KRT80

KRT80 is a type II intermediate filament keratin that functions as a pro-proliferative and pro-invasive factor across multiple cancer types by activating the PI3K/AKT signaling pathway and promoting epithelial-mesenchymal transition (PMID:32169757, PMID:39569942). KRT80 protein stability is regulated by opposing ubiquitin-editing enzymes: the deubiquitinase OTUB2 stabilizes KRT80 by removing K48- and K63-linked ubiquitin chains, while the E3 ligase RNF8 promotes its proteasomal degradation, and the AAA-ATPase VCP additionally maintains KRT80 protein levels (PMID:35110531, PMID:40146410, PMID:38495507). KRT80 expression is controlled post-transcriptionally by competing endogenous RNA axes in which long noncoding RNAs or circular RNAs (circPIP5K1A, LINC01485) sponge inhibitory microRNAs (miR-671-5p, miR-383-5p, miR-195-5p) to de-repress KRT80 translation (PMID:32169757, PMID:37782686, PMID:40647481). Downstream, KRT80 drives chemoresistance and lipogenesis through ACC1/ACLY-dependent lipid droplet assembly and enhances glycolysis via GLUT1/HK2/LDHA activation (PMID:38241178, PMID:40146410).

1. 2020 Medium

   Establishing KRT80 as a functionally relevant oncogenic factor: prior to 2020 the cellular consequences of KRT80 perturbation were unknown; siRNA knockdown in colorectal cancer cells demonstrated that KRT80 is required for cell viability, and circPIP5K1A/miR-671-5p was identified as an upstream ceRNA axis that de-represses KRT80 to activate PI3K/AKT signaling and EMT in gastric cancer.

   Evidence siRNA knockdown viability assays in CRC cells; luciferase reporter, Ago2-RIP, miR inhibitor rescue, xenograft in gastric cancer cells

   PMID:32169757 PMID:33101466

   Open questions at the time

   • No direct biochemical mechanism linking KRT80 to PI3K/AKT activation was identified
   • ceRNA axis validated in single labs only
   • Whether KRT80 intermediate filament assembly is required for signaling was not tested
2. 2022 Medium

   Identifying how KRT80 protein stability is maintained: OTUB2 was shown to directly deubiquitinate KRT80 at K48 and K63 linkages, protecting it from proteasomal degradation and enabling AKT pathway activation in gastric cancer, providing the first post-translational regulatory mechanism for KRT80.

   Evidence Co-immunoprecipitation, ubiquitination assays, OTUB2 knockdown with KRT80 rescue, proliferation assays

   PMID:35110531

   Open questions at the time

   • The E3 ligase responsible for basal KRT80 ubiquitination was not identified in this study
   • Structural basis of OTUB2–KRT80 interaction is unknown
   • Specific ubiquitinated lysine residues on KRT80 were not mapped
3. 2023 Medium

   Expanding the ceRNA regulatory network: LINC01485/miR-383-5p was identified as a second independent ceRNA axis controlling KRT80 expression, this time in colorectal cancer, where KRT80 promotes proliferation and anti-apoptotic Bcl-2/Bax signaling.

   Evidence RIP assay, dual-luciferase reporter, qRT-PCR, xenograft validation

   PMID:37782686

   Open questions at the time

   • Whether LINC01485 and circPIP5K1A axes are tissue-specific or convergent is untested
   • Direct KRT80–Bcl-2 regulatory mechanism is not defined
4. 2024 Medium

   Defining downstream metabolic effectors: KRT80 was placed upstream of ACC1/ACLY-mediated lipogenesis and lipid droplet assembly in esophageal cancer, and VCP was identified as a physical interactor that maintains KRT80 stability in lung adenocarcinoma, broadening the functional landscape beyond AKT signaling.

   Evidence IP-MS for VCP interaction with rescue; siRNA knockdown of KRT80 with ACC1/ACLY overexpression epistasis rescue; viability, migration, lipogenesis assays

   PMID:38241178 PMID:38495507

   Open questions at the time

   • How KRT80 signals to ACC1/ACLY is mechanistically undefined
   • Whether VCP acts through its segregase activity or a scaffolding role is unknown
   • The connection between lipogenesis and PI3K/AKT signaling downstream of KRT80 has not been tested
5. 2025 Medium

   Identifying the opposing E3 ligase and additional microRNA regulation: RNF8 was shown to ubiquitinate KRT80 for degradation in glioblastoma, completing the deubiquitinase–E3 ligase regulatory axis, while miR-195-5p was validated as a direct repressor of KRT80 that induces G1 arrest in colorectal cancer.

   Evidence Co-IP and co-localization for RNF8–KRT80; metabolomics linking KRT80 to glycolysis; miR-195-5p mimic transfection with cell cycle flow cytometry and in vivo CRC model

   PMID:40146410 PMID:40647481

   Open questions at the time

   • RNF8–KRT80 interaction validated in single lab; independent confirmation needed
   • Whether RNF8 and OTUB2 compete on the same KRT80 pool is untested
   • Mechanism linking KRT80 to glycolytic enzyme expression (GLUT1/HK2/LDHA) is correlative

• The direct biochemical mechanism by which a cytoskeletal intermediate filament protein activates PI3K/AKT, STAT3, and metabolic reprogramming remains unresolved; whether KRT80 functions through filament-dependent scaffolding, direct kinase interaction, or an unconventional signaling role is unknown.
• No structural or biophysical characterization of KRT80 signaling complexes exists
• Whether KRT80 intermediate filament polymerization is required for its oncogenic functions has not been tested
• The physiological role of KRT80 in normal (non-cancer) epithelial biology is essentially uncharacterized