• Bermingham DP, Hardaway JA, Refai O, Marks CR, Snider SL, Sturgeon SM, Spencer WC, Colbran RJ, Miller DM, Blakely RD. The Atypical MAP Kinase SWIP-13/ERK8 Regulates Dopamine Transporters Through a Rho-Dependent Mechanism. The Journal of neuroscience : the official journal of the Society for Neuroscience. 2017 Aug 21. PMID: 28842414 [PubMed].

Abstract 

The neurotransmitter dopamine (DA) regulates multiple behaviors across phylogeny, with disrupted DA signaling in humans associated with addiction, attention-deficit/hyperactivity disorder (ADHD), schizophrenia, and Parkinson's disease. The DA transporter (DAT) imposes spatial and temporal limits on DA action, and provides for presynaptic DA recycling to replenish neurotransmitter pools. Molecular mechanisms that regulate DAT expression, trafficking and function, particularly in vivo, remain poorly understood, though recent studies have implicated Rho-linked pathways in psychostimulant action. To identify genes that dictate the ability of DAT to sustain normal levels of DA clearance, we pursued a forward genetic screen in C. elegans based on the phenotype Swimming-induced paralysis (Swip), a paralytic behavior observed in hermaphrodite worms with loss of function dat-1 mutations. Here, we report the identity of swip-13, which encodes a highly conserved ortholog of the human atypical MAP kinase ERK8. We present evidence that SWIP-13 acts presynaptically to insure adequate levels of surface DAT expression and DA clearance. Moreover, we provide in vitro and in vivo evidence supporting a conserved pathway involving SWIP-13/ERK8 activation of Rho GTPases that dictates DAT surface expression and function.SIGNIFICANCE STATEMENTSignaling by the neurotransmitter dopamine (DA) is tightly regulated by the DA transporter (DAT), insuring efficient DA clearance after release. Molecular networks that regulate DAT are poorly understood, particularly in vivo Using a forward genetic screen in the nematode C. elegans, we implicate the atypical mitogen activated protein kinase, SWIP-13, in DAT regulation. Moreover, we provide in vitro and in vivo evidence that SWIP-13, as well as its human counterpart ERK8, regulate DAT surface availability via the activation of Rho proteins. Our findings implicate a novel pathway that regulates DA synaptic availability and that may contribute to risk for disorders linked to perturbed DA signaling. Targeting this pathway may be of value in the development of therapeutics in such disorders.