Keratin 18 is a type I cytokeratin. It is, together with its filament partner keratin 8, perhaps the most commonly found products of the intermediate filament gene family. They are expressed in single layer epithelial tissues of the body. Mutations in this gene have been linked to cryptogenic cirrhosis. Two transcript variants encoding the same protein have been found for this gene. Keratin 18 is often used together with keratin 8 and keratin 19 to differentiate cells of epithelial origin from hematopoietic cells in tests that enumerate circulating tumor cells in blood.
Background References
1. Ku N O et al. Identification of the major physiologic phosphorylation site of human keratin 18: potential kinases and a role in filament reorganization. J Cell Biol 127:161-171 (1994).
2. Ku N.O et al. Chronic hepatitis, hepatocyte fragility, and increased soluble phosphoglycokeratins in transgenic mice expressing a keratin 18 conserved arginine mutant. J Cell Biol 131:1303-1314 (1995).
Sequence Similarity
Belongs to the intermediate filament family.
Tissue Specificity
Expressed in colon, placenta, liver and very weakly in exocervix. Increased expression observed in lymph nodes of breast carcinoma.
Post-translational Modification
Phosphorylation at Ser-34 increases during mitosis. Hyperphosphorylated at Ser-53 in diseased cirrhosis liver. Phosphorylation increases by IL-6.; Proteolytically cleaved by caspases during epithelial cell apoptosis. Cleavage occurs at Asp-238 by either caspase-3, caspase-6 or caspase-7.; O-GlcNAcylation increases solubility, and decreases stability by inducing proteasomal degradation.
Western blot analysis of Cytokeratin 18 on A431 cell lysate with Rabbit anti-Cytokeratin 18 antibody (0407-1) at 1/500 dilution.
Lysates/proteins at 10 µg/Lane. Exposure time: 17 seconds; ECL: K1801
Blocking: 5% NFDM/TBST, 1 hour at room temperature Primary antibody: 0407-1, 1/500 in primary antibody dilution buffer (K1803), overnight at 4 ℃ Secondary antibody: Goat anti-Rabbit IgG-HRP (HA1001), 1/50,000 in 5% NFDM/TBST, 1 hour at room temperature
Predicted band size: 48 kDa Observed band size: 48 kDa
Western blot analysis of Cytokeratin 18 on mouse liver tissue lysate with Rabbit anti-Cytokeratin 18 antibody (0407-1) at 1/500 dilution.
Lysates/proteins at 10 µg/Lane. Exposure time: 17 seconds; ECL: K1801
Blocking: 5% NFDM/TBST, 1 hour at room temperature Primary antibody: 0407-1, 1/500 in primary antibody dilution buffer (K1803), overnight at 4 ℃ Secondary antibody: Goat anti-Rabbit IgG-HRP (HA1001), 1/50,000 in 5% NFDM/TBST, 1 hour at room temperature
Predicted band size: 48 kDa Observed band size: 48 kDa
ICC staining Cytokeratin 18 in 293T cells (green). Formalin fixed cells were permeabilized with 0.1% Triton X-100 in TBS for 10 minutes at room temperature and blocked with 1% Blocker BSA for 15 minutes at room temperature. Cells were probed with the antibody (0407-1) at a dilution of 1/100 for 1 hour at room temperature, washed with PBS. Alexa Fluor™ 488 Goat anti-Rabbit IgG was used as the secondary antibody at 1/100 dilution. The nuclear counter stain is DAPI (blue).
ICC staining Cytokeratin 18 in A549 cells (green). Formalin fixed cells were permeabilized with 0.1% Triton X-100 in TBS for 10 minutes at room temperature and blocked with 1% Blocker BSA for 15 minutes at room temperature. Cells were probed with the antibody (0407-1) at a dilution of 1/100 for 1 hour at room temperature, washed with PBS. Alexa Fluor™ 488 Goat anti-Rabbit IgG was used as the secondary antibody at 1/100 dilution. The nuclear counter stain is DAPI (blue).
ICC staining Cytokeratin 18 in SW480 cells (green). Formalin fixed cells were permeabilized with 0.1% Triton X-100 in TBS for 10 minutes at room temperature and blocked with 1% Blocker BSA for 15 minutes at room temperature. Cells were probed with the antibody (0407-1) at a dilution of 1/100 for 1 hour at room temperature, washed with PBS. Alexa Fluor™ 488 Goat anti-Rabbit IgG was used as the secondary antibody at 1/100 dilution. The nuclear counter stain is DAPI (blue).
Immunohistochemical analysis of paraffin-embedded mouse lung tissue using anti-Cytokeratin 18 antibody. The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 8.0-8.4) for 20 minutes.The tissues were blocked in 5% BSA for 30 minutes at room temperature, washed with ddH2O and PBS, and then probed with the antibody (0407-1) at 1/100 dilution, for 30 minutes at room temperature and detected using an HRP conjugated compact polymer system. DAB was used as the chrogen. Counter stained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded human liver tissue with Rabbit anti-Cytokeratin 18 antibody (0407-1) at 1/400 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (0407-1) at 1/400 dilution for 1 hour at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded human liver carcinoma tissue with Rabbit anti-Cytokeratin 18 antibody (0407-1) at 1/400 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (0407-1) at 1/400 dilution for 1 hour at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
Immunohistochemical analysis of paraffin-embedded mouse kidney tissue with Rabbit anti-Cytokeratin 18 antibody (0407-1) at 1/400 dilution.
The section was pre-treated using heat mediated antigen retrieval with Tris-EDTA buffer (pH 9.0) for 20 minutes. The tissues were blocked in 1% BSA for 20 minutes at room temperature, washed with ddH2O and PBS, and then probed with the primary antibody (0407-1) at 1/400 dilution for 1 hour at room temperature. The detection was performed using an HRP conjugated compact polymer system. DAB was used as the chromogen. Tissues were counterstained with hematoxylin and mounted with DPX.
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