A Drosophila temperature-sensitive seizure mutant in phosphoglycerate kinase disrupts ATP generation and alters synaptic function.
A novel paralytic mutant, nubian, was identified in a behavioral screen for conditional temperature-sensitive seizure mutants in Drosophila melanogaster. nubian mutants display reduced lifespan, abnormal motor behavior, altered synaptic structure, and defective neurotransmitter release. The nubian mutant disrupts phosphoglycerate kinase (PGK), an enzyme required for ATP generation in the terminal stage of the glycolytic pathway. Consistent with altered ATP generation in nubian animals, brain extracts show a threefold reduction in resting ATP levels compared with controls. Microarray analysis of nubian mutants reveals altered transcription of genes implicated in glucose and lipid metabolism. Disruption of ATP generation in nubian animals is accompanied by temperature-dependent defects in neuronal activity, with initial seizure activity, followed by an activity-dependent loss of synaptic transmission. nubian mutants also display structural defects at the synapse, with larger varicosity size but normal varicosity number, indicating that these synaptic parameters are regulated independently. Both exocytotic (NSF) and endocytotic (dynamin) ATPase/GTPase activity are required for normal synaptic transmission. Biochemical and physiological analyses indicate that synaptic defects in nubian animals are secondary to defective endocytosis, suggesting that endocytotic pathways may be generally more sensitive to altered ATP levels than those used for exocytosis. Alterations in ATP metabolism likely disrupt similar pathways in humans, because PGK deficiency is associated with mental retardation, seizures, and exercise intolerance. Given the behavioral similarities between disruptions of PGK function in Drosophila and humans, the analysis of nubian animals may reveal conserved neuronal responses associated with altered ATP generation within the brain.
Wang
Ping
P
The Picower Center for Learning and Memory, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Saraswati
Sudipta
S
Guan
Zhuo
Z
Watkins
Carol J
CJ
Wurtman
Richard J
RJ
Littleton
J Troy
JT
D000255:Adenosine Triphosphate / Q000096:biosynthesis*; D000818:Animals; D001522:Behavior, Animal / Q000502:physiology; D002874:Chromosome Mapping; D004330:Drosophila / Q000201:enzymology* / Q000235:genetics; D004594:Electrophysiology; D004705:Endocytosis / Q000235:genetics / Q000502:physiology; D005260:Female; D005820:Genetic Testing; D007814:Larva; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D016296:Mutagenesis; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010243:Paralysis / Q000209:etiology; D010735:Phosphoglycerate Kinase / Q000235:genetics* / Q000378:metabolism; D050600:SNARE Proteins; D012640:Seizures / Q000150:complications / Q000235:genetics* / Q000378:metabolism*; D013569:Synapses / Q000502:physiology; D009435:Synaptic Transmission / Q000502:physiology*; D013572:Synaptic Vesicles / Q000378:metabolism; D013696:Temperature; D033921:Vesicular Transport Proteins
D008565:Membrane Proteins; D050600:SNARE Proteins; D033921:Vesicular Transport Proteins; D000255:Adenosine Triphosphate; D010735:Phosphoglycerate Kinase