Engaged T cell antigen receptors (TCRs) initiate signaling through the adaptor protein Lat. In quiescent T cells, Lat is segregated into clusters on the cell surface, which raises the question of how TCR triggering initiates signaling. Using super-resolution fluorescence microscopy, we found that pre-existing Lat domains were neither phosphorylated nor laterally transported to TCR activation sites, which suggested that these clusters do not participate in TCR signaling. Instead, TCR activation resulted in the recruitment and phosphorylation of Lat from subsynaptic vesicles. Studies of Lat mutants confirmed that recruitment preceded and was essential for phosphorylation and that both processes were independent of surface clustering of Lat. Our data suggest that TCR ligation preconditions the membrane for vesicle recruitment and bulk activation of the Lat signaling network.

To date, health effects of exposure to the September 11, 2001 disaster in New York City have been studied in specific groups, but no studies have estimated its impact across the different exposed populations. This report provides an overview of the World Trade Center Health Registry (WTCHR) enrollees, their exposures, and their respiratory and mental health outcomes 2–3 years post-9/11. Results are extrapolated to the estimated universe of people eligible to enroll in the WTCHR to determine magnitude of impact. Building occupants, persons on the street or in transit in lower Manhattan on 9/11, local residents, rescue and recovery workers/volunteers, and area school children and staff were interviewed and enrolled in the WTCHR between September 2003 and November 2004. A total of 71,437 people enrolled in the WTCHR, for 17.4% coverage of the estimated eligible exposed population (nearly 410,000); 30% were recruited from lists, and 70% were self-identified. Many reported being in the dust cloud from the collapsing WTC Towers (51%), witnessing traumatic events (70%), or sustaining an injury (13%). After 9/11, 67% of adult enrollees reported new or worsening respiratory symptoms, 3% reported newly diagnosed asthma, 16% screened positive for probable posttraumatic stress disorder (PTSD), and 8% for serious psychological distress (SPD). Newly diagnosed asthma was most common among rescue and recovery workers who worked on the debris pile (4.1%). PTSD was higher among those who reported Hispanic ethnicity (30%), household income <$25,000 (31%), or being injured (35%). Using previously published estimates of the total number of exposed people per WTCHR eligibility criteria, we estimate between 3,800 and 12,600 adults experienced newly diagnosed asthma and 34,600–70,200 adults experienced PTSD following the attacks, suggesting extensive adverse health impacts beyond the immediate deaths and injuries from the acute event.

The extent to which the tau tracer [18F]AV-1451 can differentiate between tauopathies is unknown. By comparing patients with Alzheimer’s disease and progressive supranuclear palsy (PSP), Passamonti et al. show that [18F]AV-1451 displays greater specificity for Alzheimer-related tau pathology than PSP-related pathology. A machine learning algorithm correctly diagnosed 94% of cases.

The authors employed photoactivatable localization microscopy (PALM) and direct stochastic optical reconstruction microscopy (dSTORM) imaging and image analysis based on Ripley's K-function to quantify the distribution and heterogeneity of proteins at the cell plasma membrane. The membrane targeting sequence of the N-terminal region of the T cell receptor-pathway kinase Lck fused to the photo-convertible fluorescent protein tdEos (Lck(N10)-tdEos), clusters into sub-100 nm regions which cover approximately 7% of the cell surface. 2-channel PALM imaging of Lck(N10)-tdEos and the N-terminus of the kinase Src (Src(N15)-PS-CFP2) are demonstrated. Finally, T cell microclusters at the immune synapse are imaged at super-resolution using dSTORM, showing that conventional TIRF images contain unresolved, small clusters. These methods are generally applicable to other cell and fluorophore systems to quantify 2-D molecular clustering at nanometer scales.

Phosphorylation of the T cell antigen receptor (TCR) by the tyrosine kinase Lck is an essential step in the activation of T cells. Because Lck is constitutively active, spatial organization may regulate TCR signaling. Here we found that Lck distributions on the molecular level were controlled by the conformational states of Lck, with the open, active conformation inducing clustering and the closed, inactive conformation preventing clustering. In contrast, association with lipid domains and protein networks were not sufficient or necessary for Lck clustering. Conformation-driven Lck clustering was highly dynamic, so that TCR triggering resulted in Lck clusters that contained phosphorylated TCRs but excluded the phosphatase CD45. Our data suggest that Lck conformational states represent an intrinsic mechanism for the intermolecular organization of early T cell signaling.