Objective: To identify the LRRK2 I1371V mutational effects on astroglial biology involving glutamate metabolism and glutathione machinery.

Background: The underlying cause of most of the familial or sporadic PD occurrence is due to the autosomal dominant mutations in α-synuclein and LRRK2 gene. Most symptoms of PD can be directly attributed to the defective kinase activity of LRRK2, linked to increased phosphorylation of other proteins or decreased activation of the LRRK2 enzyme itself. I1371V is a LRRK2 mutation in Roc domain, with the largest incidence in India, impacting its GTPase function. The effect of the LRRK2 mutation I1371V in astroglial biology is barely known. The effect of the accumulation of GTP bound LRRK2 in astrocytes is yet to be elucidated.

Method: In this study, we intend to look into the effect of I1371V mutation of LRRK2 on the astroglial biology through the iPSC platform. We have derived the astrocytes, using a two-step differentiation method, from iPSCs generated from healthy individuals, serving as the healthy control astrocytes and that from PD patients with the I1371V mutation, serving as the PD astrocytes (age matched individuals). We have looked into the glutamate – glutamine cycle; from the clearance of glutamate to it conversion to glutamine and transfer to the neurons. Additionally, we have also checked the oxidative stress quenching capability of the astrocytes in terms of glutathione content and related enzyme expression.

Results: Glutamate content and the gene expression of the glutamate transporters in the PD astrocytes significantly decreased. Additionally, the conversion of glutamate to glutamine or alpha-ketoglutarate which enters the TCA cycle was impaired. Oxidative stress quenching capability of the astrocytes in terms of glutathione content was significantly reduced in the PD astrocytes. Gene expression of the enzymes involved in the glutathione machinery were also less compared to the healthy astrocytes.

Conclusion: De novo synthesis of glutamine is impaired as a result of which the transport of glutamine to the neurons was also less, indicating disorder in the intracellular glutamate metabolism. Antioxidation property of the astrocytes is compromised owing to the impaired glutathione toolkit in the PD astrocytes. Detrimental astroglial biology in astrocytes derived from the PD patient-specific iPSCs gives important clues of the niche cells being affected prior to neurodegeneration.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/mutational-effects-of-lrrk2-i1371v-in-astrocytes-derived-from-patient-specific-ipscs/