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Updated: Jun 29, 2025
Identification of Novel CK2 Kinase Substrates Using a Versatile Biochemical Approach
Published on: February 21, 2019
Chemoproteomics reveals immunogenic and tumor-associated cell surface substrates of ectokinase CK2α
Corleone S Delaveris1, Sophie Kong1, Jeff Glasgow1
1Department of Pharmaceutical Chemistry, University of California San Francisco, San Francisco, California, 94158, USA.
Abstract:
New epitopes for immune recognition provide the basis of anticancer immunity. Due to the high concentration of extracellular adenosine triphosphate in the tumor microenvironment, we hypothesized that extracellular kinases (ectokinases) could have dysregulated activity and introduce aberrant phosphorylation sites on cell surface proteins. We engineered a cell-tethered version of the extracellular kinase CK2α, demonstrated it was active on cells under tumor-relevant conditions, and profiled its substrate scope using a chemoproteomic workflow. We then demonstrated that mice developed polyreactive antisera in response to syngeneic tumor cells that had been subjected to surface hyperphosphorylation with CK2α. Interestingly, these mice developed B cell and CD4+ T cell responses in response to these antigens but failed to develop a CD8+ T cell response. This work provides a workflow for probing the extracellular phosphoproteome and demonstrates that extracellular phosphoproteins are immunogenic even in a syngeneic system.
Insights
Extracellular kinases can create new cancer antigens on cell surfaces. This study shows these altered proteins trigger immune responses, even in syngeneic models, offering new avenues for cancer immunotherapy.
Area of Science:
- Oncology
- Immunology
- Biochemistry
Background:
- Anticancer immunity relies on recognizing novel epitopes.
- The tumor microenvironment's high extracellular ATP may dysregulate extracellular kinases (ectokinases).
- Ectokinases might create aberrant phosphorylation sites on cell surface proteins, serving as potential neoantigens.
Approach:
- Engineered a cell-tethered version of the extracellular kinase CK2α.
- Confirmed CK2α activity on cells under tumor-relevant conditions.
- Utilized a chemoproteomic workflow to profile CK2α substrate scope on cell surfaces.
- Investigated immune responses in mice to hyperphosphorylated syngeneic tumor cells.
Key Points:
- Demonstrated that CK2α can hyperphosphorylate cell surface proteins.
- Showed that mice developed polyreactive antisera against CK2α-treated syngeneic tumor cells.
- Observed B cell and CD4+ T cell responses to these extracellular phosphoproteins.
- Noted a lack of CD8+ T cell response in this syngeneic system.
Conclusions:
- Developed a workflow for probing the extracellular phosphoproteome.
- Extracellular phosphoproteins are immunogenic, even in syngeneic systems.
- Suggests potential for targeting extracellular phosphorylation in cancer immunotherapy.
