Biology subjects

Nguyen, A. P. T.

Publications and source records attributed to Nguyen, A. P. T..

5 recordsLinked to original sources

bioRxiv2026

Parkinson's disease-associated LRRK2 risk variant, G2385R, enhances Rab substrate phosphorylation and impairs neuronal integrity

Mutations in the LRRK2 gene are the most frequent cause of familial Parkinsons disease (PD) whereas common variants are associated with an increased risk for sporadic PD. LRRK2 encodes a multi-domain protein displaying two functional enzymatic activities: GTPase and kinase. Familial LRRK2 mutations have been linked to alterations in its GTPase and kinase activities, elevated substrate phosphorylation, as well as increased neurotoxicity in cell and animal models. In addition to familial mutations, several common LRRK2 coding variants have been associated with PD risk in different ethnic populations. Little is known about how these coding variants modulate the risk of developing PD. In this study, we aim to evaluate whether a collection of LRRK2 coding risk variants (A419V, N551K, R1398H, R1628P, M1646T, S1647T, G2385R) modify the biochemical properties of the LRRK2 protein and LRRK2-mediated neurotoxicity using cell-based assays. With the exception of G2385R, we find that coding risk variants have minimal impact on LRRK2 steady-state protein levels, GTP-binding, phosphorylation at Ser910, Ser935, and Ser1292, and subcellular localization in human cell lines and cultured primary neurons. G2385R reduces the steady-state levels of LRRK2 and exhibits reduced phosphorylation at Ser910/Ser935 and Ser1292, consistent with diminished kinase activity. Notably, however, LRRK2 variants associated with increased PD risk (A419V, R1628P, M1646T, and G2385R) significantly elevate the levels of LRRK2-mediated Rab10 phosphorylation by two-fold in cells. In contrast, LRRK2 variants associated with reduced PD risk (N551K, R1398H, and N551K-R1398H) do not alter normal LRRK2-mediated pRab10 levels. Intriguingly, we find that both PD-risk and PD-protective LRRK2 variants can respond normally to kinase activation by different lysosomal stressors (chloroquine, nigericin and monensin) to robustly induce pRab10 levels in cells. The PD risk variant, G2385R LRRK2, significantly inhibits neurite outgrowth in primary cortical neurons compared to wild-type LRRK2. Combining each coding risk variant with the familial G2019S mutation has minimal impact on the elevated kinase activity of G2019S LRRK2 or its capacity to inhibit neurite outgrowth. Our study indicates that LRRK2-dependent Rab phosphorylation represents a relevant readout of PD risk induced by LRRK2 coding variants and demonstrates that the PD risk variant, G2385R LRRK2, creates a hyperactive kinase that can impair neuronal integrity at comparable levels to the effects of G2019S LRRK2.

neuroscience↗

bioRxiv2024

Pathological α-synuclein elicits granulovacuolar degeneration independent of tau

BackgroundPathologic heterogeneity is a hallmark of Lewy body dementia (LBD), yet the impact of Lewy pathology on co-pathologies is poorly understood. Lewy pathology, containing -synuclein, is often associated with regional tau pathology burden in LBD. Similarly, granulovacuolar degeneration bodies (GVBs) have been associated with tau pathology in Alzheimers disease. Interestingly, GVBs have been detected in a broad range of neurodegenerative conditions including both -synucleinopathies and tauopathies. Despite the frequent co-occurrence, little is known about the relationship between -synuclein, tau, and granulovacuolar degeneration. MethodsWe developed a mouse model of limbic-predominant -synucleinopathy by stereotactic injection of -synuclein pre-formed fibrils (PFFs) into the basal forebrain. This model was used to investigate the relationship of -synuclein pathology with tau and GVB formation. ResultsOur model displayed widespread -synuclein pathology with a limbic predominant distribution. Aberrantly phosphorylated tau accumulated in a subset of -synuclein inclusion-bearing neurons, often colocalized with lysosomes. Many of these same neurons also contained CHMP2b- and CK1{delta}-positive granules, established markers of GVBs, which suggests a link between tau accumulation and GVB formation. Despite this observation, GVBs were also detected in tau-deficient mice following PFF-injection, suggesting that pathological -synuclein alone is sufficient to elicit GVB formation. ConclusionsOur findings support that -synuclein pathology can independently elicit granulovacuolar degeneration. The frequent co-accumulation of tau and GVBs suggests a parallel mechanism of cellular dysfunction. The ability of -synuclein pathology to drive GVB formation in the absence of tau highlights the broader relevance of this process to neurodegeneration with relevance to the pathobiology of LBD.

neuroscience↗

bioRxiv2023

Formation of templated inclusions in a forebrain α-synuclein mouse model is independent of LRRK2

Leucine-rich repeat kinase 2 (LRRK2) and -synuclein share enigmatic roles in the pathobiology of Parkinsons disease (PD). LRRK2 mutations are a common genetic cause of PD which, in addition to neurodegeneration, often present with abnormal deposits of -synuclein in the form of Lewy-related pathology. As Lewy-related pathology is a prominent neuropathologic finding in sporadic PD, the relationship between LRRK2 and -synuclein has garnered considerable interest. However, whether and how LRRK2 might influence the accumulation of Lewy-related pathology remains poorly understood. Through stereotactic injection of mouse -synuclein pre-formed fibrils (PFF), we modeled the spread of Lewy-related pathology within forebrain regions where LRRK2 is most highly expressed. The impact of LRRK2 genotype on the formation of -synuclein inclusions was evaluated at 1-month post-injection. Neither deletion of LRRK2 nor G2019S LRRK2 knockin appreciably altered the burden of - synuclein pathology at this early timepoint. These observations fail to provide support for a robust pathophysiologic interaction between LRRK2 and -synuclein in the forebrain in vivo. There was, however, a modest reduction in microglial activation induced by PFF delivery in the hippocampus of LRRK2 knockout mice, suggesting that LRRK2 may contribute to -synuclein-induced neuroinflammation. Collectively, our data indicate that the pathological accumulation of -synuclein in the mouse forebrain is largely independent of LRRK2. HighlightsO_LIAdult mice accumulate -synuclein pathology in the hippocampus and cortex following stereotactic injection with -synuclein PFFs, with negligible influence of LRRK2 genotype. C_LIO_LIHippocampal and cortical -synuclein pathology elicits the concomitant accrual of phosphorylated tau, reactive astrogliosis, and microglial activation. C_LIO_LIAbsence of endogenous LRRK2 attenuates microglial activation in the dorsal hippocampus induced by PFFs, but not in the entorhinal cortex. C_LIO_LIAccumulation of -synuclein inclusions and related neuropathologic changes were strongly associated across the hippocampal dorsal-ventral axis, regardless of LRRK2 genotype. C_LI

neuroscience↗

bioRxiv2023

Hippocampal subfield vulnerability to α-synuclein pathology precedes neurodegeneration and cognitive dysfunction

Cognitive dysfunction is a salient feature of Parkinsons disease (PD) and Dementia with Lewy bodies (DLB). The onset of dementia reflects the spread of Lewy pathology throughout forebrain structures. The mere presence of Lewy pathology, however, provides limited indication of cognitive status. Thus, it remains unclear whether Lewy pathology is the de facto substrate driving cognitive dysfunction in PD and DLB. Through application of -synuclein fibrils in vivo, we sought to examine the influence of pathologic inclusions on cognition. Following stereotactic injection of -synuclein fibrils within the mouse forebrain, we measured the burden of -synuclein pathology at 1-, 3-, and 6-months post-injection within subregions of the hippocampus and cortex. Under this paradigm, the hippocampal CA2/3 subfield was especially susceptible to - synuclein pathology. Strikingly, we observed a drastic reduction of pathology in the CA2/3 subfield across time-points, consistent with the consolidation of -synuclein pathology into dense somatic inclusions followed by neurodegeneration. Silver-positive degenerating neurites were observed prior to neuronal loss, suggesting that this might be an early feature of fibril-induced neurotoxicity and a precursor to neurodegeneration. Critically, mice injected with -synuclein fibrils developed progressive deficits in spatial learning and memory. These findings support that the formation of -synuclein inclusions in the mouse forebrain precipitate neurodegenerative changes that recapitulate features of Lewy-related cognitive dysfunction. HighlightsO_LIMice injected with -synuclein fibrils develop hippocampal and cortical - synuclein pathology with a dynamic regional burden at 1-, 3-, and 6-months post-injection. C_LIO_LISilver-positive neuronal processes are an early and enduring degenerative feature of the fibril model, while extensive neurodegeneration of the hippocampal CA2/3 subfield is detected at 6-months post-injection. C_LIO_LIMice exhibit progressive hippocampal-dependent spatial learning and memory deficits. C_LIO_LIForebrain injection of -synuclein fibrils may be used to model aspects of Lewy-related cognitive dysfunction. C_LI

neuroscience↗

bioRxiv2019

Dopaminergic Neurodegeneration Induced by Parkinson's Disease-Linked G2019S LRRK2 is Dependent on Kinase and GTPase Activity

AO_SCPLOWBSTRACTC_SCPLOWMutations in the leucine-rich repeat kinase 2 (LRRK2) gene cause late-onset, autosomal dominant familial Parkinsons disease (PD) and represent the most common known cause of PD. LRRK2 can function as both a protein kinase and GTPase and PD-linked mutations are known to influence both of these enzymatic activities. While PD-linked LRRK2 mutations can commonly induce neuronal damage and toxicity in cellular models, the mechanisms underlying these pathogenic effects remain uncertain. Rodent models based upon familial LRRK2 mutations often lack the hallmark features of PD and robust neurodegenerative phenotypes in general. Here, we develop a robust pre-clinical model of PD in adult rats induced by the brain delivery of recombinant adenoviral vectors with neuronal-specific expression of full-length human LRRK2 harboring the most common G2019S mutation. In this model, G2019S LRRK2 induces the robust degeneration of substantia nigra dopaminergic neurons, a pathological hallmark of PD. Introduction of a stable kinase-inactive mutation or in-diet dosing with the selective kinase inhibitor, PF-360, attenuates neurodegeneration induced by G2019S LRRK2. Neuroprotection provided by pharmacological kinase inhibition is mediated by an unusual mechanism involving the selective and robust destabilization of human LRRK2 protein in the rat brain relative to endogenous LRRK2. Our study further demonstrates that dopaminergic neurodegeneration induced by G2019S LRRK2 critically requires normal GTPase activity. The introduction of hypothesis-testing mutations that increase GTP hydrolysis or impair GTP binding activity provide neuroprotection against G2019S LRRK2 via distinct mechanisms. Taken together, our data demonstrate that G2019S LRRK2 induces neurodegeneration in vivo via a mechanism that is dependent on kinase and GTPase activity. Our study provides a robust rodent model of LRRK2-linked PD and nominates kinase inhibition and modulation of GTPase activity as promising disease-modifying therapeutic targets.

neuroscience↗