Zhu C-B, Carneiro AM, Dostmann WR, Hewlett WA, Blakely RD. p38 MAPK activation elevates serotonin transport activity via a trafficking-independent, protein phosphatase 2A-dependent process. J Biol Chem 280: 15649-15658

University of Vermont, Burlington, Vermont, United States
Journal of Biological Chemistry (Impact Factor: 4.57). 05/2005; 280(16):15649-58. DOI: 10.1074/jbc.M410858200
Source: PubMed


Presynaptic, plasma membrane serotonin (5-hydroxytryptamine; 5-HT) transporters (SERTs) clear 5-HT following vesicular release and are regulated through trafficking-dependent pathways. Recently, we provided evidence for a trafficking-independent mode of SERT regulation downstream of adenosine receptor (AR) activation that is sensitive to p38 MAPK inhibitors. Here, we probe this pathway in greater detail, demonstrating elevation of 5-HT transport by multiple p38 MAPK activators (anisomycin, H(2)O(2), and UV radiation), in parallel with p38 MAPK phosphorylation, as well as suppression of anisomycin stimulation by p38 MAPK siRNA treatments. Studies with transporter-transfected Chinese hamster ovary cells reveal that SERT stimulation is shared with the human norepinephrine transporter but not the human dopamine transporter. Saturation kinetic analyses of anisomycin-SERT activity reveal a selective reduction in 5-HT K(m) supported by a commensurate increase in 5-HT potency (K(i)) for displacing surface antagonist binding. Anisomycin treatments that stimulate SERT activity do not elevate surface SERT surface density whereas stimulation is lost with preexposure of cells to the surface-SERT inactivating reagent, 2-(trimethylammonium)ethyl methane thiosulfonate. Guanylyl cyclase (1H-(1,2,4)-oxadiazolo[4,3-a]-quinoxalin-1-one) and protein kinase G inhibitors (H8, DT-2) block AR stimulation of SERT yet fail to antagonize SERT stimulation by anisomycin. We thus place p38 MAPK activation downstream of protein kinase G in a SERT-catalytic regulatory pathway, distinct from events controlling SERT surface density. In contrast, the activity of protein phosphatase 2A inhibitors (fostriecin and calyculin A) to attenuate anisomycin stimulation of 5-HT transport suggests that protein phosphatase 2A is a critical component of the pathway responsible for p38 MAPK up-regulation of SERT catalytic activity.

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    • "More important for the control of anxiety and arousal responses, A 3 ARs are physically associated with SERT, and the activation of these receptors rapidly and transiently increases this association and the surface trafficking of SERT (Zhu et al. 2011). The activation of A 3 ARs has been shown to increase serotonin uptake in an cGMP-and p38 mitogen-activated protein kinase (MAPK)-dependent way (Okada et al. 1997, 1999; Zhu et al. 2007), a response that has also been observed in stable expression systems, including RBL2H3 cells (Miller and Hoffman 1994; Zhu et al. 2004), CHO cells (Zhu et al. 2005), and the immortalized serotonergic cell line RN46A (Chang et al. 2012). "
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    ABSTRACT: Rationale The adenosine A3 receptor and the nitric oxide (NO) pathway regulate the function and localization of serotonin transporters (SERTs). These transporters regulate extracellular serotonin levels, which are correlated with defensive behavior. Objective The purpose of this study was to understand the role of the A3AR on anxiety and arousal models in zebrafish, and whether this role is mediated by the nitrergic modulation of serotonin uptake. Methods The effects of IB-MECA (0.01 and 0.1 mg/kg) were assessed in a series of behavioral tasks in adult zebrafish, as well as on extracellular serotonin levels in vivo and serotonin uptake in brain homogenates. Finally, the interaction between IB-MECA and drugs blocking voltage-dependent calcium channels (VDCCs), NO synthase, and SERT was analyzed. Results At the lowest dose, IB-MECA decreased bottom dwelling and scototaxis, while at the highest dose, it also decreased shoaling, startle probability, and melanophore responses. These effects were accompanied by an increase in brain extracellular serotonin levels. IB-MECA also concentration-dependently increased serotonin uptake in vitro. The effects of IB-MECA on extracellular 5-HT, scototaxis, and geotaxis were blocked by l-NAME, while only the effects on 5-HT and scototaxis were blocked by verapamil. In vitro, the increase in 5-HT uptake was dependent on VDCCs and NO. Finally, fluoxetine blocked the effect of IB-MECA on scototaxis, but not geotaxis. Conclusion These results suggest that the effect of IB-MECA on scototaxis are mediated by a VDCC-NO-SERT pathway. While NO seems to mediate the effects of IB-MECA on geotaxis, neither VDCCs nor SERT seems to be involved in this process.
    Psychopharmacology 11/2014; 232(10). DOI:10.1007/s00213-014-3799-4 · 3.88 Impact Factor
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    • "Supporting an acute SERT regulation, adenosine A3 receptor stimulation increased SERT uptake function in rat basophilic leukemia (RBL-2H3) cells and mouse mid-brain and hippocampal synaptosomes. This effect is thought to be mediated by both a PKG-dependent surface density increase of the SERT, and p38-MAPK dependent activation of SERT intrinsic activity (Samuvel et al., 2005; Zhu et al., 2005). Multiple signaling pathways seem to contribute to the regulation of SERT mediated 5-HT clearance (Blakely et al., 2005). "
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    ABSTRACT: Estradiol was found previously to have an antidepressant-like effect and to block the ability of selective serotonin reuptake inhibitors (SSRIs) to have an antidepressant-like effect. The antidepressant-like effect of estradiol was due to estrogen receptor β (ERβ) and/or GPR30 activation, whereas estradiol's blockade of the effect of an SSRI was mediated by ERα. This study focuses on investigating signaling pathways as well as interacting receptors associated with these two effects of estradiol. In vivo chronoamperometry was used to measure serotonin transporter (SERT) function. The effect of local application of estradiol or selective agonists for ERα (PPT) or ERβ (DPN) into the CA3 region of the hippocampus of ovariectomized (OVX) rats on 5-hydroxytryptamine (5-HT) clearance as well as on the ability of fluvoxamine to slow 5-HT clearance was examined after selective blockade of signaling pathways or that of interacting receptors. Estradiol- or DPN-induced slowing of 5-HT clearance mediated by ERβ was blocked after inhibition of MAPK/ERK1/2 but not of PI3K/Akt signaling pathways. This effect also involved interactions with TrkB, and IGF-1 receptors. Estradiol's or PPT's inhibition of the fluvoxamine-induced slowing of 5-HT clearance mediated by ERα, was blocked after inhibition of either MAPK/ERK1/2 or PI3K/Akt signaling pathways. This effect involved interactions with the IGF-1 receptor and with the metabotropic glutamate receptor 1, but not with TrkB. This study illustrates some of the signaling pathways required for the effects of estradiol on SERT function, and particularly shows that ER subtypes elicit different as well as common signaling pathways for their actions.
    The International Journal of Neuropsychopharmacology 01/2014; 17(05):1-13. DOI:10.1017/S146114571300165X · 4.01 Impact Factor
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    • "Deletion of p38a Produces Stress Resilience that controls SERT protects against the depressive-like effects of stress. Although regulation of SERT by p38 had been implicated based on in vitro studies (Zhu et al., 2005; Samuvel et al., 2005), the demonstration that stress-induced p38a MAPK causes translocation of SERT to the plasma membrane in brain provides a clear molecular explanation for stressinduced dysphoria. The data presented here show that in serotonin neurons, p38a MAPK acts to directly influence SERT trafficking and ultimately to increase the rate of serotonin reuptake . "
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    ABSTRACT: Maladaptive responses to stress adversely affect human behavior, yet the signaling mechanisms underlying stress-responsive behaviors remain poorly understood. Using a conditional gene knockout approach, the α isoform of p38 mitogen-activated protein kinase (MAPK) was selectively inactivated by AAV1-Cre-recombinase infection in specific brain regions or by promoter-driven excision of p38α MAPK in serotonergic neurons (by Slc6a4-Cre or ePet1-Cre) or astrocytes (by Gfap-CreERT2). Social defeat stress produced social avoidance (a model of depression-like behaviors) and reinstatement of cocaine preference (a measure of addiction risk) in wild-type mice, but not in mice having p38α MAPK selectively deleted in serotonin-producing neurons of the dorsal raphe nucleus. Stress-induced activation of p38α MAPK translocated the serotonin transporter to the plasma membrane and increased the rate of transmitter uptake at serotonergic nerve terminals. These findings suggest that stress initiates a cascade of molecular and cellular events in which p38α MAPK induces a hyposerotonergic state underlying depression-like and drug-seeking behaviors.
    Neuron 08/2011; 71(3):498-511. DOI:10.1016/j.neuron.2011.06.011 · 15.05 Impact Factor
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