CK2α phosphorylates CHIP for oncogenesis: A novel post-translational switch in cancer

Abstract

The post-translational regulation of tumor suppressors by oncogenic kinases remains a critical yet underexplored determinant of proteostasis reprogramming in cancer. Here, we identified the E3 ubiquitin ligase CHIP (C-terminus of Hsc70-Interacting Protein) as a direct and functionally relevant substrate of the serine/threonine kinase CK2, which is frequently overexpressed in solid tumors. Using LC/MS analysis, in silico kinase prediction, and molecular interaction mapping, we demonstrated that CK2 phosphorylates CHIP at serine 19 (represented as S19), a conserved residue within its TPR domain, thereby promoting ubiquitination and subsequent proteasomal degradation of CHIP. This phosphorylation-dependent destabilization of CHIP impairs its ability to target oncogenic substrates, such as AKT, resulting in sustained AKT phosphorylation and activation, required for oncogenesis. Clinically, we observed a robust inverse correlation between CK2 and CHIP expressions across colorectal and breast cancer patient datasets, which was validated by immunofluorescence (IF) analyses in tumor samples. Multiple functional assays revealed that CK2 suppression, either by genetic ablation or pharmacological inhibition by TBCA, restores CHIP stability, reactivates apoptotic signalling cascades, and attenuates tumor cell proliferation, migration, and 3D spheroid integrity. Moreover, CK2 blockade in syngeneic murine models diminishes primary tumor burden and metastatic dissemination, concomitant with increased CHIP accumulation and reduced AKT signalling. Mechanistically, a phosphorylation-resistant mutant of CHIP at S19 (CHIP-S19A), is refractory to CK2- mediated degradation and preserves anti-tumor functions, delineating a phosphorylation-dependent proteolytic switch as a central node in the CK2-CHIP-AKT regulatory axis. These findings establish a novel paradigm wherein an oncogenic kinase hijacks protein quality control pathway to suppress tumor suppressive activity and facilitate malignancy. Our study positions CK2 as a druggable modulator of CHIP turnover, offering a translational framework for restoring proteostatic checkpoints and constraining oncogenic signalling in aggressive cancers. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=112 SRC="FIGDIR/small/682604v1_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@8fad58org.highwire.dtl.DTLVardef@bd73dforg.highwire.dtl.DTLVardef@2746dorg.highwire.dtl.DTLVardef@129b6ad_HPS_FORMAT_FIGEXP M_FIG C_FIG