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Neurotransmitter Transporters and Flies: Tools to Study Behavior and Disease David Krantz MD, PhD Department of Psychiatry & Biobehavrioal Sciences David.

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Presentation on theme: "Neurotransmitter Transporters and Flies: Tools to Study Behavior and Disease David Krantz MD, PhD Department of Psychiatry & Biobehavrioal Sciences David."— Presentation transcript:

1 Neurotransmitter Transporters and Flies: Tools to Study Behavior and Disease David Krantz MD, PhD Department of Psychiatry & Biobehavrioal Sciences David Geffen School of Medicine at UCLA Gonda (Goldschmied) Center for Neuroscience and Genetics Research

2 Overview What are neurotransmitter transporters? How do changes in their function affect the nervous system? Why use flies to study them?

3 Cell 2 Neurotransmitters are chemicals that allow cells to communicate Cell 1 Receptors S y n a p s e Neurotransmitter

4 Neurotransmitter types Monoamines –Dopamine, Serotonin, Norepinephrine, Epineprine (Adrenalin) Actetylcholine GABA Glutamate (Peptides, Gases- not today)

5 Plasma membrane and vesicular transporters

6 Why do neurotransmitters need transporters? Oil and water dont mix Transmitters like to be in water Cell and organelle boundaries are oily Transporters bridge the water pools

7 Plasma Membrane Neurotransmitter Transporters Bröer S Br J Pharmacol , Monoamine transporters are part of one gene family -GABA and glutamate transporters are in other families Dopamine DAT Noradrenaline NET Serotonin SERT

8 Mammalian Vesicular Transporters VMAT2 in all aminergic brain cells

9 Focus on Monoamine Neurotransmitters Noradrenalin Attention Blood pressure Histamine Gastric acid release Immune response Dopamine Reward Serotonin Appetite,Mood Gastrointestinal motility

10 Dopamine transporter Serotonin Norepi. Monoamine Transporters the Major Drug Targets for Stimulants and Antidepressants Vesicular monoamine Transporter

11 Dopamine transporter Serotonin Norepi. Blockade of Plasma Membrane Amine Transporter Increases Extracellular Neurotransmitter Cocaine Ritalin Prozac Wellbutrin Zoloft

12 Dopamine transporter Serotonin Norepi. Amphetamines Reverses the Flow (Mechanism is complex) Amphetamines Methamphetamines Adderall- ADHD

13 Vesicular monoamine Transporter (VMAT2) Vesicular Transporters are Drug Targets

14 Vesicular monoamine Transporter (VMAT) Block VMAT with reserpine: Decreases monoamine storage and thus release -Antihypertensive effects -Depression Reserpine

15 What would happen if VMAT worked better? Or there was more of it? Could that change behavior? Act as a stimulant? Antidepressant?

16 Increases monoamine release Force cells to make more VMAT Record amine release More amines comes out of each vesicle (Vesicles get a little bigger) Sulzer lab Pothos et al, J. Neurosci More VMAT in vitro: Normal cells Extra VMAT

17 What about more VMAT in vivo? -No in vivo mammalian models -Make fly model -Why use flies?

18 Why use flies? -Cheap! (good for teaching!) -Conservation of genes e.g. VMAT, DAT -Cool genetic tools e.g. to make more VMAT -Short life span Genetic experiments in a month!

19 How can we tell if there are more extracellular monoamines in flies? -Look at their known functions Dopamine Grooming Locomotion Serotonin Aggression Octopamine Egg laying Locomotion

20 How can we tell if there are more extracellular monoamines in flies? -Look at their known functions Dopamine Grooming Locomotion Serotonin Aggression Octopamine Egg laying Locomotion Stimulants as positive control

21 DVMAT overexpression in vivo mimics the effects of stimulants Locomotion Grooming Chang et al 2006

22 A New Way to Increase Extracellular Amines Wellbutrin Prozac Ritalin Adderall

23 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? Parkinsons disease?

24 Antidepressants and stimulants Some mechanisms not exploited Amine agonist Activate VMAT Increase exocytotic release Block reuptake. degradation Current Drugs: No Current Drugs : VMAT neuron Aminergic Receptor Amphetamines cause efflux, not exocytotic release

25 To 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

26 Primary Screen Test drugs in dVMAT mutant Drug: Mix into food, Allow larvae to feed, record movement

27 Example 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 months Lawal et al, 2012

28 Dacarbazine was one of the hits in the screen Chemotherapeutic agent –Alkylating agent Induces emesis via serotonin release –Supports fly data Toxicity could be a problem –Limits use

29 Parse toxic vs. active bits with derivatives DacarbazineAICA Methdiazonium DNA alkylation AICA: Amino-4-imidazole-carboxamide Removes the toxic bit

30 AICA also stimulates larval locomotion Dacarbazine AICA

31 How does Dacarbazine/AICA Increase Locomotion? Increase Storage? Increase Release? Other mechanisms? Collaborate with Nigel Maidments lab

32 Potential Clinical Relevance AICA derivatives for ADHD? Depression? Parkinsons disease?

33 What are neurotransmitter transporters? Why use flies to study them? How do changes in their function affect the nervous system?

34 Questions?


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