CK1α1 is a member of the CK1 family of serine/threonine protein kinases which play an important role in diverse cell processes. CK1α1 can regulate Smo cell surface accumulation and activity in response to hedgehog. CK1α1 phosphorylate Smo at several sites and phosphorylation-deficient forms of Smo fail to accumulate on the cell surface and are unable to transduce the hedgehog signal (1). CK1α1 dynamically associates with the CBM complex on T cell receptor engagement to participate in cytokine production and lymphocyte proliferation. CK1α1 can form complex with MDM2 which then regulates the stability of p53 and E2F-1 transcription factors (2).