Presentation on theme: "David Krantz MD, PhD Department of Psychiatry & Biobehavrioal Sciences"— Presentation transcript:
1Neurotransmitter Transporters and Flies: Tools to Study Behavior and Disease David Krantz MD, PhDDepartment of Psychiatry & Biobehavrioal SciencesDavid Geffen School of Medicine at UCLAGonda (Goldschmied) Center for Neuroscience andGenetics Research
2Overview What are neurotransmitter transporters? How do changes in their function affect the nervous system?Why use flies to study them?
3Neurotransmitters are chemicals that allow cells to communicate S y n a p s eNeurotransmitterCell 2Receptors
4Neurotransmitter types MonoaminesDopamine, Serotonin, Norepinephrine, Epineprine (Adrenalin)ActetylcholineGABAGlutamate(Peptides, Gases- not today)
6Why do neurotransmitters need transporters? Oil and water don’t mixTransmitters like to be in waterCell and organelle boundaries are oilyTransporters bridge the water pools
7Plasma Membrane Neurotransmitter Transporters -Monoamine transportersare part of one gene family-GABA and glutamatetransporters are in otherfamiliesDopamineDATNoradrenalineNETSerotoninSERTBröer S Br J Pharmacol , 256.
8VMAT2 in all aminergic brain cells Mammalian Vesicular TransportersVMAT2 in all aminergic brain cells
9Focus on Monoamine Neurotransmitters DopamineRewardSerotoninAppetite,MoodGastrointestinal motilityNoradrenalinAttentionBlood pressureHistamineGastric acid releaseImmune response
10Monoamine Transporters the Major Drug Targets for Stimulants and Antidepressants Vesicular monoamineTransporterDopamine transporterSerotonin “ “Norepi “ “
12Amphetamines Reverses the Flow (Mechanism is complex) Dopamine transporterSerotonin “ “Norepi “ “AmphetaminesMethamphetaminesAdderall- ADHD
13Vesicular Transporters are Drug Targets Vesicular monoamineTransporter (VMAT2)
14Block VMAT with reserpine: Decreases monoamine storage and thus release -Antihypertensive effects -DepressionReserpineVesicular monoamineTransporter (VMAT)
15What would happen if VMAT worked better. Or there was more of it What would happen if VMAT worked better? Or there was more of it? Could that change behavior? Act as a stimulant? Antidepressant?
16Increases monoamine release More VMAT in vitro:Increases monoamine releaseForce cells to make more VMATRecord amine releaseMore amines comes out of each vesicle(Vesicles get a little bigger)“Normal cells”Extra VMATSulzer labPothos et al, J. Neurosci. 2000
17What about more VMAT in vivo? -No in vivo mammalian models-Make fly model-Why use flies?
18Why use flies? -Cheap! (good for teaching!) -”Conservation” of genes e.g. VMAT, DAT-Cool genetic toolse.g. to make more VMAT-Short life spanGenetic experiments in a month!
19How can we tell if there are more extracellular monoamines in flies How can we tell if there are more extracellular monoamines in flies? -Look at their known functionsDopamineGroomingLocomotionOctopamineEgg layingLocomotionSerotoninAggression
20How can we tell if there are more extracellular monoamines in flies How can we tell if there are more extracellular monoamines in flies? -Look at their known functionsDopamineGroomingLocomotionOctopamineEgg layingLocomotionSerotoninAggressionStimulants as positive control
21DVMAT overexpression in vivo mimics the effects of stimulants LocomotionGroomingChang et al 2006
22A New Way to Increase Extracellular Amines WellbutrinProzacRitalinAdderall
23Could we find a drug the would make VMAT work better Could we find a drug the would make VMAT work better? Or just increase exocytosis of monoamines? Could this be used to treat ADHD? depression? Parkinson’s disease?
24Antidepressants and stimulants Some mechanisms not exploited No CurrentDrugs:ActivateVMATIncrease exocytotic releaseAmine agonistReceptorVMATAminergicneuronCurrentDrugs:Block reuptake.degradationAmphetamines cause efflux, not exocytotic release
25To find drugs that might make VMAT work better… First make it work worse! Use dVMAT mutant “Sensitized genetic background”detects drug effects better than wild type
26Primary Screen Test drugs in dVMAT mutant 12456Drug:3..1042Mix into food, Allow larvae to feed, record movement123456
27Example of Primary Screen Data -Select drugs that cause 3-4 SDs above the mean-40 hits out of 1042 drugs-3 time points, 2 concentrations, 7 undergrads, 5 monthsLawal et al, 2012
28Dacarbazine was one of the “hits” in the screen Chemotherapeutic agentAlkylating agentInduces emesis via serotonin releaseSupports fly dataToxicity could be a problemLimits use
29Parse toxic vs. active bits with derivatives DacarbazineAICAMethdiazoniumDNA alkylationAICA: Amino-4-imidazole-carboxamideRemoves the toxic bit
30AICA also stimulates larval locomotion DacarbazineAICA
31How does Dacarbazine/AICA Increase Locomotion? Increase Storage?Increase Release?Other mechanisms?Collaborate with Nigel Maidment’s lab
32Potential Clinical Relevance AICA derivatives for ADHD? Depression?Parkinson’s disease?
33What are neurotransmitter transporters? Why use flies to study them?How do changes in their function affect the nervous system?