Physical and functional interaction between the dopamine transporter and the synaptic vesicle protein synaptogyrin-3.

Uptake through the dopamine transporter (DAT) represents the primary mechanism used to terminate dopaminergic transmission in brain. Although it is well known that dopamine (DA) taken up by the transporter is used to replenish synaptic vesicle stores for subsequent release, the molecular details of this mechanism are not completely understood. Here, we identified the synaptic vesicle protein synaptogyrin-3 as a DAT interacting protein using the split ubiquitin system. This interaction was confirmed through coimmunoprecipitation experiments using heterologous cell lines and mouse brain. DAT and synaptogyrin-3 colocalized at presynaptic terminals from mouse striatum. Using fluorescence resonance energy transfer microscopy, we show that both proteins interact in live neurons. Pull-down assays with GST (glutathione S-transferase) proteins revealed that the cytoplasmic N termini of both DAT and synaptogyrin-3 are sufficient for this interaction. Furthermore, the N terminus of DAT is capable of binding purified synaptic vesicles from brain tissue. Functional assays revealed that synaptogyrin-3 expression correlated with DAT activity in PC12 and MN9D cells, but not in the non-neuronal HEK-293 cells. These changes were not attributed to changes in transporter cell surface levels or to direct effect of the protein-protein interaction. Instead, the synaptogyrin-3 effect on DAT activity was abolished in the presence of the vesicular monoamine transporter-2 (VMAT2) inhibitor reserpine, suggesting a dependence on the vesicular DA storage system. Finally, we provide evidence for a biochemical complex involving DAT, synaptogyrin-3, and VMAT2. Collectively, our data identify a novel interaction between DAT and synaptogyrin-3 and suggest a physical and functional link between DAT and the vesicular DA system

Stress-Related Disorders of Family Members of Patients Admitted to the Intensive Care Unit With COVID-19

Importance: The psychological symptoms associated with having a family member admitted to the intensive care unit (ICU) during the COVID-19 pandemic are not well defined. Objective: To examine the prevalence of symptoms of stress-related disorders, primarily posttraumatic stress disorder (PTSD), in family members of patients admitted to the ICU with COVID-19 approximately 90 days after admission. Design, Setting, and Participants: This prospective, multisite, mixed-methods observational cohort study assessed 330 family members of patients admitted to the ICU (except in New York City, which had a random sample of 25% of all admitted patients per month) between February 1 and July 31, 2020, at 8 academic-affiliated and 4 community-based hospitals in 5 US states. Exposure: Having a family member in the ICU with COVID-19. Main Outcomes and Measures: Symptoms of PTSD at 3 months, as defined by a score of 10 or higher on the Impact of Events Scale 6 (IES-6). Results: A total of 330 participants (mean [SD] age, 51.2 [15.1] years; 228 [69.1%] women; 150 [52.8%] White; 92 [29.8%] Hispanic) were surveyed at the 3-month time point. Most individuals were the patients\u27 child (129 [40.6%]) or spouse or partner (81 [25.5%]). The mean (SD) IES-6 score at 3 months was 11.9 (6.1), with 201 of 316 respondents (63.6%) having scores of 10 or higher, indicating significant symptoms of PTSD. Female participants had an adjusted mean IES-6 score of 2.6 points higher (95% CI, 1.4-3.8; P \u3c .001) than male participants, whereas Hispanic participants scored a mean of 2.7 points higher compared with non-Hispanic participants (95% CI, 1.0-4.3; P = .002). Those with graduate school experience had an adjusted mean score of 3.3 points lower (95% CI, 1.5-5.1; P \u3c .001) compared with those with up to a high school degree or equivalent. Qualitative analyses found no substantive differences in the emotional or communication-related experiences between those with high vs low PTSD scores, but those with higher scores exhibited more distrust of practitioners. Conclusions and Relevance: In this cohort study, symptoms of PTSD among family members of ICU patients with COVID-19 were high. Hispanic ethnicity and female gender were associated with higher symptoms. Those with higher scores reported more distrust of practitioners