Autosomaldominantmutationsinvacuolarproteinsorting35(VPS35)havebeenidentifiedasacausalPD gene,playingaroleinthedevelopmentoflate-onsetPD.VPS35functionsasascaffoldingproteinforretromer complexthatmediatesrecyclingofcargoproteins(transmembraneproteins)fromendosomestothetrans- Golgiapparatusortheplasmamembrane.Therefore,mutationsinVPS35couldpreventorlimititsdeliveryof thecargoes,whicharecrucialforthesurvivalofdopaminergicneurons.Hence,adisruptionintherecycling pathwayofthesecargoesmayplayacrucialroleinthedemiseofdopaminergicneuronsinthesubstantia nigraofpatientswithVPS35mutations.AgreaterunderstandingofbiologyofVPS35andthepathophysiology ofmutantVPS35areessentialtothedevelopmentoftherapeuticinterventionsaimedatpreventingtheonset and/orretardingprogressionofPD.Nonetheless,thefunctionalconsequencesoftheVPS35geneticvariations inPDhavenotyetbeendiscovered.TobetterunderstandthepathogenicinvolvementofVPS35mutationsin vivo,wegeneratedatetracyclineconditionalhumanVPS35transgenic(Tg)mousewhereexpressionof mutanthumanD620NVSP35orwild-type(WT)humanVPS35proteinsisachievedinthenigrostriatal dopaminergicpathway,underthecontrolofthedopaminepathway-specifictyrosinehydroxylase(TH)-tTA driver.Utilizingthismousemodel,inaim1,wewillstudyneurochemical,neuroanatomicalandbehavioral changesusinghigh-performanceliquidchromatography,unbiasedstereologicaltechniques,andbehavioral testinginthesemiceastheyage.Inparticular,wewillexplorewhethertheoverexpressionofmutantD620N VPS35indopaminergic(DA)neuronsmayinducelossofdopaminergicneuronsduringaging.Importantly,our preliminarystudyindicatesthattherearerobustandprogressivedegenerationinthesubstantianigraofthe TH-tTA/TetP-D620NVPS35mice.Inaddition,thereisanintriguingbutpoorunderstandingofthepathogenic interplaybetweentheVPS35mutationandmitochondriadysfunctioninPD.Ourpreliminaryresultindicates thatVPS35interactswithKeap1andtheinteractionbetweenKeap1andD620NVPS35leadstoaccumulation ofKeap1,akeyregulatorofNrf2,andaconcomitantdecreaseinproteinlevelsandactivityofNrf2,amaster regulatorofoxidativestress.Inaddition,thedysregulationofKeap1/Nrf2levelsmediateD620NVPS35- inducedDAneuronaltoxicityandmitochondriadysfunctioninhumanDAneurons.
In aim2, wewill characterizeapotentialdefectinmitochondrialqualitycontrolintheD620NVPS35Tgmicerepresenting degenerationofDAneuronsandtheroleofthederegulationofKeap1/Nrf2levelsinregulatingthesedefects. Moreover,wewilldeterminewhethersuppressionofKeap1accumulationrescuesthelossofDAneuronsand mitochondriadysfunctionsinD620NVPS35Tgmice.Thisproposalmayprovideaneworvaluablegenetic mousemodelforPDwithdopaminergicneurodegenerationandanewinsightofVPS35retromerfunctionin lossofdopaminergicneuronsandmitochondriadysfunction.

Public Health Relevance

(RELEVANCE) MutationsinVPS35arethecommoncauseoffamilialPD,yetlittleisknownabouthowthisproteinfunctionsin thepathogenesisofPD.Decipheringofalteredretromerfunctionindegenerationofdopaminergicneurons throughgeneratingandcharacterizingWTandD620NVPS35transgenicmiceandunderstandingapotential pathogenicinterplaybetweenVPS35mutationandmitochondrialdysfunctionswillfurtherenhanceour understandingofVPS35-linkedPDandpromotedevelopmentofdrugsthatsloworhaltthedisease.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Exploratory/Developmental Grants (R21)
Project #
5R21NS098006-02
Application #
9418124
Study Section
Cell Death in Neurodegeneration Study Section (CDIN)
Program Officer
Sieber, Beth-Anne
Project Start
2017-02-01
Project End
2019-01-31
Budget Start
2018-02-01
Budget End
2019-01-31
Support Year
2
Fiscal Year
2018
Total Cost
Indirect Cost
Name
Johns Hopkins University
Department
Anatomy/Cell Biology
Type
Schools of Medicine
DUNS #
001910777
City
Baltimore
State
MD
Country
United States
Zip Code
21205
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Brahmachari, Saurav; Karuppagounder, Senthilkumar S; Ge, Preston et al. (2017) c-Abl and Parkinson's Disease: Mechanisms and Therapeutic Potential. J Parkinsons Dis 7:589-601