CLONING AND EXPRESSION OF THE MOUSE SEROTONIN TRANSPORTER

A mouse brain cDNA encoding the high-affinity serotonin transporter (S ERT) has been identified and characterized. The mouse transporter sequ ence (mSERT) encodes a protein of 630 amino acids which contains twelv e potential transmembrane domains (TMDs), N-linked glycosylation and k inase-mediated phosphorylation sites, and high levels of homology with rat and human SERTs. Heterologous expression of mSERT in COS-1 cells resulted in a [H-3]serotonin transport activity characterized by kinet ic saturability (K-m = 403 +/- 42 nM; V-max = 1.02 +/- 0.10 pmol/mg/mi n), Na+ and Cl- dependences (5HT:Na+:Cl- coupling ratio of 1:1:1), and sensitivity to known inhibitors of serotonin transport (including ant idepressant and psychostimulant agents). Northern analysis using mSERT cDNA as probe revealed a single 3.4 kb mRNA species expressed in mous e lung, midbrain and brainstem regions, and absent from heart and live r. In situ hybridization studies further established the specific loca lization of mSERT gene expression to the raphe nuclei of the mouse mid brain. The identified mSERT cDNA sequence provides a new tool for the evaluation of serotonin transport pharmacology in heterologous express ion systems and provides an opportunity for the evaluation of mSERT ge ne expression in a well-characterized model of mammalian development.