Seroatlas · Human Serome Atlas

IBSP

Integrin-binding sialoprotein

Also known as: BSP, BSP-II, SIAL_HUMAN, SP-II

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

Protein identityUniProt · HPA

UniProt accession
P21815
Gene
IBSP
Ensembl
ENSG00000029559
Chromosome
4
Canonical length
317 aa
Protein class
Cancer-related genes, Predicted secreted proteins
Subcellular location
Nucleoplasm,Vesicles,Cytosol
Secretome location
Secreted in other tissues

OverviewNCBI Gene

The protein encoded by this gene is a major structural protein of the bone matrix. It constitutes approximately 12% of the noncollagenous proteins in human bone and is synthesized by skeletal-associated cell types, including hypertrophic chondrocytes, osteoblasts, osteocytes, and osteoclasts. The only extraskeletal site of its synthesis is the trophoblast. This protein binds to calcium and hydroxyapatite via its acidic amino acid clusters, and mediates cell attachment through an RGD sequence that recognizes the vitronectin receptor. [provided by RefSeq, Jul 2008]

Canonical amino-acid sequenceUniProt

317 residues, UniProt reviewed canonical sequence.

>P21815|IBSP
     1  MKTALILLSI LGMACAFSMK NLHRRVKIED SEENGVFKYR PRYYLYKHAY FYPHLKRFPV
    61  QGSSDSSEEN GDDSSEEEEE EEETSNEGEN NEESNEDEDS EAENTTLSAT TLGYGEDATP
   121  GTGYTGLAAI QLPKKAGDIT NKATKEKESD EEEEEEEEGN ENEESEAEVD ENEQGINGTS
   181  TNSTEAENGN GSSGGDNGEE GEEESVTGAN AEDTTETGRQ GKGTSKTTTS PNGGFEPTTP
   241  PQVYRTTSPP FGKTTTVEYE GEYEYTGANE YDNGYEIYES ENGEPRGDNY RAYEDEYSYF
   301  KGQGYDGYDG QNYYHHQ

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against IBSP 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)
0.71
Highest tissue expression
2.5 nTPM

Expression across tissuesHPA

Tissue

  • blood vessel: 2.5 nTPM
  • pituitary gland: 1.9 nTPM
  • cerebral cortex: 0.9 nTPM
  • cervix: 0.7 nTPM
  • amygdala: 0.5 nTPM
  • cerebellum: 0.4 nTPM

Single-cell type

  • schwann cells: 1.5 nCPM
  • respiratory ciliated cells: 1.2 nCPM
  • macrophages: 0.8 nCPM
  • distal convoluted tubule cells: 0.7 nCPM
  • extravillous trophoblasts: 0.7 nCPM
  • lactotrophs: 0.7 nCPM

Immune cell

  • basophil: 0 nTPM
  • classical monocyte: 0 nTPM
  • eosinophil: 0 nTPM
  • gdT-cell: 0 nTPM
  • intermediate monocyte: 0 nTPM
  • MAIT T-cell: 0 nTPM

Brain region

  • thalamus: 4.7 nTPM
  • pons: 1.6 nTPM
  • medulla oblongata: 1.1 nTPM
  • midbrain: 0.8 nTPM
  • cerebellum: 0.6 nTPM
  • white matter: 0.4 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)
1.46
gnomAD pLI
0
gnomAD missense Z
0.46
DepMap mean gene effect
0.16
DepMap dependency class
none

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 2% 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

  • Integrin-binding sialoprotein
  • Bone sialoprotein II (BSP-II)

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

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

IBSP is annotated as secreted, so native IBSP 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 IBSP as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/IBSP. 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).

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