Browsing by Subject "GTPase"

Now showing 1 - 7 of 7
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    Covalent Fragment Screening Identifies Rgl2 RalGEF Cysteine for Targeted Covalent Inhibition of Ral GTPase Activation
    (Wiley, 2022) Bum-Erdene, Khuchtumur; Ghozayel, Mona K.; Xu, David; Meroueh, Samy O.; Biochemistry and Molecular Biology, School of Medicine
    Ral GTPases belong to the RAS superfamily, and they are directly activated by K-RAS. The RalGEF pathway is one of the three major K-RAS signaling pathways. Ral GTPases do not possess a cysteine nucleophile to develop a covalent inhibitor following the strategy that led to a K-RAS G12C therapeutic agent. However, several cysteine amino acids exist on the surface of guanine exchange factors that activate Ral GTPases, such as Rgl2. Here, we screen a library of cysteine electrophile fragments to determine if covalent bond formation at one of the Rgl2 surface cysteines could inhibit Ral GTPase activation. We found several chloroacetamide and acrylamide fragments that inhibited Ral GTPase exchange by Rgl2. Site-directed mutagenesis showed that covalent bond formation at Cys-284, but not other cysteines, leads to inhibition of Ral activation by Rgl2. Follow-up time- and concentration-dependent studies of derivatives identified by substructure search of commercial libraries further confirmed Cys-284 as the reaction site and identified the indoline fragments as the most promising series for further development. Cys-284 is located outside of the Ral•Rgl2 interface on a loop that has several residues that come in direct contact with Ral GTPases. Our allosteric covalent fragment inhibitors provide a starting point for the development of small-molecule covalent inhibitors to probe Ral GTPases in animal models.
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    P18: Novel Anticancer Peptide from Induced Tumor-Suppressing Cells Targeting Breast Cancer and Bone Metastasis
    (MDPI, 2024-06-15) Cui, Changpeng; Huo, Qingji; Xiong, Xue; Na, Sungsoo; Mitsuda, Masaru; Minami, Kazumasa; Li, Baiyan; Yokota, Hiroki; Anatomy, Cell Biology and Physiology, School of Medicine
    Background: The skeletal system is a common site for metastasis from breast cancer. In our prior work, we developed induced tumor-suppressing cells (iTSCs) capable of secreting a set of tumor-suppressing proteins. In this study, we examined the possibility of identifying anticancer peptides (ACPs) from trypsin-digested protein fragments derived from iTSC proteomes. Methods: The efficacy of ACPs was examined using an MTT-based cell viability assay, a Scratch-based motility assay, an EdU-based proliferation assay, and a transwell invasion assay. To evaluate the mechanism of inhibitory action, a fluorescence resonance energy transfer (FRET)-based GTPase activity assay and a molecular docking analysis were conducted. The efficacy of ACPs was also tested using an ex vivo cancer tissue assay and a bone microenvironment assay. Results: Among the 12 ACP candidates, P18 (TDYMVGSYGPR) demonstrated the most effective anticancer activity. P18 was derived from Arhgdia, a Rho GDP dissociation inhibitor alpha, and exhibited inhibitory effects on the viability, migration, and invasion of breast cancer cells. It also hindered the GTPase activity of RhoA and Cdc42 and downregulated the expression of oncoproteins such as Snail and Src. The inhibitory impact of P18 was additive when it was combined with chemotherapeutic drugs such as Cisplatin and Taxol in both breast cancer cells and patient-derived tissues. P18 had no inhibitory effect on mesenchymal stem cells but suppressed the maturation of RANKL-stimulated osteoclasts and mitigated the bone loss associated with breast cancer. Furthermore, the P18 analog modified by N-terminal acetylation and C-terminal amidation (Ac-P18-NH2) exhibited stronger tumor-suppressor effects. Conclusions: This study introduced a unique methodology for selecting an effective ACP from the iTSC secretome. P18 holds promise for the treatment of breast cancer and the prevention of bone destruction by regulating GTPase signaling.
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    Parkinson's disease-associated mutations in the GTPase domain of LRRK2 impair its nucleotide-dependent conformational dynamics
    (American Society for Biochemistry and Molecular Biology, 2019-04-12) Wu, Chun-Xiang; Liao, Jingling; Park, Yangshin; Reed, Xylena; Engel, Victoria A.; Hoang, Neo C.; Takagi, Yuichiro; Johnson, Steven M.; Wang, Mu; Federici, Mark; Nichols, R. Jeremy; Sanishvili, Ruslan; Cookson, Mark R.; Hoang, Quyen Q.; Biochemistry and Molecular Biology, School of Medicine
    Mutation in leucine-rich repeat kinase 2 (LRRK2) is a common cause of familial Parkinson's disease (PD). Recently, we showed that a disease-associated mutation R1441H rendered the GTPase domain of LRRK2 catalytically less active and thereby trapping it in a more persistently “on” conformation. However, the mechanism involved and characteristics of this on conformation remained unknown. Here, we report that the Ras of complex protein (ROC) domain of LRRK2 exists in a dynamic dimer–monomer equilibrium that is oppositely driven by GDP and GTP binding. We also observed that the PD-associated mutations at residue 1441 impair this dynamic and shift the conformation of ROC to a GTP-bound–like monomeric conformation. Moreover, we show that residue Arg-1441 is critical for regulating the conformational dynamics of ROC. In summary, our results reveal that the PD-associated substitutions at Arg-1441 of LRRK2 alter monomer–dimer dynamics and thereby trap its GTPase domain in an activated state.
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    A revised 1.6 Å structure of the GTPase domain of the Parkinson’s disease-associated protein LRRK2 provides insights into mechanisms
    (Cold Spring Harbor Laboratory Press, 2019) Wu, Chun-Xiang; Liao, Jingling; Park, Yangshin; Hoang, Neo C.; Engel, Victoria A.; Wan, Li; Oh, Misook; Sanishvili, Ruslan; Takagi, Yuichiro; Johnson, Steven M.; Wang, Mu; Federici, Mark; Nichols, R. Jeremy; Beilina, Alexandra; Reed, Xylena; Cookson, Mark R.; Hoang, Quyen Q.; Biochemistry and Molecular Biology, School of Medicine
    Leucine-rich repeat kinase 2 (LRRK2) is a large 286 kDa multi-domain protein whose mutation is a common cause of Parkinson’s disease (PD). One of the common sites of familial PD-associated mutations occurs at residue Arg-1441 in the GTPase domain of LRRK2. Previously, we reported that the PD-associated mutation R1441H impairs the catalytic activity of the GTPase domain thereby traps it in a persistently "on" state. More recently, we reported that the GTPase domain of LRRK2 exists in a dynamic dimer-monomer equilibrium where GTP binding shifts it to the monomeric conformation while GDP binding shifts it back to the dimeric state. We also reported that all of the PD-associated mutations at Arg-1441, including R1441H, R1441C, and R1441G, impair the nucleotide-dependent dimer-monomer conformational dynamics of the GTPase domain. However, the mechanism of this nucleotide-dependent conformational dynamics and how it is impaired by the mutations at residue Arg-1441 remained unclear. Here, we report a 1.6 Å crystal structure of the GTPase domain of LRRK2. Our structure has revealed a dynamic switch region that can be differentially regulated by GTP and GDP binding. This nucleotide-dependent regulation is impaired when residue Arg-1441 is substituted with the PD-associated mutations due to the loss of its exquisite interactions consisting of two hydrogen bonds and a π-stacking interaction at the dimer interface.
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    Roc, the G-domain of the Parkinson's disease-associated protein LRRK2
    (Elsevier, 2022-12) Park, Yangshin; Liao, Jingling; Hoang, Quyen Q.; Biochemistry and Molecular Biology, School of Medicine
    Mutation in LRRK2 (Leucine-rich repeat kinase 2) is a common cause of Parkinson’s disease. Aberrant LRRK2 kinase activity is associated with disease pathogenesis, and thus it is an attractive drug target for combating PD. Intense efforts in the past nearly two decades have focused on developing small-molecule inhibitors of the kinase domain of LRRK2, which have identified potent kinase inhibitors. However, most LRRK2 kinase inhibitors have shown adverse effects; therefore, alternative mechanism-based strategies are desperately needed. In this review, we will discuss the new insights gleaned from recent cryo-EM structures of LRRK2 towards understanding the mechanisms of actions of LRRK2 and explore the potential new therapeutic avenues.
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    Roc, the G-domain of the Parkinson’s disease-associated protein LRRK2
    (Elsevier, 2022) Park, Yangshin; Liao, Jingling; Hoang, Quyen Q.; Biochemistry and Molecular Biology, School of Medicine
    Mutation in LRRK2 (Leucine-rich repeat kinase 2) is a common cause of Parkinson’s disease. Aberrant LRRK2 kinase activity is associated with disease pathogenesis, and thus it is an attractive drug target for combating PD. Intense efforts in the past nearly two decades have focused on developing small-molecule inhibitors of the kinase domain of LRRK2, which have identified potent kinase inhibitors. However, most LRRK2 kinase inhibitors have shown adverse effects; therefore, alternative mechanism-based strategies are desperately needed. In this review, we will discuss the new insights gleaned from recent cryo-EM structures of LRRK2 towards understanding the mechanisms of actions of LRRK2 and explore the potential new therapeutic avenues.
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    Structure and Function of the G Domain of Parkinson's Disease-Associated Protein LRRK2
    (2019-08) Wu, Chunxiang; Hoang, Quyen Q.; Foroud, Tatiana M.; Hurley, Thomas D.; Johnson, Steven M.; Zhang, Zhong-Yin
    Mutations in the gene encoding for leucine rich repeats kinase 2 (LRRK2) are commonly found in Parkinson’s disease. Recently, we found that the disease-associated point mutations at residue R1441 in the G domain (ROC) of LRRK2 resulted in perturbation of its GTPase activity. In this study, we compare the biochemical and biophysical properties of the ROC domain of LRRK2 carrying the PD-associated mutations at residue R1441 with those of the wild-type. We found that the disease-associated mutations (R1441C/G/H) showed marked quaternary structure compared to wild-type, in that the latter existed in solution in both monomeric and dimeric conformations dynamically regulated by GDP/GTP binding state, while we detected only monomeric conformation for three disease-associated mutants. To understand the structural basis for this plasticity and the activity reduction in the mutants, we solved a 1.6 Å crystal structure of the wild type ROC that shows a stable dimeric conformation in which the switch motifs and inter-switch regions mediate extensive interactions at the dimer interface. Residue R1441, where PD-associated mutations occur, forms exquisite interactions at the interface, thus suggesting a critical role of this residue in maintaining a dynamic dimer-monomer interconversion and conformational flexibility of the switch motifs. Consistently, substituting R1441 for other arbitrary mutations (R1441K/S/T) lead to similar perturbation of GTPase activity and dimerization defects as observed in the disease-associated mutants. Locking the ROC domain in either dimeric or monomeric conformations by engineered disulfide bond alters the binding affinity to GTP (but not GDP) and significantly reduce GTPase activity, thus suggesting that the dynamic dimer-monomer interconversion and conformational plasticity are essential for ROC function as a molecular switch modulating the kinase activity of LRRK2.