Considerable attention has been paid to perfluoroalkyl compounds (PFCs) because of their worldwide presence in humans, wildlife, and environment. A wide variety of toxicological effects is well supported in animals, including testicular toxicity and male infertility. For these reasons, the understanding of epidemiological associations and of the molecular mechanisms involved in the endocrine-disrupting properties of PFCs on human reproductive health is a major concern.

The mechanisms underlying sterol transport in mammalian cells are poorly understood. In particular, how cholesterol internalized from HDL is made available to the cell for storage or modification is unknown. Here, we describe three ER-resident proteins (Aster-A, -B, -C) that bind cholesterol and facilitate its removal from the plasma membrane. The crystal structure of the central domain of Aster-A broadly resembles the sterol-binding fold of mammalian StARD proteins, but sequence differences in the Aster pocket result in a distinct mode of ligand binding. The Aster N-terminal GRAM domain binds phosphatidylserine and mediates Aster recruitment to plasma membrane-ER contact sites in response to cholesterol accumulation in the plasma membrane. Mice lacking Aster-B are deficient in adrenal cholesterol ester storage and steroidogenesis because of an inability to transport cholesterol from SR-BI to the ER. These findings identify a nonvesicular pathway for plasma membrane to ER sterol trafficking in mammals.

The translationally silent 100S ribosome is a poorly understood form of the dimeric 70S complex that is ubiquitously found in all bacterial phyla. Eliminating the hibernating 100S ribosome leads to translational derepression, ribosome instability, antibiotic sensitivity, and biofilm defects in some bacteria. In Firmicutes, such as the opportunistic pathogen , a 190-amino acids protein called ibernating- romoting actor (HPF) dimerizes and conjoins two 70S ribosomes through a direct interaction between the HPF homodimer, with each HPF monomer tethered on an individual 70S complex. While the formation of the 100S ribosome in γ-proteobacteria and cyanobacteria is exclusively induced during post-exponential growth phase and darkness, respectively, the 100S ribosomes in Firmicutes are constitutively produced from the lag-logarithmic phase through the post stationary phase. Very little is known about the regulatory pathways that control expression and 100S ribosome abundance. Here, we show that a general stress response (GSR) sigma factor (SigB) and a GTP-sensing transcription factor (CodY) integrate nutrient and thermal signals to regulate synthesis in , resulting in enhanced virulence of the pathogen in a mouse model of septicemic infection. CodY-dependent regulation of is strain-specific. Epistasis analysis further demonstrates that CodY functions upstream of the GSR pathway in a condition-dependent manner. The results reveal an important link between stress physiology, ribosome metabolism and infection biology.The dimerization of 70S ribosomes (100S complex) plays an important role in translational regulation and infectivity of the major human pathogen Although the dimerizing factor HPF has been characterized biochemically, the pathways that regulate 100S ribosome abundance remain elusive. We identify a metabolite and nutrient-sensing transcription factor CodY that serves both as an activator and a repressor of expression in a nutrient and temperature-dependent manners. Furthermore, CodY-mediated activation of masks a secondary transcript derived from a general stress response SigB promoter. CodY and SigB regulate a repertoire of virulence genes. The unexpected link between ribosome homeostasis and the two master virulence regulators provides new opportunities for alternative druggable sites.

Regulatory T (Treg) cells induce an immunosuppressive microenvironment that is a major obstacle for successful tumor immunotherapy. Dissecting the regulatory mechanisms between energy metabolism and functionality in Treg cells will provide insight toward developing novel immunotherapies against cancer. Here we report that human naturally occurring and tumor-associated Treg cells exhibit distinct metabolic profiles with selectivity for glucose metabolism compared with effector T cells. Treg-mediated accelerated glucose consumption induces cellular senescence and suppression of responder T cells through cross-talk. TLR8 signaling selectively inhibits glucose uptake and glycolysis in human Treg cells, resulting in reversal of Treg suppression. Importantly, TLR8 signaling-mediated reprogramming of glucose metabolism and function in human Treg cells can enhance anti-tumor immunity in vivo in a melanoma adoptive transfer T cell therapy model. Our studies identify mechanistic links between innate signaling and metabolic regulation of human Treg suppression, which may be used as a strategy to advance tumor immunotherapy.

Halogens are widely used highly toxic chemicals that pose potential threat to humans due to their abundance. Halogens such bromine (Br) cause severe pulmonary and systemic injuries however, the mechanisms of their toxicity are largely unknown. Here we demonstrate that Br and reactive brominated species produced in the lung and released in blood, reach the heart and cause acute cardiac ultrastructural damage and dysfunction in rats. Br-induced cardiac damage was demonstrated by acute (3-24h) increases in circulating troponin I, hFABP and NT-proBNP. Transmission electron microscopy demonstrated acute (3-24h) cardiac contraction band necrosis, disruption of z-discs, and mitochondrial swelling and disorganization.Echocardiography and hemodynamic analysis revealed left ventricular (LV) systolic and diastolic dysfunction at 7 days. Plasma and the LV tissue had increased levels of brominated fatty acids. 2-bromohexadecanal (Br-HDA) injected into the LV cavity of a normal rat caused acute LV enlargement with extensive disruption of the sarcomeric architecture and mitochondrial damage. There was extensive infiltration of neutrophils and increased myeloperoxidase levels in the hearts of Br or Br reactant exposed rats. Increased bromination of SERCA and increased phosphalamban after Br inhalation decreased cardiac SERCA activity by 70%. SERCA inactivation was accompanied by increased calcium sensitive LV calpain activity. A calpain specific inhibitor MDL28170 administered within 1h after exposure significantly decreased calpain activity and acute mortality. Bromine inhalation and formation of reactive brominated species caused acute cardiac injury and myocardial damage that can lead to heart failure.

Lysine glutarylation (Kglu) of mitochondrial proteins is associated with glutaryl-CoA dehydrogenase (GCDH) deficiency, which impairs lysine/tryptophan degradation and causes destruction of striatal neurons during catabolic crisis with subsequent movement disability. By investigating the role of Kglu modifications in this disease, we compared the brain and liver glutarylomes of Gcdh-deficient mice. In the brain, we identified 73 Kglu sites on 37 mitochondrial proteins involved in various metabolic degradation pathways. Ultrastructural immunogold studies indicated that glutarylated proteins are heterogeneously distributed in mitochondria, which are exclusively localized in glial cells. In liver cells, all mitochondria contain Kglu-modified proteins. Glutarylation reduces the catalytic activities of the most abundant glutamate dehydrogenase (GDH) and the brain-specific carbonic anhydrase 5b and interferes with GDH-protein interactions. We propose that Kglu contributes to the functional heterogeneity of mitochondria and may metabolically adapt glial cells to the activity and metabolic demands of neighboring GCDH-deficient neurons.

Coagulation factor II, or prothrombin, is a multi-domain glycoprotein that is essential for life and a key target of anticoagulant therapy. In plasma, prothrombin circulates in two forms at equilibrium, "closed" (~80%) and "open" (~20%), brokered by the flexibility of the linker regions. Its structure remained elusive until recently when our laboratory solved the first X-ray crystal structure of the zymogen locked in the predominant closed form. Because of this technical breakthrough, fascinating aspects of the biology of prothrombin have started to become apparent, and with this, novel and important questions arise. Here, we examine the significance of the "closed"/"open" equilibrium in the context of the mechanism of thrombin generation. Further, we discuss the potential translational opportunities for the development of next-generation anticoagulants that arise from this discovery. By providing a structural overview of each alternative conformation, this minireview also offers a relevant example of modern structural biology and establishes a practical workflow to elucidate the structural features of analogous clotting and complement factors.