Florey Department of Neuroscience and Mental Health - Research Publications

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    The interplay between lipids and dopamine on alpha-synuclein oligomerization and membrane binding
    Pham, CLL ; Cappai, R (PORTLAND PRESS LTD, 2013-01-01)
    The deposition of α-syn (α-synuclein) as amyloid fibrils and the selective loss of DA (dopamine) containing neurons in the substantia nigra are two key features of PD (Parkinson's disease). α-syn is a natively unfolded protein and adopts an α-helical conformation upon binding to lipid membrane. Oligomeric species of α-syn have been proposed to be the pathogenic species associated with PD because they can bind lipid membranes and disrupt membrane integrity. DA is readily oxidized to generate reactive intermediates and ROS (reactive oxygen species) and in the presence of DA, α-syn form of SDS-resistant soluble oligomers. It is postulated that the formation of the α-syn:DA oligomers involves the cross-linking of DA-melanin with α-syn, via covalent linkage, hydrogen and hydrophobic interactions. We investigate the effect of lipids on DA-induced α-syn oligomerization and studied the ability of α-syn:DA oligomers to interact with lipids vesicles. Our results show that the interaction of α-syn with lipids inhibits the formation of DA-induced α-syn oligomers. Moreover, the α-syn:DA oligomer cannot interact with lipid vesicles or cause membrane permeability. Thus, the formation of α-syn:DA oligomers may alter the actions of α-syn which require membrane association, leading to disruption of its normal cellular function.
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    The human testis-determining factor SRY localizes in midbrain dopamine neurons and regulates multiple components of catecholamine synthesis and metabolism
    Czech, DP ; Lee, J ; Sim, H ; Parish, CL ; Vilain, E ; Harley, VR (WILEY, 2012-07-01)
    The male gender is determined by the sex-determining region on the Y chromosome (SRY) transcription factor. The unexpected action of SRY in the control of voluntary movement in male rodents suggests a role in the regulation of dopamine transmission and dopamine-related disorders with gender bias, such as Parkinson's disease. We investigated SRY expression in the human brain and function in vitro. SRY immunoreactivity was detected in the human male, but not female substantia nigra pars compacta, within a sub-population of tyrosine hydroxylase (TH) positive neurons. SRY protein also co-localized with TH positive neurons in the ventral tegmental area, and with GAD-positive neurons in the substantia nigra pars reticulata. Retinoic acid-induced differentiation of human precursor NT2 cells into dopaminergic cells increased expression of TH, NURR1, D2 R and SRY. In the human neuroblastoma cell line, M17, SRY knockdown resulted in a reduction in TH, DDC, DBH and MAO-A expression; enzymes which control dopamine synthesis and metabolism. Conversely, SRY over-expression increased TH, DDC, DBH, D2 R and MAO-A levels, accompanied by increased extracellular dopamine levels. A luciferase assay demonstrated that SRY activated a 4.6 kb 5' upstream regulatory region of the human TH promoter/nigral enhancer. Combined, these results suggest that SRY plays a role as a positive regulator of catecholamine synthesis and metabolism in the human male midbrain. This ancillary genetic mechanism might contribute to gender bias in fight-flight behaviours in men or their increased susceptibility to dopamine disorders, such as Parkinson's disease and schizophrenia.
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    Conventional Concepts and New Perspectives for Understanding the Addictive Properties of Inhalants
    Duncan, JR ; Lawrence, AJ (JAPANESE PHARMACOLOGICAL SOC, 2013-08-01)
    The abuse of inhaled chemical vapors is a growing problem especially among adolescent populations. This is partly driven by the fact that inhaled products are cheap, accessible, and provide a rapid 'high'. In the brain inhalants have multiple effects. They are neurotoxic, targeting primarily white matter pathways, which is believed to underlie the long-term neurological consequences associated with repeated use. Inhalants are also addictive, resulting in adaptive responses in pathways mediating reward and reinforcement. This includes an ability to alter dopaminergic cell firing and result in long-term mesocorticolimbic dopaminergic dysfunction. However, growing evidence suggests that the reinforcing properties of inhalants may also be driven by their ability to affect neurotransmitter systems other than the dopaminergic system. Both glutamatergic and g-aminobutyric acid (GABA)ergic systems are emerging as key targets of inhalants with differential responses observed following either acute or chronic exposures. These responses appear particularly important in circuits which appear vulnerable to inhalants and which can also modulate dopaminergic function such as the corticostriatal pathway. Thus in combination with the effects of inhalants on dopaminergic systems, our increased understanding of the role(s) of glutamatergic and GABAergic systems provide new and exciting targets to consider for intervention strategies to limit inhalant use.