Abstract:Background: Multiple missense mutations in Leucine-rich repeat kinase 2 (LRRK2) are associated with familial forms of late onset Parkinson's disease (PD), the most common age-related movement disorder. The dysfunction of dopamine transmission contributes to PD-related motor symptoms. Interestingly, LRRK2 is more abundant in the dopaminoceptive striatal spiny projection neurons (SPNs) compared to the dopamine-producing nigrostriatal dopaminergic neurons. Aging is the most important risk factor for PD and other … Show more
“…Nuclei in G2019S LRRK2-expressing cells were more circular and appeared larger in size compared to naïve and WT LUHMES cells. Just as the WT and G2019S clones, L10WT and G14GS, express equivalent LRRK2 levels, this phenotype is attributable to the increased kinase activity of the mutant protein, in accordance with a recent study ( Chen et al, 2020 ). Fig.…”
Section: Resultssupporting
confidence: 91%
“…With respect to LRRK2, recent studies have reported abnormal nuclear shape and disorganized nuclear envelope structure in neural precursor cells and hippocampal neurons of PD patients carrying the LRRK2 G2019S mutation ( Liu et al, 2012 ; Shani et al, 2019 ) and in DA neurons of transgenic mice expressing the LRRK2 R1441C mutation ( Tsika et al, 2014 ). While this paper was in preparation, Chen et al (2020) have shown that LRRK2 G2019S caused an increase in nuclear size in dopaminoceptive striatal spiny projection neurons, and that this phenomenon was regulated by LRRK2 kinase activity. Altogether, these findings have highlighted a key physiological role of LRRK2 in maintaining nuclear morphology and genome integrity and suggest that nuclear abnormalities with LRRK2 mutants are likely due to LRRK2 loss of function.…”
Parkinson's disease (PD) is a fatal neurodegenerative disorder which is primarily caused by the degeneration and loss of dopaminergic neurons of the substantia nigra in the ventral midbrain. Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of late-onset PD identified to date, with G2019S being the most frequent LRRK2 mutation, which is responsible for up to 1-2% of sporadic PD and up to 6% of familial PD cases. As no treatment is available for this devastating disease, developing new therapeutic strategies is of foremost importance. Cellular models are commonly used for testing of novel potential neuroprotective compounds. However, current cellular PD models either lack physiological relevance to dopaminergic neurons or are too complex and costly for scaling-up the production process and for screening purposes. In order to combine biological relevance and throughput, we have developed a PD model in Lund human mesencephalic (LUHMES) cell-derived dopaminergic neurons by over-expressing WT and G2019S LRRK2 proteins. We show that these cells can differentiate into dopaminergic-like neurons and that expression of mutant LRRK2 causes a range of different phenotypes, including reduced nuclear eccentricity, altered mitochondrial and lysosomal morphologies, and increased dopaminergic cell death. This model could be used to elucidate G2019S LRRK2-mediated dopaminergic neural dysfunction and to identify novel molecular targets for disease intervention. In addition, our model could be applied to high-throughput and phenotypic screenings for the identification of novel PD therapeutics.
“…Nuclei in G2019S LRRK2-expressing cells were more circular and appeared larger in size compared to naïve and WT LUHMES cells. Just as the WT and G2019S clones, L10WT and G14GS, express equivalent LRRK2 levels, this phenotype is attributable to the increased kinase activity of the mutant protein, in accordance with a recent study ( Chen et al, 2020 ). Fig.…”
Section: Resultssupporting
confidence: 91%
“…With respect to LRRK2, recent studies have reported abnormal nuclear shape and disorganized nuclear envelope structure in neural precursor cells and hippocampal neurons of PD patients carrying the LRRK2 G2019S mutation ( Liu et al, 2012 ; Shani et al, 2019 ) and in DA neurons of transgenic mice expressing the LRRK2 R1441C mutation ( Tsika et al, 2014 ). While this paper was in preparation, Chen et al (2020) have shown that LRRK2 G2019S caused an increase in nuclear size in dopaminoceptive striatal spiny projection neurons, and that this phenomenon was regulated by LRRK2 kinase activity. Altogether, these findings have highlighted a key physiological role of LRRK2 in maintaining nuclear morphology and genome integrity and suggest that nuclear abnormalities with LRRK2 mutants are likely due to LRRK2 loss of function.…”
Parkinson's disease (PD) is a fatal neurodegenerative disorder which is primarily caused by the degeneration and loss of dopaminergic neurons of the substantia nigra in the ventral midbrain. Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common genetic cause of late-onset PD identified to date, with G2019S being the most frequent LRRK2 mutation, which is responsible for up to 1-2% of sporadic PD and up to 6% of familial PD cases. As no treatment is available for this devastating disease, developing new therapeutic strategies is of foremost importance. Cellular models are commonly used for testing of novel potential neuroprotective compounds. However, current cellular PD models either lack physiological relevance to dopaminergic neurons or are too complex and costly for scaling-up the production process and for screening purposes. In order to combine biological relevance and throughput, we have developed a PD model in Lund human mesencephalic (LUHMES) cell-derived dopaminergic neurons by over-expressing WT and G2019S LRRK2 proteins. We show that these cells can differentiate into dopaminergic-like neurons and that expression of mutant LRRK2 causes a range of different phenotypes, including reduced nuclear eccentricity, altered mitochondrial and lysosomal morphologies, and increased dopaminergic cell death. This model could be used to elucidate G2019S LRRK2-mediated dopaminergic neural dysfunction and to identify novel molecular targets for disease intervention. In addition, our model could be applied to high-throughput and phenotypic screenings for the identification of novel PD therapeutics.
“…They show specifically how this LRRK2 mutant forms periodically repeating dimers, which then polymerize in a helical array onto MTs. The cellular phenotypes associated with G2019S, I2020T, and R1441C/Y1699C and other PD-associated mutations include perturbation of MT-related processes such as vesicular trafficking, autophagy, cilia formation, and nuclear/mitochondria morphology, so it is very likely that LRRK2 dysfunction physiologically interferes globally with dynamic cross-talk with MTs ( 9 , 29 – 31 ).…”
Section: Discussionmentioning
confidence: 99%
“…Familial PD mutations in LRRK2 lead to altered cellular phenotypes such as microtubule (MT)-associated filament formation, impeded vesicular trafficking, as well as changes in nuclear morphology ( 4 – 7 ). Some of these PD mutations such as G2019S in the kinase domain lead to increased kinase activity while others do not ( 7 – 9 ), so what actually drives PD is thus still ambiguous, although it is clear that the kinase domain plays an important pathogenic role. Two of the four most common PD mutations, G2019S and I2020T, are located in the highly conserved DFGψ motif, which in LRRK2 is DYGI.…”
To explore how pathogenic mutations of the multidomain leucine-rich repeat kinase 2 (LRRK2) hijack its finely tuned activation process and drive Parkinson’s disease (PD), we used a multitiered approach. Most mutations mimic Rab-mediated activation by “unleashing” kinase activity, and many, like the kinase inhibitor MLi-2, trap LRRK2 onto microtubules. Here we mimic activation by simply deleting the inhibitory N-terminal domains and then characterize conformational changes induced by MLi-2 and PD mutations. After confirming that LRRK2RCKW retains full kinase activity, we used hydrogen-deuterium exchange mass spectrometry to capture breathing dynamics in the presence and absence of MLi-2. Solvent-accessible regions throughout the entire protein are reduced by MLi-2 binding. With molecular dynamics simulations, we created a dynamic portrait of LRRK2RCKW and demonstrate the consequences of kinase domain mutations. Although all domains contribute to regulating kinase activity, the kinase domain, driven by the DYGψ motif, is the allosteric hub that drives LRRK2 regulation.
“…Together, these reports could be interpreted as evidence for slightly slower maturation in LKO scenarios, over the first couple of weeks in vitro . Nevertheless, a recent study reported forebrain atrophy and reduced dendritic complexity in SPNs of 12- (but not 2-) month-old LKO mice, accompanied by changes in nuclear morphology and some motor impairment compared to WT mice, in contrast to hyperactivity observed in younger LKO mice (Chen et al, 2020 ). Thus, investigating age-dependent changes in dendritic morphology in an ex vivo context may warrant further attention.…”
Section: No Lrrk2 No Problem? Silencing Redundancy and Target Valimentioning
Since the discovery of
LRRK2
mutations causal to Parkinson’s disease (PD) in the early 2000s, the LRRK2 protein has been implicated in a plethora of cellular processes in which pathogenesis could occur, yet its physiological function remains elusive. The development of genetic models of LRRK2 PD has helped identify the etiological and pathophysiological underpinnings of the disease, and may identify early points of intervention. An important role for LRRK2 in synaptic function has emerged in recent years, which links LRRK2 to other genetic forms of PD, most notably those caused by mutations in the synaptic protein α-synuclein. This point of convergence may provide useful clues as to what drives dysfunction in the basal ganglia circuitry and eventual death of substantia nigra (SN) neurons. Here, we discuss the evolution and current state of the literature placing LRRK2 at the synapse, through the lens of knock-out, overexpression, and knock-in animal models. We hope that a deeper understanding of LRRK2 neurobiology, at the synapse and beyond, will aid the eventual development of neuroprotective interventions for PD, and the advancement of useful treatments in the interim.
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