Brain central regions in courtship sound production in Drosophila melanogaster

There are debates about the function of the two main central brain structures of insects--mushroom bodies and the central complex--in the control of motor co-ordination and triggering of different behaviour programs including sound production. To throw additional light onto this problem we analysed the parameters of the love song produced by 5-day old males courting for 5 minutes a fertilised CS female at 25 degrees C, in two wild-type strains of Drosophila melanogaster (Berlin and CS), hydroxyurea (HU)-treated flies (chemical ablation of the mushroom bodies) two mushroom body mutants (mbm1 and mud1), two central complex mutants (ccbKS127 and cexKS181) and a mutant cxbN71 with defects both in the mushroom bodies and in the central complex. It was found that the love song of HU-treated flies devoid of the mushroom bodies is very similar to that of wild-type flies. In mbm1 and mud1 the main parameters of the song (interpulse interval, IPI, and train duration) are slightly shifted from those of wild type but the sharpness of tuning of the pulse oscillator is the same. The flies of all these strains are equal to wild-type strains in mating success (% of copulations with virgins in 10-min test). On the contrary, the songs of the central complex mutants differ from those of wild-type flies. First of all, the sharpness of tuning of the pulse oscillator is destroyed,--the IPIs become highly variable. The pulses often are much longer and polycyclic as in well known cacophony mutant. The mean duration of pulse trains is much shorter. The males of the mutant cexKS181 usually court violently, but in most cases abnormal sounds are produced. Both cexKS181 and ccbKS127 males are much less successful in matings in comparison to wild-type flies. One can conclude that the central complex plays probably a very important role in the control of singing, whereas the mushroom bodies are practically not involved in this function.     

Role of LIM Kinase 1 in Dopaminergic and Serotonergic Neurons in Genome Stability,Learning and Memory during Stress Response to Weakening of Earth’s Magnetic Field in Drosophila

Journal of Evolutionary Biochemistry and Physiology - The paper continues the cycle of studies on the evolutionary link between the mechanisms of stress response formation and cognitive functions...     

Stacking interaction and its role in kynurenic acid binding to glutamate ionotropic receptors

Stacking interaction is known to play an important role in protein folding, enzyme-substrate and ligand-receptor complex formation. It has been shown to make a contribution into the aromatic antagonists binding with glutamate ionotropic receptors (iGluRs), in particular, the complex of NMDA receptor NR1 subunit with the kynurenic acid (KYNA) derivatives. The specificity of KYNA binding to the glutamate receptors subtypes might partially result from the differences in stacking interaction. We have calculated the optimal geometry and binding energy of KYNA dimers with the four types of aromatic amino acid residues in Rattus and Drosophila ionotropic iGluR subunits. All ab initio quantum chemical calculations were performed taking into account electron correlations at MP2 and MP4 perturbation theory levels. We have also investigated the potential energy surfaces (PES) of stacking and hydrogen bonds (HBs) within the receptor binding site and calculated the free energy of the ligand-receptor complex formation. The energy of stacking interaction depends both on the size of aromatic moieties and the electrostatic effects. The distribution of charges was shown to determine the geometry of polar aromatic ring dimers. Presumably, stacking interaction is important at the first stage of ligand binding when HBs are weak. The freedom of ligand movements and rotation within receptor site provides the precise tuning of the HBs pattern, while the incorrect stacking binding prohibits the ligand-receptor complex formation.     

Courtship behavior,communicative sound production and resistance to stress in Drosophila mutants with defective <Emphasis Type="Italic">agnostic</Emphasis> gene coding for LIMK1

To elucidate the role of one of the main elements of signal cascade of actin remodeling—LIM-kinase 1 (LIMK1)—in the control of animal behavior we have studied the characteristics of courtship behavior, parameters of acoustic communicative signals and their resistance to heat shock (HS, 37°C, 30 min) in Drosophila melanogaster males with the agn ^ts3 mutation in the agnostic locus which contains CG1848 gene for LIMK1. The data obtained were compared with the results of our previous similar investigation on wild type CS males [1]. Flies were divided into 4 groups. The males of control groups were not subjected to heat shock. Other groups were comprised of males subjected to heat shock either at the beginning of larval development when the mushroom body neuroblasts are predominantly dividing (groups HS1), or at the prepupal stage when the brain central complex is developing (groups HS2), or at the imago stage 1 hour before the test (groups HS). All males were tested at the age of 5 days. Virgin and fertilized CS females were used as courtship objects. Comparison of control groups of the wild type (CS) and mutant strains has shown that the mutation agn ^ts3 does not affect the main parameters of courtship behavior (courtship latency, the rapidity of achieving copulation, courtship efficiency) but leads to: a decrease in sexual activity, an increase in duration of sound trains in the songs and to a slight increase in the rate and stability of singing pacemakers. When compared to wild type, the agn ^ts3 males are more resistant to HS given 1 hour before the test. After HS their courtship intensity does not decrease and the main parameters of their courtship behavior and communicative sound signals either do not change, or appear to be even better stabilized. The frequency of distorted sound pulses (an indicator of frequency of impairments in the activity pattern of neuro-motor circuits of the singing center) decreases, and the working rate and stability of pacemakers of the pulse and the sine songs increases. Therefore, although the sharply elevated LIMK1 and p-cofilin levels detected by immunofluorescent techniques in the cells of agn ^ts3 mutants can lead to dramatic defects in learning and memory [2] accompanied by a decline of motivation of males, they do not appreciably affect the neuro-motor coordination during singing. The higher resistance of characteristics of the mutant behavior and communicative sound signals to heat shock is in agreement with the fact that the extremely high LIMK1 and P-cofilin levels fall down to normal values after HS and both the learning acquisition and memory formation are restored.     

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 agn ^ts3 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.     

Combination of Hypomorphic Mutations of the Drosophila Homologues of Aryl Hydrocarbon Receptor and Nucleosome Assembly Protein Family Genes Disrupts Morphogenesis,Memory and Detoxification

Aryl hydrocarbon receptor is essential for biological responses to endogenous and exogenous toxins in mammals. Its Drosophila homolog spineless plays an important role in fly morphogenesis. We have previously shown that during morphogenesis spineless genetically interacts with CG5017 gene, which encodes a nucleosome assembly factor and may affect cognitive function of the fly. We now demonstrate synergistic interactions of spineless and CG5017 in pathways controlling oxidative stress response and long-term memory formation in Drosophila melanogaster. Oxidative stress was induced by low doses of X-ray irradiation of flies carrying hypomorphic mutation of spineless, mutation of CG5017, and their combination. To determine the sensitivity of these mutants to pharmacological modifiers of the irradiation effect, we irradiated flies growing on standard medium supplemented by radiosensitizer furazidin and radioprotector serotonin. The effects of irradiation were investigated by analyzing leg and antenna morphological structures and by using real-time PCR to measure mRNA expression levels for spineless, Cyp6g1 and Gst-theta genes. We also examined long-term memory in these mutants using conditioned courtship suppression paradigm. Our results show that the interaction of spineless and CG5017 is important for regulation of morphogenesis, long-term memory formation, and detoxification during oxidative stress. Since spineless and CG5017 are evolutionary conserved, these results must be considered when evaluating the risk of combining similar mutations in other organisms, including humans.     

The role of stacking interactions in the mechanisms of binding of the glycine site of NMDA-receptor with antagonists and 3-hydroxykynurenine

Ab initio quantum chemical calculations of benzene dimer, benzene dimer with 5,7 clorination of one aromatic ring, 3-hydroxykynurenine, and kunurenic acid molecules situated above Phe484 aromatic ring of receptor binding site fragment were carried out in order to investigate the role of stacking interaction in the binding of agonists and antagonists with the glycine site of the NMDA receptor NR1 subunit. All calculations were done with the help of GAMESS 6.4 software with 6-31G** atomic gaussian basal functions with complete optimization of geometry and taking into account the electron correlation up to the second-order Moller-Plesset perturbation theory. It was shown that the parallel dislodged conformations of the benzene dimer is energetically most advantageous. Successive substitution of chlorine atoms for the protons of one aromatic ring in 7 and 5 positions leads to an increase in stacking-interaction energy and a mutual displacement of aromatic rings. In the case of kunurenic acid and its derivatives, which are NMDA receptor antagonists, the increase in the energy of stacking interactions leads to the strengthening of inhibition of the ion channel, whereas the 3-hydroxykynurenine molecule is neither agonist, nor antagonist for the glycine site of the NMDA receptor due to the sterical constraints.