There is increasing evidence that Parkinson?s disease (PD) is intricately linked to mitochondrial abnormalities: familial forms of the disease are linked to mitochondrial quality control proteins PINK1, Parkin, and Fbxo7; mitochondria of DA neurons have the highest rates of mtDNA mutations; and small molecule mitochondrial toxinsproducepreferentialdegenerationofdopaminergicneuronsinmice.PTENInducedKinase1(PINK1)isa master regulator of mitochondrial quality control. In the presence of a depolarized mitochondrion, PINK1 is stabilized on the outer mitochondrial membrane, where it recruits and phosphorylates ubiquitin and Parkin, blocksmitochondrialfusionandtraffickingandultimatelytriggersmitochondrialautophagy.Further,PINK1can drivemitochondrialbiogenesisbydirectlyphosphorylatingPARIS,andcanopposealpha-?synucleinandamyloid toxicityandproteotoxicstressmoregenerally. Geneticmanipulationsthatdriveaccumulationofdamagedmitochondriahaveasignificanteffectoncellhealth, leadingustobelievethatmitochondrialproblemsinthedopaminergicneuronsofthesubstantianigramaybe causing energy failure and/or an increased generation of reactive oxygen species, and ultimately neuronal death.Thishypothesisappearstobefurthersupportedbythefactthatmorethan50mutationsinthekinase PINK1 have been associated with the development of autosomal recessive PD. In addition, overexpression of wild-?type PINK1, but not the catalytically compromised PD-?associated PINK1G309D mutant can rescue this defectinmitophagyandprotectcellsfromoxidativestress. Our founding team discovered that it is possible to selectively amplify PINK1 activity through a novel ?neo-? substrate?mechanism.ThedownstreamconsequencesofamplifiedPINK1activitycanbeseeninhigherrates ofParkinrecruitmenttostressedmitochondria,reducedmitochondrialmotility,and,ultimately,lowerlevelsof apoptosis vs. healthy controls. This therapeutic strategy is that it doesn?t interfere with PINK1?s endogenous regulation;rather,itonlyamplifiesPINK1activitywhenPINK1isstabilizedonadepolarizedmitochondrion.We believethatthepharmacologicalamplificationofPINK1kinaseactivity,actingthroughtheclearanceofdefective mitochondria and PINK1-?related suppression of apoptosis, could prove a powerful mechanism through which totreatPD. In this SBIR project we will conduct lead optimization. We have already made great strides in our chemistry program,significantlyboostingtheoralPKpropertiesandpotencyofourPINK1neo-?substrates.Webelievethat bytheendofthisgrantwewillhaveidentifiedamoleculesuitableforfinalproofofconceptinvivostudies,with INDenablingstudiestofollow.
PublicHealthRelevance Parkinson?sdiseaseaffectsover1,000,000Americans,anumberthat?sexpectedtogrow significantlyby2040.AccordingtoastudypublishedinMovementDisorders(2013),theUnited Statesalreadysuffersmorethan$14.4billioninannualeconomiclossesowingtothedisease, andthatanalysisexcludestheimpactoncaregiversandfamilies.Weaimtodevelopthefirst disease-?modifyingtherapyforParkinson?sdisease,reducingthestrainofPDonAmerica?s healthcaresystemandensuringahigherqualityoflifeofpatientsandtheirfamilies.
