Parkin Deficiency Research Articles

Deficiency of parkin causes neurodegeneration and accumulation of pathological α-synuclein in monkey models.

Parkinson's disease (PD) is characterized by age-dependent neurodegeneration and the accumulation of toxic phosphorylated α-synuclein (pS129-α-syn). The mechanisms underlying these crucial pathological changes remain unclear. Mutations in parkin RBR E3 ubiquitin protein ligase (PARK2), the gene encoding parkin that is phosphorylated by PTEN-induced putative kinase 1 (PINK1) to participate in mitophagy, cause early onset PD. However, current parkin-KO mouse and pig models do not exhibit neurodegeneration. In the current study, we utilized CRISPR/Cas9 technology to establish parkin-deficient monkey models at different ages. We found that parkin deficiency leads to substantia nigra neurodegeneration in adult monkey brains and that parkin phosphorylation decreases with aging, primarily due to increased insolubility of parkin. Phosphorylated parkin is important for neuroprotection and the reduction of pS129-α-syn. Consistently, overexpression of WT parkin, but not a mutant form that cannot be phosphorylated by PINK1, reduced the accumulation of pS129-α-syn. These findings identify parkin phosphorylation as a key factor in PD pathogenesis and suggest it as a promising target for therapeutic interventions.

Protective effects of Parkin knockout on asthma-induced changes in juvenile mice: inflammation, airway resistance, and oxidative stress

Objective This study aimed to explore the effects of Parkin (Prkn) knockout in a juvenile mouse model of asthma. Methods Prkn knockout (KO) and wild type (WT) mice were utilized to establish a juvenile mouse asthma model. The asthma model involved exposure to hyperoxia/ovalbumin (OVA), encompassing hyperoxia from postnatal day 1 (P1) to P7, sensitization on P21 and P28, and challenge from P36 to P42. Room air/phosphate-buffered saline (PBS) served as the control condition. Following airway resistance measurement, bronchoalveolar lavage fluid (BALF) was collected for cellular analysis, and lung tissues were subjected to histological examination and oxidative stress assessment. Serum levels of ovalbumin-specific immunoglobulin E (IgE), total IgE, interleukin-4 (IL-4), IL-5, and IL-13 were quantified using enzyme-linked immunosorbent assay (ELISA). Results WT mice exposed to hyperoxia/OVA showed decreased body weight and increased airway resistance compared to those exposed to control condition. Conversely, KO mice exhibited increased body weight under asthma conditions. KO mice with asthma had reduced total cell counts, along with lower levels of lymphocytes, eosinophils, and neutrophils, compared to WT asthma mice. Histological assessment showed attenuated inflammation and reduced collagen deposition in KO mice relative to WT mice, with lower serum levels of inflammatory markers and improved lung oxidative stress profiles. No significant differences were observed between KO and WT mice under room air/PBS conditions. Conclusions Parkin knockout in juvenile mice mitigates asthma-related alterations in airway resistance, histopathological changes, inflammation status, and oxidative stress. These findings highlight a protective role of Parkin deficiency against asthma-associated pathologies.

Parkin deficiency exacerbates particulate matter-induced injury by enhancing airway epithelial necroptosis

Exposure to fine particulate matter (PM) disrupts the function of airway epithelial barriers causing cellular stress and damage. However, the precise mechanisms underlying PM-induced cellular injury and the associated molecular pathways remain incompletely understood. In this study, we used intratracheal instillation of PM in C57BL6 mice and PM treatment of the BEAS-2B cell line as in vivo and in vitro models, respectively, to simulate PM-induced cellular damage and inflammation. We collected lung tissues and bronchoalveolar lavage fluids to assess histopathological changes, necroptosis, and airway inflammation. Our findings reveal that PM exposure induces necroptosis in mouse airway epithelial cells. Importantly, concurrent administration of a receptor interacting protein kinases 3 (RIPK3) inhibitor or the deletion of the necroptosis effector mixed-lineage kinase domain-like protein (MLKL) effectively attenuated PM-induced airway inflammation. PM exposure dose-dependently induces the expression of Parkin, an E3 ligase we recently reported to play a pivotal role in necroptosis through regulating necrosome formation. Significantly, deletion of endogenous Parkin exacerbates inflammation by enhancing epithelial necroptosis. These results indicate that PM-induced Parkin expression plays a crucial role in suppressing epithelial necroptosis, thereby reducing airway inflammation. Overall, these findings offer valuable mechanistic insights into PM-induced airway injury and identify a potential target for clinical intervention.

Synaptotagmins family affect glucose transport in retinal pigment epithelial cells through their ubiquitination-mediated degradation and glucose transporter-1 regulation.

Synaptotagmins (SYTs) are a family of 17 membrane transporters that function as calcium ion sensors during the release of Ca2+-dependent neurotransmitters and hormones. However, few studies have reported whether members of the SYT family play a role in glucose uptake in diabetic retinopathy (DR) through Ca2+/glucose transporter-1 (GLUT1) and the possible regulatory mechanism of SYTs. To elucidate the role of the SYT family in the regulation of glucose transport in retinal pigment epithelial cells and explore its potential as a therapeutic target for the clinical management of DR. DR was induced by streptozotocin in C57BL/6J mice and by high glucose medium in human retinal pigment epithelial cells (ARPE-19). Bioinformatics analysis, reverse transcriptase-polymerase chain reaction, Western blot, flow cytometry, ELISA, HE staining, and TUNEL staining were used for analysis. Six differentially expressed proteins (SYT2, SYT3, SYT4, SYT7, SYT11, and SYT13) were found between the DR and control groups, and SYT4 was highly expressed. Hyperglycemia induces SYT4 overexpression, manipulates Ca2+ influx to induce GLUT1 fusion with the plasma membrane, promotes abnormal expression of the glucose transporter GLUT1 and excessive glucose uptake, induces ARPE-19 cell apoptosis, and promotes DR progression. Parkin deficiency inhibits the proteasomal degradation of SYT4 in DR, resulting in SYT4 accumulation and enhanced GLUT1 fusion with the plasma membrane, and these effects were blocked by oe-Parkin treatment. Moreover, dysregulation of the myelin transcription factor 1 (Myt1)-induced transcription of SYT4 in DR further activated the SYT4-mediated stimulus-secretion coupling process, and this process was inhibited in the oe-MYT1-treated group. Our study reveals the key role of SYT4 in regulating glucose transport in retinal pigment epithelial cells during the pathogenesis of DR and the underlying mechanism and suggests potential therapeutic targets for clinical DR.

PARKIN is not required to sustain OXPHOS function in adult mammalian tissues

Loss-of-function variants in the PRKN gene encoding the ubiquitin E3 ligase PARKIN cause autosomal recessive early-onset Parkinson’s disease (PD). Extensive in vitro and in vivo studies have reported that PARKIN is involved in multiple pathways of mitochondrial quality control, including mitochondrial degradation and biogenesis. However, these findings are surrounded by substantial controversy due to conflicting experimental data. In addition, the existing PARKIN-deficient mouse models have failed to faithfully recapitulate PD phenotypes. Therefore, we have investigated the mitochondrial role of PARKIN during ageing and in response to stress by employing a series of conditional Parkin knockout mice. We report that PARKIN loss does not affect oxidative phosphorylation (OXPHOS) capacity and mitochondrial DNA (mtDNA) levels in the brain, heart, and skeletal muscle of aged mice. We also demonstrate that PARKIN deficiency does not exacerbate the brain defects and the pro-inflammatory phenotype observed in mice carrying high levels of mtDNA mutations. To rule out compensatory mechanisms activated during embryonic development of Parkin-deficient mice, we generated a mouse model where loss of PARKIN was induced in adult dopaminergic (DA) neurons. Surprisingly, also these mice did not show motor impairment or neurodegeneration, and no major transcriptional changes were found in isolated midbrain DA neurons. Finally, we report a patient with compound heterozygous PRKN pathogenic variants that lacks PARKIN and has developed PD. The PARKIN deficiency did not impair OXPHOS activities or induce mitochondrial pathology in skeletal muscle from the patient. Altogether, our results argue that PARKIN is dispensable for OXPHOS function in adult mammalian tissues.

Parkin deficiency promotes liver cancer metastasis by TMEFF1 transcription activation via TGF-β/Smad2/3 pathway.

Parkin (PARK2) deficiency is frequently observed in various cancers and potentially promotes tumor progression. Here, we showed that Parkin expression is downregulated in liver cancer tissues, which correlates with poor patient survival. Parkin deficiency in liver cancer cells promotes migration and metastasis as well as changes in EMT and metastasis markers. A negative correlation exists between TMEFF1 and Parkin expression in liver cancer cells and tumor tissues. Parkin deficiency leads to upregulation of TMEFF1 which promotes migration and metastasis. TMEFF1 transcription is activated by Parkin-induced endogenous TGF-β production and subsequent phosphorylation of Smad2/3 and its binding to TMEFF1 promotor. TGF-β inhibitor and TMEFF1 knockdown can reverse shParkin-induced cell migration and changes of EMT markers. Parkin interacts with and promotes the ubiquitin-dependent degradation of HIF-1α/HIF-1β and p53, which accounts for the suppression of TGF-β production. Our data have revealed that Parkin deficiency in cancer leads to the activation of the TGF-β/Smad2/3 pathway, resulting in the expression of TMEFF1 which promotes cell migration, EMT, and metastasis in liver cancer cells.

Parkin deficiency suppresses antigen presentation to promote tumor immune evasion and immunotherapy resistance.

Parkin is an E3 ubiquitin ligase that plays a key role in the development of Parkinson's disease. Parkin defects also occur in numerous cancers, and a growing body of evidence indicates that Parkin functions as a tumor suppressor that impedes a number of cellular processes involved in tumorigenesis. Here, we generated murine and human models that closely mimic the advanced-stage tumors where Parkin deficiencies are found to provide deeper insights into the tumor suppressive functions of Parkin. Loss of Parkin expression led to aggressive tumor growth that was associated with poor tumor antigen presentation and limited antitumor CD8+ T cell infiltration and activation. The effect of Parkin deficiency on tumor growth was lost following depletion of CD8+ T cells. In line with previous findings, Parkin deficiency was linked with mitochondria-associated metabolic stress, PTEN degradation, and enhanced AKT activation. Increased AKT signaling led to dysregulation of antigen presentation, and treatment with the AKT inhibitor MK2206-HCl restored antigen presentation in Parkin-deficient tumors. Analysis of data from clear cell renal cell carcinoma patients indicated that Parkin expression was downregulated in tumors and that low expression correlated with reduced overall survival. Furthermore, low Parkin expression correlated with reduced patient response to immunotherapy. Overall, these results identify a role for Parkin deficiency in promoting tumor immune evasion that may explain the poor prognosis associated with loss of Parkin across multiple types of cancer.

Longitudinal in vivo metabolic labeling reveals tissue-specific mitochondrial proteome turnover rates and proteins selectively altered by parkin deficiency

Our study utilizes a longitudinal isotopic metabolic labeling approach in vivo in combination with organelle fraction proteomics to address the role of parkin in mitochondrial protein turnover in mice. The use of metabolic labeling provides a method to quantitatively determine the global changes in protein half-lives whilst simultaneously assessing protein expression. Studying two diverse mitochondrial populations, we demonstrated the median half-life of brain striatal synaptic mitochondrial proteins is significantly greater than that of hepatic mitochondrial proteins (25.7 vs. 3.5 days). Furthermore, loss of parkin resulted in an overall, albeit modest, increase in both mitochondrial protein abundance and half-life. Pathway and functional analysis of our proteomics data identified both known and novel pathways affected by loss of parkin that are consistent with its role in both mitochondrial quality control and neurodegeneration. Our study therefore adds to a growing body of evidence suggesting dependence on parkin is low for basal mitophagy in vivo and provides a foundation for the investigation of novel parkin targets.

Mitophagy alleviates AIF-mediated spleen apoptosis induced by AlCl3 through Parkin stabilization in mice.

Aluminium (Al) accumulates in the spleen and causes spleen apoptosis. Mitochondrial dyshomeostasis represents primary mechanisms of spleen apoptosis induced by Al. Apoptosis-inducing factor (AIF) is located in the gap of the mitochondrial membrane and can be released into the nucleus, leading to apoptosis. Phosphatase and tensin homolog (PTEN)-induced putative kinase1 (PINK1)/E3 ubiquitin ligase PARK2 (Parkin)-mediated mitophagy maintains mitochondrial homeostasis by removing damaged mitochondria, but its function in AIF-mediated spleen apoptosis induced by Al is not clear. In our study, aluminium trichloride (AlCl3) was diluted in water for 90d and administered to 75 male C57BL/6N mice at 0, 44.8, 59.8, 89.7, and 179.3mg/kg body weight. AlCl3 triggered PINK1/Parkin pathway-mediated mitophagy, induced AIF release and AIF-mediated spleen apoptosis. AlCl3 was administered to sixty male C57BL/6N mice of wild type and Parkin knockout for 90d at 0 and 179.3mg/kg body weight. The results indicated that Parkin deficiency decreased mitophagy, aggravated mitochondrial damage, AIF release and AIF-mediated spleen apoptosis induced by AlCl3. According to our results, PINK1/Parkin-mediated mitophagy and AIF-mediated spleen apoptosis are caused by AlCl3, whereas mitophagy is protective in AIF-mediated apoptosis induced by AlCl3.

Parkin deficiency exacerbates fasting-induced skeletal muscle wasting in mice

Parkinson’s Disease (PD) is a chronic and progressive neurodegenerative disease manifesting itself with tremors, muscle stiffness, bradykinesia, dementia, and depression. Mutations of mitochondrial E3 ligase, PARKIN, have been associated with juvenile PD. Previous studies have characterized muscle atrophy and motor deficits upon loss of functional Parkin in fly and rodent models. However, the mechanisms behind pathophysiology of Parkin deficient muscle remains to be elusive. Here, results suggested that knock down of Parkin significantly increases proteolytic activities in skeletal muscle cell line, the C2C12 myotubes. However, the atrogene levels increase moderately in Parkin deficient cell line. To further investigate the role of Parkin in skeletal muscle atrophy, Parkin knock out (KO) and wild type mice were subjected to 48 h starvation. After 48 h fasting, a greater reduction in skeletal muscle weights was observed in Parkin KO mice as compared to age matched wild type control, suggesting elevated proteolytic activity in the absence of Parkin. Subsequent microarray analyses revealed further enhanced expression of FOXO and ubiquitin pathway in fasted Parkin KO mice. Furthermore, a greater reduction in the expression of cytoskeleton genes was observed in Parkin KO mice following 48 h fasting. Collectively, these results suggest that Parkin deficiency exacerbates fasting-induced skeletal muscle wasting, through upregulating genes involved in catabolic activities in skeletal muscle.

Abstract P2073: Rbx2-CRL5 Mediates Mitochondrial Ubiquitination And Mitophagy To Maintain Myocardial Homeostasis Independent Of Parkin

The ubiquitin (Ub) ligase Parkin has been recognized as a central player in mitophagy. In contrast to its presumed importance in the heart, ablation of Parkin fails to impact homeostatic mitophagy and cardiac function in both young and aging mice, suggesting compensation from other mitochondrial Ub ligases. However, the identities of such additional mitochondrial Ub ligases, as well as their physiological significance in the heart, remain unclear. Here, we demonstrate that Cullin-RING Ub ligase 5 (CRL5) plays a key role in the control of mitochondrial homeostasis in cardiomyocytes. CRL5 belongs to the family of Cullin-RING Ub ligases (CRLs) and consists of the RING box protein RBX2, scaffold protein Cullin 5 (Cul5), and one of 38 substrate receptor proteins. Analysis of the mitochondrial outer membrane-interacting proteome revealed a robust association of CRLs with mitochondria. Pharmacological and genetic perturbations of CRLs inhibited mitochondrial ubiquitination and mitophagy. Subcellular fractionation, live-cell imaging and immunogold electron microscopy further revealed that RBX2 and Cul5, two core components of CRL5, are quickly recruited to mitochondria upon mitochondrial depolarization. Depletion of RBX2 or Cul5 inhibited mitochondrial ubiquitination and turnover, impaired mitochondrial function, and increased cell death in cardiomyocytes. Importantly, RBX2 deficiency did not alter Parkin expression, had a more robust inhibitory effect on mitochondrial ubiquitination compared to Parkin deficiency, and remained effective in the absence of Parkin. Moreover, loss of RBX2 attenuated Parkin-mediated ubiquitination, suggesting its dominant, Parkin-independent actions in mitochondria. In vivo , deletion of RBX2 in adult mouse hearts suppressed mitophagic activity and provoked accumulation of damaged mitochondria in myocardium, leading to rapid development of dilated cardiomyopathy and heart failure. Finally, RBX2 was upregulated in pressure overloaded mouse hearts but downregulated in human failing hearts, further supporting its protective role in the heart. Taken together, our data allow us to propose RBX2-CRL5 as a mitochondrial Ub ligase and a physiological regulator of mitochondrial and cardiac integrity.

Parkin Insufficiency Accentuates High-Fat Diet–Induced Cardiac Remodeling and Contractile Dysfunction Through VDAC1-Mediated Mitochondrial Ca2+ Overload

Mitochondrial Ca2+ overload contributes to obesity cardiomyopathy, yet mechanisms that directly regulate it remain elusive. The authors investigated the role of Parkin on obesity-induced cardiac remodeling and dysfunction in human hearts and a mouse model of 24-week high-fat diet (HFD) feeding. Parkin knockout aggravated HFD-induced cardiac remodeling and dysfunction, mitochondrial Ca2+ overload, and apoptosis without affecting global metabolism, blood pressure, and aortic stiffness. Parkin deficiency unmasked HFD-induced decline in voltage-dependent anion channel (VDAC) type 1 degradation through the ubiquitin-proteasome system but not other VDAC isoforms or mitochondrial Ca2+ uniporter complex. These data suggest that Parkin-mediated proteolysis of VDAC type 1 is a promising therapeutic target for obesity cardiomyopathy.

PINK1/Parkin-Mediated Mitophagy Plays a Protective Role in Albumin Overload-Induced Renal Tubular Cell Injury

Proteinuria is an important symptom of chronic kidney disease irrespective of its initial pathogenesis. Mitochondrial dysfunction is an early pathophysiological event in proteinuria-induced tubular damage. Mitophagy, the selective degradation of damaged mitochondria targeted by autophagy, contributes to mitochondrial homeostasis and is primarily regulated by the PTEN-induced kinase 1 (PINK1)/Parkin pathway. In this study, we evaluated the function of mitophagy in proteinuria-induced tubular injury and mechanism. HK-2 cells were transfected with Parkin siRNA or Parkin overexpression plasmids for 48 h followed by treatment with albumin (8 mg/mL) for 8 h. JC-1 staining, ATP detection, and reactive oxygen species (ROS) detection were used to determine mitochondrial function. Immunoblot, LC3/mitochondria co-localization analyses, and Mito-Keima were employed to detect mitophagy. Immunoblot analysis and TUNEL were used to detect apoptosis. Albumin overload induced mitochondrial dysfunction and mitophagy activation in HK-2 cells. Parkin knockdown inhibited albumin overload induced-mitophagy. Parkin overexpression further upregulated albumin overload induced-mitophagy. Parkin deficiency aggravated albumin overload-induced mitochondrial dysfunction and the overproduction of ROS, resulting in increased cell injury. Contrarily, Parkin overexpression helped maintain mitochondrial function and attenuate ROS generation, contributing to cell protection. Our results suggest that by clearing damaged mitochondria and maintaining mitochondrial function, PINK1/Parkin-mediated mitophagy contributed to tubular cell survival during albumin overload. PINK1/Parkin-mediated mitophagy may be a potential therapeutic target for proteinuria in tubular epithelial cells.

Abstract 521: Parkin Has Non-canonical Roles In Macrophage Lipid Metabolism With Effects On Atherosclerosis

Defects in the E3 ubiquitin ligase Parkin are sine qua non of Parkinson and related neurodegenerative diseases. Loss of ubiquitination of distinct targets leads to accumulation of cytotoxic protein aggregates, loss of mitophagy, and defects in lipid metabolism. Given the critical role of these processes in plaque macrophages, we set out to define the role of Parkin in atherosclerosis. Pro-atherogenic LDLR-KO mice were transplanted with bone marrow (BM) from wild type and Parkin-KO mice and lesion formation stimulated by 4 months of Western diet feeding. Mice transplanted with wild type BM developed lipid-rich atherosclerotic plaques in both the aortic root and whole aorta replete with foam cell macrophages. In contrast, mice transplanted with Parkin-deficient BM had significantly reduced plaque burden with concomitant reductions in lipid content, foam cell macrophages, and surrogates of plaque complexity including reduced lesional apoptosis and necrotic core formation. The paradoxical atherogenic role for Parkin including development of lipid-laden foam cell macrophages led us to focus on the impact of Parkin in macrophage lipid handling. We find that Parkin mediates the ubiquitination and stabilization of scavenger receptor CD36, a key lipid transporter in macrophages. Parkin-null macrophages had reduced expression of CD36 and concomitant reductions in oxLDL uptake. Further, Parkin deficiency decreased cholesterol efflux in macrophages exacerbating macrophage lipid storage. These results suggest that the non-canonical functions of Parkin in lipid metabolism outweigh its traditional cytoprotective roles in macrophages and mediate its deleterious effects on atherosclerotic progression.

Abstract 14210: Impaired Mitophagy and Reduced Parkin Expression in Human Pulmonary Arterial Smooth Muscle Cells (PASMCs) in Pulmonary Arterial Hypertension (PAH)

Introduction: Mitophagy is the key mitochondrial quality control process of selective removal of damaged mitochondria which is necessary for maintaining cellular homeostasis. While studies have demonstrated that abnormalities in mitochondrial metabolism drive a hyperproliferative phenotype of pulmonary vasculature in PAH, there is limited understanding of mitophagy dysregulation in PAH. Recent studies have shown that hypoxia induced Parkin/Pink1-mediated mitophagy promotes vascular remodeling, however another report suggests that loss of Pink1 and reduced mitophagy in hypoxia promotes PASMC proliferation. The role and mechanisms of altered mitochondrial dynamics/mitophagy dysregulation in driving pulmonary vascular remodeling in PAH remain incompletely understood. Hypothesis: We hypothesized that impaired mitophagy and reduced Parkin expression may drive the apoptosis-resistant, hyperproliferative phenotype in PAH PASMCs. Methods: Mitophagy was assessed in human PASMCs from control donors and PAH patients stably expressing mtKeima protein and in lungs from hypoxia-exposed mtKeima transgenic mice. Parkin expression was assessed by Western blotting and immunocytochemistry. Immunofluorescence staining for Parkin was performed in lungs from mice exposed to chronic hypoxia. Human PASMCs from control donors were transfected with siControl and siParkin and assessed for proliferation and apoptosis by Ki67 and Annexin V/PI flow cytometry and PCNA expression. Results: PASMCs from PAH patients showed reduced KeimaRed vs. KeimaGreen ratio compared to control donors indicating reduced mitophagy i.e. further confirmed by decreased Parkin in PAH PASMCs. Parkin deficient PASMCs demonstrated more Ki67 and less Annexin V/PI positive cells and increased PCNA. Interestingly, lungs from hypoxia-exposed mtKeima transgenic mice showed increased KeimaRed vs. KeimaGreen ratio and increased Parkin in lungs of hypoxia-exposed mice. Conclusions: PAH PASMCs demonstrate impaired mitophagy and reduced Parkin expression; Parkin deficiency promotes proliferation and inhibits apoptosis in PASMCs. Our findings suggest that Parkin may regulate remodeling phenotypes in PASMCs and thus may represent a potential therapeutic target in PAH.

AMPK activates Parkin independent autophagy and improves post sepsis immune defense against secondary bacterial lung infections

Metabolic and bioenergetic plasticity of immune cells is essential for optimal responses to bacterial infections. AMPK and Parkin ubiquitin ligase are known to regulate mitochondrial quality control mitophagy that prevents unwanted inflammatory responses. However, it is not known if this evolutionarily conserved mechanism has been coopted by the host immune defense to eradicate bacterial pathogens and influence post-sepsis immunosuppression. Parkin, AMPK levels, and the effects of AMPK activators were investigated in human leukocytes from sepsis survivors as well as wild type and Park2−/− murine macrophages. In vivo, the impact of AMPK and Parkin was determined in mice subjected to polymicrobial intra-abdominal sepsis and secondary lung bacterial infections. Mice were treated with metformin during established immunosuppression. We showed that bacteria and mitochondria share mechanisms of autophagic killing/clearance triggered by sentinel events that involve depolarization of mitochondria and recruitment of Parkin in macrophages. Parkin-deficient mice/macrophages fail to form phagolysosomes and kill bacteria. This impairment of host defense is seen in the context of sepsis-induced immunosuppression with decreased levels of Parkin. AMPK activators, including metformin, stimulate Parkin-independent autophagy and bacterial killing in leukocytes from post-shock patients and in lungs of sepsis-immunosuppressed mice. Our results support a dual role of Parkin and AMPK in the clearance of dysfunctional mitochondria and killing of pathogenic bacteria, and explain the immunosuppressive phenotype associated Parkin and AMPK deficiency. AMPK activation appeared to be a crucial therapeutic target for the macrophage immunosuppressive phenotype and to reduce severity of secondary bacterial lung infections and respiratory failure.

PINK1/Parkin-Mediated Mitophagy Plays a Protective Role in the Bone Impairment Caused by Aluminum Exposure.

The pollution of aluminum (Al) in agricultural production and its wide application in food processing greatly increase the chance of human and animal exposure. Al can accumulate in bone and cause bone diseases by inducing oxidative stress. Mitophagy can maintain normal cell function by degrading damaged mitochondria and scavenging reactive oxygen species. However, the role of mitophagy in the bone impairment caused by Al is unknown. In this study, we demonstrated that PTEN induced putative kinase 1 (PINK1)/ E3 ubiquitin ligase PARK2 (Parkin)-mediated mitophagy was activated in the bone impairment caused by Al in vivo. Then, the Al-induced mitophagy in Parkin-deficient mice and MC3T3-E1 cells were decreased. Meanwhile, Parkin deficiency exacerbated the bone impairment, mitochondrial damage, and oxidative stress under Al exposure, both in vivo and in vitro. In general, the results reveal that Al exposure can activate PINK1/Parkin-mediated mitophagy, and the PINK1/Parkin-mediated mitophagy plays a protective role in the bone impairment caused by Al.

Applying the RatWalker System for Gait Analysis in a Genetic Rat Model of Parkinson's Disease.

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. Gait abnormalities, including decreased arm swing, slower walking speed, and shorter steps are common in PD patients and appear early in the course of disease. Thus, the quantification of motor patterns in animal models of PD will be important for phenotypic characterization during disease course and upon therapeutic treatment. Most cases of PD are idiopathic; however, the identification of hereditary forms of PD uncovered gene mutations and variants, such as loss-of-function mutations in Pink1 and Parkin, two proteins involved in mitochondrial quality control that could be harnessed to create animal models. While mice are resistant to neurodegeneration upon loss of Pink1 and Parkin (single and combined deletion), in rats, Pink1 but not Parkin deficiency leads to nigral DA neuron loss and motor impairment. Here, we report the utility of FTIR imaging to uncover gait changes in freely walking young (2 months of age) male rats with combined loss of Pink1 and Parkin prior to the development of gross visually apparent motor abnormality as these rats age (observed at 4-6 months), characterized by hindlimb dragging as previously reported in Pink1 knockout (KO) rats.

Applying the RatWalker System for Gait Analysis in a Genetic Rat Model of Parkinson's Disease

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by the loss of dopaminergic (DA) neurons in the substantia nigra pars compacta. Gait abnormalities, including decreased arm swing, slower walking speed, and shorter steps are common in PD patients and appear early in the course of disease. Thus, the quantification of motor patterns in animal models of PD will be important for phenotypic characterization during disease course and upon therapeutic treatment. Most cases of PD are idiopathic; however, the identification of hereditary forms of PD uncovered gene mutations and variants, such as loss-of-function mutations in Pink1 and Parkin, two proteins involved in mitochondrial quality control that could be harnessed to create animal models. While mice are resistant to neurodegeneration upon loss of Pink1 and Parkin (single and combined deletion), in rats, Pink1 but not Parkin deficiency leads to nigral DA neuron loss and motor impairment. Here, we report the utility of FTIR imaging to uncover gait changes in freely walking young (2 months of age) male rats with combined loss of Pink1 and Parkin prior to the development of gross visually apparent motor abnormality as these rats age (observed at 4-6 months), characterized by hindlimb dragging as previously reported in Pink1 knockout (KO) rats.

Characterization of a Cul9\u2013Parkin double knockout mouse model for Parkinson\u2019s disease

Mitochondrial quality control is essential for the long-term survival of postmitotic neurons. The E3 ubiquitin ligase Parkin promotes the degradation of damaged mitochondria via mitophagy and mutations in Parkin are a major cause of early-onset Parkinson’s disease (PD). Surprisingly however, mice deleted for Parkin alone are rather asymptomatic for PD-related pathology, suggesting that other complementary or redundant mitochondrial quality control pathways may exist in neurons. Mitochondrial damage is often accompanied by the release of toxic proteins such as cytochrome c. We have reported that once in the cytosol, cytochrome c is targeted for degradation by the E3 ligase CUL9 in neurons. Here we examined whether CUL9 and Parkin cooperate to promote optimal neuronal survival in vivo. We generated mice deficient for both Cul9 and Parkin and examined them for PD-related phenotypes. Specifically, we conducted assays to examine behavioural deficits (locomotor, sensory, memory and learning) and loss of dopaminergic neurons in both males and females. Our results show that the loss of Cul9 and Parkin together did not enhance the effect of Parkin deficiency alone. These results indicate that while both Parkin and CUL9 participate in mitochondrial quality control, neurons likely have multiple redundant mechanisms to ensure their long-term survival.