Involvement of GDNF and LIMK1 and heat shock proteins in drosophila learning and memory formation

Molecular mechanisms of the synapse and dendrite integrity maintenance and their disruption in psychiatric and neurodegenerative diseases (NDD) are being studied intensively to identify target genes for therapeutic activities. It is suggested that synapse is a tripartite system in which glia, alongside with well-studied pre- and postsynaptic neurons, represents a third, poorly studied partner in synaptic transmission involved in a positive feedback loop between the other two partners. It is the glia cell-derived neurotrophic factor (GDNF) and the transmembrane proteins, neuregulins, that mediate bidirectional coupling between presynaptic neurons and their postsynaptic targets. Neuregulins are structurally related to the epidermal growth factor and have a cytoplasmic domain that interacts with intracellular LIM kinase 1 (LIMK1), the key enzyme of actin remodeling. Since neurons and axons that do not receive a sufficient GDNF supply are at risk of degeneration and synapse elimination, GDNF became a central target factor in human NDD therapy. The delivery of GDNF-producing stem cells to the nidus of neurodegeneration by transplantation surgery is an efficient tool for NDD treatment. A new approach is proposed based on the use of the Drosophila heat shock (hs) promoter that responds to the mammalian body temperature and ensures constant expression of the human GDNF gene. The Drosophila models facilitate studying the role of each component of the bidirectional signaling between pre- and postsynaptic neurons in the development of the key diagnostic NDD symptom—a defective memory formation resulted from synaptic atrophy. To assess the efficiency of memory formation depending on the level of GDNF and LIMK1 brain expression, we used the Drosophila strains simulating different nervous system disorders: GDNF, the transgenic flies that carry the human GDNF gene under hs-promoter, l(1)ts403, the mutants with disruption of heat shock proteins (HSPs) mRNA nuclear trafficking, and agnts3 carrying a mutation in LIMK1 gene. We investigated at the behavioral (learning/memory) level the functional connections between GDNF, LIMK1 and HSP signaling transductions that might offer promising targets for complex approaches to NDD treatment.