL1 is exposed to circulating antibodies and is a prime autoantibody target that could block, deplete, or overstimulate it.

Annotation status

The present source text does not explicitly label CX3CL1 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/CX3CL1. Study-independent annotations aggregated from UniProt, Human Protein Atlas, PubMed, IEDB, Pfam, InterPro, Gene Ontology, AlphaFold, gnomAD, DepMap, ClinVar, TCGA. Catalog release seroatlas-reviewed-human-uniprot-20260313.

Seroatlas is the reference for exploring autoantibody and antibody serology at the human-protein level: the autoreactome and human serome, multiplex serology (HuProt, HuScan, VirScan, PhIP-Seq).

© 2026 · Seroatlas, Discover Oregon LLC · Terms of use

Loading the interactive Seroatlas protein explorer...