Casein Kinase 2 Alpha Phosphorylation Of Cortactin Governs Actin Cytoskeletal Regulation Of Invadopodia Function

Malregulation of signal transduction events controlling cortical actin cytoskeleton dynamics is responsible for to enhancing tumor cell motility and invasion. The actin‐binding protein cortactin facilitates branched actin network formation through activation of the actin related protein (Arp) 2/3 complex. Increased cortactin expression due to gene amplification is observed in many cancers, corresponding with increased tumor progression and poor patient outcome. In many cancer types, elevated Arp2/3 complex activation is responsible for driving increased migration and extracellular matrix (ECM) degradation by governing invadopodia formation and activity. While cortactin‐mediated activation of Arp2/3 complex has been well established, the objective of this study is to identify upstream signaling pathways responsible for modulating the interaction between cortactin and Arp2/3 complex in invasive carcinoma cells. We have determined that casein kinase (CK) 2α is responsible for disrupting the ability of cortactin to bind and/or activate Arp2/3 complex. CK2α directly phosphorylates cortactin at a conserved threonine 24 (T24) adjacent to the canonical Arp2/3 binding motif in the cortactin amino‐terminal acidic (NTA) domain. CK2α phosphorylation of cortactin T24 impairs the ability of cortactin to activate Arp2/3 actin nucleation as determined by spectrofluorometric analysis. Decreased invadopodia formation and ECM degradation activity is observed in head and neck squamous cell carcinoma (HNSCC) cells with shRNA‐mediated CK2α knockdown, expression of a CK2α phosphorylation‐null cortactin mutant (T24A), and with treatment of the Phase I CK2α inhibitor CX‐4945 (Silmitasertib). Collectively, these data suggest that CK2α‐mediated cortactin phosphorylation at T24 is a critical event in regulating the interaction with Arp2/3 complex, identifying a key anti-invasive mechanism impacted by targeted anti-CK2α therapeutics. Citation Format: Steven M. Markwell, Amanda Gatesman Ammer, Erik T. Interval, Dorothy A. Schafer, River A. Hames, Scott A. Weed. Casein kinase 2 alpha phosphorylation of cortactin governs actin cytoskeletal regulation of invadopodia function. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5067.