Immunological synapses are initiated by signaling in discrete T cell receptor (TCR) microclusters and play an important role in T cell differentiation and effector functions. Synapse formation involves orchestrated motion of microclusters toward the center of the contact area with the antigen-presenting cell. Microcluster movement is associated with centripetal actin flow, but the role of motor proteins is unknown. Here we show that myosin IIA was necessary for complete assembly and movement of TCR microclusters and that activated myosin IIA was recruited to the synapse. In the absence of myosin IIA or its ATPase activity, T cell signaling was interrupted downstream of Lck and the synapse was destabilized. Thus, TCR signaling and subsequent immunological synapse formation are active processes dependent on myosin IIA.

Disulfide bond formation in secretory proteins occurs primarily in the endoplasmic reticulum (ER), where multiple enzyme families catalyze cysteine cross-linking. Quiescin sulfhydryl oxidase 1 (QSOX1) is an atypical disulfide catalyst, localized to the Golgi apparatus or secreted from cells. We examined the physiological function for extracellular catalysis of de novo disulfide bond formation by QSOX1. QSOX1 activity was required for incorporation of laminin into the extracellular matrix (ECM) synthesized by fibroblasts, and ECM produced without QSOX1 was defective in supporting cell-matrix adhesion. We developed an inhibitory monoclonal antibody against QSOX1 that could modulate ECM properties and undermine cell migration.

Neuro-immune interactions enable mutual regulation of the nervous and immune systems. To date, evidence exists for manipulations of immune cells by neurotransmitters in the periphery. In this study, we suggest the existence of a pathway by which the brain affects immune cells. The pathway we describe here is mediated by dopamine receptors expressed on activated T cells, termed blasts. Blasts can cross the blood brain barrier regardless of antigen specificity and can therefore encounter neurotransmitters in the brain. We show that blasts have a unique response to dopaminergic activation, which has no counterpart in resting T cells. Dopaminergic activation of blasts induces a Th1 bias in their cytokine profile and causes changes in surface marker expression. We further suggest that these changes can subsequently be transferred to peripheral T cells. We have tested this pathway in two in vivo systems: in rats exogenously administered with L-dopa, and in schizophrenia, which is characterized by a central nervous system-restricted increase in dopamine. In both models, peripheral T cells exhibit similar features to those of dopaminergically activated blasts. The existence of such a pathway by which the brain can regulate immune cells opens a conceptually new direction in neuro-immune interactions.

Summary The respiratory and intestinal tracts are exposed to physical and biological hazards accompanying the intake of air and food. Likewise, the vasculature is threatened by inflammation and trauma. Mucin glycoproteins and the related von Willebrand factor guard the vulnerable cell layers in these diverse systems. Colon mucins additionally house and feed the gut microbiome. Here, we present an integrated structural analysis of the intestinal mucin MUC2. Our findings reveal the shared mechanism by which complex macromolecules responsible for blood clotting, mucociliary clearance, and the intestinal mucosal barrier form protective polymers and hydrogels. Specifically, cryo-electron microscopy and crystal structures show how disulfide-rich bridges and pH-tunable interfaces control successive assembly steps in the endoplasmic reticulum and Golgi apparatus. Remarkably, a densely O-glycosylated mucin domain performs an organizational role in MUC2. The mucin assembly mechanism and its adaptation for hemostasis provide the foundation for rational manipulation of barrier function and coagulation.

Immunological synapse (IS) formation involves receptor–ligand pair clustering and intracellular signaling molecule recruitment with a coincident removal of other membrane proteins away from the IS. As microfilament–membrane linkage is critical to this process, we investigated the involvement of ezrin and moesin, the two ezrin/radixin/moesin proteins expressed in T cells. We demonstrate that ezrin and moesin, which are generally believed to be functionally redundant, are differentially localized and have important and complementary functions in IS formation. Specifically, we find that ezrin directly interacts with and recruits the signaling kinase ZAP-70 to the IS. Furthermore, the activation of ezrin by phosphorylation is essential for this process. In contrast, moesin dephosphorylation and removal, along with CD43, are necessary to prepare a region of the cell cortex for IS. Thus, ezrin and moesin have distinct and critical functions in the T cell cortex during IS formation.