Cysteine oxidation triggers amyloid fibril formation of the tumor suppressor p16 INK4A

Redox Biol. 2020 Jan;28:101316. doi: 10.1016/j.redox.2019.101316. Epub 2019 Sep 3.


The tumor suppressor p16INK4A induces cell cycle arrest and senescence in response to oncogenic transformation and is therefore frequently lost in cancer. p16INK4A is also known to accumulate under conditions of oxidative stress. Thus, we hypothesized it could potentially be regulated by reversible oxidation of cysteines (redox signaling). Here we report that oxidation of the single cysteine in p16INK4A in human cells occurs under relatively mild oxidizing conditions and leads to disulfide-dependent dimerization. p16INK4A is an all α-helical protein, but we find that upon cysteine-dependent dimerization, p16INK4A undergoes a dramatic structural rearrangement and forms aggregates that have the typical features of amyloid fibrils, including binding of diagnostic dyes, presence of cross-β sheet structure, and typical dimensions found in electron microscopy. p16INK4A amyloid formation abolishes its function as a Cyclin Dependent Kinase 4/6 inhibitor. Collectively, these observations mechanistically link the cellular redox state to the inactivation of p16INK4A through the formation of amyloid fibrils.

Keywords: Amyloids; Cysteine oxidation; Protein aggregation; Redox signaling; Structural biology.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amyloid / chemistry
  • Cell Cycle
  • Cellular Senescence
  • Cyclin-Dependent Kinase Inhibitor p16 / chemistry*
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism*
  • Cysteine / chemistry*
  • HEK293 Cells
  • Humans
  • Models, Molecular
  • Oxidation-Reduction
  • Protein Multimerization
  • Protein Structure, Secondary


  • Amyloid
  • CDKN2A protein, human
  • Cyclin-Dependent Kinase Inhibitor p16
  • Cysteine