Kinase activity of casein kinase 1 delta (CK1δ) is modulated by protein kinase C α (PKCα) by site-specific phosphorylation within the kinase domain of CK1δ

Water lily (Nuphar) bioactive extracts have been widely used in traditional medicine owing to their multiple applications against human ailments. Phyto-active Nuphar extracts and their purified and synthetic derivatives have attracted the attention of ethnobotanists and biochemists. Here, we report that 6,6′-dihydroxythiobinupharidine (DTBN), purified from extracts of Nuphar lutea (L.) Sm. leaves, is an effective inhibitor of the kinase activity of members of the protein kinase C (PKC) family using in vitro and in silico approaches. We demonstrate that members of the conventional subfamily of PKCs, PKCα and PKCγ, were more sensitive to DTBN inhibition as compared to novel or atypical PKCs. Molecular docking analysis demonstrated the interaction of DTBN, with the kinase domain of PKCs depicting the best affinity towards conventional PKCs, in accordance with our in vitro kinase activity data. The current study reveals novel targets for DTBN activity, functioning as an inhibitor for PKCs kinase activity. Thus, this and other data indicate that DTBN modulates key cellular signal transduction pathways relevant to disease biology, including cancer.

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Caspase processing activates atypical protein kinase C ζ by relieving autoinhibition and destabilizes the protein

Biochemical Journal ◽

10.1042/bj20030926 ◽

2003 ◽

Vol 375 (3) ◽

pp. 663-671 ◽

Cited By ~ 29

Author(s):

Lucinda SMITH ◽

Zhi WANG ◽

Jeffrey B. SMITH

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Hela Cells ◽

Half Life ◽

Kinase Activity ◽

Ubiquitin Proteasome System ◽

Kinase Domain ◽

Kinase C ◽

Pkc Ζ

Treatment of HeLa cells with tumour necrosis factor α (TNFα) induced caspase processing of ectopic PKC (protein kinase C) ζ, which converted most of the holoenzyme into the freed kinase domain and increased immune-complex kinase activity. The goal of the present study was to determine the basis for the increased kinase activity that is associated with caspase processing of PKC ζ. Atypical PKC ι is largely identical with PKC ζ, except for a 60-amino-acid segment that lacks the caspase-processing sites of the ζ isoform. Replacement of this segment of PKC ζ with the corresponding segment of PKC ι prevented caspase processing and activation of the kinase function. Processing of purified recombinant PKC ζ by caspase 3 in vitro markedly increased its kinase activity. Caspase processing activated PKC ζ in vitro or intracellularly without increasing the phosphorylation of Thr410 of PKC ζ, which is required for catalytic competency. The freed kinase domain of PKC ζ had a much shorter half-life than the holoenzyme in transfected HeLa cells and in non-transfected kidney epithelial cells. Treatment with TNF-α shortened the half-life of the kinase domain protein, and proteasome blockade stabilized the protein. Studies of kinase-domain mutants indicate that a lack of negative charge at Thr410 can shorten the half-life of the freed kinase domain. The present findings indicate that the freed kinase domain has substantially higher kinase activity and a much shorter half-life than the holoenzyme because of accelerated degradation by the ubiquitin–proteasome system.

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Identification of Key Phospholipids That Bind and Activate Atypical PKCs

Biomedicines ◽

10.3390/biomedicines9010045 ◽

2021 ◽

Vol 9 (1) ◽

pp. 45

Author(s):

Suresh Velnati ◽

Sara Centonze ◽

Federico Girivetto ◽

Daniela Capello ◽

Ricardo M. Biondi ◽

...

Keyword(s):

Protein Kinase C ◽

Protein Kinase ◽

Phosphatidic Acid ◽

Kinase Activity ◽

Membrane Lipids ◽

Atypical Protein Kinase C ◽

Atypical Protein Kinase ◽

Kinase C ◽

Specific Regulation ◽

Phosphatidylinositol 4

PKCζ and PKCι/λ form the atypical protein kinase C subgroup, characterised by a lack of regulation by calcium and the neutral lipid diacylglycerol. To better understand the regulation of these kinases, we systematically explored their interactions with various purified phospholipids using the lipid overlay assays, followed by kinase activity assays to evaluate the lipid effects on their enzymatic activity. We observed that both PKCζ and PKCι interact with phosphatidic acid and phosphatidylserine. Conversely, PKCι is unique in binding also to phosphatidylinositol-monophosphates (e.g., phosphatidylinositol 3-phosphate, 4-phosphate, and 5-phosphate). Moreover, we observed that phosphatidylinositol 4-phosphate specifically activates PKCι, while both isoforms are responsive to phosphatidic acid and phosphatidylserine. Overall, our results suggest that atypical Protein kinase C (PKC) localisation and activity are regulated by membrane lipids distinct from those involved in conventional PKCs and unveil a specific regulation of PKCι by phosphatidylinositol-monophosphates.

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