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 (Roc_R1441H) 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.Mutation in leucine-rich-repeat kinase 2 (LRRK2) is a common cause of Parkinson disease (PD) (1–5). LRRK2 is a large (2,527-aa) multidomain protein consisting of seven putative domains (2), including a Ras-like GTPase domain called Ras of complex proteins (Roc), followed by a domain called C-terminal of Roc (COR), which is then followed by a kinase domain (Kin). It remains unclear how perturbations of these activities result in disease; however, the most common mutation in LRRK2-associated PD, G2019S in the kinase domain, shows higher kinase activity than wild type; therefore, its overactivation might be associated with disease pathogenesis (6).The tandem Roc-COR-Kin arrangement suggests that their activities might be coupled such that the GTPase activity of Roc might modulate the kinase activity. Indeed, several studies have shown that GTP binding to the Roc domain regulates the activity of the Kin domain (7, 8). Moreover, a PD-associated mutation in the Roc domain (R1441C) has been shown to have higher kinase activity (9), thus suggesting that mutations in the Roc domain, also up-regulate kinase activity.Understanding the function of Roc and its mechanism of action is important for understanding the mechanism of PD pathogenesis and therapeutic development. However, because of the lack sufficient quantity of protein samples amendable for detailed investigations, the biochemical properties and enzymatic activities of the Roc domain of LRRK2 are poorly understood.Here, we describe a stably folded construct of human Roc domain that enabled us to investigate quantitatively its biochemical and enzymatic properties. The results revealed that a PD-causing mutation R1441H in the Roc domain renders it less active at hydrolyzing GTP, as well as having higher affinity for GTP, than its wild-type counterpart, thereby increasing the residence time of its GTP-bound “active state,” which is associated with PD pathogenesis (8).     

Prevalence,specificity and risk of red blood cell alloantibodies among hospitalised Hubei Han Chinese patients

Background

The prevalence, specificity and risk of red blood cell alloantibodies vary widely among different geographic areas, races, and diseases and according to different methods of study, but no data are available on the Chinese Han population, who were investigated in the present study.

Materials and methods

Antibody screening was conducted among 42,517 hospitalised Hubei Han Chinese individuals using column agglutination technology. Samples that were positive in antibody screening were subjected to antibody identification by the tube test. Clinical data, including gender, age, race, transfusion history and records of alloantibody detection, transfusion reactions or haemolytic disease of the newborn, were collected to analyse the prevalence and specificity of alloantibodies and complications associated with them.

Results

A total of 212 patients with alloantibodies were identified among 42,517 patients, yielding a prevalence of 0.50% in this study. Significantly different prevalence rates were observed according to age and sex. The most frequently identified alloantibodies were anti-E (87/212, 41.0%), anti-D (45/212, 21.2%), anti-M (41/212, 19.3%) and a combination of anti-E and anti-c (13/212, 6.1%). Haemolytic disease was observed in 13 infants with anti-D, three infants with anti-E and one infant with anti-Fy^a alloantibodies. Delayed haemolytic transfusion reactions occurred in four patients with alloantibodies.

Discussion

In hospitalised Hubei Han Chinese individuals, the overall prevalence of alloantibodies was 0.50%, with anti-E, anti-D and anti-M being the most frequently identified alloantibodies. These results indicate that anti-D and anti-E alloantibodies were major risk factors for haemolytic disease of the newborn or delayed haemolytic transfusion reactions in this study population.     

Autophagy and oxidative stress in gliomas with IDH1 mutations

IDH1 mutations in gliomas associate with longer survival. Prooxidant and antiproliferative effects of IDH1 mutations and its d-2-hydroxyglutarate (2-HG) product have been described in vitro, but inconsistently observed. It is also unclear whether overexpression of mutant IDH1 in wild-type cells accurately phenocopies the effects of endogenous IDH1-mutations on tumor apoptosis and autophagy. Herein we investigated the effects of 2-HG and mutant IDH1 overexpression on proliferation, apoptosis, oxidative stress, and autophagy in IDH1 wild-type glioma cells, and compared those results with patient-derived tumors. 2-HG reduced viability and proliferation of U87MG and LN18 cells, triggered apoptosis in LN18 cells, and autophagy in U87MG cells. In vitro studies and flank xenografts of U87MG cells overexpressing R132H IDH1 exhibited increased oxidative stress, including increases of both manganese superoxide dismutase (MnSOD) and p62. Patient-derived IDH1-mutant tumors showed no significant differences in apoptosis or autophagy, but showed p62 accumulation and actually trended toward reduced MnSOD expression. These data indicate that mutant IDH1 and 2-HG can induce oxidative stress, autophagy, and apoptosis, but these effects vary greatly according to cell type.     

Emotion dysregulation as a maintenance factor of borderline personality disorder features

We examined within-individual changes in emotion dysregulation over the course of one year as a maintenance factor of borderline personality disorder (BPD) features. We evaluated the extent to which (1) BPD symptom severity at baseline predicted within-individual changes in emotion dysregulation and (2) within-individual changes in emotion dysregulation predicted four BPD features at 12-month follow-up: affective instability, identity disturbances, negative relationships, and impulsivity. The specificity of emotion dysregulation as a maintaining mechanism of BPD features was examined by controlling for a competing intervening variable, interpersonal conflict. BPD symptoms at baseline predicted overall level and increasing emotion dysregulation. Additionally, increasing emotion dysregulation predicted all four BPD features at 12-month follow-up after controlling for BPD symptoms at baseline. Further, overall level of emotion dysregulation mediated the association between BPD symptom severity at baseline and both affective instability and identity disturbance at 12-month follow-up, consistent with the notion of emotion dysregulation as a maintenance factor. Future research on the malleability of emotion dysregulation in laboratory paradigms and its effects on short-term changes in BPD features is needed to inform interventions.     

Whipple disease revealed by lung involvement: a case report and literature review

We report the case of a man with a history of intermittent fever and arthritis who presented with a dry cough and associated lung involvement, who was eventually given the diagnosis of Whipple disease. The pulmonary symptoms preceded the development of GI manifestations. Five years later, periodic acid-Schiff (PAS)-positive macrophages were identified in duodenal biopsy specimens and polymerase chain reaction for Tropheryma whipplei was positive in the duodenum, stools, saliva, and cerebrospinal fluid. Pulmonary T whipplei was retrospectively confirmed by positive PAS staining and immunoreactivity to specific antibodies in endobronchial biopsy specimens. Antibiotic treatment was followed by remission. A literature review identified eight other cases of Whipple disease presenting with lung parenchymal involvement, predominantly interstitial lung disease (ILD), and without initial GI symptoms. In the absence of GI symptoms, a diagnosis of Whipple disease should be considered in middle-aged men presenting with ILD or lung nodules, if the patient has a history of unexplained arthralgia and/or fever. The association of mediastinal adenopathy or pleural effusion offers additional concern. Whipple disease may be fatal in the absence of treatment, but prolonged antibiotic treatment often leads to complete remission.     

Small fibre dysfunction,microvascular complications and glycaemic control in type 1 diabetes: a case–control study

Aims/hypothesis  

The aim of this study was to determine the influence of microvascular disease on C-fibre function in patients with type 1 diabetes of moderate duration.     

Mouse hypothalamic GT1-7 cells demonstrate AMPK-dependent intrinsic glucose-sensing behaviour

Aims/hypothesis  

Hypothalamic glucose-excited (GE) neurons contribute to whole-body glucose homeostasis and participate in the detection of hypoglycaemia. This system appears defective in type 1 diabetes, in which hypoglycaemia commonly occurs. Unfortunately, it is at present unclear which molecular components required for glucose sensing are produced in individual neurons and how these are functionally linked. We used the GT1-7 mouse hypothalamic cell line to address these issues.