Sam68 Is Required for DNA Damage Responses via Regulating Poly(ADP-ribosyl)ation.

The rapid and robust synthesis of polymers of adenosine diphosphate (ADP)-ribose (PAR) chains, primarily catalyzed by poly(ADP-ribose) polymerase 1 (PARP1), is crucial for cellular responses to DNA damage. However, the precise mechanisms through which PARP1 is activated and PAR is robustly synthesized are not fully understood. Here, we identified Src-associated substrate during mitosis of 68 kDa (Sam68) as a novel signaling molecule in DNA damage responses (DDRs).

Intraluminal containment of commensal outgrowth in the gut during infection-induced dysbiosis.

Shifts in commensal microbiota composition are emerging as a hallmark of gastrointestinal inflammation. In particular, outgrowth of γ-proteobacteria has been linked to the etiology of inflammatory bowel disease and the pathologic consequences of infections. Here we show that following acute Toxoplasma gondii gastrointestinal infection of mice, control of commensal outgrowth is a highly coordinated process involving both the host response and microbial signals.

Inflammatory monocytes regulate pathologic responses to commensals during acute gastrointestinal infection.

The commensal flora can promote both immunity to pathogens and mucosal inflammation. How commensal-driven inflammation is regulated in the context of infection remains poorly understood. Here, we show that during acute mucosal infection of mice with Toxoplasma gondii, inflammatory monocytes acquire a tissue-specific regulatory phenotype associated with production of the lipid mediator prostaglandin E2 (PGE2).

p38 and OGT sequestration into viral inclusion bodies in cells infected with human respiratory syncytial virus suppresses MK2 activities and stress granule assembly.

Respiratory syncytial virus (RSV) forms cytoplasmic inclusion bodies (IBs) that are thought to be sites of nucleocapsid accumulation and viral RNA synthesis. The present study found that IBs also were the sites of major sequestration of two proteins involved in cellular signaling pathways. These are phosphorylated p38 mitogen-activated protein kinase (MAPK) (p38-P), a key regulator of cellular inflammatory and stress responses, and O-linked N-acetylglucosamine (OGN) transferase (OGT), an enzyme that catalyzes the posttranslational addition of OGN to protein targets to regulate cellular processes, including signal transduction, transcription, translation, and the stress response.

Making friends in out-of-the-way places: how cells of the immune system get together and how they conduct their business as revealed by intravital imaging.

A central characteristic of the immune system is the constantly changing location of most of its constituent cells. Lymphoid and myeloid cells circulate in the blood, and subsets of these cells enter, move, and interact within, then leave organized lymphoid tissues. When inflammation is present, various hematopoietic cells also exit the vasculature and migrate within non-lymphoid tissues, where they carry out effector functions that support host defense or result in autoimmune pathology.

Stromal cell networks regulate lymphocyte entry, migration, and territoriality in lymph nodes.

After entry into lymph nodes (LNs), B cells migrate to follicles, whereas T cells remain in the paracortex, with each lymphocyte type showing apparently random migration within these distinct areas. Other than chemokines, the factors contributing to this spatial segregation and to the observed patterns of lymphocyte movement are poorly characterized. By combining confocal, electron, and intravital microscopy, we showed that the fibroblastic reticular cell network regulated naive T cell access to the paracortex and also supported and defined the limits of T cell movement within this domain, whereas a distinct follicular dendritic cell network similarly served as the substratum for movement of follicular B cells.

An extended vision for dynamic high-resolution intravital immune imaging.

The past few years have seen the application of confocal and especially two-photon microscopy to the dynamic high-resolution imaging of lymphocytes and antigen presenting cells within organs such as lymph nodes and thymus. After summarizing some of the published results obtained to date using these methods, we describe our view of how this technology will develop and be applied in the near future. This includes its extension to a wide variety of non-lymphoid tissues, to the tracking of functional responses in addition to migratory behavior, to the analysis of molecular events previously studied only in vitro, to dissection of the interplay between hematopoietic and stromal elements, to visualization of a wider array of cell types including neutrophils, macrophages, NK cells, NKT cells and others, and to the interaction of the host with infectious agents.

Microfluidic shear devices for quantitative analysis of cell adhesion.

We describe the design, construction, and characterization of microfluidic devices for studying cell adhesion and cell mechanics. The method offers multiple advantages over previous approaches, including a wide range of distractive forces, high-throughput performance, simplicity in experimental setup and control, and potential for integration with other microanalytic modules. By manipulating the geometry and surface chemistry of the microdevices, we are able to vary the shear force and the biochemistry during an experiment.

Co-regulation of cell adhesion by nanoscale RGD organization and mechanical stimulus.

Integrin-mediated cell adhesion is central to cell survival, differentiation and motility. Many cell responses induced by integrins require both receptor occupancy and receptor aggregation, and appear to be regulated by both biochemical and biophysical means. Multidomain extracellular matrix molecules may serve to foster integrin aggregation by presenting local clusters of adhesion ligands, a hypothesis supported by studies with synthetic substrates showing that cell adhesion and migration are enhanced when adhesion ligands are presented in nanoscale clusters.