Oligomerization of Human Dopamine Transporter (hDAT)

Abstract

Monoamine transporters of the SCL6 family are found on presynaptic neurons and terminate the neurotransmission by the reuptake of neurotransmitters. The family of monoamine transporters includes the transporters for dopamine (DAT), serotonin (SERT) and norepinephrine (NET) which couple substrate transport with ion gradients of sodium and chloride. Dysfunction of these transporters can lead to clinically important disease states, for instance to depression. It has been shown that monoamine transporters and other members of the family exist in oligomeric form in cells and studies reported that different oligomeric sizes are present at the level of the plasma membrane. There is a wealth of reports regarding the residues critical for oligomerization, however, the binding orientation and possible hierarchies of the many putative oligomerization interfaces are poorly understood. In this study, we extensively scrutinized the oligomeric forms of the human DAT using molecular dynamics simulations and applying the MARTINI coarse grained force field. Two monomers of DAT were inserted into a POPC membrane in random orientations. Subsequently, the assembly of the monomers were analyzed over 2 μs time for 500 independent systems resulting in a total of 1ms simulation time. The convergence of the whole ensemble is quantified by the interaction energy plot, the number of conformers and their orientations is shown by the density plot. This study indicates that DAT forms dimers through four distinct orientations. These results allowed us to propose a testable hypothesis of residues located within the oligomeric interface.