Olfactory dysfunction in Parkinsonism caused by PINK1 mutations

Hyposmia is a common nonmotor feature of Parkinson's disease (PD) and has been variably detected in monogenic Parkinsonisms. To assess olfactory dysfunction in PINK1‐related Parkinsonism, we evaluated olfactory detection threshold, odor discrimination, and odor identification in five groups of subjects: sporadic PD (n = 19), PINK1 homozygous (n = 7), and heterozygous (n = 6) parkinsonian patients, asymptomatic PINK1 heterozygous carriers (n = 12), and Italian healthy subjects (n = 67). All affected subjects and all healthy heterozygotes but one resulted hyposmic, with most patients in the range of functional anosmia or severe hyposmia. Detection threshold was more preserved and discrimination more impaired in patients with PINK1 mutations than in PD cases. Alterations of detection and discrimination were observed also in PINK1 asymptomatic heterozygotes. On the contrary, odor identification appeared to be mostly related to the disease status, as it was impaired in nearly all patients (including PD and PINK1 cases) and preserved in healthy heterozygotes. Our data indicate that olfactory dysfunction is common in PINK1 Parkinsonism and consists typically in defective odor identification and discrimination. A milder olfactory deficit, mostly involving discrimination, can be found in asymptomatic heterozygotes, possibly indicating an underlying preclinical neurodegenerative process. © 2009 Movement Disorder Society     

Homozygous and heterozygous PINK1 mutations: considerations for diagnosis and care of Parkinson's disease patients.

The first mutations described in PINK1 were homozygous. More recently, heterozygous mutations have been reported but the role of heterozygosity in disease pathogenesis is still debated. We describe two unrelated cases with PINK1 mutations (homozygous nonsense and heterozygous missense) that highlight issues regarding the role of heterozygous mutations and the utility of genetic screening in patient care.     

PINK1 mutations in a Brazilian cohort of early‐onset Parkinson's disease patients

Data on the frequency of PINK1 mutations in Brazilian patients with early‐onset Parkinson's disease (EOPD) are lacking. The aim of this report was to investigate mutations of the PINK1 gene in a cohort of Brazilian patients with EOPD. Sixty consecutive familial or sporadic EOPD patients were included. All eight PINK1 exons and exon‐intron boundaries were analyzed. We did not find any pathogenic mutation of PINK1 in our cohort. Single Nucleotide Polymorphisms (SNP) were identified in 46.7% of the patients and in 45.9% of controls (P = 0.9). The SNPs identified in our patients had already been described in previous reports. The results of our study support the hypothesis that mutations in PINK1 may not be a relevant cause of EOPD. In Brazil, if we consider only EOPD patients, it seems that parkin and LRRK2 mutations are more common. © 2009 Movement Disorder Society     

The contribution of Parkin,PINK1 and DJ‐1 genes to selective neuronal degeneration in Parkinson's disease

Parkinson's disease (PD) is characterised by selective and severe degeneration of the substantia nigra pars compacta and the locus coeruleus (LC), which underlies the most prominent symptoms. Although α‐synuclein accumulation has long been established to play a causal role in the disease, it alone cannot explain the selective degenerative pattern. Recent evidence shows that the selective vulnerability could arise due to the large presence of cytosolic catecholamines and Ca²⁺ ions in the substantia nigra pars compacta and LC specifically that can be aberrantly affected by α‐synuclein accumulation. Moreover, each has its own toxic potential, and disturbance of one can exacerbate the toxic effects of the others. This presents a mechanism unique to these areas that can lead to a vicious degenerative cycle. Interestingly, in familial variants of PD, the exact same brain areas are affected, implying the underlying process is likely the same. However, the exact disease mechanisms of many of these genetic variants remain unclear. Here, we review the effects of the PD‐related genes Parkin, PINK1 and DJ‐1. We establish that these mutant varieties can set in motion the same degenerative process involving α‐synuclein, cytosolic catecholamines and Ca²⁺. Additionally, we show indications that model organisms might not accurately represent all components of this central mechanism, explaining why Parkin, PINK1 and DJ‐1 model organisms often lack a convincing PD‐like phenotype.     

Familial Parkinsonism with digenic parkin and PINK1 mutations

To clarify the genetic correlation between parkin and PINK1, we screened for PINK1 mutations in 175 parkinsonism patients with parkin mutations. We detected two sibling pairs and one sporadic patient carrying both parkin and PINK1 mutations. The age at onset of Parkinsonism of patients with the digenic mutations was lower than that of patients with the same parkin mutation alone. In addition, two of three patients carrying both parkin and PINK1 mutations had schizophrenia. These findings indicate that PINK1 mutation might modify parkin mutation‐positive Parkinsonism, and PINK1 mutations might be associated withpsychiatric disorders. © 2008 Movement Disorder Society     

PINK1 phosphorylates transglutaminase 2 and blocks its proteasomal degradation

Parkinson's disease (PD) is characterized by progressive dopaminergic neuronal loss and the formation of abnormal protein aggregates, referred to as Lewy bodies (LBs). PINK1 is a serine/threonine protein kinase that protects cells from stress‐induced mitochondrial dysfunction. PINK1 gene mutations cause one form of autosomal recessive early‐onset PD. Transglutaminase 2 (TG2) is an intracellular protein cross‐linking enzyme that has an important role in LB formation during PD pathogenesis. This study identifies PINK1 as a novel TG2 binding partner and shows that PINK1 stabilizes the half‐life of TG2 via inhibition of TG2 ubiquitination and subsequent proteasomal degradation. PINK1 affects TG2 stability in a kinase‐dependent manner. In addition, PINK1 directly phosphorylates TG2 in carbonyl cyanide m‐chlorophenyl hydrazine‐induced mitochondrial damaged states, thereby enhancing TG2 accumulation and intracellular protein cross‐linking products. This study further confirms the functional link between upstream PINK1 and downstream TG2 in Drosophila melanogaster. These data suggest that PINK1 positively regulates TG2 activity, which may be closely associated with aggresome formation in neuronal cells. © 2014 Wiley Periodicals, Inc.     

Induction of parkinsonism‐related proteins in the spinal motor neurons of transgenic mouse carrying a mutant SOD1 gene

Amyotrophic lateral sclerosis is a progressive and fatal disease caused by selective death of motor neurons, and a number of these patients carry mutations in the superoxide dismutase 1 (SOD1) gene involved in ameliorating oxidative stress. Recent studies indicate that oxidative stress and disruption of mitochondrial homeostasis is a common mechanism for motor neuron degeneration in amyotrophic lateral sclerosis and the loss of midbrain dopamine neurons in Parkinson's disease. Therefore, the present study investigated the presence and alterations of familial Parkinson's disease‐related proteins, PINK1 and DJ‐1, in spinal motor neurons of G93ASOD1 transgenic mouse model of amyotrophic lateral sclerosis. Following onset of disease, PINK1 and DJ‐1 protein expression increased in the spinal motor neurons. The activated form of p53 also increased and translocated to the nuclei of spinal motor neurons, followed by increased expression of p53‐activated gene 608 (PAG608). This is the first report demonstrating that increased expression of PAG608 correlates with activation of phosphorylated p53 in spinal motor neurons of an amyotrophic lateral sclerosis model. These results provide further evidence of the profound correlations between spinal motor neurons of amyotrophic lateral sclerosis and parkinsonism‐related proteins. © 2010 Wiley‐Liss, Inc.     

Late onset sporadic Parkinson's disease caused by PINK1 mutations: Clinical and functional study

Homozygous or compound heterozygous mutations in the PINK1 gene represent the second most frequent cause of autosomal recessive parkinsonism after Parkin. The phenotype differs from idiopathic Parkinson's disease for earlier onset, slower disease progression, and better response to therapy. Indeed, the rare patients with onset above 50 years are usually relatives of early‐onset probands. Here, we report the first occurrence of compound heterozygous PINK1 mutations in a sporadic patient with a phenotype indistinguishable from idiopathic Parkinson's disease (PD), with onset in the late seventh decade, rapid progression and good response to levodopa that waned with time. Both mutations (p.A244G and p.V317I) were found to abolish the protective effect of wild‐type PINK1 against staurosporine‐induced apoptosis. These findings further expand the clinical spectrum of PINK1‐related parkinsonism to include late onset, typical PD, and underline the existing difficulties in discriminating between mendelian parkinsonism and idiopathic PD. © 2008 Movement Disorder Society     

A Parkinson's disease gene,DJ‐1, repairs brain injury through Sox9 stabilization and astrogliosis

Defects in repair of damaged brain accumulate injury and contribute to slow‐developing neurodegeneration. Here, we report that a deficiency of DJ‐1, a Parkinson's disease (PD) gene, delays repair of brain injury due to destabilization of Sox9, a positive regulator of astrogliosis. Stereotaxic injection of ATP into the brain striatum produces similar size of acute injury in wild‐type and DJ‐1‐knockout (KO) mice. However, recovery of the injury is delayed in KO mice, which is confirmed by 9.4T magnetic resonance imaging and tyrosine hydroxylase immunostaining. DJ‐1 regulates neurite outgrowth from damaged neurons in a non‐cell autonomous manner. In DJ‐1 KO brains and astrocytes, Sox9 protein levels are decreased due to enhanced ubiquitination, resulting in defects in astrogliosis and glial cell‐derived neurotrophic factor/ brain‐derived neurotrophic factor expression in injured brain and astrocytes. These results indicate that DJ‐1 deficiency causes defects in astrocyte‐mediated repair of brain damage, which may contribute to the development of PD.     

Inhibition of the mitochondrial calcium uniporter rescues dopaminergic neurons in pink1−/− zebrafish

Mutations in PTEN‐induced putative kinase 1 (PINK1) are a cause of early onset Parkinson's disease (PD). Loss of PINK1 function causes dysregulation of mitochondrial calcium homeostasis, resulting in mitochondrial dysfunction and neuronal cell death. We report that both genetic and pharmacological inactivation of the mitochondrial calcium uniporter (MCU), located in the inner mitochondrial membrane, prevents dopaminergic neuronal cell loss in pink1^Y431* mutant zebrafish (Danio rerio) via rescue of mitochondrial respiratory chain function. In contrast, genetic inactivation of the voltage dependent anion channel 1 (VDAC1), located in the outer mitochondrial membrane, did not rescue dopaminergic neurons in PINK1 deficient D. rerio. Subsequent gene expression studies revealed specific upregulation of the mcu regulator micu1 in pink1^Y431* mutant zebrafish larvae and inactivation of micu1 also results in rescue of dopaminergic neurons. The functional consequences of PINK1 deficiency and modified MCU activity were confirmed using a dynamic in silico model of Ca²⁺ triggered mitochondrial activity. Our data suggest modulation of MCU‐mediated mitochondrial calcium homeostasis as a possible neuroprotective strategy in PINK1 mutant PD.     

The rs1572931 polymorphism of the RAB7L1 gene promoter is associated with reduced risk of Parkinson's disease

Abstract

Introduction:

Parkinson's disease (PD) is one of the most common neurologic disorders affecting about 2% of people over 65?years old and both genetic and environmental factors are involved in its aetiology. The genetic part includes several genes and polymorphisms that are the direct cause of disease or its susceptibility factor. The rs1572931 polymorphism of RAB7L1 gene, located in the promoter region, has been recently studied and shown to be strongly associated with reducing risk of PD. In this study, we aim to investigate its association with PD in Iranian population.

Methods:

We examined the association of rs1572931 polymorphism with PD in 490 unrelated Patients and 490 normal controls by PCR–RFLP method in Iranian subjects.

Results:

A significant difference in genotype and allele frequencies was observed between patients and controls (p value?=?0.003, OR (95% CI)?=?0.71(0.56–0.90)). The TT genotype and the T allele were both significantly less frequent in PD cases.

Conclusion:

Our results confirmed the protective effect of the rs1572931 SNP on PD and replicated the results of previous studies, in Iranian subjects. We suggest further studies in other populations.     

褪黑素通过上调泛醌―细胞色素C还原酶核心蛋白1抑制MPP+诱导的MN9D细胞凋亡和线粒体损伤

目的 探讨褪黑素（melatonin,MT）在1-甲基-4-苯基-吡啶离子（1-methyl-4-phenylpyridinium ion,MPP⁺）诱导的帕金森病体外模型中的作用及分子机制。方法 将MN9D细胞分为对照组、MPP⁺组、MT组、治疗组。采用细胞计数试剂盒8检测MT和MPP⁺对细胞活力的影响;采用线粒体膜电位检测试剂盒（JC-1）评价线粒体功能;Hoechst/PI双染法检测细胞凋亡;通过免疫荧光蛋白质印迹法（Western blotting）检测凋亡相关蛋白［Cleaved-Caspase 3和细胞色素C（cytochrome C,CytC）］以及泛醌―细胞色素C还原酶核心蛋白1（ubiquinol-cytochrome C reductase core protein 1,UQCRC1）蛋白的表达;采用干扰RNA技术沉默MN9D细胞中UQCRC1的表达,然后采用Western blotting检测凋亡相关蛋白表达。结果 MT可以减轻MPP⁺诱导的细胞活力下降（P<0.05）;恢复MPP⁺造成的线粒体膜电位下降（P<0.05）;减少MPP⁺诱导的凋亡细胞数量（P<0.05）;抑制凋亡蛋白（CytC和Cleaved-Caspase3）的表达（P<0.05）;上调UQCRC1的表达（P<0.05）。沉默UQCRC1后,MT组和治疗组的UQCRC1表达均下降（P<0.05）;MT对MPP⁺诱导细胞凋亡的保护作用下降（P<0.05）;凋亡蛋白（CytC和Cleaved-Caspase3）的表达增加（P<0.05）。结论 MT对 MPP⁺诱导的多巴胺能神经元损伤具有保护作用,其机制可能是通过上调UQCRC1抑制神经元凋亡。 [国际神经病学神经外科学杂志, 2023, 50(3): 26-31]     

In the hypoxic central nervous system,endothelial cell proliferation is followed by astrocyte activation,proliferation, and increased expression of the α6β4 integrin and dystroglycan

Cerebral hypoxia induces a profound angiogenic response in the central nervous system (CNS). Using a mouse model of chronic cerebral hypoxia, we previously demonstrated that angiogenic vessels in the hypoxic CNS show marked upregulation of the extracellular matrix (ECM) protein fibronectin, along with increased expression of its major receptor, α5β1 integrin on brain endothelial cells (BEC). As cerebral hypoxia also leads to glial activation, the aim of the current study was to define the temporal relationship between BEC responses and glial cell activation in this model of cerebral hypoxia. This revealed that BEC fibronectin/α5β1 integrin expression and proliferation both reached maximal level after 4‐day hypoxia. Interestingly, up to 4‐day hypoxia, all dividing cells were BEC, but at later time‐points proliferating astrocytes were also observed. GFAP staining revealed that hypoxia induced marked astrocyte activation that reached maximal level between 7‐ and 14‐day hypoxia. As newly formed cerebral capillaries require ensheathment by astrocyte end‐feet to acquire mature brain endothelium characteristics, we next examined how expression of astrocyte end‐feet adhesion molecules is regulated by hypoxia. This showed that the astrocyte adhesion receptors α6β4 integrin and dystroglycan were both markedly upregulated, with a time‐course that closely resembled astrocyte activation. Taken together, this evidence shows that cerebral hypoxia promotes first an endothelial response, in which fibronectin promotes BEC proliferation. This is then followed by an astrocyte response, involving astrocyte activation, proliferation, and reorganization of astrocyte end‐feet, which correlates with increased expression of astrocyte end‐feet adhesion molecules. © 2010 Wiley‐Liss, Inc.     

Neuroprotective agent chlomethiazole attenuates c-fos, c-jun, and AP-1 activation through inhibition of p38 MAP kinase.

Recent evidence suggests that stress-activated protein kinases expressed in glial cells have very important roles during cerebral ischemia. The neuroprotective agent chlomethiazole, which is known to enhance the conductance at the GABA(A) receptor complex, is presently in clinical trials for the treatment of severe stroke. Here the authors suggested that chlormethiazole has anti-inflammatory properties because it potently and selectively inhibited p38 mitogen-activated protein (MAP) kinase in primary cortical glial cultures. The inhibition of p38 MAP kinase resulted in the attenuation of the induction of c-fos and c-jun mRNA and AP-1 DNA binding by lipopolysaccharide (LPS). In addition, chlomethiazole inhibited the activation of an AP-1-dependent luciferase reporter plasmid in SK-N-MC human neuroblastoma cells in response to glutamate. Chlomethiazole inhibited the p38 MAP kinase activity as revealed by the decrease in the LPS-induced phosphorylation of the substrates ATF-2 and hsp27, whereas the phosphorylation status of the p38 MAP kinase itself was unaffected. Interestingly, chlomethiazole exhibited an IC(50) of approximately 2 micromol/L for inhibition of c-fos mRNA expression, indicating 25 to 75 times higher potency than reported EC(50) values for enhancing GABA(A) chloride currents. The results indicated a novel mechanism of action of chlomethiazole, and provided support for a distinctive role of p38 MAP kinase in cerebral ischemia.     

Functional modulation of parkin through physical interaction with SUMO-1

Parkinson disease (PD) is the second most common neurodegenerative disorder and is characterized by the extensive and progressive loss of dopaminergic neurons in the CNS substantia nigra pars compacta region. Mutations in the parkin gene, which encodes for E3 ubiquitin ligase, have been implicated in autosomal recessive juvenile parkinsonism, an early-onset and common familial form of PD. Although several parkin substrates have already been identified, the molecular mechanism underlying the regulation of enzymatic activity of parkin has yet to be clarified. In a previous study, we demonstrated that RanBP2 becomes a new target for parkin E3 ubiquitin ligase and is processed via parkin-mediated ubiquitination and subsequent proteasomal degradation. RanBP2, which is localized in the cytoplasmic filament of the nuclear pore complex, belongs to the small ubiquitin-related modifier (SUMO) E3 ligase family. Here we show that parkin appears to bind selectively to the SUMO-1 in vivo and in vitro. Moreover, the physical association of SUMO-1 with parkin results in an increase in the nuclear transport of parkin as well as its self-ubiquitination. Our findings suggest that the E3 ubiquitin ligase activity of parkin and its intracellular localization may be modulated through the SUMO-1 association.