Involved in the uptake of thrombin-antithrombin complexes by hepatic cells (By similarity). When phosphorylated, plays a role in filament reorganization. Involved in the delivery of mutated CFTR to the plasma membrane. Together with KRT8, is involved in interleukin-6 (IL-6)-mediated barrier protection. Heterotetramer of two type I and two type II keratins. KRT18 associates with KRT8 (PubMed:24940650). Interacts with PLEC isoform 1C, when in a heterodimer with KRT8 (PubMed:24940650). Interacts with the thrombin-antithrombin complex (By similarity). Interacts with PNN and mutated CFTR. Interacts with YWHAE, YWHAH and YWHAZ only when phosphorylated. Interacts with DNAJB6, TCHP and TRADD. Interacts with FAM83H (PubMed:23902688). Interacts with EPPK1 (By similarity). (Microbial infection) Interacts with hepatitis C virus/HCV core protein. Expressed in colon, placenta, liver and very weakly in exocervix. Increased expression observed in lymph nodes of breast carcinoma. By IL6/interleukin-6. 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. The disease is caused by variants affecting the gene represented in this entry. There are two types of cytoskeletal and microfibrillar keratin: I (acidic; 40-55 kDa) and II (neutral to basic; 56-70 kDa). Belongs to the intermediate filament family.