keratin, type 2 cytoskeletal 4; cytokeratin-4; CK-4; keratin-4; K4 (KRT4 CYK4)

Function

• cytokeratin-4 is generally associated with cytokeratin-13

Structure

• type 2 keratin
• heterotetramer of 2 type 1 & 2 type 2 keratins
• belongs to the intermediate filament family

Expression

• detected in the suprabasal layer of stratified epithelium of the esophagus, exocervix, vagina, mouth & lingual mucosa, & in cells & cell clusters in the mucosa & serous gland ducts of the esophageal submucosa (at protein level)
• expressed widely in the exocervix & esophageal epithelium, with lowest levels detected in the basal cell layer

Pathology

• defects in KRT4 are a cause of white sponge nevus of Cannon

Polymorphism

• 3 alleles of K4 are known: K4A2, K4A1 & K4B

More general terms

• cytokeratin, epithelial keratins or soft alpha-keratins
• phosphoprotein

Database

• UniProt: http://www.uniprot.org/uniprot/P19013.html
• Entrez gene: http://www.ncbi.nlm.nih.gov/sites/entrez?db=gene&cmd=Retrieve&dopt=Graphics&list_uids=3851
• Kegg: http://www.genome.jp/dbget-bin/www_bget?hsa:3851
• OMIM: https://mirror.omim.org/entry/123940
• OMIM: https://mirror.omim.org/entry/193900