.ALPHA.-Synuclein Aggregation and Transmission Are Enhanced by Leucine-Rich Repeat Kinase 2 in Human Neuroblastoma SH-SY5Y Cells

Abstract

Parkinson disease (PD) is the second most common neurodegenerative disease. The muscle rigidity, tremor, and bradykinesia that are characteristic of PD patients, are caused by dopaminergic neuron death in the substantia nigra. One of the well-known pathological hallmarks inside the cells is the presence of inclusion bodies called Lewy bodies (LB) that include aggregates of a-synuclein. Since a-synuclein and leucine-rich repeat kinase 2 (LRRK2) cause familial forms of PD that resembles sporadic PD pathologically, these genetic mutations provide important molecular tools to investigate PD pathogenesis. 1) Although the etiology of PD remains unclear, the production of aggregated a-synuclein is a key step in PD pathogenesis. 2)a-Synuclein plays an important role in PD pathology and neuronal cell death. [3][4][5] Point mutations (A30P, E46K, and A53T) and multiplication of the gene a-synuclein are linked to the early-onset of PD pathology. The increased severity of PD and earlier age of onset have been reported to correlate with increased a-synuclein dosage.6) The physiological function of a-synuclein found in pre-synapus remains undefined. Several studies have indicated that a-synuclein regulates intracellular transport of synaptic vesicles underlying neurotransmitter release.7-14) a-Synuclein may also be involved in mitochondrial complex I function, 15,16) and has been reported to impair macroautophagy. 17)Until recently, a-synuclein was considered to exert pathogenic effects inside the cells. However, a-synuclein can be detected in human cerebrospinal fluid (CSF) and plasma.18)The accumulation of aggregated a-synuclein spreads from lower brainstem into the limbic system and neocortex, suggesting a mechanism underlying pathological propagation of PD such as Prion diseases.19) Some groups have reported that aggregated a-synuclein can be released into extracellular media by exocytosis through exosomes and propagated by direct neuron-to-neuron transmission. [20][21][22] LRRK2 is a large 2527 amino acid protein consisting of several functional domains including a Ras-like small GTPase domain (ROC), a carboxy-terminal of Roc (COR) domain, and a kinase domain. The various mutations in LRRK2 are involved in PD, such as R1441C, R1441G in the Roc domain, Y1699C in the COR domain, and G2019S, I2020T in the kinase domain. Among them, G2019S mutation clearly increases kinase activity, which is required for PD pathology.23,24) G2019S mutation has been shown to increase kinase activity by 2 to 3 fold. However, normal function and kinase substrates of LRRK2 remain unclear. Although mutant LRRK2 was toxic when overexpressed in cultured cells 25,26) and Drosophila, 27,28) loss of neurons was not observed in transgenic mice overexpressing R1441G and R1441C mutants. 29,30) Loss of LRRK2 did not cause neurodegeneration and neuropathological changes. LRRK2 mutations cause clinically typical PD features, ranging from nigral degeneration without LB to nigral degeneration with widespread LB or neurofibrillary tangles. 31)The neuronal cell...

Can Parkinson's disease pathology be propagated from one neuron to another?

“…These modifications include truncated and ubiquinated αsyn, and also phosphorylation which perhaps is the most studied modification (Oueslati et al, 2010). Leucine-rich repeat kinase 2 (LRRK-2) has been identified as a crucial protein in the pathology of PD and a recent paper highlights a direct role in transmission and aggregation of αsyn (Kondo et al, 2011). This report follows previous work that has shown kinase inhibitors and phosphatase activity are protective in different models of PD (Lee et al, 2011a;.…”

LRRK2 Promotes Tau Accumulation, Aggregation and Release

“…Previously, the G2019S LRRK2 mutant was also described to enhance the aggregate formation and phosphorylation of alpha-synuclein, and to contribute to alpha-synuclein release into the extracellular medium [48]. Tau release via membrane vesicles was demonstrated upon its overexpression in HEK-293 cells [49].…”

The SH-SY5Y cell line in Parkinson’s disease research: a systematic review

“…The additive effects that are caused by co-expression of familial PD genes can also be observed in this cell line (e.g. cotransfection of α-synuclein and LRRK2 enhances the formation of aggregates, phosphorylation, cell-to-cell transmission and extracellular release of α-synuclein [90]). Therefore, SH-SY5Y cells represent an attractive tool to study most cellular alterations linked to PD and strategies to ameliorate their effects, but a careful experimental setting is required when analyzing α-synuclein aggregation, since the findings vary between studies.…”