| Casein kinase 1α (CK1α) is a ubiquitously expressed serine/threonine kinase of the CK1 family that preferentially phosphorylates acidic or pre-phosphorylated substrates and serves as a central regulator of multiple signaling pathways, including Wnt/β‑catenin, circadian, mTOR and inflammasome networks. The kinase comprises a conserved catalytic domain with an N‑terminal lobe that binds ATP and a C‑terminal lobe that engages substrates, flanked by short regulatory regions that influence subcellular localization and interaction with scaffolding proteins at membranes, cytoskeleton and kinetochores. In the Wnt pathway, CK1α phosphorylates β‑catenin at Ser45 within the N‑terminal degron, priming it for subsequent GSK3β phosphorylation and recognition by the β‑TrCP E3 ligase, thereby promoting β‑catenin ubiquitination and proteasomal degradation and acting as an established negative regulator of canonical Wnt signaling in development and Wnt-driven cancers. CK1α also phosphorylates components of the circadian clock, such as PER1 and PER2, modulating their stability and nuclear localization and contributing to the timing of transcriptional oscillations that underlie circadian rhythm control. In nutrient sensing, CK1α functions as a positive regulator of mTORC1 and mTORC2: it phosphorylates the mTOR inhibitor DEPTOR, marking it for ubiquitination and degradation, which relieves inhibition of mTOR complexes and enhances downstream signaling to S6K and Akt in response to amino acids and growth factors, integrating CK1α into control of cell growth, metabolism and survival. In innate immunity, CK1α phosphorylates NLRP3 on defined serine residues, and this modification inhibits assembly of the NLRP3 inflammasome, reducing caspase‑1 activation and IL‑1β production and positioning CK1α as a brake on pyroptotic and inflammatory responses; small-molecule modulators that enhance CK1α phosphorylation of NLRP3 can suppress inflammasome-driven pathology. CK1α also contributes to chromosome segregation and cytoskeletal regulation: it localizes to kinetochores and spindle structures and has been implicated in controlling kinetochore–microtubule attachments during mitosis, and in epithelial cells, CK1α-mediated keratin cytoskeleton disassembly supports migration and wound closure, linking its kinase activity to cell division and motility. CK1α loss or inhibition can stabilize β‑catenin and contribute to Wnt-addicted tumor growth, while overactive CK1α may enhance mTOR signaling in metabolic disease; conversely, pharmacologic CK1α activation is being explored to dampen NLRP3 inflammasome activity and as a strategy to target Wnt-driven cancers such as colorectal and prostate cancer by reinforcing β‑catenin turnover. |
