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In addition to determining biological sex, sex hormones are known to influence health and disease via regulation of immune cell activities and modulation of target-organ susceptibility to immune-mediated damage. Systemic autoimmune disorders, such as systemic lupus erythematosus, rheumatoid arthritis, and multiple sclerosis are more prevalent in females, while cancer shows the opposite pattern. Sex hormones have been repeatedly suggested to play a part in these biases. In this review, we will discuss how androgens and the expression of functional androgen receptor affect immune cells and how this may dampen or alter immune response(s) and affect autoimmune disease incidences and progression.

The serotonin transporter (SERT) terminates neurotransmission by removing serotonin from the synaptic cleft. In addition, it is the site of action of antidepressants (which block the transporter) and of amphetamines (which induce substrate efflux). We explored the functional importance of the N terminus in mediating the action of amphetamines by focusing initially on the highly conserved threonine residue at position 81, a candidate site for phosphorylation by protein kinase C. Molecular dynamics simulations of the wild type SERT, compared with its mutations SERTT81A and SERTT81D, suggested structural changes in the inner vestibule indicative of an opening of the inner vestibule. Predictions from this model (e.g. the preferential accumulation of SERTT81A in the inward conformation, its reduced turnover number, and a larger distance between its N and C termini) were verified. Most importantly, SERTT81A (and the homologous mutations in noradrenaline and dopamine) failed to support amphetamine-induced efflux, and this was not remedied by aspartate at this position. Amphetamine-induced currents through SERTT81A were comparable with those through the wild type transporter. Both abundant Na+ entry and accumulation of SERTT81A in the inward facing conformation ought to favor amphetamine-induced efflux. Thus, we surmised that the N terminus must play a direct role in driving the transporter into a state that supports amphetamine-induced efflux. This hypothesis was verified by truncating the first 64 amino acids and by tethering the N terminus to an additional transmembrane helix. Either modification abolished amphetamine-induced efflux. We therefore conclude that the N terminus of monoamine transporters acts as a lever that sustains reverse transport.

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1These authors contributed equally to this study.Abbreviations used: ASP + , 4-(4-diethylaminostyryl)-N-methylpyridinium iodide; CaMKII, Ca 2+ /calmodulin-dependent protein kinase II; D2Rs, dopamine D 2 receptor short variant; DAT, dopamine transporter; ER, endoplasmic reticulum; ESCRT, endosomal sorting complex required for transport; FRET, fluorescence resonance energy transfer; GFP, green fluorescent protein; GPCR, G-protein coupled receptor; GPR, G-protein coupled receptor; GST, glutathione-S-transferase; NEDD4-2, neuronal precursor cell expressed, developmentally down-regulated 4-2; NET, norepinephrine transporter; NSS, neurotransmitter : sodium symporters; PD, Parkinson's disease; PDZ, PSD-95/Discs-large/ZO-1 homology; PICK1, protein interacting with C kinase-1; PKC, protein kinase C; PMA, phorbol 12-myristate 13-acetate; SERT, serotonin transporter; siRNA, small interfering RNA; VMAT, vesicular monoamine transporter. AbstractThe dopamine transporter (DAT) plays a key role in regulating dopaminergic signalling in the brain by mediating rapid clearance of dopamine from the synaptic clefts. The psychostimulatory actions of cocaine and amphetamine are primarily the result of a direct interaction of these compounds with DAT leading to attenuated dopamine clearance and for amphetamine even increased dopamine release. In the last decade, intensive efforts have been directed towards understanding the molecular and cellular mechanisms governing the activity and availability of DAT in the plasma membrane of the presynaptic neurons. This has led to the identification of a plethora of different kinases, receptors and scaffolding proteins that interact with DAT and hereby either modulate the catalytic activity of the transporter or regulate its trafficking and degradation. Several new tools for studying DAT regulation in live cells have also recently become available such as fluorescently tagged cocaine analogues and fluorescent substrates.Here we review the current knowledge about the role of protein-protein interactions in DAT regulation as well as we describe the most recent methodological developments that have been established to overcome the challenges associated with the study of DAT in endogenous systems. Keywords: biogenic amines, dopaminergic neurons, monoamines, neurotransmitter transporters, reuptake, trafficking. by analysis of DAT knock-out mice that are characterized by a dopamine-deficient but functional hyperdopaminergic state as a result of reduced dopamine clearance and reduced vesicular storage of dopamine (Giros et al. 1996;Jones et al. 1998). DAT is the primary target for widely abused psychostimulants, such as cocaine (Giros et al. 1996;Chen et al. 2006;Thomsen et al. 2009) and amphetamines (Giros et al. 1996;Fumagalli et al. 1998). Cocaine acts as a competitive inhibitor that binds to the DAT substrate binding site and blocks transport activity (Beuming et al. 2008) whereas amphetamine is a substrate of the transporter capable of promoting DAT mediated dopamine release (Wall et al. 1995;Sitte e...

Dopamine regulates reward, cognition, and locomotor functions. By mediating rapid reuptake of extracellular dopamine, the dopamine transporter is critical for spatiotemporal control of dopaminergic neurotransmission. Here, we use super-resolution imaging to show that the dopamine transporter is dynamically sequestrated into cholesterol-dependent nanodomains in the plasma membrane of presynaptic varicosities and neuronal projections of dopaminergic neurons. Stochastic optical reconstruction microscopy reveals irregular dopamine transporter nanodomains (∼70 nm mean diameter) that were highly sensitive to cholesterol depletion. Live photoactivated localization microscopy shows a similar dopamine transporter membrane organization in live heterologous cells. In neurons, dual-color dSTORM shows that tyrosine hydroxylase and vesicular monoamine transporter-2 are distinctively localized adjacent to, but not overlapping with, the dopamine transporter nanodomains. The molecular organization of the dopamine transporter in nanodomains is reversibly reduced by short-term activation of NMDA-type ionotropic glutamate receptors, implicating dopamine transporter nanodomain distribution as a potential mechanism to modulate dopaminergic neurotransmission in response to excitatory input.

Autoantibodies are of central importance in the pathogenesis of Ab-mediated autoimmune disorders. The murine lupus susceptibility locus Nba2 on chromosome 1 and the syntenic human locus are associated with a loss of immune tolerance that leads to antinuclear Ab production. To identify gene intervals within Nba2 that control the development of autoantibody-producing B cells and to determine the cellular components through which Nba2 genes accomplish this, we generated congenic mice expressing various Nba2 intervals where genes for the FcγR, SLAM, and IFN-inducible families are encoded. Analysis of congenic strains demonstrated that the FcγR and SLAM intervals independently controlled the severity of autoantibody production and renal disease, yet are both required for lupus susceptibility. Deregulated homeostasis of terminally differentiated B cells was found to be controlled by the FcγR interval where FcγRIIb-mediated apoptosis of germinal center B cells and plasma cells was impaired. Increased numbers of activated plasmacytoid dendritic cells that were distinctly CD19+ and promoted plasma cell differentiation via the proinflammatory cytokines IL-10 and IFNα were linked to the SLAM interval. These findings suggest that SLAM and FcγR intervals act cooperatively to influence the clinical course of disease through supporting the differentiation and survival of autoantibody-producing cells.