Progression of pathology in PINK1-deficient mouse brain from splicing via ubiquitination, ER stress, and mitophagy changes to neuroinflammation

Abstract

BackgroundPINK1 deficiency causes the autosomal recessive PARK6 variant of Parkinson’s disease. PINK1 activates ubiquitin by phosphorylation and cooperates with the downstream ubiquitin ligase PARKIN, to exert quality control and control autophagic degradation of mitochondria and of misfolded proteins in all cell types.MethodsGlobal transcriptome profiling of mouse brain and neuron cultures were assessed in protein-protein interaction diagrams and by pathway enrichment algorithms. Validation by quantitative reverse transcriptase polymerase chain reaction and immunoblots was performed, including human neuroblastoma cells and patient primary skin fibroblasts.ResultsIn a first approach, we documented Pink1-deleted mice across the lifespan regarding brain mRNAs. The expression changes were always subtle, consistently affecting “intracellular membrane-bounded organelles”. Significant anomalies involved about 250 factors at age 6 weeks, 1300 at 6 months, and more than 3500 at age 18 months in the cerebellar tissue, including Srsf10, Ube3a, Mapk8, Creb3, and Nfkbia. Initially, mildly significant pathway enrichment for the spliceosome was apparent. Later, highly significant networks of ubiquitin-mediated proteolysis and endoplasmic reticulum protein processing occurred. Finally, an enrichment of neuroinflammation factors appeared, together with profiles of bacterial invasion and MAPK signaling changes—while mitophagy had minor significance. Immunohistochemistry showed pronounced cellular response of Iba1-positive microglia and GFAP-positive astrocytes; brain lipidomics observed increases of ceramides as neuroinflammatory signs at old age.In a second approach, we assessed PINK1 deficiency in the presence of a stressor. Marked dysregulations of microbial defense factors Ifit3 and Rsad2 were consistently observed upon five analyses: (1) Pink1 −/− primary neurons in the first weeks after brain dissociation, (2) aged Pink1 −/− midbrain with transgenic A53T-alpha-synuclein overexpression, (3) human neuroblastoma cells with PINK1-knockdown and murine Pink1 −/− embryonal fibroblasts undergoing acute starvation, (4) triggering mitophagy in these cells with trifluoromethoxy carbonylcyanide phenylhydrazone (FCCP), and (5) subjecting them to pathogenic RNA-analogue poly(I:C). The stress regulation of MAVS, RSAD2, DDX58, IFIT3, IFIT1, and LRRK2 was PINK1 dependent. Dysregulation of some innate immunity genes was also found in skin fibroblast cells from PARK6 patients.ConclusionsThus, an individual biomarker with expression correlating to progression was not identified. Instead, more advanced disease stages involved additional pathways. Hence, our results identify PINK1 deficiency as an early modulator of innate immunity in neurons, which precedes late stages of neuroinflammation during alpha-synuclein spreading.Electronic supplementary materialThe online version of this article (doi:10.1186/s12974-017-0928-0) contains supplementary material, which is available to authorized users.

Atxn2-CAG100-KnockIn mouse spinal cord shows progressive TDP43 pathology associated with cholesterol biosynthesis suppression

“…The reasoning behind the screening of so subtle changes comes from research into Parkinson’s disease (PD), where 2-fold dosage increase of the disease protein alpha-synuclein was shown to trigger disease onset at ages of 30 years, 1.5-fold increase causes onset around 50 years, and 1.3-fold increase starts disease after 70 years of age [19, 34, 191]. The survey of 1.2-fold global transcriptome dysregulations in a PD mouse model correctly discovered neuroinflammatory changes as initial molecular pathology, which were later found to be crucial for a successful rescue [193, 205]. Given that ATXN2 mutations also trigger mitochondrial dysfunction as in PD, and that SCA2 may manifest with a Parkinsonian phenotype [142, 181, 186, 187, 223], we assessed here if distortion of such pathways becomes relevant by subtle dysregulations at several points.…”

Parkin deficiency modulates NLRP3 inflammasome activation by attenuating an A20‐dependent negative feedback loop

“…Mitochondrial quality control (MQC) plays a key role in attenuating this pathway, by preserving a cohort of functional mitochondria within the cell (Lazarou, ; Zhong et al, ). Several studies have linked Parkin and PINK1 to innate immunity (Greene, Whitworth, Andrews, Parker, & Pallanck, ; Matheoud et al, ; Torres‐Odio et al, ). A loss of PARK2 function increases susceptibility to mycobacterial infection and sensitivity to inflammation‐related dopaminergic (DA) neuron degeneration (Chopra et al, ; Frank‐Cannon et al, ; Lazarou, ; Manzanillo et al, ; Mira et al, ), while the expression of PARK2 and PINK1 is stimulated by hepatitis viruses (Khan, Syed, Kim, & Siddiqui, ).…”

Paroxetine suppresses reactive microglia-mediated but not lipopolysaccharide-induced inflammatory responses in primary astrocytes

“…A number of PD-associated gene products such as α-synuclein, PINK1 and DJ-1 have been implicated in astrocyte dysfunction. Exposure to mutant α-synuclein and deficiency in PINK1 lead to activation of both microglia and astrocytes and generation of a large amount of neuroinflammatory factors [10][11][12]. PINK1 deficiency also inhibits the differentiation of neural stem cells into astrocytes [13], and causes proliferation defect in astrocytes which may result in a delay in the wound healing process [14].…”