Proteins of the 14-3-3 family are well known modulators of the leucine-rich repeat kinase 2 (LRRK2) regulating kinase activity, cellular localization, and ubiquitylation. Although binding between those proteins has been investigated, a comparative study of all human 14-3-3 isoforms interacting with LRRK2 is lacking so far. In a comprehensive approach, we quantitatively analyzed the interaction between the seven human 14-3-3 isoforms and LRRK2-derived peptides covering both, reported and putative 14-3-3 binding sites. We observed that phosphorylation is an absolute prerequisite for 14-3-3 binding and generated binding patterns of 14-3-3 isoforms to interact with peptides derived from the N-terminal phosphorylation cluster (S910 and S935), the Roc domain (S1444) and the C-terminus. The tested 14-3-3 binding sites in LRRK2 preferentially were recognized by the isoforms γ and η, whereas the isoforms and especially σ showed the weakest or no binding. Interestingly, the possible pathogenic mutation Q930R in LRRK2 drastically increases binding affinity to a peptide encompassing pS935. We then identified the autophosphorylation site T2524 as a so far not described 14-3-3 binding site at the very C-terminus of LRRK2. Binding affinities of all seven 14-3-3 isoforms were quantified for all three binding regions with pS1444 displaying the highest affinity of all measured singly phosphorylated peptides. The strongest binding was detected for the combined phosphosites S910 and S935, suggesting that avidity effects are important for high affinity interaction between 14-3-3 proteins and LRRK2.
To explore how pathogenic mutations of the multidomain leucine-rich repeat kinase 2 (LRRK2) hijack its finely tuned activation process and drive Parkinson’s disease (PD), we used a multitiered approach. Most mutations mimic Rab-mediated activation by “unleashing” kinase activity, and many, like the kinase inhibitor MLi-2, trap LRRK2 onto microtubules. Here we mimic activation by simply deleting the inhibitory N-terminal domains and then characterize conformational changes induced by MLi-2 and PD mutations. After confirming that LRRK2RCKW retains full kinase activity, we used hydrogen-deuterium exchange mass spectrometry to capture breathing dynamics in the presence and absence of MLi-2. Solvent-accessible regions throughout the entire protein are reduced by MLi-2 binding. With molecular dynamics simulations, we created a dynamic portrait of LRRK2RCKW and demonstrate the consequences of kinase domain mutations. Although all domains contribute to regulating kinase activity, the kinase domain, driven by the DYGψ motif, is the allosteric hub that drives LRRK2 regulation.
3′,5′-cyclic adenosine monophosphate (cAMP) dependent protein kinase or protein kinase A (PKA) has served as a prototype for the large family of protein kinases that are crucially important for signal transduction in eukaryotic cells. The PKA catalytic subunits are encoded by the two major genes PRKACA and PRKACB, respectively. The PRKACA gene encodes two known splice variants, the ubiquitously expressed Cα1 and the sperm-specifically expressed Cα2. In contrast, the PRKACB gene encodes several splice variants expressed in a highly cell and tissue-specific manner. The Cβ proteins are called Cβ1, Cβ2, Cβ3, Cβ4 and so-called abc variants of Cβ3 and Cβ4. Whereas Cβ1 is ubiquitously expressed, Cβ2 is enriched in immune cells and the Cβ3, Cβ4 and their abc variants are solely expressed in neuronal cells. All Cα and Cβ splice variants share a kinase-conserved catalytic core and a C-terminal tail encoded by exons 2 through 10 in the PRKACA and PRKACB genes, respectively. All Cα and Cβ splice variants with the exception of Cα1 and Cβ1 are hyper-variable at the N-terminus. Here, we will discuss how the PRKACA and PRKACB genes have developed as paralogs that encode distinct and functionally non-redundant proteins. The fact that Cα and Cβ splice variant mutations are associated with numerous diseases further opens new windows for PKA-induced disease pathologies.
In a multi-tiered approach, we explored how Parkinson's Disease-related mutations hijack the finely tuned activation process of Leucine-Rich Repeat Kinase 2 (LRRK2) using a construct containing the ROC, Cor, Kinase and WD40 domains (LRRK2RCKW). We hypothesized that the N-terminal domains shield the catalytic domains in an inactive state. PD mutations, type-I LRRK2 inhibitors, or physiological Rab GTPases can unleash the catalytic domains while the active kinase conformation, but not kinase activity, is essential for docking onto microtubules. Mapping solvent accessible regions of LRRK2RCKW employing hydrogen-deuterium exchange mass spectrometry (HDX-MS) revealed how inhibitor binding is sensed by the entire protein. Molecular Dynamics simulations of the kinase domain elucidated differences in conformational dynamics between wt and mutants of the DYGψ motif. While all domains contribute to regulating kinase activity and spatial distribution, the kinase domain, driven by the DYGψ motif, coordinates domain crosstalk and serves as an intrinsic hub for LRRK2 regulation.
Background: Leucine-Rich Repeat Kinase 2 (LRRK2) is a complex multi-domain protein where LRRK2-mutations are associated with Parkinson´s Disease (PD). To explore how pathogenic PD-mutations hijack the finely tuned activation process of LRRK2, we here used a multi-tiered approach. Methods: First, the spatial and temporal distribution of full-length LRRK2 was investigated by a real-time cell-based assay in the presence and absence of LRRK2-kinase inhibitors. In a 2nd layer we explored the consequences of PD mutations as well as removal of the N-terminal domains employing a construct containing the ROC, Cor, Kinase and WD40 domains (LRRK2RCKW). We focused on the biochemical characterization of LRRK2RCKW variants based on kinase assays using Rab8a or LRRKtide as substrates. Next, we used hydrogen-deuterium exchange mass spectrometry (HDX-MS) to map the solvent accessible regions of LRRK2RCKW in the presence and absence of the LRRK2 inhibitor MLi-2. Finally, Molecular Dynamics simulations on the kinase domain were applied to elucidate differences in breathing dynamics between wild type and mutants of the DYGψ motif. Results: Our cellular approaches revealed that the kinase inhibitors MLi-2 and rebastinib both freeze the kinase domain in a stable conformation, however, only MLi-2 resembles an active conformation and induces filament formation. LRRK2RCKW showed, regardless of the mutation it was combined with, filament formation, indicating a shielding function of the N-terminal domains. This shielding function is impaired for pathogenic mutations in full length LRRK2. LRRK2RCKW retained kinase activity similar to full-length LRRK2. HDX-MS provided a comprehensive allosteric portrait of the kinase domain and revealed how MLi-2 binding is sensed by the entire protein. Molecular Dynamics simulations suggest that, while all domains contribute to regulating kinase activity and spatial distribution, it is the highly dynamic kinase domain, driven by the DYGψ motif, that coordinates the overall domain crosstalk and serves as a regulatory hub for the intrinsic regulation of LRRK2.Conclusion: These studies confirm our hypothesis that the N-terminal scaffolding domains shield the catalytic domains in an inactive state. PD mutations, MLi-2, or Rab GTPases can all unleash the catalytic domains while the active kinase conformation, but not kinase activity, is essential for docking onto microtubules.
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