ABSTRACT
The innate immune system is critical for clearing infection, and is tightly regulated to avert excessive tissue damage. Nod1/2-Rip2 signaling, which is essential for initiating the innate immune response to bacterial infection and ER stress, is subject to many regulatory mechanisms. In this study, we found that LRRK2, encoded by a gene implicated in Crohn's disease, leprosy and familial Parkinson's disease, modulates the strength of Nod1/2-Rip2 signaling by enhancing Rip2 phosphorylation. LRRK2 deficiency markedly reduces cytokine production in macrophages upon Nod2 activation by muramyl dipeptide (MDP), Nod1 activation by D-gamma-Glu-meso-diaminopimelic acid (iE-DAP) or ER stress. Our biochemical study shows that the presence of LRRK2 is necessary for optimal phosphorylation of Rip2 upon Nod2 activation. Therefore, this study reveals that LRRK2 is a new positive regulator of Rip2 and promotes inflammatory cytokine induction through the Nod1/2-Rip2 pathway.
Subject(s)
Animals , Humans , Mice , Cytokines , Genetics , Allergy and Immunology , HEK293 Cells , Immunity, Innate , Genetics , Inflammation , Genetics , Allergy and Immunology , Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 , Genetics , Allergy and Immunology , Mice, Knockout , Nod1 Signaling Adaptor Protein , Genetics , Allergy and Immunology , Nod2 Signaling Adaptor Protein , Genetics , Allergy and Immunology , Phosphorylation , Genetics , Allergy and Immunology , Receptor-Interacting Protein Serine-Threonine Kinase 2 , Genetics , Allergy and Immunology , Receptor-Interacting Protein Serine-Threonine Kinases , Genetics , Allergy and Immunology , Signal Transduction , Genetics , Allergy and ImmunologyABSTRACT
<p><b>INTRODUCTION</b>The G2385R and R1628P LRRK2 gene variants have been associated with an increased risk of Parkinson's disease (PD) in the Asian population. Recently, a new LRRK2 gene variant, A419V, was reported to be a third risk variant for PD in Asian patients. Our objective was to investigate this finding in our cohort of Asian subjects.</p><p><b>MATERIALS AND METHODS</b>Eight hundred and twenty-eight subjects (404 PD patients, and 424 age and gender-matched control subjects without neurological disorders) were recruited. Genotyping was done by Taqman® allelic discrimination assay on an Applied Biosystems 7500 Fast Real-Time PCR machine.</p><p><b>RESULTS</b>The heterozygous A419V genotype was found in only 1 patient with PD, compared to 3 in the control group (0.4% vs 1.3%), giving an odds ratio of 0.35 (95% confidence interval (CI), 0.01 to 3.79; P = 0.624).</p><p><b>CONCLUSION</b>A419V is not an important LRRK2 risk variant in our Asian cohort of patients with PD. Our data are further supported by a literature review which showed that 4 out of 6 published studies reported a negative association of this variant in PD.</p>
Subject(s)
Adolescent , Adult , Aged , Aged, 80 and over , Female , Humans , Male , Middle Aged , Young Adult , Alanine , Genetics , Case-Control Studies , China , Ethnology , Cohort Studies , Cytosine , Gene Frequency , Genetic Variation , Genetics , Genotype , Heterozygote , India , Ethnology , Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 , Malaysia , Ethnology , Parkinson Disease , Genetics , Polymorphism, Genetic , Genetics , Protein Serine-Threonine Kinases , Genetics , Risk Factors , Singapore , Thymine , Valine , GeneticsABSTRACT
Mutations in LR RK2 (Leucine rich repeat kinase 2) are a major cause of Parkinson's disease (PD). We and others reported recently that expression of the pathogenic gainof-function mutant form of LRRK2, LRRK2 G2019S, induces mitochondrial fission in neurons through DLP1. Here we provide evidence that expression of LRRK2 G2019S stimulates mitochondria loss or mitophagy. We have characterized several LRRK2 interacting proteins and found that LRRK2 interacts with ULK1 which plays an essential role in autophagy. Knockdown of either ULK1 or DLP1 expression with shRNAs suppresses LRRK2 G2019S expression-induced mitochondrial clearance, suggesting that LRRK2 G2019S expression induces mitochondrial fission through DLP1 followed by mitophagy via an ULK1 dependent pathway. In addition to ULK1, we found that LRRK2 interacts with the endogenous MKK4/7, JIP3 and coordinates with them in the activation of JNK signaling. Interestingly, LRRK2 G2019S-induced loss of mitochondria can also be suppressed by 3 different JNK inhibitors, implying the involvement of the JNK pathway in the pathogenic mechanism of mutated LRRK2. Thus our findings may provide an insight into the complicated pathogenesis of PD as well as some clues to the development of novel therapeutic strategies.
Subject(s)
Humans , Amino Acid Substitution , Autophagosomes , Metabolism , Pathology , Autophagy-Related Protein-1 Homolog , Chemistry , Genetics , Metabolism , GTP Phosphohydrolases , Genetics , Metabolism , Gene Knockdown Techniques , HeLa Cells , Intracellular Signaling Peptides and Proteins , Chemistry , Genetics , Metabolism , Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 , Chemistry , Genetics , Metabolism , MAP Kinase Signaling System , Microtubule-Associated Proteins , Genetics , Metabolism , Mitophagy , Genetics , Physiology , Mitochondrial Proteins , Genetics , Metabolism , Mutant Proteins , Chemistry , Genetics , Metabolism , Mutation , Parkinson Disease , Genetics , Metabolism , Pathology , Protein Interaction Domains and Motifs , Recombinant Proteins , Chemistry , Genetics , MetabolismABSTRACT
The leucine-rich repeat kinase2 (LRRK2) has been identified to be the gene causing autosomal dominant inherited Parkinson's disease(PD)8. The clinical features of this type of PD are similar to those of idiopathic PD, but the pathological changes are diverse. The mutation types and frequencies of the LRRK2 distribute unevenly in different populations. LRRK2 is a large complex protein with multiple functions and expresses widely in human body. Sequence alignment shows that LRRK2 might be a multiple function kinase for substrate phosphorylation and might also act as a scaffolding protein. Further study on the physiological function and pathogenic mechanism of LRRK2 will help to find out the possible pathogenesis and new treatment for PD.
Subject(s)
Animals , Humans , Racial Groups , Genetics , Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 , Mutation , Parkinson Disease , Genetics , Pathology , Protein Serine-Threonine Kinases , Chemistry , Genetics , Metabolism , Sequence AlignmentABSTRACT
The recent identification of a common genetic variant (LRRK2 G2385R) which is associated with a two-fold increased risk of sporadic Parkinson's Disease (PD) in two independent Chinese populations in Singapore and Taiwan has generated considerable excitement. Thus far, this variant appears specific for the Asian population, emphasising further that ethnic-specific effects should be considered in genetic association studies. Cautious optimism is advised as we await more scientific studies and clarification if this risk variant is specific to ethnic Chinese race. Our in-vitro studies suggest the Gly2385Arg variant is biologically relevant and it might act through pro-apoptotic mechanisms, especially under cellular stresses. This may provide a partial explanation why some carriers develop the disease while others do not. The presence of other epigenetic factors, gene-gene and gene-environmental interaction could modulate the phenotype expression. Further validation of these findings would be needed to confirm this variant as the single most important common genetic risk factor in ethnic Chinese and/or Asian PD patients. The identification of the LRRK2 Gly2385Arg variant could potentially facilitate the development of clinical, bioimaging, genetic and biological biomarkers, useful in the monitoring and neuroprotective therapy in asymptomatic individuals.