Phosphorylation of CK1{delta}: identification of Ser 370} as the major phosphorylation site targeted by PKA in vitro and in vivo

Georgios Giamas , Heidrun Hirner , Levani Shoshiashvili , Arnhild Grothey , Susanne Gessert , Michael Kühl , Doris Henne-Bruns , Constantinos E. Vorgias , Uwe Knippschild (1)

1 Visceral- and Transplantation Surgery

The involvement of CK1δ in the regulation of multiple cellular processes implies a tight regulation of its activity on different levels. At the protein level reversible phosphorylation plays an important role in modulating the activity of CK1δ. In the present study, we show that PKA, Akt, CLK2 and PKCα phosphorylate CK1δ. PKA was identified as the major cellular CK1δ C-terminal targeted protein kinase (CK1δCK) activity phosphorylating CK1δ in vitro and in vivo, since i) PKA is detectable in the CK1δCK kinase peak fraction of fractionated MiaPaCa-2 cell extracts, ii) PKA shares nearly identical kinetic properties to CK1δCK and (iii) both, PKA and CK1δCK, phosphorylate CK1δ at Ser370 in vitro. Furthermore, phosphorylation of CK1δ by PKA decreases substrate phosphorylation of CK1δ in vitro. Mutation of Ser370 to alanine increases the affinity of CK1δ to phosphorylate β-casein and the GST-p53 1-64} fusion protein in vitro and enhances the formation of an ectopic dorsal axis during Xenopus laevis development. Anchorage of PKA and CK1δ to centrosomes is mediated through AKAP450. Interestingly, preincubation of MiaPaCa-2 cells with the synthetic peptide St-Ht31, which prevents the binding between AKAP450 and the regulatory subunit RII of PKA, results in a 6-fold increase of the activity of CK1δ. In summary, we conclude that PKA phosphorylates CK1δ predominantly at Ser370 in vitro and in vivo and that site-specific phosphorylation of CK1δ by PKA plays an important role in modulating CK1δ dependent processes.

Mots clés: Life Sciences

Georgios Giamas, Heidrun Hirner, Levani Shoshiashvili, Arnhild Grothey, Susanne Gessert, et al.. Phosphorylation of CK1{delta}: identification of Ser 370} as the major phosphorylation site targeted by PKA in vitro and in vivo. Biochemical Journal, 2007, 406 (3), pp.389-398. ⟨10.1042/BJ20070091⟩. ⟨hal-00478739⟩