Project description:Developmental and epileptic encephalopathies (DEEs) are a group of rare childhood disorders characterized by severe epilepsy and cognitive deficits. Numerous DEE genes have been discovered thanks to advances in genomic diagnosis, yet putative molecular links between these disorders are unknown. CDKL5 deficiency disorder (CDD, DEE2), one of the most common genetic epilepsies, is caused by loss-of-function mutations in the brain-enriched kinase CDKL5. To elucidate CDKL5 function, we looked for CDKL5 substrates using a SILAC-based phosphoproteomic screen. We identified the voltage-gated Ca2+ channel Cav2.3 (encoded by CACNA1E) as a novel physiological target of CDKL5 in mice and humans. Recombinant channel electrophysiology and interdisciplinary characterization of Cav2.3 phosphomutant mice revealed that loss of Cav2.3 phosphorylation leads to channel gain-of-function via slower inactivation and enhanced cholinergic stimulation, resulting in increased neuronal excitability. Our results thus show that CDD is partly a channelopathy. The properties of unphosphorylated Cav2.3 closely resemble those described for CACNA1E gain-of-function mutations causing DEE69, a disorder sharing clinical features with CDD. We show that these two single-gene diseases are mechanistically related and could be ameliorated with Cav2.3 inhibitors.
Project description:Mutations in the human CDKL5 gene have been shown to cause infantile spasms, as well as Rett syndrome-like phenotype. Because CDKL5 is subjected to X chromosome inactivation (XCI), individual cells from CDKL5 mutation girls either express the wild-type or mutant allele, likely resulting in different consequences at both the cellular and molecular levels. To identify these consequences, we carried out gene expression profiling on clonal populations derived from primary cultures of three patientsM-^R fibroblasts expressing either allele. A total of 16 up-regulated and 20 down-regulated genes were identified. The differentially expressed gene products, mostly involved in differentiation and oxidative stress may be related to a mechanism underlying mental retardation and epilepsy. Among these differentially expressed proteins, the apoptosis signal-regulated kinase MAP3K5 expression was found to be altered in non-neuronal, but also in neuronal CDKL5 deficient cells. Due to the fact that MAP3K5 activates MAP kinase pathway, which mediates signals leading to both differentiation and survival in neuronal cells, we suggest that a CDKL5 deficit may induce changes in synaptic plasticity in patientM-^Rs brain.
Project description:Axoplasmic proteomics from sciatic or centrally projecting branches of sciatic DRG identifies unique protein enrichment and signalling pathways, including prior and subsequent to a spinal regeneration-incompetent versus sciatic regeneration-competent axonal injury.
Project description:Cdkl5 Deficiency Disorder (CDD) is caused by variants in the protein kinase CDKL5, leading to symptoms such as seizures, developmental delay, and severe intellectual disability. The Chlamydomonas homologue of human CDKL5 is the flagellar protein LF5, whose absence results in a long flagella phenotype. We found that mouse CDKL5 similarly localizes within cilia, and its loss causes long cilia. Chlamydomonas cells lacking CDKL5 exhibit altered flagellar waveforms and reduced motility. CDKL5 kinase activity is essential for flagella length control and proper localization as a kinase-dead mutant, CDKL5(K33R), fails to rescue the long flagella phenotype and does not properly localize to the proximal end of flagella. In wild-type cells, CDKL5 is highly phosphorylated at residues S162, T164, and Y166 within its activation loop and can undergo autophosphorylation in vitro. Interestingly, CDKL5 lacking kinase activity maintains similar phosphorylation at these residues. However, CDKL5 isolated from cells that lack the protein kinase LF2 has reduced activation loop phosphorylation, diminished autophosphorylation capacity, and altered ciliary localization, suggesting that LF2 phosphorylates CDKL5’s activation loop to regulate its kinase activity. Disruption of Cdk20, the mouse ortholog of LF2, likewise alters the ciliary localization of Cdkl5 in primary cilia. CDKL5 likely regulates intraflagellar transport (IFT) as the loss CDKL5 increased the ciliary abundance of IFT proteins while decreasing the phosphorylation of IFT74.
Project description:Cdkl5 Deficiency Disorder (CDD) is caused by variants in the protein kinase CDKL5, leading to symptoms such as seizures, developmental delay, and severe intellectual disability. The Chlamydomonas homologue of human CDKL5 is the flagellar protein LF5, whose absence results in a long flagella phenotype. We found that mouse CDKL5 similarly localizes within cilia, and its loss causes long cilia. Chlamydomonas cells lacking CDKL5 exhibit altered flagellar waveforms and reduced motility. CDKL5 kinase activity is essential for flagella length control and proper localization as a kinase-dead mutant, CDKL5K33R, fails to rescue the long flagella phenotype and does not properly localize to the proximal end of flagella. In wild-type cells, CDKL5 is highly phosphorylated at residues S162, T164, and Y166 within its activation loop and can undergo autophosphorylation in vitro. Interestingly, CDKL5 lacking kinase activity maintains similar phosphorylation at these residues. However, CDKL5 isolated from cells that lack the protein kinase LF2 has reduced activation loop phosphorylation, diminished autophosphorylation capacity, and altered ciliary localization, suggesting that LF2 phosphorylates CDKL5’s activation loop to regulate its kinase activity. Disruption of Cdk20, the mouse ortholog of LF2, likewise alters the ciliary localization of Cdkl5 in primary cilia. CDKL5 likely regulates intraflagellar transport (IFT) as the loss CDKL5 increased the ciliary abundance of IFT proteins while decreasing the phosphorylation of IFT74.
Project description:Loss-of-function mutations in CDKL5 kinase causes severe neurodevelopmental delay and early-onset seizures. Identification of CDKL5 substrates is key to understanding its function. Using chemical genetics, we found that CDKL5 phosphorylates three microtubule-associated proteins: MAP1S, EB2 and ARHGEF2, and determined the phosphorylation sites. Substrate phosphorylations are greatly reduced in CDKL5 knockout mice, verifying these as physiological substrates. In CDKL5 knockout mouse neurons, dendritic microtubules have longer EB3-labelled plus-end growth duration and these altered dynamics are rescued by reduction of MAP1S levels through shRNA expression, indicating that CDKL5 regulates microtubule dynamics via phosphorylation of MAP1S. We show that phosphorylation by CDKL5 is required for MAP1S dissociation from microtubules. Additionally, anterograde cargo trafficking is compromised in CDKL5 knockout mouse dendrites. Finally, EB2 phosphorylation is reduced in patient-derived human neurons. Our results reveal a novel activity-dependent molecular pathway in dendritic microtubule regulation and suggest a pathological mechanism which may contribute to CDKL5 deficiency disorder.
Project description:Global phosphoproteomic screen to identify the first cellular substrates of CDKL5. CDKL5 knock-out U2OS cells and CDKL5 wt U2OS cells were generated for the TMT-based phosphoproteomic. Thi leads to the identification and further validation of several phosphopetides of MAP1S, CEP131 and CDKL5 itself. The phosphoproteomic analysis allowed the identification of the first cellular substrates for CDKL5 kinase.
Project description:The dorsoventral gradient of BMP signaling plays an essential role in embryonic patterning, with high BMP signal activating ventral-lateral mesoderm markers directly, and low BMP signal inducing neural tissues. The Zinc finger SWIM domain-containing protein 4 (zswim4) is expressed in the dorsal blastopore lip at the onset of Xenopus gastrula and then enriched at the forming neuroectoderm at mid-gastrula stages. Overexpression of zswim4 in Xenopus embryos causes inhibition of the anterior axis and shortened, curved body, and knockdown or knockout of zswim4 disturbed embryonic body axis formation and head development. The expression of ventral-lateral mesoderm marker genes was reduced after zswim4 overexpression and increased in embryos with zswim4 knockdown. Neural marker genes were repressed in zswim4 morphant. Mechanistically Zswim4 attenuates BMP signal through reducing protein stability of Smad1 in both Xenopus embryos and HEK293T cells. Zswim4 interacts with Smad1 and promotes ubiquitination of Smad1 in HEK293T cells. To identify the interaction partner of Zswim4 in regulating Smad1 stability, we performed SILAC based IP in HEK293T cells, and the precipitates were analyzed by Mass Spectrometry.
Project description:DNA/RNA helicase Upf1 seems to interact with axonal transcripts in response to nerve growth factor (NGF, A. Ludanyi, M. Gaspari and A. Riccio, unpublished data). In order to shed light on Upf1 mechanism of action and to identify potential associations with molecules having cleavage activity, we performed an AP-MS experiment comprising Upf1 immunoprecipitation, on-beads digestion, isotopic labelling (18O) and quantitative LC-MS/MS analysis.
Project description:BRCA2 maintains genome stability by facilitating DNA repair via homologous recombination and replication fork stability. Loss of BRCA2 is deleterious for survival of normal cells, but is paradoxically tolerated in cancer cells. Using quantitative mass-spectrometry, differences in protein expression were identified that might shed light on how breast cancer cells (HCC38) survive in the absence of BRCA2.