Mutations in the LRRK2 gene are the most common cause of autosomal dominant PD, however, the cellular pathways mediating LRRK2-induced neurodegeneration remain unclear. We have identified a novel interaction between LRRK2 and the PD-linked gene product, VPS35. VPS35 functions as a component of the retromer complex which mediates retrograde transport of endosomal protein cargo. Previous studies suggest that familial LRRK2 mutants induce retromer deficiency in mammalian cells and mouse brain, however, a critical validation of this potential mechanism is currently lacking. To extend these prior studies, we have evaluated the functional interaction of LRRK2 and VPS35 in neuronal and rodent LRRK2 models. We observe the robust interaction and colocalization of LRRK2 and VPS35 in human cells. Familial PD mutations in either protein have a limited effect on their interaction whereas functional mutations support a stronger interaction of VPS35 with kinase-inactive LRRK2. We find that VPS35 serves as a modest substrate of LRRK2 kinase activity in vitro, whereas familial VPS35 mutations fail to alter LRRK2 kinase activity in cells. We demonstrate that familial mutations in LRRK2 fail to alter the steady-state levels of endogenous retromer subunits when overexpressed in human cell lines or rat primary cortical neurons. Furthermore, we find no evidence for altered retromer protein levels in distinct brain regions of human G2019S LRRK2 transgenic mice or in G2019S mutant and idiopathic PD brains relative to control brains. Finally, we show that VPS35 heterozygous mice do not exhibit increased susceptibility to dopaminergic degeneration induced by acute or chronic expression of human G2019S LRRK2 in the nigrostriatal pathway. Our data reveal an interaction of LRRK2 with VPS35 but fail to provide clear evidence for a retromer deficiency induced by mutant LRRK2 in PD-relevant models.
|Commitee:||Ma, Jiyan, Melcher, Karsten, Lee, Michael|
|School:||Van Andel Research Institute|
|School Location:||United States -- Michigan|
|Source:||DAI-B 81/8(E), Dissertation Abstracts International|
|Subjects:||Neurosciences, Molecular biology, Cellular biology|
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