18 research outputs found
Parkinson Disease-Associated Mutation R1441H in LRRK2 Prolongs the “Active State” of its GTPase Domain
Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD). A disease-causing point mutation R1441H/G/C in the GTPase domain of LRRK2 leads to overactivation of its kinase domain. However, the mechanism by which this mutation alters the normal function of its GTPase domain [Ras of complex proteins (Roc)] remains unclear. Here, we report the effects of R1441H mutation (RocR1441H) on the structure and activity of Roc. We show that Roc forms a stable monomeric conformation in solution that is catalytically active, thus demonstrating that LRRK2 is a bona fide self-contained GTPase. We further show that the R1441H mutation causes a twofold reduction in GTPase activity without affecting the structure, thermal stability, and GDP-binding affinity of Roc. However, the mutation causes a twofold increase in GTP-binding affinity of Roc, thus suggesting that the PD-causing mutation R1441H traps Roc in a more persistently activated state by increasing its affinity for GTP and, at the same time, compromising its GTP hydrolysis
Synthesis and Characterization of the Optical Properties of Pt-TiO 2
Composite Pt-doped TiO2 nanotubes (Pt-TNTs) were synthesized via alkaline fusion-hydrothermal method (AFHM) under ambient atmosphere pressure. Further systematic characterization of Pt-TNTs was performed by using XPS, surface photovoltage spectroscopy (SPS), electric field-induced surface photovoltage spectroscopy (FISPS), UV-Vis diffuse reflectance spectrophotometry (UV-Vis), TEM, and XRD. XPS spectrum showed double peaks which accounted for the presence of platinum dioxide and platinum oxide (PtO2 and PtO, PtOxδ+). Composition analysis showed that the particulate matters on surface of Pt-TNTs were composed of PtOxδ+ and TiO2. The results of SPS and FISPS demonstrated that the bound exciton showed sub-band gap transition characteristics with the asymmetric changes of photoelectric property corresponding to changes in polarity and strength of the external electric field. Furthermore, the influence of the changed microstructure morphology of Pt-doped TNTs on both the photovoltage spectroscopy and the lifetime of photogenerated carriers which occurred at the interfaces of Pt-TNTs was observed. Result of XRD indicated that a mixture of anatase and rutile phases prevailed in Pt-TNTs. Contact potential barriers consisting of PtOxδ+, anatase, rutile, and PtOxδ+ are presumed to form upon PtOxδ+ particle that deposited on the surface of Pt-TNTs
Parkinson's disease-associated mutations in the GTPase domain of LRRK2 impair its nucleotide-dependent conformational dynamics
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
A revised 1.6 Å structure of the GTPase domain of the Parkinson’s disease-associated protein LRRK2 provides insights into mechanisms
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
Roco Proteins and the Parkinson’s Disease-Associated LRRK2
Small G-proteins are structurally-conserved modules that function as molecular on-off switches. They function in many different cellular processes with differential specificity determined by the unique effector-binding surfaces, which undergo conformational changes during the switching action. These switches are typically standalone monomeric modules that form transient heterodimers with specific effector proteins in the ‘on’ state, and cycle to back to the monomeric conformation in the ‘off’ state. A new class of small G-proteins called “Roco„ was discovered about a decade ago; this class is distinct from the typical G-proteins in several intriguing ways. Their switch module resides within a polypeptide chain of a large multi-domain protein, always adjacent to a unique domain called COR, and its effector kinase often resides within the same polypeptide. As such, the mechanisms of action of the Roco G-proteins are likely to differ from those of the typical G-proteins. Understanding these mechanisms is important because aberrant activity in the human Roco protein LRRK2 is associated with the pathogenesis of Parkinson’s disease. This review provides an update on the current state of our understanding of the Roco G-proteins and the prospects of targeting them for therapeutic purposes
Roc, the G-domain of the Parkinson’s disease-associated protein LRRK2
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
Short-Term Effects of Carbonaceous Components in PM2.5 on Pulmonary Function: A Panel Study of 37 Chinese Healthy Adults
Objectives: To explore the health effects of indoor/outdoor carbonaceous compositions in PM2.5 on pulmonary function among healthy students living in the local university campus. Methods: Daily peak expiratory flow (PEF) and forced expiratory volume in 1 second (FEV1) were measured among 37 healthy students in the morning and evening for four two-week periods. Concurrent concentrations of indoor and outdoor PM2.5 (particulate matter with an aerodynamic diameter ≤ 2.5μm), carbonaceous components in PM2.5, ambient temperature, and relative humidity in the study area were also obtained. Mixed-effects model was applied to evaluate the associations between carbonaceous components and lung function. Different lags for the carbonaceous components were investigated. Results: In single-pollutant model, a 10 μg/m3 increase of indoor and outdoor EC (elemental carbon) associated with −3.93 (95%CI: −6.89, −0.97) L/min and −3.21 (95%CI: −5.67, −0.75) L/min change in evening PEF at lag 0 day, respectively. Also, a 10 μg/m3 increase of indoor and outdoor POC (primary organic carbon) concentration was significantly associated with −5.82 (95%CI: −10.82, −0.81) L/min and −7.32 (95%CI: −12.93, −1.71) L/min change of evening PEF at lag 0 day. After adjusting total mass of PM2.5, indoor EC consistently had a significant adverse impact on evening PEF and FEV1 at lag3 day and a cumulative effect at lag0-3 day. Conclusions: This study suggests that carbonaceous components in PM2.5 indeed have impacts on pulmonary function among healthy young adults especially on evening PEF. Thus, the local mitigation strategies on pollution are needed
The Association between Preterm Birth and Ambient Air Pollution Exposure in Shiyan, China, 2015–2017
Shortening of the gestational duration has been found associated with ambient air pollution exposure. However, the critical exposure windows of ambient air pollution for gestational duration remain inconsistent, and the association between ambient air pollution and early term births (ETB, 37 to 38 weeks) has rarely been studied relative to preterm births (PTB, 28–37 weeks). A time-series study was conducted in Shiyan, a medium-sized city in China. Birth information was collected from the Shiyan Maternity and Child Health Hospital, and 13,111 pregnant women who gave birth between 2015 and 2017 were included. Data of the concentrations of air pollutants, including PM10, PM2.5, NO2, and SO2 and meteorological data, were collected in the corresponding gestational period. The Cox regression analysis was performed to estimate the relationship between ambient air pollution exposure and the risk of preterm birth after controlling the confounders, including maternal age, education, Gravidity, parity, fetal gender, and delivery mode. Very preterm birth (VPTB, 28–32 weeks) as a subtype of PTB was also incorporated in this study. The risk of VPTB and ETB was positively associated with maternal ambient air pollution exposure, and the correlation of gaseous pollutants was stronger than particulate matter. With respect to exposure windows, the critical trimester of air pollutants for different adverse pregnancy outcomes was different. The exposure windows of PM10, PM2.5, and SO2 for ETB were found in the third trimester, with HRs (hazard ratios) of 1.06 (95%CI: 1.04, 1.09), 1.07 (95%CI: 1.04, 1.11), and 1.28 (95%CI: 1.20, 1.35), respectively. However, for NO2, the second and third trimesters exhibited similar results, the HRs reaching 1.10 (95%CI: 1.03, 6.17) and 1.09 (95%CI: 1.03,1.15), respectively. This study extends and strengthen the evidence for a significant correlation between the ambient air pollution exposure during pregnancy and the risk of not only PTB but, also, ETB. Moreover, our findings suggest that the exposure windows during pregnancy vary with different air pollutants and pregnancy outcomes