Seroatlas · Human Serome Atlas

SMIM18

Small integral membrane protein 18

Also known as: SIM18_HUMAN

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

Protein identityUniProt · HPA

UniProt accession
P0DKX4
Gene
SMIM18
Ensembl
ENSG00000253457
Chromosome
8
Canonical length
95 aa
Protein class
Predicted intracellular proteins, Predicted membrane proteins
Subcellular location
Nucleoplasm,Centrosome

OverviewNCBI Gene

Predicted to be located in membrane. [provided by Alliance of Genome Resources, Jul 2025]

Canonical amino-acid sequenceUniProt

95 residues, UniProt reviewed canonical sequence.

>P0DKX4|SMIM18
     1  MASSHWNETT TSVYQYLGFQ VQKIYPFHDN WNTACFVILL LFIFTVVSLV VLAFLYEVLD
    61  CCCCVKNKTV KDLKSEPNPL RSMMDNIRKR ETEVV

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against SMIM18 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
Unknown
Secreted
No
Transmembrane segments
1
Mean surface accessibility (rSASA)
0.52
Highest tissue expression
8.8 nTPM

Expression across tissuesHPA

Tissue

  • hypothalamus: 8.8 nTPM
  • cerebellum: 7.4 nTPM
  • cerebral cortex: 5.8 nTPM
  • pituitary gland: 5 nTPM
  • hippocampal formation: 4.3 nTPM
  • midbrain: 4.1 nTPM

Single-cell type

  • corticotrophs: 25 nCPM
  • adipocytes: 24 nCPM
  • other brain neurons: 16 nCPM
  • epicardial cells: 14 nCPM
  • cardiomyocytes: 13 nCPM
  • retinal bipolar cells: 13 nCPM

Immune cell

  • plasmacytoid DC: 1.4 nTPM
  • naive CD8 T-cell: 1.3 nTPM
  • basophil: 1.2 nTPM
  • gdT-cell: 1.1 nTPM
  • MAIT T-cell: 1.1 nTPM
  • T-reg: 1 nTPM

Brain region

  • midbrain: 11 nTPM
  • cerebellum: 9.8 nTPM
  • hypothalamus: 7.9 nTPM
  • pons: 7.6 nTPM
  • medulla oblongata: 6.1 nTPM
  • cerebral cortex: 6 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)
1.66
gnomAD pLI
0.17
gnomAD missense Z
0.98
DepMap mean gene effect
0.09
DepMap dependency class
none

OntologyGO

Cellular components

Protein domainsUniProt · Pfam · InterPro

KeywordsUniProt

Antibody and autoantibody relevanceSeroatlas analysis

Seroatlas reads SMIM18 as an antibody target. Whether an autoantibody or antibody against SMIM18 could matter depends on whether native SMIM18 is physically reachable, whether the body needs it intact, and whether it acts in a disease-relevant tissue.

SMIM18 is annotated as predominantly intracellular. Intracellular proteins are common autoantibody markers, becoming visible to the immune system after cell injury or altered processing, but are usually markers of disease rather than direct drivers.

Annotation status

The present source text does not explicitly label SMIM18 as an autoantigen. Seroatlas presents hypothesis context only and does not manufacture a known-serology claim.

Canonical record: https://seroatlas.com/gene/SMIM18. 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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