Molecular cloning of the mouse dopamine transporter and pharmacological comparison with the human homologue

Drug abuse is a serious problem in the United States and in the world. Coca ine and amphetamines, widely used drugs of abuse, bind to dopamine (DA), se rotonin, and norepinephrine transporters with high affinity and block their functions. It is believed that the dopamine transporter plays a key role i n the mechanism of cocaine addiction. Because a good portion of our knowled ge about drug addiction is derived from studying mouse as an animal model, it is essential to compare the properties of dopamine transporter from huma n and mouse. We report here the cloning of the mouse dopamine transporter ( mDAT) cDNA and its expression and comparison with the human DAT. The 3.4 ki lobase (kb) cDNA encodes a polypeptide that is 93.5% identical to the hDAT, with 619 amino acid residues and a calculated molecular weight of 68.8 kDa . Dopamine transporters from mouse and human were stably expressed in the s ame parental MDCK cells and their properties were compared. The Michaelis-M enten constant K-m values are 2.0 mu M for mDAT and 2.4 mu M for hDAT. Mous e and human DAT were also compared for drug inhibition profiles. Dopamine t ransporters from the two species have the same sensitivity to amphetamine ( K-d: 0.75 mu M) and bupropion (K-d: 1.5 mu M). However, hDAT is more sensit ive than mDAT to cocaine (K-d: 0.14 mu M and 0.29 mu M respectively) and to ritalin (K-d: 0.038 mu M and 0.12 mu M respectively). The cloning of mDAT cDNA provides an important tool for further study of the mechanism of drug addiction using mouse as an animal model. (C) 1999 Elsevier Science B.V. Al l rights reserved.