title: Dominant-negative effects of LRRK2 heterodimers: a possible mechanism of neurodegeneration in Parkinson's disease caused by LRRK2 I2020T mutation.
abstract: Leucine-rich repeat kinase 2 (LRRK2) is the molecule responsible for autosomal-dominant Parkinson's disease (PD), PARK8, but the etiologic effects of its mutation remain unknown. In the present study, we investigated a novel mechanism for the neurodegeneration induced by I2020T mutant LRRK2. Using native gel electrophoresis and immunoprecipitation, we found that wild-type (WT) LRRK2 formed a heterodimer with I2020T LRRK2 in transfected cells, and that the heterodimer exhibited a markedly lower intracellular protein level than the WT/WT-homodimer. An increased amount of I2020T LRRK2 decreased the protein level of co-transfected WT LRRK2. A pulse-chase experiment revealed that the intracellular protein lifetime of WT LRRK2 was shortened by co-transfection with I2020T LRRK2. These results suggest that I2020T LRRK2 enhances the intracellular degradation of WT LRRK2 through WT/I2020T-heterodimer formation. Overexpression of WT LRRK2 in HEK293 cells increased the phosphorylation level of Akt1 (S473), a possible physiological substrate of LRRK2, and made cells resistant to hydrogen peroxide-induced apoptosis. However, both Akt1 phosphorylation and apoptosis resistance were reduced in WT/I2020T-expressing cells in comparison with WT/WT-expressing cells. Reduction of Akt1 phosphorylation and apoptosis resistance were also evident when a neuroblastoma SH-SY5Y clone overexpressing WT LRRK2 was transfected with the I2020T LRRK2. Altogether, these results suggest that the I2020T mutation enhances the intracellular degradation of LRRK2 through WT/I2020T-heterodimer formation, leading to reduced Akt1 phosphorylation and diminished protectivity against apoptosis. Our findings suggest the possibility of a dominant-negative mechanism of neurodegeneration in PD caused by I2020T LRRK2 mutation.
authors.affiliation: Division of Clinical Immunology, Graduate School of Medical Sciences, Kitasato University, Kanagawa, Japan.
authors.forename: Etsuro
authors.initials: E
authors.lastname: Ohta
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Kawakami
authors.forename: Makoto
authors.initials: M
authors.lastname: Kubo
authors.forename: Fumiya
authors.initials: F
authors.lastname: Obata
mesh_terms: D017209:Apoptosis; D057809:HEK293 Cells; D006801:Humans; D047468:Immunoprecipitation; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D009154:Mutation; D010300:Parkinson Disease / Q000201:enzymology* / Q000235:genetics / Q000473:pathology*; D010766:Phosphorylation; D055503:Protein Multimerization; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt
chemical_list: C495280:LRRK2 protein, human; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt