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A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration.

ABSTRACT: Protein phosphorylation is a ubiquitous mechanism for cellular signal propagation, and signaling network complexity presents a challenge to protein kinase substrate identification. Few targets of Polo-like kinases are known, despite their significant role in coordinating cell-cycle progression. Here, we combine chemical-genetic, bioinformatic, and proteomic tools for Polo-like kinase substrate identification. Specific pharmacological inhibition of budding yeast Polo-like kinase, Cdc5, resulted in a misaligned preanaphase spindle and subsequently delayed anaphase nuclear migration, revealing a Cdc5 function. A cellular screen for Cdc5 substrates identified Spc72, a spindle pole body (SPB) component and microtubule anchor required for nuclear positioning. Spc72 bound to the Cdc5 PBD in a mitosis-specific manner, was phosphorylated by Cdc5 in vitro, and demonstrated a loss of mitotic phosphorylation in vivo upon Cdc5 inhibition. Finally, an examination of Cdc5 binding by SPB-localized proteins expanded our knowledge of Cdc5 function at the SPB.

SUBMITTER: Snead JL

PROVIDER: S-EPMC2215327 | biostudies-literature | 2007 Nov

REPOSITORIES: biostudies-literature

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A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration.

Snead Jennifer L JL Sullivan Matthew M Lowery Drew M DM Cohen Michael S MS Zhang Chao C Randle David H DH Taunton Jack J Yaffe Michael B MB Morgan David O DO Shokat Kevan M KM

Chemistry & biology 20071101 11

Protein phosphorylation is a ubiquitous mechanism for cellular signal propagation, and signaling network complexity presents a challenge to protein kinase substrate identification. Few targets of Polo-like kinases are known, despite their significant role in coordinating cell-cycle progression. Here, we combine chemical-genetic, bioinformatic, and proteomic tools for Polo-like kinase substrate identification. Specific pharmacological inhibition of budding yeast Polo-like kinase, Cdc5, resulted i ...[more]

PMID: 18022565

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Project description:Mitosis is coordinated by carefully controlled phosphorylation and ubiquitin-mediated proteolysis. Polo-like kinase 1 (Plk1) plays a central role in regulating mitosis and cytokinesis by phosphorylating target proteins. Yet, Plk1 is itself a target for posttranslational modification by phosphorylation and ubiquitination. We developed a chemical-genetic complementation assay to evaluate the functional significance of 34 posttranslational modifications (PTMs) on human Plk1. To do this, we used human cells that solely express a modified analog-sensitive Plk1 (Plk1AS) and complemented with wildtype Plk1. The wildtype Plk1 provides cells with a functional Plk1 allele in the presence of 3-MB-PP1, a bulky ATP-analog inhibitor that specifically inhibits Plk1AS. Using this approach, we evaluated the ability of 34 singly non-modifiable Plk1 mutants to complement Plk1AS in the presence of 3-MB-PP1. Mutation of the T-loop activating residue T210 and adjacent T214 are lethal, but surprisingly individual mutation of the remaining 32 posttranslational modification sites did not disrupt the essential functions of Plk1. To evaluate redundancy, we simultaneously mutated all phosphorylation sites in the kinase domain except for T210 and T214 or all sites in the C-terminal polo-box domain (PBD). We discovered that redundant phosphorylation events within the kinase domain are required for accurate chromosome segregation in anaphase but those in the PBD are dispensable. We conclude that PTMs within the T-loop of Plk1 are essential and nonredundant, additional modifications in the kinase domain provide redundant control of Plk1 function, and those in the PBD are dispensable for essential mitotic functions of Plk1. This comprehensive evaluation of Plk1 modifications demonstrates that although phosphorylation and ubiquitination are important for mitotic progression, many individual PTMs detected in human tissue may have redundant, subtle, or dispensable roles in gene function.

Project description:Microglial overactivation is actively involved in the pathogenesis of neurodegenerative diseases. Polo-like kinase 2 (PLK2) is a serine/threonine protein kinase associated with the regulation of synaptic plasticity and centriole duplication. Here, we identified PLK2 as an important early response gene in lipopolysaccharide (LPS)-stimulated microglial cells. Knockdown or inhibition of PLK2 remarkably attenuated LPS-induced expression of pro-inflammatory factors such as IL-1β, IL-6, COX2, TNF-α, and iNOS in microglial cells via suppressing the IKKβ-NF-κB signaling pathway. Notably, overexpression of PLK2 induced expression of pro-inflammatory factors and NF-κB transcriptional activation in the absence of inflammatory stimuli. Mechanistically, co-immunoprecipitation experiments revealed association between PLK2 and IKKβ, whereas GST pull-down assay showed no direct interaction between PLK2 and IKKβ. Proteomic analysis and in vitro kinase assay identified heat shock protein 90 alpha (HSP90α), a regulator of IKKβ activity, as a novel PLK2 substrate. Knockdown or pharmacological inhibition of HSP90α abolished PLK2-mediated activation of NF-κB transcriptional activity and microglial inflammatory activation. Furthermore, phosphoproteomic analysis pinpointed Ser252 and Ser263 on HSP90α as novel phosphorylation targets of PLK2. Subsequent functional studies demonstrated that re-expression of phosphor-dead mutation of these two phosphorylation sites on HSP90α failed to rescue the PLK2-induced activation of the NF-κB signaling. Lastly, conditional knockout of PLK2 in microglial cells dramatically ameliorated neuroinflammation and subsequent dopaminergic neuron loss in an intracranial LPS-induced mouse PD model. The present study revealed, for the first time, that PLK2 promoted microglial activation through the phosphorylation of HSP90α and subsequent activation of the IKKβ-NF-κB signaling pathway. Consequently, PLK2 emerges as a potential therapeutic target for the amelioration of neuroinflammation-related diseases.

Project description:Microglial overactivation is actively involved in the pathogenesis of neurodegenerative diseases. Polo-like kinase 2 (PLK2) is a serine/threonine protein kinase associated with the regulation of synaptic plasticity and centriole duplication. Here, we identified PLK2 as an important early response gene in lipopolysaccharide (LPS)-stimulated microglial cells. Knockdown or inhibition of PLK2 remarkably attenuated LPS-induced expression of pro-inflammatory factors such as IL-1β, IL-6, COX2, TNF-α,and iNOS in microglial cells via suppressing the IKKβ-NF-κB signaling pathway.Notably, overexpression of PLK2 induced expression of pro-inflammatory factors and NF-κB transcriptional activation in the absence of inflammatory stimuli. Mechanistically,co-immunoprecipitation experiments revealed association between PLK2 and IKKβ, whereas GST pull-down assay showed no direct interaction between PLK2 and IKKβ. Proteomic analysis and in vitro kinase assay identified heat shock protein 90 alpha (HSP90α), a regulator of IKKβ activity, as a novel PLK2 substrate. Knockdown or pharmacological inhibition of HSP90α abolished PLK2-mediated activation of NF-κB transcriptional activity and microglial inflammatory activation. Furthermore,phosphoproteomic analysis pinpointed Ser252 and Ser263 on HSP90α as novel phosphorylation targets of PLK2. Subsequent functional studies demonstrated that re-expression of phosphor-dead mutation of these two phosphorylation sites on HSP90α failed to rescue the PLK2-induced activation of the NF-κB signaling. Lastly, conditional knockout of PLK2 in microglial cells dramatically ameliorated neuroinflammation and subsequent dopaminergic neuron loss in an intracranial LPS-induced mouse PD model. The present study revealed, for the first time, that PLK2 promoted microglial activation through the phosphorylation of HSP90α and subsequent activation of the IKKβ-NF-κB signaling pathway. Consequently, PLK2 emerges as a potential therapeutic target for the amelioration of neuroinflammation-related diseases.

Dataset Information

A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration.

Publications

A coupled chemical-genetic and bioinformatic approach to Polo-like kinase pathway exploration.

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