Norepinephrine (NE) uptake through the NE transporter (NET) is the primary mechanism to ter-minate the action of this neurotransmitter. Dysregulation of brain NE levels is associated with various conditions, including attention deficits, depression, and Alzheimer's disease. Recently, we identified an interaction between the related dopamine (DA) transporter (DAT) and G protein βγ subunits. Activation of Gβγ in cells and brain slices leads to DA efflux through DAT. However, the potential interaction between Gβγ and NET has not been reported. Here, we used a combina-tion of molecular modeling approaches to elucidate the structural details of the NET/Gβγ inter-action, supported by experimental evidence. Through 1.5µs of molecular dynamic simulation, we observed a favorable NET/Gβγ interaction mediated by the intracellular carboxy terminus of NET. As a consequence, the binding energy of NE for NET also changes resulting in alterations of the electrostatic profile of NET. We propose that these changes mediate the NE efflux effect. Fi-nally, we provide experimental evidence demonstrating that Gβγ physically interacts with NET and that the Gβγ activator mSIRK induces NE efflux through the transporter. These findings identified a novel interaction between Gβγ and NET and highlighted its potential implications in the regulation of NE neurotransmission and associated disorders.

Atypical antipsychotic drugs were introduced in the early 1990th. Unlike typical antipsychotics, which are effective only against positive symptoms of schizophrenia, atypical antipsychotics show effectiveness against negative and cognitive symptoms as well. Furthermore, they are effective not only in psychotic, but also in affective disorders, by their own or as adjuncts to antidepressant drugs. While typical antipsychotics act, almost exclusively, via dopamine-2 (D2) receptors, atypical target serotonin-1A/1B/2A/2C (5-HT1A/1B/2A/2C), α1/2-adrenergic, and/or histamine-1 (H1) receptors as well. Blocking of 5-HT1A/1B autoreceptors, inducing their early desensitization, and/or activation of α1-adrenoceptors, allow some atypical drugs to enhance 5-HT transmission. Blocking of 5-HT2A/2C and/or α2-adrenoceptors enable some atypical antipsychotics to stimulate catecholamine transmission and/or diminish the inhibition of catecholamine neurons induced by some antidepressants. It is possible, that the activation of H1 and/or blocking of H3 boost monoamine transmission as well, via a mechanism involving stimulation of firing activity of dopamine neurons. The experimental drugs with antipsychotic potential, acting on adenosine and trace amino associated (TAAR) receptors, might be effective in mood disorders as well, because of the ability to modulate the excitability of monoamine-secreting neurons and to potentiate extracellular concentrations of monoamines in the limbic areas of the brain.

Parkinson’s disease (PD) is an aging-related and the second most common neurodegenerative disease after Alzheimer’s disease. The main symptoms of PD are movement disorders accompanied with deficiency of neurotransmitter dopamine (DA) in the striatum due to cell death of the nigro-striatal DA neurons. Two main histopathological hallmarks exist in PD: cytosolic inclusion bodies termed Lewy bodies that mainly consist of α-synuclein protein, the oligomers of which produced by misfolding are regarded to be neurotoxic, causing DA cell death; and black pigments termed neuromelanin (NM) that are contained in DA neurons and markedly decrease in PD. Synthesis of human NM is regarded to be similar to that of melanin in melanocytes; Melanin synthesis in skin is via DOPAquinone (DQ) by tyrosinase, whereas NM synthesis in DA neurons is via DAquinone (DAQ) by tyrosine hydroxylase (TH) and aromatic L-amino acid decarboxylase (AADC). DA in cytoplasm is highly reactive and is assumed to be oxidized spontaneously or by an unidentified tyrosinase to DAQ and then synthesized to NM. Intracellular NM accumulation above a specific threshold was reported to be associated to DA neuron death and PD phenotypes. This review reports recent progress in biosynthesis and pathophysiology of NM in PD.