The mouse/human cross-species heterodimer of leucine-rich repeat kinase 2: Possible significance in the transgenic model mouse of Parkinson's disease

Leucine-rich repeat kinase (LRRK2) is the causal molecule of autosomal dominant Parkinson's disease (PD). We previously reported that intracellular degradation of wild-type (WT) LRRK2 is promoted by formation of heterodimers with the I2020T mutant LRRK2. In the present study, we investigated whether this is also the case for mouse/human cross-species heterodimers, which could be formed in transgenic mice. First, by co-transfection and immunoprecipitation, we identified the cross-species heterodimer of mouse LRRK2 and human LRRK2. Next, we found that the protein level of mouse LRRK2 decreased when co-transfected with human I2020T LRRK2, but not with human WT LRRK2. These results suggested that degradation of mouse LRRK2 was promoted by formation of a cross-species heterodimer with the mutant LRRK2. In I2020T LRRK2-transgenic mice, the lower protein level of brain LRRK2 in comparison with control mice, together with higher expression of the mRNA, suggested that endogenous LRRK2 was degraded by formation of cross-species heterodimers. Our results suggest a new concept of cross-species dimer/oligomer formation in transgenic disease-model mice.