Dopamine transporter oligomerization involves the scaffold domain, but spares the bundle domain.

The human dopamine transporter (hDAT) is located on presynaptic neurons, where it plays an essential role in limiting dopaminergic signaling by temporarily curtailing high neurotransmitter concentration through rapid re-uptake. Transport by hDAT is energized by transmembrane ionic gradients. Dysfunction of this transporter leads to disease states, such as Parkinson's disease, bipolar disorder or depression. It has been shown that hDAT and other members of the monoamine transporter family exist in oligomeric forms at the plasma membrane. Several residues are known to be involved in oligomerization, but interaction interfaces, oligomer orientation and the quarternary arrangement in the plasma membrane remain poorly understood. Here we examine oligomeric forms of hDAT using a direct approach, by following dimerization of two randomly-oriented hDAT transporters in 512 independent simulations, each being 2 µs in length. We employed the DAFT (docking assay for transmembrane components) approach, which is an unbiased molecular dynamics simulation method to identify oligomers, their conformations and populations. The overall ensemble of a total of >1 ms simulation time revealed a limited number of symmetric and asymmetric dimers. The identified dimer interfaces include all residues known to be involved in dimerization. Importantly, we find that the surface of the bundle domain is largely excluded from engaging in dimeric interfaces. Such an interaction would typically lead to inhibition by stabilization of one conformation, while substrate transport relies on a large scale rotation between the inward-facing and the outward-facing state.

The meaning of spasticity to people with multiple sclerosis: what can health professionals learn?

PURPOSE: Multiple sclerosis (MS) is the most common disabling neurological condition affecting young adults. One third of people on an American registry of people with MS (PWMS) reported having activities affected by spasticity. The psychosocial effects of spasticity in people with MS have been shown to be distressing and detrimental to emotional and social relationships when investigated from a psychology perspective. This paper investigates the impact of spasticity on the lives of people living with MS from a physiotherapeutic perspective. METHOD: This study involved 12 semi-structured interviews with individuals experiencing MS-related spasticity. Ten sets of data were analyzed following framework analysis principles. RESULTS: Results suggest spasticity effects life experience of these PWMS in diverse and complex ways. Physical, psychological and social consequences of spasticity are closely linked and can be far reaching. CONCLUSIONS: Therapists need to be aware of links between specific physical symptoms and their psychosocial consequences if they want to improve peoples' quality of life. This paper provides in depth qualitative research evidence for the complexity of the spasticity experience for each individual, strengthening the argument for a patient-centred approach to treatment. These results also support the case for targeted interventions with effectiveness recorded in a patient-centred way. IMPLICATIONS FOR REHABILITATION: • Spasticity is suggested here to affect the lives of individuals with multiple sclerosis in diverse and far reaching ways. Therapists need to investigate this fully in subjective assessment to impact on people's quality of life. • Direct links were identified between treatable physical symptoms and far reaching consequences of spasticity. • Knowledge about the complexity of the spasticity experience for each individual will allow therapists to target interventions appropriately and accurately record effectiveness in a patient-centred way.