Activation of FADD-Dependent Neuronal Death Pathways as a Predictor of Pathogenicity for LRRK2 Mutations.
BACKGROUND
Despite the plethora of sequence variants in LRRK2, only a few clearly segregate with PD. Even within this group of pathogenic mutations, the phenotypic profile can differ widely.


OBJECTIVE
We examined multiple properties of LRRK2 behavior in cellular models over-expressing three sequence variants described in Greek PD patients in comparison to several known pathogenic and non-pathogenic LRRK2 mutations, to determine if specific phenotypes associated with pathogenic LRRK2 can be observed in other less-common sequence variants for which pathogenicity is unclear based on clinical and/or genetic data alone.


METHODS
The oligomerization, activity, phosphorylation, and interaction with FADD was assessed in HEK293T cells over-expressing LRRK2; while the induction of neuronal death was determined by quantifying apoptotic nuclei in primary neurons transiently expressing LRRK2.


RESULTS
One LRRK2 variant, A211V, exhibited a modest increase in kinase activity, whereas only the pathogenic mutants G2019S and I2020T displayed significantly altered auto-phosphorylation. We observed an induction of detergent-insoluble high molecular weight structures upon expression of pathogenic LRRK2 mutants, but not the other LRRK2 variants. In contrast, each of the variants tested induced apoptotic death of cultured neurons similar to pathogenic LRRK2 in a FADD-dependent manner.


CONCLUSIONS
Overall, despite differences in some properties of LRRK2 function such as kinase activity and its oligomerization, each of the LRRK2 variants examined induced neuronal death to a similar extent. Furthermore, our findings further strengthen the notion of a convergence on the extrinsic cell death pathway common to mutations in LRRK2 that are capable of inducing neuronal death.
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Katerina
K
Melachroinou
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Emmanouela
E
Leandrou
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Polytimi-Eleni
PE
Valkimadi
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Anna
A
Memou
Department of Neurogenetics, Institute of Biomedical Research & Technology (CERETETH), Larissa, Greece.|Department of Neurology, University of Thessaly School of Medicine, Larissa, Greece.
Georgios
G
Hadjigeorgiou
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.|Second Department of Neurology, University of Athens Medical School, Athens, Greece.
Leonidas
L
Stefanis
Division of Basic Neurosciences, Biomedical Research Foundation of the Academy of Athens, Athens, Greece.
Hardy J
HJ
Rideout
D016923:Cell Death; D002460:Cell Line; D002478:Cells, Cultured; D053200:Fas-Associated Death Domain Protein / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2 / Q000235:genetics* / Q000378:metabolism; D009154:Mutation; D009474:Neurons / Q000378:metabolism / Q000473:pathology*; D010300:Parkinson Disease / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D010766:Phosphorylation; D060066:Protein Interaction Maps; D015398:Signal Transduction
C505533:FADD protein, human; D053200:Fas-Associated Death Domain Protein; D006160:Guanosine Triphosphate; C495280:LRRK2 protein, human; D000071158:Leucine-Rich Repeat Serine-Threonine Protein Kinase-2