The role of the LRRK2 gene in Parkinsonism

Parkinson’s disease (PD), like many common age-related conditions, has been recognized to have a substantial genetic component. Multiple lines of evidence suggest that Leucine-rich repeat kinase 2 (LRRK2) is a crucial factor to understanding the etiology of PD. LRRK2 is a large, widely expressed, multi-domain and multifunctional protein. LRRK2 mutations are the major cause to inherited and sporadic PD. In this review, we discuss the pathology and clinical features which show diversity and variability of LRRK2-associated PD. In addition, we do a thorough literature review and provide theoretical data for gene counseling. Further, we present the evidence linking LRRK2 to various possible pathogenic mechanism of PD such as α-synuclein, tau, inflammatory response, oxidative stress, mitochondrial dysfunction, synaptic dysfunction as well as autophagy-lysosomal system. Based on the above work, we investigate activities both within GTPase and outside enzymatic regions in order to obtain a potential therapeutic approach to solve the LRRK2 problem.     

Current knowledge and recent insights into the genetic basis of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is the most frequent motor neuron disease, affecting the upper and/or lower motor neurons. However, extramotor symptoms can also occur; cognitive deficits are present in more than 40% of patients and 5–8% of ALS patients develop frontotemporal dementia. There is no effective treatment for ALS and median survival is 2–3 years after onset.Amyotrophic lateral sclerosis is a genetically heterogeneous disorder with monogenic forms as well as complex genetic etiology. Currently, complex genetic risk factors are of minor interest for routine diagnostic testing or counseling of patients and their families. By contrast, a monogenic cause can be identified in 70% of familial and 10% of sporadic ALS cases. The most frequent genetic cause is a noncoding hexanucleotide repeat expansion in the C9orf72 gene. In recent years, high-throughput sequencing technologies have helped to identify additional monogenic and complex risk factors of ALS.Genetic counseling should be offered to all ALS patients and their first- and possibly second-degree relatives, and should include information about the possibilities and limitations of genetic testing. Routine diagnostic testing should at least encompass the most frequently mutated disease genes (C9orf72, SOD1, TDP-43, FUS). Targeted sequencing approaches including further disease genes may be applied. Caution is warranted as the C9orf72 repeat expansion cannot be detected by routine sequencing technologies and testing by polymerase chain reaction (PCR) is failure-prone.Predictive testing is possible in families in which a genetic cause has been identified, but the limitations of genetic testing (i.?e., the problems of incomplete penetrance, variable expressivity and possible oligogenic inheritance) have to be explained to the families.     

Parkin stabilizes PINK1 through direct interaction

Parkinson disease (PD) is the most common movement disorder and is characterized by dopaminergic dysfunction. The majority of PD cases are sporadic; however, the discovery of genes linked to rare familial forms of the disease has provided crucial insight into the molecular mechanisms of disease pathogenesis. Multiple genes mediating familial forms of Parkinson’s disease (PD) have been identified, such as parkin (PARK2) and phosphatase and tensin homologue deleted on chromosome ten (PTEN)-induced putative kinase 1: PINK1 (PARK6). Here, we showed that Parkin directly interacts with PINK1, but did not bind to pathogenic PINK1 mutants. Parkin, but not its pathogenic mutants, stabilizes PINK1 by interfering with its degradation via the ubiquitin-mediated proteasomal pathway. In addition, the interaction between Parkin and PINK1 resulted in reciprocal reduction of their solubility. Our results indicate that Parkin regulates PINK1 stabilization via direct interaction with PINK1, and operates through a common pathway with PINK1 in the pathogenesis of early-onset PD.     

PARK2 gene variants in Korean patients with Parkinson’s disease

Mutations in PARK2 are considered a common cause of Parkinson’s disease (PD). To assess the frequency of PARK2 mutations in the Korean population, we screened the PARK2 gene in 83 Korean PD patients: two young onset (YO, ≤ 49), 32 middle onset (MO, 50–69) and 49 late onset (LO, ≥ 70). Detection of the point mutations was performed by direct sequencing of the PARK2 exons, and exonic rearrangements were analyzed using multiplex ligation-dependent probe amplification. Five known PARK2 variants were identified in 53 (63.9 %) of the Korean PD patients: two missense mutations (Y267H and M458L) and three polymorphisms (S167N, L272I and V380L). We also found an increased frequency of PARK2 variants in PD patients and a lowered PD age at onset (AAO) in those having two variants, suggesting that the genetic variation in PARK2 gene might be a genetic risk factor of PD in Korean population.     

The relevance of <Emphasis Type="Italic">ABCA1</Emphasis> R219K polymorphisms and serum ABCA1 protein concentration to Parkinson’s disease pathogenesis and classification: a case–control study

To investigate the relevance of ABCA1 R219K polymorphisms and serum ABCA1 protein concentration to Parkinson’s disease (PD) pathogenesis and classification in Chinese population. Between June 2013 to January 2014, 108 patients diagnosed with PD at Department of Neurology, Tangshan People’s Hospital, Tangshan were enrolled in the PD group, and 123 healthy individuals, from Health Screening Center of the same hospital, with matched age, gender, and education were enrolled in the control group. Polymerase chain reaction–restriction fragment length polymorphism method was used to detect ABCA1 R219K polymorphisms and enzyme-linked immunosorbent assay used to measure serum ABCA1 concentrations. Frequencies of R/K and K/K genotypes, and K allele of ABCA1 R219K polymorphisms were significantly lower in the PD group than the control group (all P < 0.05). Significant differences existed in distributions of genotype frequencies, including R/R, R/K and K/K, between PD and control group of each classification (all P < 0.05). ABCA1 concentrations were significantly different in the PD and control group (P < 0.05); also ABCA1 concentrations were very different among PD patients with different genotypes (all P < 0.05). Serum concentrations of ABCA1were significantly different among PD patients in different classifications (all P < 0.05), suggesting the negative correlation between ABCA1 serum concentration and PD classification (r = ?0.776, P < 0.05). And serum concentrations of ABCA1 showed obvious differences among cases with three different genotypes in each classification (all P < 0.05). ABCA1 R219K polymorphisms and serum concentration were associated with pathogenesis and classification of PD, and K allele may be a protective genetic factor.     

No genetic association between attention-deficit/hyperactivity disorder (ADHD) and Parkinson’s disease in nine ADHD candidate SNPs

Attention-deficit/hyperactivity disorder (ADHD) and Parkinson’s disease (PD) involve pathological changes in brain structures such as the basal ganglia, which are essential for the control of motor and cognitive behavior and impulsivity. The cause of ADHD and PD remains unknown, but there is increasing evidence that both seem to result from a complicated interplay of genetic and environmental factors affecting numerous cellular processes and brain regions. To explore the possibility of common genetic pathways within the respective pathophysiologies, nine ADHD candidate single nucleotide polymorphisms (SNPs) in seven genes were tested for association with PD in 5333 cases and 12,019 healthy controls: one variant, respectively, in the genes coding for synaptosomal-associated protein 25 k (SNAP25), the dopamine (DA) transporter (SLC6A3; DAT1), DA receptor D4 (DRD4), serotonin receptor 1B (HTR1B), tryptophan hydroxylase 2 (TPH2), the norepinephrine transporter SLC6A2 and three SNPs in cadherin 13 (CDH13). Information was extracted from a recent meta-analysis of five genome-wide association studies, in which 7,689,524 SNPs in European samples were successfully imputed. No significant association was observed after correction for multiple testing. Therefore, it is reasonable to conclude that candidate variants implicated in the pathogenesis of ADHD do not play a substantial role in PD.     

Multiple Causes for Delay in Arrival at Hospital in Acute Stroke Patients in Aydin, Turkey

Background

Mutations in the genes PRKN and LRRK2 are the most frequent known genetic lesions among Parkinson's disease patients. We have previously reported that in the Portuguese population the LRRK2 c.6055G > A; p.G2019S mutation has one of the highest frequencies in Europe.

Methods

Here, we follow up on those results, screening not only LRRK2, but also PRKN, SNCA and PINK1 in a cohort of early-onset and late-onset familial Portuguese Parkinson disease patients. This series comprises 66 patients selected from a consecutive series of 132 patients. This selection was made in order to include only early onset patients (age at onset below 50 years) or late-onset patients with a positive family history (at least one affected relative). All genes were sequenced bi-directionally, and, additionally, SNCA, PRKN and PINK1 were subjected to gene dosage analysis.

Results

We found mutations both in LRRK2 and PRKN, while the remaining genes yielded no mutations. Seven of the studied patients showed pathogenic mutations, in homozygosity or compound heterozygosity for PRKN, and heterozygosity for LRRK2.

Conclusion

Mutations are common in Portuguese patients with Parkinson's disease, and these results clearly have implications not only for the genetic diagnosis, but also for the genetic counseling of these patients.     

Uncovering the roles of PINK1 and parkin in mitophagy

Parkinson disease (PD) is the second most prevalent neurodegenerative disorder, and thus elucidation of the pathogenic mechanism and establishment of a fundamental cure is essential in terms of public welfare. Fortunately, our understanding of the pathogenesis of two types of recessive familial PDs—early-onset familial PD caused by dysfunction of the PTEN-induced putative kinase 1 (PINK1) gene and autosomal recessive juvenile Parkinsonism (ARJP) caused by a mutation in the Parkin gene—has evolved and continues to expand.Key words: PINK1, parkin, ubiquitin, mitochondria, autophagy, mitophagy, membrane potential, quality controlSince the cloning of PINK1 and Parkin, numerous papers have been published about the corresponding gene products, but the mechanism by which dysfunction of PINK1 and/or Parkin causes PD remain unclear. Parkin encodes a ubiquitin ligase E3, a substrate recognition member of the ubiquitination pathway, whereas PINK1 encodes a mitochondria-targeted serine-threonine kinase that contributes to the maintenance of mitochondrial integrity. Based on their molecular functions, it is clear that Parkin-mediated ubiquitination and PINK1 phosphorylation are key events in disease pathogenesis. The underlying mechanism, however, is not as well defined and claims of pathogenicity, until recently, remained controversial. Although Parkin''s E3 activity was clearly demonstrated in vitro, we were unable to show a clear E3 activity of Parkin in cell/in vivo. In addition, despite a predicted mitochondrial localization signal for PINK1, we were unable to detect PINK1 on mitochondria by either immunoblotting or immunocytochemistry. More confusingly, overexpression of nontagged PINK1 mainly localized to the cytoplasm under steady state conditions.Work by Dr. Youle''s group at the National Institutes of Health in 2008, however, offered new insights. They reported that Parkin associated with depolarized mitochondria and that Parkin-marked mitochondria were subsequently cleared by autophagy. Soon after their publication, we also examined the function of Parkin and PINK1 following a decrease in mitochondrial membrane potential. Our findings, described below (Fig. 1), have contributed to the development of a mechanism explaining pathogenicity.Open in a separate windowFigure 1Model of mitochondrial quality control mediated by PINK1 and Parkin. Under steady-state conditions, the mature 60 kDa PINK1 is constantly cleaved by an unknown protease to a 50 kDa intermediate form that is subsequently degraded, presumably by the proteasome (upper part). The protein, however, is stabilized on depolarized mitochondria because the initial processing event is inhibited by a decrease in mitochondrial membrane potential (lower part). Accumulated PINK1 recruits cytosolic Parkin onto depolarized mitochondria resulting in activation of its E3 activity. Parkin then ubiquitinates a mitochondrial substrate(s). As a consequence, damaged mitochondria are degraded via mitophagy. Ub, ubiquitin.(1) We sought to determine the subcellular localization of endogenous PINK1, and realized that endogenous PINK1 is barely detectable under steady-state conditions. However, a decrease in mitochondrial membrane-potential following treatment with the mitochondrial uncoupler carbonyl cyanide m-chlorophenylhydrazone (CCCP) results in the gradual accumulation of endogenous PINK1 on mitochondria. Importantly, when CCCP is washed out, the accumulated endogenous PINK1 rapidly disappears (within 30 min) both in the presence and absence of cycloheximide. These results support the hypothesis that PINK1 is constantly transported to the mitochondria, but is rapidly degraded in a membrane potential-dependent manner (see below for details). We speculate that PINK1 is stabilized by a decrease in mitochondrial membrane potential and as a result accumulates on depolarized mitochondria.(2) We examined the potential role of PINK1 in the mitochondrial recruitment of Parkin. In control MEFs (PINK1^+/+), Parkin is selectively recruited to the mitochondria following CCCP treatment, and subsequently results in the selective disappearance of the mitochondria via autophagy (called mitophagy). In sharp contrast, Parkin is not translocated to the mitochondria in PINK1 knockout (PINK1^−/−) MEFs following CCCP treatment, and subsequent mitochondrial degradation is also completely impeded. These results suggest that PINK1 is “a Parkin-recruitment factor” that recruits Parkin from the cytoplasm to damaged mitochondria in a membrane potential-dependent manner for mitophagy.(3) We monitored the E3 activity of Parkin using an artificial pseudo-substrate fused to Parkin in cells. Parkin''s E3 activity was repressed under steady-state conditions; however, we find that Parkin ubiquitinates the pseudo-substrate when it is retrieved to the depolarized mitochondria, suggesting that activation of the latent Parkin E3 activity is likewise dependent on a decrease in mitochondrial membrane potential.(4) PINK1 normally exists as either a long (approximately 60 kDa) or a short (approximately 50 kDa) protein. Because the canonical mitochondrial targeting signal (matrix targeting signal) is cleaved after import into the mitochondria, the long form has been designated as the precursor and the short form as the mature PINK1. However, our subcellular localization study of endogenous PINK1 following CCCP treatment shows that the long form is recovered in the mitochondrial fraction, suggesting that it is not the pre-import precursor form. Moreover, by monitoring the degradation process of PINK1 following recovery of membrane potential, we realized that the short form of PINK1 transiently appears soon after CCCP is washed out and then later disappears, suggesting that the processed form of PINK1 is an intermediate in membrane-potential-dependent degradation. In conclusion, these results imply that PINK1 cleavage does not reflect a canonical maturation process accompanying mitochondrial import as initially thought, but rather represents constitutive degradation in healthy mitochondria by a two-step mechanism; i.e., first limited processing and subsequent complete degradation probably via the proteasome.(5) PINK1 accumulation by decrease of membrane potential and subsequent recruitment of Parkin onto mitochondria are presumably etiologically important because they are impeded for the most part by disease-linked mutations of PINK1 or Parkin.These results, together with reports by other groups, strongly suggest that recessive familial PD is caused by dysfunction of quality control for depolarized mitochondria.At present, we do not know whether the aforementioned pathogenic mechanism of recessive familial PD can be generalized to prevalent sporadic PD. However, the clinical symptoms of recessive familial PD caused by dysfunction of PINK1 or Parkin resembles that of idiopathic PD except early-onset pathogenesis, and thus it is plausible that there is a common pathogenic mechanism. We accordingly believe that our results provide solid insight into the molecular mechanisms of PD pathogenesis, not only for familial forms caused by Parkin and PINK1 mutations, but also the major sporadic form of PD.To fully understand the molecular mechanism of PINK1-Parkin-mediated mitophagy, further details need to be addressed including: identifying the protease(s) that processes PINK1 in a mitochondrial membrane-potential dependent manner and that presumably monitors mitochondrial integrity; identifying a physiological substrate(s) of PINK1; determining the molecular mechanism underlying Parkin activation; and identifying the protein(s) linking Parkin-mediated ubiquitination to mitophagy. A detailed mechanism of the aforementioned events will be the focus of future research, however, we feel our conclusion that PINK1 and Parkin function in the removal of depolarized mitochondria is evident and hope that our studies will provide a solid foundation for further studies.     

X-chromosomale Intelligenzminderung

X-linked intellectual disability (XLID) is a heterogeneous disorder; more than 100 XLID genes have been identified so far. Fragile X syndrome with CGG repeat expansions in the 5’-UTR of FMR1, is the most frequent monogenic form of ID. Other XLID genes with a comparatively high prevalence of mutations are ATRX, RPS6KA3, GPC3, SLC16A2, SLC6A8, and ARX. The causes of XLID are distributed as follows: molecular genetically proven mutations in 90% and copy-number variations (CNVs) in approximately 10%. Common CNVs are duplications of Xq28 that include MECP2 and the Xp11.22 duplication syndrome, with overexpression of HUWE1. Using current investigative methods, mutations in X?chromosomal genes can be proven to be the underlying cause in approximately 10% of male patients with ID. Over the next few years, new discoveries are to be expected, primarily in the noncoding regions of the X?chromosome, where further causes of the preponderance in male patients, which has not yet been fully explained, are presumably to be sought.     

Impact of neutrophil-to-lymphocyte ratio on periprocedural myocardial infarction in patients undergoing non-urgent percutaneous coronary revascularisation

Background

Pro-thrombotic conditions importantly influence myocardial perfusion and procedural results after percutaneous coronary intervention (PCI). The neutrophil-to-lymphocyte ratio (NLR) has emerged as a predictor of cardiovascular events and of long-term prognosis, especially in ST-elevation myocardial infarction patients undergoing primary PCI. The aim of our study was to evaluate the role of NLR on periprocedural myocardial infarction (MI) in patients undergoing non-urgent PCI.

Methods

In a consecutive cohort of 1542 patients undergoing PCI, myonecrosis biomarkers were determined at 6, 12, 24 and 48 hours post-procedure. Patients were divided into quintiles according to NLR values. Periprocedural myonecrosis was defined as a troponin I increase of 3 times the upper limit of normal or as 50?% of an elevated baseline value, whereas periprocedural MI was defined as a CK-MB increase of 3 times the upper limit of normal or 50?% of baseline.

Results

Higher NLR was related to age, established risk factors and cardiovascular history. NLR was associated with severe coronary artery disease (p = 0.009), tighter stenosis (p < 0.001), coronary calcifications (p = 0.005), intracoronary thrombus or thrombectomy use (p < 0.001), TIMI flow pre- and post-PCI (p < 0.001), and inversely to restenosis (p = 0.04) and use of a drug-eluting stent (p = 0.001). NLR did not influence the occurrence of myonecrosis (p = 0.75; adjusted OR (95?% CI) = 0.99 (0.63–1.54), p = 0.96), but was associated with a higher occurrence of periprocedural MI, even after correction for baseline differences (p = 0.03; adjusted OR (95?% CI) = 1.33 (1.02–2.3), p = 0.02), with NLR ≥ 3 best predicting the risk of periprocedural MI at the receiver operating characteristic curve analysis.

Conclusion

In patients undergoing non-urgent PCI, a higher NLR increases the risk of periprocedural MI, especially for values ≥ 3.

     

Caenorhabditits elegans LRK-1 and PINK-1 Act Antagonistically in Stress Response and Neurite Outgrowth

Mutations in two genes encoding the putative kinases LRRK2 and PINK1 have been associated with inherited variants of Parkinson disease. The physiological role of both proteins is not known at present, but studies in model organisms have linked their mutants to distinct aspects of mitochondrial dysfunction, increased vulnerability to oxidative and endoplasmic reticulum stress, and intracellular protein sorting. Here, we show that a mutation in the Caenorhabditits elegans homologue of the PTEN-induced kinase pink-1 gene resulted in reduced mitochondrial cristae length and increased paraquat sensitivity of the nematode. Moreover, the mutants also displayed defects in axonal outgrowth of a pair of canal-associated neurons. We demonstrate that in the absence of lrk-1, the C. elegans homologue of human LRRK2, all phenotypic aspects of pink-1 loss-of-function mutants were suppressed. Conversely, the hypersensitivity of lrk-1 mutant animals to the endoplasmic reticulum stressor tunicamycin was reduced in a pink-1 mutant background. These results provide the first evidence of an antagonistic role of PINK-1 and LRK-1. Due to the similarity of the C. elegans proteins to human LRRK2 and PINK1, we suggest a common role of both factors in cellular functions including stress response and regulation of neurite outgrowth. This study might help to link pink-1/PINK1 and lrk-1/LRRK2 function to the pathological processes resulting from Parkinson disease-related mutants in both genes, the first manifestations of which are cytoskeletal defects in affected neurons.Mutations in the Parkinson disease (PD)²-related gene PINK1 have been associated with increased sensitivity to oxidative stress and mitochondrial dysfunction (1–4). Although a series of reports support a localization of PINK1 only in mitochondria (5–7), recent studies have shown that a portion of endogenous PINK1 is also distributed to the cytoplasm (8–11). Notably, the cytoplasmic kinase activity and not the mitochondrial targeting of PINK1 seems to be prerequisite of its protective effects against mitochondrial stress (12).The GTPase-regulated kinase LRRK2, another gene associated with familial PD, has been linked to the biogenesis and regulation of vesicular transport (13, 14). In support of this notion, the C. elegans lrk-1, the LRRK2 homologue, has recently been shown to be involved in synaptobrevin-associated vesicular transport (15). Moreover, the Dictyostelium homologue of LRRK2/LRK-1 proteins, GbpC, a cGMP-binding protein is required for the normal phosphorylation and cytoskeletal assembly of myosin (16). Based on this data, it had been anticipated that PINK1/PINK-1 and LRRK2/LRK-1 might be involved in distinct cellular functions, whereas pathological mutations in both genes, leading either to loss-of-function (PINK1) or gain-of-function (LRRK2), result in a similar phenotype, the loss of dopaminergic neurons.In the present study, we found a functional connection between their Caenorhabditits elegans homologues pink-1 and lrk-1. We demonstrate that loss of C. elegans pink-1 results in oxidative stress sensitivity and neurite outgrowth defects. All aspects of pink-1 deficiency were suppressed in the absence of lrk-1 that, as a single mutant, displayed a profound hypersensitivity to the ER stressor tunicamycin. Because the latter phenotype was in turn suppressed by deleting pink-1, our results support an antagonistic role of pink-1 and lrk-1 in stress response and neuronal activities.     

Genetik der Parkinson-Krankheit

In addition to the nine well-defined monogenic forms of Parkinson’s disease, there are numerous known genetic risk and protective variants that modulate the risk of Parkinson’s disease. Among the monogenic forms, three (PARK1/PARK4, PARK8, PARK17) follow an autosomal dominant mode of inheritance, whereas six are recessively inherited (PARK2, PARK6, PARK7, PARK9, PARK14, PARK15). Six forms have clinical characteristics very similar to those of idiopathic Parkinson’s disease (PARK1/PARK4, PARK2, PARK6, PARK7, PARK8, PARK17). Among the latter forms, late-onset PARK8 with mutations in the LRRK2 gene and early-onset PARK2 caused by mutations in the Parkin gene are by far the most common. Both the monogenic and the idiopathic forms of Parkinson’s disease share common pathophysiological mechanisms involving oxidative modification, impaired protein degradation and mitochondrial dysfunction. Therefore, monogenic forms of Parkinson’s disease can serve as human model diseases for the idiopathic forms.     

突触囊泡循环障碍与帕金森病

帕金森病是人类第二大神经退行性疾病,虽然通过对帕金森病遗传家族的研究已发现不少与之相关的致病基因,然而其病因尚不清楚。在已发现的与帕金森病相关基因中,α-synuclein、LRRK2、Parkin、PINK1以及DJ-1也在调节神经元突触前囊泡的神经递质释放以及突触前囊泡循环过程中发挥重要作用。最近的一些研究表明突触前囊泡循环障碍在帕金森病发病过程中扮演重要角色。本文对上述基因在突触囊泡循环以及其突变导致帕金森病病程中的作用作一概述,并推测囊泡循环障碍在帕金森病发病过程中的作用机理,最后指出目前在该研究领域需要解决的一些问题。     

Earliest Divergence of Stagodontid (Mammalia: Marsupialiformes) Feeding Strategies from the Late Cretaceous (Turonian) of North America

Two new unequivocal stagodontids, Fumodelphodon pulveris, gen. et. sp. nov., and Hoodootherium praeceps, gen. et. sp. nov., are described from the Turonian (~92 Ma) Smoky Hollow Member of the Straight Cliffs Formation, of southern Utah, USA. Mammals from this time period are poorly represented; the recovery of these two large stagodontids demonstrates the early emergence of faunal elements mostly associated with the later Cretaceous. These taxa represent the earliest stagodontids with crushing premolars (Fumodelphodon) and sectorial premolars (Hoodootherium), morphologically similar to the well-known stagodontids Didelphodon and Eodelphis, respectively. The similar morphologies suggest that these two new genera may be early members of later Cretaceous stagodontid clades, implying a ~ 7 Ma ghost lineage leading to Eodelphis and a ~ 15 Ma ghost lineage to Didelphodon. A reexamination of stagodontid characters suggests a basal placement of Pariadens within Stagodontidae, contrary to some recent studies. The discovery of two new stagodontids bearing lower molars morphologically similar to, but premolars distinct from, Eodelphis highlights the importance of the specialized premolar morphology for resolving the relationships between genera within Stagodontidae.     

Role of Glucose Metabolism and ATP in Maintaining PINK1 Levels during Parkin-mediated Mitochondrial Damage Responses

Mutations in several genes, including PINK1 and Parkin, are known to cause autosomal recessive cases of Parkinson disease in humans. These genes operate in the same pathway and play a crucial role in mitochondrial dynamics and maintenance. PINK1 is required to recruit Parkin to mitochondria and initiate mitophagy upon mitochondrial depolarization. In this study, we show that PINK1-dependent Parkin mitochondrial recruitment in response to global mitochondrial damage by carbonyl cyanide m-chlorophenylhydrazine (CCCP) requires active glucose metabolism. Parkin accumulation on mitochondria and subsequent Parkin-dependent mitophagy is abrogated in glucose-free medium or in the presence of 2-deoxy-d-glucose upon CCCP treatment. The defects in Parkin recruitment correlate with intracellular ATP levels and can be attributed to suppression of PINK1 up-regulation in response to mitochondria depolarization. Low levels of ATP appear to prevent PINK1 translation instead of affecting PINK1 mRNA expression or reducing its stability. Consistent with a requirement of ATP for elevated PINK1 levels and Parkin mitochondrial recruitment, local or individual mitochondrial damage via photoirradiation does not affect Parkin recruitment to damaged mitochondria as long as a pool of functional mitochondria is present in the photoirradiated cells even in glucose-free or 2-deoxy-d-glucose-treated conditions. Thus, our data identify ATP as a key regulator for Parkin mitochondrial translocation and sustaining elevated PINK1 levels during mitophagy. PINK1 functions as an AND gate and a metabolic sensor coupling biogenetics of cells and stress signals to mitochondria dynamics.     

Diagnosis of takotsubo cardiomyopathy is increasing over time in patients presenting as ST-elevation myocardial infarction

Background

Takotsubo cardiomyopathy often presents with the clinical signs of ST-elevation myocardial infarction (STEMI). The increase in scientific publications addressing this relatively rare condition may result in higher awareness and diagnosis of takotsubo cardiomyopathy.

Aim

To assess the observed prevalence per year of takotsubo cardiomyopathy in a large registry of patients with STEMI, during a 12-year inclusion period.

Method

All patients presenting with STEMI at a large regional cardiology clinic were entered into a database (n = 8,413, mean age 63 ± 13 years). Takotsubo cardiomyopathy was diagnosed in 42 patients (0.5?%). Years of evaluation were defined as ‘early years’ (January 2002 to December 2007; n = 4350) and ‘later years’ (January 2008 to December 2013). Multivariable analyses were performed to adjust for differences in demographical and clinical variables.

Results

In later years, the age of STEMI patients was slightly higher (64 ± 13 vs. 63 ± 13 years, p < 0.001), with more patients with clinical symptoms of shock (10 vs. 7?%, p < 0.001) or a history of percutaneous coronary intervention or hypertension (10 vs. 8?%, p = 0.001 and 37 vs. 34?%, p < 0.001). Smoking and a positive family history were less often observed during later years (39 vs. 46?%, p < 0.001 and 37 vs. 42?% p < 0.001). Patients with takotsubo cardiomyopathy were more often female (81 vs. 27?%, p = 0.001). Takotsubo cardiomyopathy was more often diagnosed in the later period (0.7 vs. 0.3?%, OR 2.4, 95?% CI 1.2–4.6, p = 0.009). The higher prevalence of takotsubo cardiomyopathy in recent years remained significant after adjustment for differences in patient characteristics (OR 2.1, 95?% CI 1.1–4.3).

Conclusion

Takotsubo cardiomyopathy is currently more often diagnosed in patients with STEMI compared with in earlier years. This is probably due to the increased scientific and clinical awareness among doctors, but the prevalence is still low.

     

Trends in patient characteristics and clinical outcome over 8 years of transcatheter aortic valve implantation

Aim

In the evolving field of transcatheter aortic valve implantations (TAVI) we aimed to gain insight into trends in patient and procedural characteristics as well as clinical outcome over an 8?year period in a real-world TAVI population.

Methods

We performed a single-centre retrospective analysis of 1,011 consecutive patients in a prospectively acquired database. We divided the cohort into tertiles of 337 patients; first interval: January 2009–March 2013, second interval: March 2013–March 2015, third interval: March 2015–October 2016.

Results

Over time, a clear shift in patient selection was noticeable towards lower surgical risks including Society of Thoracic Surgeons predicted risk of mortality score and comorbidity. The frequency of transfemoral TAVI increased (from 66.5 to 77.4%, p?=?0.0015). Device success improved (from 62.0 to 91.5%, p?<?0.0001) as did the frequency of symptomatic relief (≥1 New York Heart Association class difference) (from 73.8 to 87.1%, p?=?0.00025). Complication rates decreased, including in-hospital stroke (from 5.0 to 2.1%, p?=?0.033) and pacemaker implantations (from 10.1 to 5.9%, p?=?0.033). Thirty-day mortality decreased (from 11.0 to 2.4%, p?<?0.0001); after adjustment for patient characteristics, a mortality-risk reduction of 72% was observed (adjusted hazard ratio [HR]: 0.28, 95% confidence interval [CI]: 0.13–0.62). One-year mortality rates decreased (from 23.4 to 11.4%), but this was no longer significant after a landmark point was set at 30 days (mortality from 31 days until 1 year) (adjusted HR: 0.69, 95% CI: 0.41–1.16, p?=?0.16).

Conclusion

A clear shift towards a lower-risk TAVI population and improved clinical outcome was observed over an 8?year period. Survival after TAVI improved impressively, mainly as a consequence of decreased 30-day mortality.