Extracellular loops matter:Subcellular location and function of the lysine transporter Lyp1 from Saccharomyces cerevisiae

Yeast amino acid transporters of the APC superfamily are responsible for the proton motive force-driven uptake of amino acids into the cell, which for most secondary transporters is a reversible process. The l-lysine proton symporter Lyp1 of Saccharomyces cerevisiae is special in that the Michaelis constant from out-to-in transport ((Formula presented.) ) is much lower than (Formula presented.) , which allows accumulation of l-lysine to submolar concentration. It has been proposed that high intracellular lysine is part of the antioxidant mechanism of the cell. The molecular basis for the unique kinetic properties of Lyp1 is unknown. We compared the sequence of Lyp1 with APC para- and orthologues and find structural features that set Lyp1 apart, including differences in extracellular loop regions. We screened the extracellular loops by alanine mutagenesis and determined Lyp1 localization and activity and find positions that affect either the localization or activity of Lyp1. Half of the affected mutants are located in the extension of extracellular loop 3 or in a predicted α-helix in extracellular loop 4. Our data indicate that extracellular loops not only connect the transmembrane helices but also serve functionally important roles

GM-CSF drives dysregulated hematopoietic stem cell activity and pathogenic extramedullary myelopoiesis in experimental spondyloarthritis

Dysregulated hematopoiesis occurs in several chronic inflammatory diseases, but it remains unclear how hematopoietic stem cells (HSCs) in the bone marrow (BM) sense peripheral inflammation and contribute to tissue damage in arthritis. Here, we show the HSC gene expression program is biased toward myelopoiesis and differentiation skewed toward granulocyte-monocyte progenitors (GMP) during joint and intestinal inflammation in experimental spondyloarthritis (SpA). GM-CSF-receptor is increased on HSCs and multipotent progenitors, favoring a striking increase in myelopoiesis at the earliest hematopoietic stages. GMP accumulate in the BM in SpA and, unexpectedly, at extramedullary sites: in the inflamed joints and spleen. Furthermore, we show that GM-CSF promotes extramedullary myelopoiesis, tissue-toxic neutrophil accumulation in target organs, and GM-CSF prophylactic or therapeutic blockade substantially decreases SpA severity. Surprisingly, besides CD4+ T cells and innate lymphoid cells, mast cells are a source of GM-CSF in this model, and its pathogenic production is promoted by the alarmin IL-33

Biomechanical characterization of a micro/macroporous polycaprolactone tissue integrating vascular graft

The objective of the present study was to characterize the short-term biomechanical properties of cast micro/macroporous poly(caprolactone) (PCL) tubes intended for application as tissue integrating blood vessel substitutes. Micro/macroporous PCL vascular grafts (5.5 mm internal diameter, 7.5 mm external diameter) with defined macropore structures were produced by rapidly cooling PCL solutions containing dispersed gelatin particles in dry ice, followed by solvent and gelatin extraction. A Bose-Enduratec BioDynamic chamber configured for cardiovascular applications was used to measure the diametrical stability (dilation) of tubular samples under hydrodynamic flow conditions at 37 °C. Microporous PCL tubes withstood the hydrodynamic stresses induced by short, 2-min duration flow rates up to 1000 mL/min, which resulted in estimated internal pressures in excess of arterial pressure (80–130 mmHg). Micro/macroporous PCL tubes having a maximum macroporosity of 23% accommodated the hydrodynamic stresses generated by short duration, flow rates up to 1000 mL/min, which resulted in estimated internal pressures similar to venous pressure (30 mmHg).The dilation of microporous PCL tubes under short, (5 min) pulsatile flow conditions (1 Hz) increased from 10 to 100 μm with increasing mean flow rate from 50 to 500 mL/min. Both microporous and macroporous tubes exhibited a burst strength higher than 900 mmHg under hydrostatic fluid pressure, which is in excess of arterial pressure (80–130 mmHg) by a factor of approximately 7. Quantitative analysis of the macropore structure was performed using micro-computed tomography for correlation with mechanical properties and cell growth rates. Mouse fibroblasts efficiently colonized the external surface of macroporous PCL materials over 8 days in cell culture and cell numbers were higher by a factor of two compared with microporous PCL. These findings demonstrate that micro/macroporous PCL tubes designed for vascular tissue engineering can accommodate the hydrodynamic stresses generated by short duration, simulated blood flow conditions and exhibit good potential for integration with host tissue. © 2010 Biomedical Engineering Society

Neuroendocrine Neoplasms of the Upper Aerodigestive Tract, Ear, and Salivary Glands

Neuroendocrine neoplasms (NENs) of the head and neck (H&N) region include a heterogeneous group of neoplastic proliferations arising in the nasal cavity, paranasal sinuses, nasopharynx, larynx, salivary glands, middle ear, and skin. In addition to epithelial neoplasms, H&N paraganglioma and olfactory neuroblastoma can be included in this group. The morphological and clinical features of H&N NENs depend on several different factors, including their degree of differentiation, site of origin, and molecular background. Indeed, H&N NENs encompass a wide spectrum of neoplasms, ranging from indolent neuroendocrine tumors to highly aggressive neuroendocrine carcinomas