The Regulatory Role Of A Novel GAP Protein MRG In Mutant LRRK2 Functions During The Pathogenesis Of Parkinson Disease

Parkinson’s disease(PD)is a major neurodegenerative disease with unknown etiology.Recently,studies on familial PD led to the identification of several disease-associated genes including leucine-rich repeat kinase 2(LRRK2).While numerous studies unveiled the role of the elevated kinase activity of the mutant LRRK2 in PD pathogenesis,the functional regulatory mechanisms of the scaffold protein remain elusive.More specifically,with both intrinsic GTPase activity and kinase activity exited within LRRK2,their intramolecular interaction and regulation are poorly understood.Previously,our laboratory has identified a novel Rac1GAP(MRG)that interacted with the Roc-GTPase domain of LRRK2 with specific GAP activity.This thesis work intended to extend this biochemical studies on MRG to explore its functional regulatory role on PD related intrinsic enzymatic activities at the levels of biochemical,cellular and animal model.Our main results are: 1)The interaction between MRG and LRRK2 is dependent on the activity of Roc-GTPase;2)Overexpressed MRG could significantly decrease the kinase activity of mutant LRKR2 in vitro;3)Overexpression of MRG could abolish the abnormal retrograde trafficking of cargo protein CI-M6 PR induced by the mutant of LRRK2;4)Overexpressed MRG could inhibit the increased autophagy in differentiated neuronal cell line SH-SY5 Y induced by mutant LRRK2;5)MRG protein overexpression can reverse the neuritic shortening caused by mutant LRRK2;6)The transgenic overexpressed MRG in Drosophila could reduce the abnormal behavior as well as improve the survival rate of the mutant LRRK2 flies.Our results strongly suggested that the novel GAP protein MRG can functionally regulate the intrinsic GTPase activity of LRRK2 and further alter the kinase activity through intramolecular mechanism.Thus,this work provides not only better understanding on how LRRK2 and its mutant variants are involved in the pathogenesis of PD but also a new insight in drug design in PD clinical therapeutic applications.