Visualization and molecular analysis of nuclear import of protein kinase CK2 subunits in living cells

Martel, Véronique; Filhol, Odile; Nueda, Arsenio; Gerber, Delphine; Benítez, María José; Cochet, Claude

doi:10.1007/978-1-4615-1723-8_10

Cited by 19 publications

(24 citation statements)

References 43 publications

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“…However, these studies do not exclude the possibility that tetrameric CK2 complexes undergo regulated disassembly in cells. In fact, recent evidence from dynamic localization studies of the individual CK2 subunits provides indications of independent movements of CK2α and CK2β within cells [110]. In a similar vein, the surface contacts between the catalytic and regulatory subunits of CK2 that were revealed by the recent crystal structure of tetrameric CK2 were considerably fewer than the surface contacts typically observed in stable protein complexes [29].…”

Section: Figure 3 Possible Mechanisms Of Regulation Of Ck2mentioning

confidence: 92%

Protein kinase CK2: structure, regulation and role in cellular decisions of life and death

Litchfield

2003

Biochemical Journal

1,131

1,097

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Protein kinase CK2 ('casein kinase II') has traditionally been classified as a messenger-independent protein serine/threonine kinase that is typically found in tetrameric complexes consisting of two catalytic (alpha and/or alpha') subunits and two regulatory beta subunits. Accumulated biochemical and genetic evidence indicates that CK2 has a vast array of candidate physiological targets and participates in a complex series of cellular functions, including the maintenance of cell viability. This review summarizes current knowledge of the structural and enzymic features of CK2, and discusses advances that challenge traditional views of this enzyme. For example, the recent demonstrations that individual CK2 subunits exist outside tetrameric complexes and that CK2 displays dual-specificity kinase activity raises new prospects for the precise elucidation of its regulation and cellular functions. This review also discusses a number of the mechanisms that contribute to the regulation of CK2 in cells, and will highlight emerging insights into the role of CK2 in cellular decisions of life and death. In this latter respect, recent evidence suggests that CK2 can exert an anti-apoptotic role by protecting regulatory proteins from caspase-mediated degradation. The mechanistic basis of the observation that CK2 is essential for viability may reside in part in this ability to protect cellular proteins from caspase action. Furthermore, this anti-apoptotic function of CK2 may contribute to its ability to participate in transformation and tumorigenesis.

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Section: Figure 3 Possible Mechanisms Of Regulation Of Ck2mentioning

confidence: 92%

Protein kinase CK2: structure, regulation and role in cellular decisions of life and death

Litchfield

2003

Biochemical Journal

1,131

1,097

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“…In our previous study, the N-terminal region of CK2␣ located between residues 74 and 77 ( 74 KKKK 77 ) was characterized as a functional nuclear localization signal (NLS), and it was observed that mutation of K75 and K77 severely impaired the nuclear import of the corresponding GFP-CK2␣ fusion constructs (25). The functionality of this NLS was further probed by mutating its basic residues to alanine in the wild-type CK2␣ ( Fig.…”

Section: Identification Of An Nls In Ck2␣mentioning

confidence: 99%

“…In a previous study, the behavior of CK2 subunits fused to GFP was characterized in living cells (25). The expressed fusion proteins were functional and interacted with endogenous CK2.…”

mentioning

confidence: 99%

“…Cell lysates were centrifuged, and the supernatants were precleared with protein A-Sepharose beads and then incubated for 2 h with anti-CK2␤ serum (1/500) or anti-GFP (1/500) (Roche) followed by a 45-min incubation with protein ASepharose beads. Beads were washed three times in lysis buffer and used either for kinase assays or resolved by SDS-PAGE and immunoblotted as previously described (25).…”

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confidence: 99%

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Live-Cell Fluorescence Imaging Reveals the Dynamics of Protein Kinase CK2 Individual Subunits

Filhol

Nueda

Martel

et al. 2003

Molecular and Cellular Biology

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126

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Protein kinase CK2 is a multifunctional enzyme which has long been described as a stable heterotetrameric complex resulting from the association of two catalytic (␣ or ␣) and two regulatory (␤) subunits. To track the spatiotemporal dynamics of CK2 in living cells, we fused its catalytic ␣ and regulatory ␤ subunits with green fluorescent protein (GFP). Both CK2 subunits contain nuclear localization domains that target them independently to the nucleus. Imaging of stable cell lines expressing low levels of GFP-CK2␣ or GFP-CK2␤ revealed the existence of CK2 subunit subpopulations exhibiting differential dynamics. Once in the nucleus, they diffuse randomly at different rates. Unlike CK2␤, CK2␣ can shuttle, showing the dynamic nature of the nucleocytoplasmic trafficking of the kinase. When microinjected in the cytoplasm, the isolated CK2 subunits are rapidly translocated into the nucleus, whereas the holoenzyme complex remains in this cell compartment, suggesting an intramolecular masking of the nuclear localization sequences that suppresses nuclear accumulation. However, binding of FGF-2 to the holoenzyme triggers its nuclear translocation. Since the substrate specificity of CK2␣ is dramatically changed by its association with CK2␤, the control of the nucleocytoplasmic distribution of each subunit may represent a unique potential regulatory mechanism for CK2 activity.Protein kinase CK2 is a ubiquitous serine/threonine protein kinase, generally described as a stable ␣ 2 ␤ 2 tetramer, where ␣ and ␤ are the catalytic and regulatory subunits, respectively (3). Although its signaling function has long remained obscure, the importance of CK2 is suggested by the evolutionary conservation of the enzyme and by the fact that the disruption of both Saccharomyces cerevisiae genes encoding CK2 catalytic subunits is a lethal event (29). In addition to its role in embryonic development and terminal differentiation, the enzyme is required for normal cell cycle progression (20,30). At last, a function of CK2 in cell survival has recently emerged (1).Many of the identified CK2 substrates that are critical for cell proliferation and viability are localized in different cellular compartments. However, there is controversy as to the localization of CK2 and where its substrates are phosphorylated. Although the current prevailing view of CK2 is a tetrameric enzyme, accumulating evidence also indicates that free populations of both CK2 subunits can exist and exert specific functions in the cell (18, 37). At least in vitro, CK2␤ exerts a central role in modulating the catalytic activity of CK2 (26). Consequently, it is suspected that in vivo, the substrate specificity of the enzyme is likely to be determined both by subcellular localization and by affinity for its regulatory subunit that brings the kinase in proximity to the substrate.In a previous study, the behavior of CK2 subunits fused to GFP was characterized in living cells (25). The expressed fusion proteins were functional and interacted with endogenous CK2. Both subunits were mostl...

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“…However, with a few substrates (calmodulin, mdm-2), CK2β is a potent inhibitor of the phosphorylation catalysed by CK2α (Meggio et al 1994). There is increasing evidence that the individual subunits occur in addition to the holoenzyme (Martel et al 2001;Stigare et al 1993;Romero-Oliva et al 2003). CK2 has been reported to be involved in many neurodegenerative, inflammatory, vascular and bone tissue diseases and in tumorigenesis.…”

Section: Introductionmentioning

confidence: 99%

Cellular regulators of protein kinase CK2

Montenarh

2010

Cell Tissue Res

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Protein phosphorylation is a key regulatory post-translational modification and is involved in the control of many cellular processes. Protein kinase CK2, formerly known as casein kinase II, which is a ubiquitous and highly conserved protein serine/threonine kinase, plays a central role in the control of a variety of pathways in cell proliferation, transformation, apoptosis and senescence. An understanding of the regulation of such a central protein kinase would greatly help our comprehension of the regulation of many pathways in cellular regulation. A number of reviews have addressed the detection, the development, and the characterization of inhibitors of CK2. The present review focuses on possible natural regulators of CK2, i.e. proteins and other cellular factors that bind to CK2 and thereby regulate its activity.

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Visualization and molecular analysis of nuclear import of protein kinase CK2 subunits in living cells

Cited by 19 publications

References 43 publications

Protein kinase CK2: structure, regulation and role in cellular decisions of life and death

Protein kinase CK2: structure, regulation and role in cellular decisions of life and death

Live-Cell Fluorescence Imaging Reveals the Dynamics of Protein Kinase CK2 Individual Subunits

Cellular regulators of protein kinase CK2

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