structures of the Dot/Icm T4SS identify the DotA-IcmX complex as the gatekeeper for effector translocation.

The Dot/Icm machine in is one of the most versatile type IV secretion systems (T4SSs), with a remarkable capacity to translocate over 330 different effector proteins across the bacterial envelope into host cells. At least 27 Dot and Icm proteins are required for assembly and function of the system, yet the architecture and activation mechanism remain poorly understood at the molecular level. Here, we deploy cryo-electron microscopy to reveal structures of the Dot/Icm machine at near-atomic resolution.

Vesicle docking and fusion pore modulation by the neuronal calcium sensor Synaptotagmin-1.

Synaptotagmin-1 (Syt1) is a major calcium sensor for rapid neurotransmitter release in neurons and hormone release in many neuroendocrine cells. It possesses two tandem cytosolic C2 domains that bind calcium, negatively charged phospholipids, and the neuronal SNARE complex. Calcium binding to Syt1 triggers exocytosis, but how this occurs is not well understood.

The Use of Next-Generation Sequencing to Assist in the Diagnosis of Atypical Vasculitis.

Vasculitis can be challenging to diagnose, especially when vessels of multiple sizes are affected and manifestations do not classically fit into defined rheumatic disease entities. We present the case of a 58-year-old Caucasian woman who presented with headache and altered mental status, with subsequent left-sided hemiparesis and hemispatial neglect eight days after a dental procedure. She was found to have extensive multi-focal ischemic infarctions secondary to vasculitis affecting multiple intracranial blood vessels.

The T4bSS of Legionella features a two-step secretion pathway with an inner membrane intermediate for secretion of transmembrane effectors.

To promote intracellular survival and infection, Legionella spp. translocate hundreds of effector proteins into eukaryotic host cells using a type IV b protein secretion system (T4bSS). T4bSS are well known to translocate soluble as well as transmembrane domain-containing effector proteins (TMD-effectors) but the mechanisms of secretion are still poorly understood.

Vesicle docking and fusion pore modulation by the neuronal calcium sensor Synaptotagmin-1.

Synaptotagmin-1 (Syt1) is a major calcium sensor for rapid neurotransmitter release in neurons and hormone release in many neuroendocrine cells. It possesses two tandem cytosolic C2 domains that bind calcium, negatively charged phospholipids, and the neuronal SNARE complex. Calcium binding to Syt1 triggers exocytosis, but how this occurs is not well understood.

The T4bSS of features a two-step secretion pathway with an inner membrane intermediate for secretion of transmembrane effectors.

To promote intracellular survival and infection, translocate hundreds of effector proteins into eukaryotic host cells using a type IV b protein secretion system (T4bSS). T4bSS are well known to translocate soluble as well as transmembrane domain-containing effector proteins (TMD-effectors) but the mechanisms of secretion are still poorly understood. Herein we investigated the secretion of hydrophobic TMD-effectors, of which about 80 were previously reported to be encoded by A proteomic analysis of fractionated membranes revealed that TMD-effectors are targeted to and inserted into the bacterial inner membranes of independent of the presence of a functional T4bSS.

Musculoskeletal manifestations of syphilis in adults: secondary syphilis presenting with ankle inflammatory arthritis and bone involvement with calvarial and sternal lesions. What the rheumatologist needs to know.

Although the incidence of syphilis reached a historic low in 2000, the number of incident cases has since increased in men and women across the USA. In 2019, men who have sex with men (MSM) accounted for 57% of all primary and secondary (P&S) syphilis cases, and about half of MSM with P&S syphilis are living with human immunodeficiency virus (HIV) infection. Days after infection, Treponema pallidum disseminates and invades tissues distant from the site of inoculation.

Evaluation of an automated phenotyping algorithm for rheumatoid arthritis.

To better understand the challenges of generally implementing and adapting computational phenotyping approaches, the performance of a Phenotype KnowledgeBase (PheKB) algorithm for rheumatoid arthritis (RA) was evaluated on a University of California, Los Angeles (UCLA) patient population, focusing on examining its performance on ambiguous cases. The algorithm was evaluated on a cohort of 4,766 patients, along with a chart review of 300 patients by rheumatologists against accepted diagnostic guidelines. The performance revealed low sensitivity towards specific subtypes of positive RA cases, which suggests revisions in features used for phenotyping.

Proteins DotY and DotZ modulate the dynamics and localization of the type IVB coupling complex of Legionella pneumophila.

Legionella pneumophila is an opportunistic pathogen infecting alveolar macrophages and protozoa species. Legionella utilizes a Type IV Secretion System (T4SS) to translocate over 300 effector proteins into its host cell. In a recent study, we have isolated and solved the cryo-EM structure of the Type IV Coupling Complex (T4CC), a large cytoplasmic determinant associated with the inner membrane that recruits effector proteins for delivery to the T4SS for translocation.

Mechanism of effector capture and delivery by the type IV secretion system from Legionella pneumophila.

Legionella pneumophila is a bacterial pathogen that utilises a Type IV secretion (T4S) system to inject effector proteins into human macrophages. Essential to the recruitment and delivery of effectors to the T4S machinery is the membrane-embedded T4 coupling complex (T4CC). Here, we purify an intact T4CC from the Legionella membrane.

Applying Live Cell Imaging and Cryo-Electron Tomography to Resolve Spatiotemporal Features of the Legionella pneumophila Dot/Icm Secretion System.

The Dot/Icm secretion system of Legionella pneumophila is a complex type IV secretion system (T4SS) nanomachine that localizes at the bacterial pole and mediates the delivery of protein and DNA substrates to target cells, a process generally requiring direct cell-to-cell contact. We have recently solved the structure of the Dot/Icm apparatus by cryo-electron tomography (cryo-ET) and showed that it forms a cell envelope-spanning channel that connects to a cytoplasmic complex. Applying two complementary approaches that preserve the native structure of the specimen, fluorescent microscopy in living cells and cryo-ET, allows in situ visualization of proteins and assimilation of the stoichiometry and timing of production of each machine component relative to other Dot/Icm subunits.

Apixaban as a Rare Cause of Leukocytoclastic Vasculitis.

Apixaban is a rare cause of leukocytoclastic vasculitis (LCV). To our knowledge, there is only one other reported case due to apixaban in the literature. We present a case of apixaban-induced leukocytoclastic vasculitis in a 95-year-old male.

Analysis of Dot/Icm Type IVB Secretion System Subassemblies by Cryoelectron Tomography Reveals Conformational Changes Induced by DotB Binding.

Type IV secretion systems (T4SSs) are sophisticated nanomachines used by many bacterial pathogens to translocate protein and DNA substrates across a host cell membrane. Although T4SSs have important roles in promoting bacterial infections, little is known about the biogenesis of the apparatus and the mechanism of substrate transfer. Here, high-throughput cryoelectron tomography (cryo-ET) was used to visualize T4SSs (also known as Dot/Icm secretion machines) in both the whole-cell context and at the cell pole.

A unique cytoplasmic ATPase complex defines the Legionella pneumophila type IV secretion channel.

Type IV secretion systems (T4SSs) are complex machines used by bacteria to deliver protein and DNA complexes into target host cells. Conserved ATPases are essential for T4SS function, but how they coordinate their activities to promote substrate transfer remains poorly understood. Here, we show that the DotB ATPase associates with the Dot-Icm T4SS at the Legionella cell pole through interactions with the DotO ATPase.

Synaptojanin 2 is a druggable mediator of metastasis and the gene is overexpressed and amplified in breast cancer.

Amplified HER2, which encodes a member of the epidermal growth factor receptor (EGFR) family, is a target of effective therapies against breast cancer. In search for similarly targetable genomic aberrations, we identified copy number gains in SYNJ2, which encodes the 5'-inositol lipid phosphatase synaptojanin 2, as well as overexpression in a small fraction of human breast tumors. Copy gain and overexpression correlated with shorter patient survival and a low abundance of the tumor suppressor microRNA miR-31.

Identification of two Legionella pneumophila effectors that manipulate host phospholipids biosynthesis.

The intracellular pathogen Legionella pneumophila translocates a large number of effector proteins into host cells via the Icm/Dot type-IVB secretion system. Some of these effectors were shown to cause lethal effect on yeast growth. Here we characterized one such effector (LecE) and identified yeast suppressors that reduced its lethal effect.

Poor cerebral inflammatory response in eIF2B knock-in mice: implications for the aetiology of vanishing white matter disease.

Background: Mutations in any of the five subunits of eukaryotic translation initiation factor 2B (eIF2B) can lead to an inherited chronic-progressive fatal brain disease of unknown aetiology termed leucoencephalopathy with vanishing white matter (VWM). VWM is one of the most prevalent childhood white matter disorders, which markedly deteriorates after inflammation or exposure to other stressors. eIF2B is a major housekeeping complex that governs the rate of global protein synthesis under normal and stress conditions.

Negative regulation of the endocytic adaptor disabled-2 (Dab2) in mitosis.

Mitotic cells undergo extensive changes in shape and size through the altered regulation and function of their membrane trafficking machinery. Disabled 2 (Dab2), a multidomain cargo-specific endocytic adaptor and a mediator of signal transduction, is a potential integrator of trafficking and signaling. Dab2 binds effectors of signaling and trafficking that localize to different intracellular compartments.

Monoubiquitinylation regulates endosomal localization of Lst2, a negative regulator of EGF receptor signaling.

Genetic screens performed in worms identified major regulators of the epidermal growth factor receptor (EGFR) pathway, including the ubiquitin ligase Cbl/SLI-1. Here we focus on the less-characterized Lst2 protein and confirm suppression of MAPK signals. Unexpectedly, human Lst2, a monoubiquitinylated phosphoprotein, does not localize to endosomes, despite an intrinsic phosphoinositol-binding FYVE domain.

Dab2 regulates clathrin assembly and cell spreading.

The recruitment of clathrin to the membrane and its assembly into coated pits results from its interaction with endocytic adaptors and other regulatory proteins in the context of a specific lipid microenvironment. Dab2 (disabled 2) is a mitotic phosphoprotein and a monomeric adaptor for clathrin-mediated endocytosis. In the present study, we employed GFP (green fluorescent protein) fusion constructs of different isoforms and mutants of rat Dab2 and characterized their effect on the size, distribution and dynamics of clathrin assemblies.

Protection of lipids from oxidation by epicatechin, trans-resveratrol, and gallic and caffeic acids in intestinal model systems.

Consumption of polyphenols is associated with health promotion through diet, although many are poorly absorbed in animals and humans alike. Lipid peroxides may reach the intestine and initiate deleterious oxidation. Here we measured inhibition of the oxidation of linoleic acid (LA) in authentic fluid from rat small intestine (RIF) by two dietary polyphenols, a flavonoid, epicatechin (EC), and a stilbene, resveratrol (RV), and by gallic (GA) and caffeic (CA) acids, and their partition coefficients.