16 research outputs found
Quantitative proteomic analysis of the influence of lignin on biofuel production by Clostridium acetobutylicum ATCC 824
Background: Clostridium acetobutylicum has been a focus of research because of its ability to produce high-value
compounds that can be used as biofuels. Lignocellulose is a promising feedstock, but the ligninâcelluloseâhemicellulose
biomass complex requires chemical pre-treatment to yield fermentable saccharides, including cellulose-derived
cellobiose, prior to bioproduction of acetoneâbutanolâethanol (ABE) and hydrogen. Fermentation capability is
limited by lignin and thus process optimization requires knowledge of lignin inhibition. The effects of lignin on cellular
metabolism were evaluated for C. acetobutylicum grown on medium containing either cellobiose only or cellobiose
plus lignin. Microscopy, gas chromatography and 8-plex iTRAQ-based quantitative proteomic technologies were
applied to interrogate the effect of lignin on cellular morphology, fermentation and the proteome.
Results: Our results demonstrate that C. acetobutylicum has reduced performance for solvent production when
lignin is present in the medium. Medium supplemented with 1 g Lâ1
of lignin led to delay and decreased solvents
production (ethanol; 0.47 g Lâ1
for cellobiose and 0.27 g Lâ1
for cellobiose plus lignin and butanol; 0.13 g Lâ1
for cellobiose
and 0.04 g Lâ1
for cellobiose plus lignin) at 20 and 48 h, respectively, resulting in the accumulation of acetic
acid and butyric acid. Of 583 identified proteins (FDR < 1 %), 328 proteins were quantified with at least two unique
peptides. Up- or down-regulation of protein expression was determined by comparison of exponential and stationary
phases of cellobiose in the presence and absence of lignin. Of relevance, glycolysis and fermentative pathways were
mostly down-regulated, during exponential and stationary growth phases in presence of lignin. Moreover, proteins
involved in DNA repair, transcription/translation and GTP/ATP-dependent activities were also significantly affected
and these changes were associated with altered cell morphology.
Conclusions: This is the first comprehensive analysis of the cellular responses of C. acetobutylicum to lignin at metabolic
and physiological levels. These data will enable targeted metabolic engineering strategies to optimize biofuel
production from biomass by overcoming limitations imposed by the presence of lignin
Human cytomegalovirus latency-associated proteins elicit immune-suppressive IL-10 producing CD4âș T cells.
Human cytomegalovirus (HCMV) is a widely prevalent human herpesvirus, which, after primary infection, persists in the host for life. In healthy individuals, the virus is well controlled by the HCMV-specific T cell response. A key feature of this persistence, in the face of a normally robust host immune response, is the establishment of viral latency. In contrast to lytic infection, which is characterised by extensive viral gene expression and virus production, long-term latency in cells of the myeloid lineage is characterised by highly restricted expression of viral genes, including UL138 and LUNA. Here we report that both UL138 and LUNA-specific T cells were detectable directly ex vivo in healthy HCMV seropositive subjects and that this response is principally CD4âș T cell mediated. These UL138-specific CD4âș T cells are able to mediate MHC class II restricted cytotoxicity and, importantly, show IFNÎł effector function in the context of both lytic and latent infection. Furthermore, in contrast to CDCD4âș T cells specific to antigens expressed solely during lytic infection, both the UL138 and LUNA-specific CD4âș T cell responses included CD4âș T cells that secreted the immunosuppressive cytokine cIL-10. We also show that cIL-10 expressing CD4âș T-cells are directed against latently expressed US28 and UL111A. Taken together, our data show that latency-associated gene products of HCMV generate CD4âș T cell responses in vivo, which are able to elicit effector function in response to both lytic and latently infected cells. Importantly and in contrast to CD4âș T cell populations, which recognise antigens solely expressed during lytic infection, include a subset of cells that secrete the immunosuppressive cytokine cIL-10. This suggests that HCMV skews the T cell responses to latency-associated antigens to one that is overall suppressive in order to sustain latent carriage in vivo
Pupil-Sparing Oculomotor Nerve Paresis as an Early Symptom of Unruptured Internal Carotid-Posterior Communicating Artery Aneurysms -Three Case Reports-
ASARM peptides: PHEX-dependent and -independent regulation of serum phosphate
Increased acidic serine aspartate-rich MEPE-associated motif (ASARM) peptides cause mineralization defects in X-linked hypophosphatemic rickets mice (HYP) and âdirectlyâ inhibit renal phosphate uptake in vitro. However, ASARM peptides also bind to phosphate-regulating gene with homologies to endopeptidases on the X chromosome (PHEX) and are a physiological substrate for this bone-expressed, phosphate-regulating enzyme. We therefore tested the hypothesis that circulating ASARM peptides also âindirectlyâ contribute to a bone-renal PHEX-dependent hypophosphatemia in normal mice. Male mice (n = 5; 12 wk) were fed for 8 wk with a normal phosphorus and vitamin D3 diet (1% Pi diet) or a reduced phosphorus and vitamin D3 diet (0.1% Pi diet). For the final 4 wk, transplantation of mini-osmotic pumps supplied a continuous infusion of either ASARM peptide (5 mg·dayâ1·kgâ1) or vehicle. HYP, autosomal recessive hypophosphatemic rickets (ARHR), and normal mice (no pumps or ASARM infusion; 0.4% Pi diet) were used in a separate experiment designed to measure and compare circulating ASARM peptides in disease and health. ASARM treatment decreased serum phosphate concentration and renal phosphate cotransporter (NPT2A) mRNA with the 1% Pi diet. This was accompanied by a twofold increase in serum ASARM and 1,25-dihydroxy vitamin D3 [1,25 (OH)2D3] levels without changes in parathyroid hormone. For both diets, ASARM-treated mice showed significant increases in serum fibroblast growth factor 23 (FGF23; +50%) and reduced serum osteocalcin (â30%) and osteopontin (â25%). Circulating ASARM peptides showed a significant inverse correlation with serum Pi and a significant positive correlation with fractional excretion of phosphate. We conclude that constitutive overexpression of ASARM peptides plays a âcomponentâ PHEX-independent part in the HYP and ARHR hypophosphatemia. In contrast, with wild-type mice, ASARM peptides likely play a bone PHEX-dependent role in renal phosphate regulation and FGF23 expression. They may also coordinate FGF23 expression by competitively modulating PHEX/DMP1 interactions and thus bone-renal mineral regulation