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91.
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Schild L Heyken A de Groot PW Hiller E Mock M de Koster C Horn U Rupp S Hube B 《Eukaryotic cell》2011,10(1):98-109
The cell wall of the human-pathogenic fungus Candida albicans is a robust but also dynamic structure which mediates adaptation to changing environmental conditions during infection. Sap9 and Sap10 are cell surface-associated proteases which function in C. albicans cell wall integrity and interaction with human epithelial cells and neutrophils. In this study, we have analyzed the enzymatic properties of Sap9 and Sap10 and investigated whether these proteases cleave proteins on the fungal cell surface. We show that Sap9 and Sap10, in contrast to other aspartic proteases, exhibit a near-neutral pH optimum of proteolytic activity and prefer the processing of peptides containing basic or dibasic residues. However, both proteases also cleaved at nonbasic sites, and not all tested peptides with dibasic residues were processed. By digesting isolated cell walls with Sap9 or Sap10, we identified the covalently linked cell wall proteins (CWPs) Cht2, Ywp1, Als2, Rhd3, Rbt5, Ecm33, and Pga4 as in vitro protease substrates. Proteolytic cleavage of the chitinase Cht2 and the glucan-cross-linking protein Pir1 by Sap9 was verified using hemagglutinin (HA) epitope-tagged versions of both proteins. Deletion of the SAP9 and SAP10 genes resulted in a reduction of cell-associated chitinase activity similar to that upon deletion of CHT2, suggesting a direct influence of Sap9 and Sap10 on Cht2 function. In contrast, cell surface changes elicited by SAP9 and SAP10 deletion had no major impact on the phagocytosis and killing of C. albicans by human macrophages. We propose that Sap9 and Sap10 influence distinct cell wall functions by proteolytic cleavage of covalently linked cell wall proteins. 相似文献
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Birkenfeld AL Lee HY Guebre-Egziabher F Alves TC Jurczak MJ Jornayvaz FR Zhang D Hsiao JJ Martin-Montalvo A Fischer-Rosinsky A Spranger J Pfeiffer AF Jordan J Fromm MF König J Lieske S Carmean CM Frederick DW Weismann D Knauf F Irusta PM De Cabo R Helfand SL Samuel VT Shulman GI 《Cell metabolism》2011,14(2):184-195
Reduced expression of the Indy (I'm Not Dead, Yet) gene in D.?melanogaster and its homolog in C.?elegans prolongs life span and in D.?melanogaster augments mitochondrial biogenesis in a manner akin to caloric restriction. However, the cellular mechanism by which Indy does this is unknown. Here, we report on the knockout mouse model of the mammalian Indy (mIndy) homolog, SLC13A5. Deletion of mIndy in mice (mINDY(-/-) mice) reduces hepatocellular ATP/ADP ratio, activates hepatic AMPK, induces PGC-1α, inhibits ACC-2, and reduces SREBP-1c levels. This signaling network promotes hepatic mitochondrial biogenesis, lipid oxidation, and energy expenditure and attenuates hepatic de novo lipogenesis. Together, these traits protect mINDY(-/-) mice from the adiposity and insulin resistance that evolve with high-fat feeding and aging. Our studies demonstrate a profound effect of mIndy on mammalian energy metabolism and suggest that mINDY might be a therapeutic target for the treatment of obesity and type 2 diabetes. 相似文献
95.
Diana Walluscheck Kathrin Reissig Khuloud Bajbouj Oliver Ullrich Roland Hartig Hala Gali‐Muhtasib Antje Diestel Albert Roessner Regine Schneider‐Stock 《Journal of cellular and molecular medicine》2011,15(7):1528-1541
Besides the well‐understood DNA damage response via establishment of G2 checkpoint arrest, novel studies focus on the recovery from arrest by checkpoint override to monitor cell cycle re‐entry. The aim of this study was to investigate the role of Chk1 in the recovery from G2 checkpoint arrest in HCT116 (human colorectal cancer) wt, p53–/– and p21–/– cell lines following H2O2 treatment. Firstly, DNA damage caused G2 checkpoint activation via Chk1. Secondly, overriding G2 checkpoint led to (i) mitotic slippage, cell cycle re‐entry in G1 and subsequent G1 arrest associated with senescence or (ii) premature mitotic entry in the absence of p53/p21WAF1 causing mitotic catastrophe. We revealed subtle differences in the initial Chk1‐involved G2 arrest with respect to p53/p21WAF1: absence of either protein led to late G2 arrest instead of the classic G2 arrest during checkpoint initiation, and this impacted the release back into the cell cycle. Thus, G2 arrest correlated with downstream senescence, but late G2 arrest led to mitotic catastrophe, although both cell cycle re‐entries were linked to upstream Chk1 signalling. Chk1 knockdown deciphered that Chk1 defines long‐term DNA damage responses causing cell cycle re‐entry. We propose that recovery from oxidative DNA damage‐induced G2 arrest requires Chk1. It works as cutting edge and navigates cells to senescence or mitotic catastrophe. The decision, however, seems to depend on p53/p21WAF1. The general relevance of Chk1 as an important determinant of recovery from G2 checkpoint arrest was verified in HT29 colorectal cancer cells. 相似文献
96.
Hoorn EJ Walsh SB McCormick JA Fürstenberg A Yang CL Roeschel T Paliege A Howie AJ Conley J Bachmann S Unwin RJ Ellison DH 《Nature medicine》2011,17(10):1304-1309
Calcineurin inhibitors (CNIs) are immunosuppressive drugs that are used widely to prevent rejection of transplanted organs and to treat autoimmune disease. Hypertension and renal tubule dysfunction, including hyperkalemia, hypercalciuria and acidosis, often complicate their use. These side effects resemble familial hyperkalemic hypertension, a genetic disease characterized by overactivity of the renal sodium chloride cotransporter (NCC) and caused by mutations in genes encoding WNK kinases. We hypothesized that CNIs induce hypertension by stimulating NCC. In wild-type mice, the CNI tacrolimus caused salt-sensitive hypertension and increased the abundance of phosphorylated NCC and the NCC-regulatory kinases WNK3, WNK4 and SPAK. We demonstrated the functional importance of NCC in this response by showing that tacrolimus did not affect blood pressure in NCC-knockout mice, whereas the hypertensive response to tacrolimus was exaggerated in mice overexpressing NCC. Moreover, hydrochlorothiazide, an NCC-blocking drug, reversed tacrolimus-induced hypertension. These observations were extended to humans by showing that kidney transplant recipients treated with tacrolimus had a greater fractional chloride excretion in response to bendroflumethiazide, another NCC-blocking drug, than individuals not treated with tacrolimus; renal NCC abundance was also greater. Together, these findings indicate that tacrolimus-induced chronic hypertension is mediated largely by NCC activation, and suggest that inexpensive and well-tolerated thiazide diuretics may be especially effective in preventing the complications of CNI treatment. 相似文献
97.
Köhler J Breitbach K Renner C Heitsch AK Bast A van Rooijen N Vogelgesang S Steinmetz I 《Microbes and infection / Institut Pasteur》2011,13(11):914-922
Staphylococcus aureus is a pathogen that often causes severe nosocomial infections including pneumonia. The present study was designed to examine innate phagocyte mediated immune mechanisms using a previously described murine S. aureus Newman pneumonia model. We found that BALB/c mice represent a more susceptible mouse strain compared to C57BL/6 mice after intranasal S. aureus Newman challenge. Depletion experiments revealed that neutrophils are a crucial determinant for resistance whereas depletion of alveolar macrophages protected mice to some degree from acute pulmonary S. aureus challenge. C57BL/6 mice lacking the subunit gp91phox of the NADPH-oxidase (gp91phox−/− mice) proved to be highly susceptible against the pathogen. In contrast, C57BL/6 inducible nitric oxidase synthase deficient (iNOS−/−) mice did not differ in their clinical outcome after infection. Neither bone marrow macrophages from iNOS−/− nor from gp91phox−/− mice were impaired in controlling intracellular persistence of S. aureus. Our data suggest that neutrophil and NADPH-oxidase mediated mechanisms are essential components in protecting the host against pulmonary S. aureus Newman challenge. On contrary, macrophages as well as NO mediated mechanisms do not seem to play a critical role for resistance in this model. 相似文献
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T-cell based IFN-γ release assays do not permit distinction of active tuberculosis (TB) from successfully treated disease or latent M. tuberculosis infection. We postulated that IFN-γ and IL-2 cytokine profiles of antigen-specific T cells measured by flow-cytometry ex vivo might correlate with TB disease activity in vivo. Tuberculin (PPD), ESAT-6 and CFP-10 were used as stimuli to determine antigen-specific cytokine profiles in CD4 T cells from 24 patients with active TB and 28 patients with successfully treated TB using flow-cytometry. Moreover, 25 individuals with immunity consistent with latent M. tuberculosis infection and BCG-vaccination, respectively, were recruited. Although the frequency of cytokine secreting PPD reactive CD4 T cells was higher in patients with active TB compared to patients with treated TB (median 0.81% vs. 0.39% of CD4 T cells, p?=?0.02), the overlap in frequencies precluded distinction between the groups on an individual basis. When assessing cytokine profiles, PPD specific CD4 T cells secreting both IFN-γ and IL-2 predominated in treated TB, latent infection and BCG-vaccination, whilst in active TB the cytokine profile was shifted towards cells secreting IFN-γ only (p<0.0001). Cytokine profiles of ESAT-6 or CFP-10 reactive CD4 T cells did not differ between the groups. Receiver operator characteristics (ROC) analysis revealed that frequencies of PPD specific IFN-γ/IL-2 dual-positive T cells below 56% were an accurate marker for active TB (specificity 100%, sensitivity 70%) enabling effective discrimination from non-active states. In conclusion, a frequency lower than 56% IFN-γ/IL-2 dual positive PPD-specific circulating CD4 T-cells is strongly indicative of active TB. 相似文献
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