Casein kinase 1 delta and Casein kinase 1 epsilon (CK1δ/ε)

Casein kinase 1 delta (CK1δ) and epsilon (CK1ε) are highly conserved serine/threonine protein kinases that serve as essential regulators of the mammalian circadian clock and multiple oncogenic signaling pathways [1.2.1, 1.3.3]. They function as the primary molecular pacemakers by phosphorylating PERIOD (PER) proteins, which targets them for degradation and thus dictates the timing of the circadian cycle [1.4.1]. Beyond their role in chronobiology, CK1δ/ε are integral to the Wnt/beta-catenin, Hedgehog, and Hippo pathways, where they modulate cell proliferation, survival, and DNA damage responses [1.3.1, 1.3.4]. Dysregulation of these isoforms is frequently observed in various cancers, including breast and hematologic malignancies, as well as in neurodegenerative diseases like Alzheimer's, where they contribute to pathological Tau phosphorylation [1.2.1, 1.4.3]. Pharmacological targeting of CK1δ/ε primarily involves ATP-competitive small-molecule inhibitors, such as PF-05251749 and umbralisib, which are being investigated for their potential to treat sleep disorders and cancer [1.2.4, 1.3.2]. However, the high degree of homology between these isoforms and their ubiquitous expression present significant challenges for achieving therapeutic selectivity and avoiding systemic side effects related to circadian disruption [1.2.5, 1.3.5].

Other names

CK1 deltaCK1 epsilonCSNK1DCSNK1ECasein kinase I isoform deltaCasein kinase I isoform epsilonCKI-deltaCKI-epsilonHCKIE

ATP-competitive inhibition of the kinase domain, preventing the phosphorylation of downstream substrates such as PER2, Tau, and beta-catenin.