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:
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
Overview What are neurotransmitter transporters? How do changes in their function affect the nervous system? Why use flies to study them?
Cell 2 Neurotransmitters are chemicals that allow cells to communicate Cell 1 Receptors S y n a p s e Neurotransmitter
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
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
Mammalian Vesicular Transporters VMAT2 in all aminergic brain cells
Dopamine transporter Serotonin Norepi. Amphetamines Reverses the Flow (Mechanism is complex) Amphetamines Methamphetamines Adderall- ADHD
Vesicular monoamine Transporter (VMAT2) Vesicular Transporters are Drug Targets
Vesicular monoamine Transporter (VMAT) Block VMAT with reserpine: Decreases monoamine storage and thus release -Antihypertensive effects -Depression Reserpine
What would happen if VMAT worked better? Or there was more of it? Could that change behavior? Act as a stimulant? Antidepressant?
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
What about more VMAT in vivo? -No in vivo mammalian models -Make fly model -Why use flies?
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!
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
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
DVMAT overexpression in vivo mimics the effects of stimulants Locomotion Grooming Chang et al 2006
A New Way to Increase Extracellular Amines Wellbutrin Prozac Ritalin Adderall
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?
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
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
Primary Screen Test drugs in dVMAT mutant Drug: Mix into food, Allow larvae to feed, record movement
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
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
Parse toxic vs. active bits with derivatives DacarbazineAICA Methdiazonium DNA alkylation AICA: Amino-4-imidazole-carboxamide Removes the toxic bit
AICA also stimulates larval locomotion Dacarbazine AICA
How does Dacarbazine/AICA Increase Locomotion? Increase Storage? Increase Release? Other mechanisms? Collaborate with Nigel Maidments lab