Cell cycle-dependent localization of casein kinase I to mitotic spindles.

Abstract

Casein kinase I (CKI) is a class of protein kinases ubiquitous to all eukaryotic cells. Recently, cDNA clones encoding several bovine CKI isoforms have been sequenced that show high sequence identity to the 1IRR25 gene product of the budding yeast Saccharomyces cerevisiae; MRRM is required for normal cellular growth, nuclear segreption, DNA repair, and melosis. We have raised polyclonal antibodies to a human erythroid 34-kDa CMI and have sequenced a portion of this kinase. The amino acid sequence identifies the CKI as the a-CKI isoform, which is 62% identical to the HRR25 protein kinase. By use of immunofluorescence, the a-CKI has been localized to vesicular cytolic structures and to the centrosome in interphase cells. As cels progress into mitosis, centrospheric stining increases and, in mitosis, a-CKI associates with kinetochore fibers. This lo tion suggests that a-CKI, like HRR25, plays a role in the segregation of chromosomes during mitosis and may be cell cycleregulated both in humans and in yeast.Casein kinase I (CKI) activity is ubiquitous in eukaryotes from human to yeast (1). CKI is an unusual protein kinase in that it has been isolated in active form from the cytosol, membranes, and nuclei (1-3). Generally, CKI from the cytosol or membranes of mammalian cells has an apparent molecular mass of 30-37 kDa (1-3). When CKI has been purified from nuclei, a larger range has been reported, 25-55 kDa (1). Indeed, a 46-kDa casein kinase from yeast is conserved in vertebrates and is located in the nucleus in mouse cells (4). CKI from human erythrocytes is a monomer when purified and has a molecular size of 34-36 kDa, depending upon the phosphorylation state of the enzyme (1, 2, 5).CKI phosphorylates the cytoskeletal proteins myosin, ankyrin, troponin, spectrin, and protein 4.1; neural filaments; neural cellular adhesion molecules; RNA polymerases I and II; translation initiation factors 4B, 4E, and 5; tRNA synthetases; simian virus 40 large T antigen; the insulin receptor; the regulatory subunit (phosphatase inhibitor 2) of protein phosphatase 1; the erythrocyte anion transporter; and metabolic enzymes, including glycogen synthase (reviewed in ref. 1). Some of these substrates undergo defined functional changes when phosphorylated by CKI. For example, in vivo, protein phosphatase 1 (phosphatase inhibitor 2) appears to be phosphorylated by CKI and this inhibits the phosphatase activity (6).Glycogen synthase, when phosphorylated by cAMPdependent protein kinase and then by CKI, is potently inhibited (7). This suggests that CKI phosphorylates substrates synergistically with other protein kinases. In other words, there is a sequence or hierarchy of phosphorylation. Indeed, (2,3). In erythrocytes, the assembly of CKI onto membranes is regulated by PIP2. The protein kinase activity is also inhibited by PIP2, and this occurs over a small change in the total PIP2 content in the membranes (3). This unusual pattern of inhibition may occur as a result of the sequestration of membrane PIP2 into "pools" and may prov...

Protein kinases in control of the centrosome cycle

“…Ca 2 /calmodulin kinases II [40] MT stability? Casein kinase I-K [41] Casein kinase II [42] Fyn [43] Signaling in T lymphocytes. Phosphoinositide 3-kinase [44] LK6 [45] PKC-d [46] Phosphatases d :…”

IC261, a specific inhibitor of the protein kinases casein kinase 1-delta and -epsilon, triggers the mitotic checkpoint and induces p53-dependent postmitotic effects

“…For example, DMCK1 (the homologue of CK1a in D. melanogaster), is activated following DNA damage and relocates to the nucleus (Santos et al, 1996), while mammalian CK1a is located at the mitotic spindle and the Oncogene (2000) 19, 5303 ± 5313 ã 2000 Macmillan Publishers Ltd All rights reserved 0950 ± 9232/00 $15.00 www.nature.com/onc *Correspondence: U Knippschildcentrosomes in both mouse ®broblasts and oocytes (Brockman et al, 1992;Gross et al, 1997). Recently we showed that CK1d is recruited to the mitotic spindle and the centrosomes following treatment with etoposide or g-irradiation in rodent cells (Behrend et al, 2000).…”

The Role of Casein Kinase 1 in Meiosis

“…In mammalian cells, CK1α was first reported to localize to vesicular cytolic structures and centrosome in interphase cells, and then associated with spindles in mitosis [9]; CK1δ was localized to centrosomes, co-localized with γ-tubulin and was associated with the mitotic spindles under DNA damage; and CK1ε was concentrated at centrosomes [31]. Cell treated with IC261 caused mitotic spindle defects and cell cycle arrest.…”

“…The CK1 isoforms was found to play an important role in cancer progression in different types of tumors [28]. The localization of CKlα in the mitosis was researched by immunofluorescent studies using mouse fibroblasts and CHO cells [9]. In interphase cells, CK1α was localized to vesicular cytosolic structures.…”

“…CK1 phosphorylates the cytoskeletal proteins myosin, ankyrin, troponin, spectrin, and protein 4.1; neural filaments; neural cellular adhesion molecules; RNA polymerases I and II; translation initiation factors 4B, 4E, and 5; tRNA synthetases; simian virus 40 large T antigen; the insulin receptor; the regulatory subunit (phosphatase inhibitor 2) of protein phosphatase 1; the erythrocyte anion transporter; and metabolic enzymes, including glycogen synthase [9,11]. Some of these substrates undergo defined functional changes when phosphorylated by CKI.…”