Date of Award

1-1-2022

Publication Type

Thesis

Degree Name

M.Sc.

Department

Biological Sciences

Keywords

Drosophila melanogaster, Neuromuscular junction, Phosphoinositide 4-kinase, Phosphoinositides, Presynaptic, Synaptic boutons

Supervisor

J. Dason

Supervisor

D. Marquardt

Rights

info:eu-repo/semantics/embargoedAccess

Abstract

Phosphoinositides (PI) are lipid molecules reversibly phosphorylated by kinases at the 3’, 4’ and 5’ -OH groups of their myoinositol ring, producing seven PI species. PIs act in a dynamic and acute manner at the synapse, facilitated by multiple kinases that synthesize their respective PI species at the precise location and time. There are three phosphatidylinositol 4-kinase (PI4K) genes that encode three different PI4K enzymes (PI4KII, PI4KIIIβ (fwd) and PI4KIIIα) to synthesize PI4P (converted to PIP2), serving vital functions at the synapse. PIs participate in signaling events, protein recruitment, marking membrane identity, regulating channels and transporters, synaptic growth, exocytosis, and endocytosis. Previous work with PI4KII null mutants has shown effects on synaptic morphology, but not for neurotransmitter release, and fwd null mutants have shown no effects on synaptic morphology or neurotransmitter release. These studies may emphasize a pattern of functional redundancy of PI4Ks, and the necessity to explore synaptic phenotypes of mutants for multiple enzymes in the PI pathway. This thesis examined a fwd3, PI4KII double mutant for effects on neurotransmitter release and synaptic morphology at the Drosophila NMJ. This double mutant showed decreased neurotransmitter release, and increased synaptic growth compared to controls. PI4KII single mutants showed no difference in neurotransmitter release, and increased synaptic growth compared to controls.fwd single mutants showed decreased neurotransmitter release, and decreased synaptic growth. These data show that the PI pathway has wide-ranging effects in synaptic function, where PI4KII and fwd have different effects at the synapse. A second objective of this thesis involved generating transgenic flies that express an optogenetic tool to manipulate PI levels more acutely at the presynaptic membrane. This optogenetic tool will help to further decipher the diverse effects that PIs have on neurotransmitter release and synaptic morphology.

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