Seroatlas · Human Serome Atlas

HAPLN4

Hyaluronan and proteoglycan link protein 4

Also known as: BRAL2, HPLN4_HUMAN, KIAA1926

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

Protein identityUniProt · HPA

UniProt accession: Q86UW8
Gene: HAPLN4
Ensembl: ENSG00000187664
Chromosome: 19
Canonical length: 402 aa
Protein class: Predicted secreted proteins
Secretome location: Secreted in brain

OverviewNCBI Gene

Predicted to be a structural constituent of synapse-associated extracellular matrix. Predicted to be involved in GABAergic synaptic transmission; nervous system development; and skeletal system development. Predicted to be located in extracellular region. Predicted to be active in extracellular space; perineuronal net; and synapse. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

402 residues, UniProt reviewed canonical sequence.

>Q86UW8|HAPLN4
     1  MVCARAALGP GALWAAAWGV LLLTAPAGAQ RGRKKVVHVL EGESGSVVVQ TAPGQVVSHR
    61  GGTIVLPCRY HYEAAAHGHD GVRLKWTKVV DPLAFTDVFV ALGPQHRAFG SYRGRAELQG
   121  DGPGDASLVL RNVTLQDYGR YECEVTNELE DDAGMVKLDL EGVVFPYHPR GGRYKLTFAE
   181  AQRACAEQDG ILASAEQLHA AWRDGLDWCN AGWLRDGSVQ YPVNRPREPC GGLGGTGSAG
   241  GGGDANGGLR NYGYRHNAEE RYDAFCFTSN LPGRVFFLKP LRPVPFSGAA RACAARGAAV
   301  AKVGQLFAAW KLQLLDRCTA GWLADGSARY PIVNPRARCG GRRPGVRSLG FPDATRRLFG
   361  VYCYRAPGAP DPAPGGWGWG WAGGGGWAGG ARDPAAWTPL HV

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against HAPLN4 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: Secreted
Secreted: Yes
Transmembrane segments: 0
Mean surface accessibility (rSASA): 0.37
Highest tissue expression: 42 nTPM

Expression across tissuesHPA

Tissue

cerebral cortex: 42 nTPM
small intestine: 15 nTPM
liver: 12 nTPM
duodenum: 12 nTPM
cerebellum: 11 nTPM
hypothalamus: 11 nTPM

Single-cell type

other brain neurons: 12 nCPM
brain inhibitory neurons: 12 nCPM
brain excitatory neurons: 12 nCPM
oligodendrocyte progenitor cells: 3.3 nCPM
proximal tubule cells: 3.1 nCPM
bergmann glia: 0.9 nCPM

Immune cell

basophil: 0.5 nTPM
neutrophil: 0.1 nTPM
classical monocyte: 0 nTPM
eosinophil: 0 nTPM
gdT-cell: 0 nTPM
intermediate monocyte: 0 nTPM

Brain region

cerebral cortex: 259 nTPM
pons: 124 nTPM
white matter: 102 nTPM
thalamus: 96 nTPM
medulla oblongata: 94 nTPM
hypothalamus: 68 nTPM

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): 0.74
gnomAD pLI: 0.01
gnomAD missense Z: 1.73
DepMap mean gene effect: -0.21
DepMap dependency class: selective

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 HAPLN4 as an antibody target. Whether an autoantibody or antibody against HAPLN4 could matter depends on whether native HAPLN4 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

HAPLN4 is annotated as secreted, so native HAPLN4 circulates and is directly accessible to antibodies. Secreted and cell-surface proteins are the autoantibody targets most likely to act like drugs, blocking or depleting the native protein.

Annotation status

The present source text does not explicitly label HAPLN4 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

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