cornulin (tumor-related protein, squamous epithelial heat shock protein 53, 53 kD squamous epithelial-induced stress protein, 58 kD heat shock protein, 53 kD putative Ca+2-binding protein, CRNN, c1orf10, DRC1, PDRC1, SEP53)
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Function
- survival factor that participates in the clonogenicity of squamous esophageal epithelium cell lines, attenuates deoxycholic acid (DCA)-induced apoptotic cell death & release of Ca+2
- when overexpressed in oral squamous carcinoma cell lines, regulates negatively cell proliferation by the induction of G1 arrest
- binds Ca+2 with an affinity similar to that of the S100 proteins
Structure
- homodimer
- EF-hand is necessary for the colony survival activity to protect cells from death induced by exposure to DCA
- belongs to the S100-fused protein family
- contains 1 EF-hand domain
Compartment
Expression
- squamous epithelia cell-specific
- expressed in the esophagus (periphery of the cells of the granular & the upper spinous layers), foreskin (granular & lower cornified cells), scalp skin (granular layer), inner root sheath of the hair follicle & in primary keratinocytes (at protein level)
- expressed in the squamous epithelium of the cervix, esophagus, foreskin & larynx
- expressed in the fetal bladder & scalp skin
- expressed at very low levels in the lung, kidney, uterus, skeletal muscle, heart & fetal brain
- up-regulated after heat shock, ponasterone A & deoxycholic acid
Pathology
- undetectable or barely detectable in esophageal & oral squamous cell carcinoma compared with the matched adjacent normal esophageal mucosa
- undetectable or barely detectable in larynx & esophagus from patients with pH-documented laryngopharyngeal reflux