CLDN18

Protein identityUniProt · HPA

UniProt accession

P56856

Gene

CLDN18

Ensembl

ENSG00000066405

Chromosome

3

Canonical length

261 aa

Protein class

Predicted membrane proteins

Subcellular location

Cell Junctions

OverviewNCBI Gene

This gene encodes a member of the claudin family. Claudins are integral membrane proteins and components of tight junction strands. Tight junction strands serve as a physical barrier to prevent solutes and water from passing freely through the paracellular space between epithelial or endothelial cell sheets, and also play critical roles in maintaining cell polarity and signal transductions. This gene is upregulated in patients with ulcerative colitis and highly overexpressed in infiltrating ductal adenocarcinomas. PKC/MAPK/AP-1 (protein kinase C/mitogen-activated protein kinase/activator protein-1) dependent pathway regulates the expression of this gene in gastric cells. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Jun 2010]

Canonical amino-acid sequenceUniProt

261 residues, UniProt reviewed canonical sequence.

>P56856|CLDN18
     1  MSTTTCQVVA FLLSILGLAG CIAATGMDMW STQDLYDNPV TSVFQYEGLW RSCVRQSSGF
    61  TECRPYFTIL GLPAMLQAVR ALMIVGIVLG AIGLLVSIFA LKCIRIGSME DSAKANMTLT
   121  SGIMFIVSGL CAIAGVSVFA NMLVTNFWMS TANMYTGMGG MVQTVQTRYT FGAALFVGWV
   181  AGGLTLIGGV MMCIACRGLA PEETNYKAVS YHASGHSVAY KPGGFKASTG FGSNTKNKKI
   241  YDGGARTEDE VQSYPSKHDY V

LocalizationUniProt · AlphaFold · HPA

Whether an antibody against CLDN18 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

4

Mean surface accessibility (rSASA)

0.4

Highest tissue expression

684 nTPM

Expression across tissuesHPA

DiseaseUniProt · ClinVar · IEDB · PubMed

Four sources answering four different questions about CLDN18.

Disease | ImmuneIEDB

Conditions an epitope on CLDN18 was assayed in.

• stomach cancer T cell

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)

1.27

gnomAD pLI

0

gnomAD missense Z

0.61

DepMap mean gene effect

0.09

DepMap dependency class

selective

Cancer expressionTCGA

Across TCGA tumor cohorts, this protein is over-expressed in roughly 1% of surveyed tumor types (aggregate summary; per-cohort expression, alteration, and survival load in the interactive view).

OntologyGO

Biological processes

• bicellular tight junction assembly
• calcium-independent cell-cell adhesion via plasma membrane cell-adhesion molecules
• cell adhesion
• cellular response to estrogen stimulus
• digestive tract development
• epithelial cell proliferation
• epithelial fluid transport
• lung alveolus development
• negative regulation of bone resorption
• negative regulation of osteoclast development
• negative regulation of protein localization to nucleus
• negative regulation of tumor necrosis factor-mediated signaling pathway
• organ growth
• protein localization to nucleus
• response to ethanol
• tight junction organization

Molecular functions

• identical protein binding
• structural molecule activity

Cellular components

• bicellular tight junction
• cell-cell junction
• lateral plasma membrane
• plasma membrane

Protein domainsUniProt · Pfam · InterPro

• PMP-22/EMP/MP20/Claudin
• Claudin
• Claudin, conserved site
• PMP-22/EMP/MP20/Claudin family
• Claudin-18

KeywordsUniProt

• Cell junction
• Cell membrane
• Membrane
• Phosphoprotein
• Tight junction
• Transmembrane
• Transmembrane helix

InteractionsUniProt · HPA

Protein binding partners of CLDN18 in the human serome: UniProt-annotated complex subunits plus reported interactors. Each links to its own Seroatlas record.

• CLDN19
• YAP1
• TJP2
• TJP1