Cellular zinc levels are modulated by TRPML1-TMEM163 interaction.

Mucolipidosis type IV (MLIV) is caused by loss of function mutations in the TRPML1 ion channel. We previously reported that tissue zinc levels in MLIV were abnormally elevated; however, the mechanism behind this pathologic accumulation remains unknown. Here, we identify transmembrane (TMEM)-163 protein, a putative zinc transporter, as a novel interacting partner for TRPML1. Evidence from yeast two-hybrid, tissue expression pattern, co-immunoprecipitation, mass spectrometry and confocal microscopy studies confirmed the physical association of TMEM163 with TRPML1. This interaction is disrupted when a part of TMEM163's N-terminus was deleted. Further studies to define the relevance of their interaction revealed that the plasma membrane (PM) levels of TMEM163 significantly decrease when TRPML1 is co-expressed in HEK-293 cells, while it mostly localizes within the PM when co-expressed with a mutant TRPML1 that distributes mostly in the PM. Meanwhile, co-expression of TMEM163 does not alter TRPML1 channel activity, but its expression levels in MLIV patient fibroblasts are reduced, which correlate with marked accumulation of zinc in lysosomes when these cells are acutely exposed to exogenous zinc (100 µM). When TMEM163 is knocked down or when TMEM163 and TRPML1 are co-knocked down in HEK-293 cells treated overnight with 100 nm zinc, the cells have significantly higher intracellular zinc levels than untreated control. Overall, these findings suggest that TMEM163 and TRPML1 proteins play a critical role in cellular zinc homeostasis, and thus possibly explain a novel mechanism for the pathological overload of zinc in MLIV disease.

Symptoms of Anxiety, Depression, and Stress among Families of Critically Ill Patients with COVID-19: A Longitudinal Clinical Trial.

Rationale: Families of critically ill patients with coronavirus disease (COVID-19) may be at particularly high risk for anxiety, depression, and post-traumatic stress disorder after hospital discharge. Objectives: To assess symptoms of anxiety, depression, and stress among families of patients with COVID-19 during and after intensive care unit (ICU) admissions and to use qualitative methods to determine the sources of emotional distress. Methods: Families of patients with COVID-19 who participated in an ICU study were approached for participation in this post-hospital discharge study. Participants completed the Hospital Anxiety and Depression Scale (HADS) and the Impact of Events Scale-Revised (IES-R) at up to three points during the ICU stay and once after the ICU stay. Mixed-effects models were used to compare trajectories of HADS and IES-R scores over the ICU and post-ICU periods. Telephone interviews with participants were evaluated using thematic content analysis. Results: Among the 90 families that participated from September 2020 to April 2021, 47 respective patients were alive and 43 were deceased. Average HADS anxiety, HADS depression, and IES-R scores after hospital discharge were significantly higher (greater symptom burden) among families of deceased versus surviving patients: 9.2 (95% confidence interval [CI], 7.8-10.6) versus 6.3 (95% CI, 4.9-7.6) (P < 0.01), 7.1 (95% CI, 5.7-8.6) versus 3.2 (95% CI, 2.3-4.1) (P < 0.001), and 36.1 (95% CI, 31.0-41.2) versus 20.4 (95% CI, 16.1-24.8) (P < 0.001), respectively. HADS anxiety and HADS depression scores began to diverge during the ICU stay, whereas IES-R scores diverged after the stay for families of surviving versus deceased patients. Qualitative analysis confirmed a higher burden of psychological symptoms among families of deceased patients. Memories from the ICU stay became a focal point for participants who lost their loved ones, whereas families of surviving patients were able to look positively toward the future. In addition, families of deceased patients often viewed friends and family as sources of stress, whereas families of surviving patients typically viewed their community as a source of support. Conclusions: Patient death was associated with symptoms of anxiety, depression, and post-traumatic stress disorder among families of ICU patients with COVID-19. Psychological support interventions may be most beneficial for families of patients who died of COVID-19. Clinical trial registered with www.clinicaltrials.gov (NCT04501445).