Penicillium decumbens T. is an important filamentous fungus for the production of cellulases to effectively degrade lignocellulose for second generation biofuel production. In order to enhance the capability of Penicillium decumbens to produce cellulases, we constructed a creB (a deubiquitinating enzyme encoding gene) deletion cassette, and generated a creB knockout strain with homologous double crossover recombination. This mutation resulted in a detectable decrease of carbon catabolite repression (CCR) effect. The filter paper activity, endoglucanase activity, xylanase activity and exoglucanase activity of the deltacreB strain increased by 1.8, 1.71, 2.06 and 2.04 fold, respectively, when comparing with the parent strain Ku-39. A 2.68 fold increase of extracellular protein concentration was also observed. These results suggest that the deletion of creB results in CCR derepression. These data also suggest that CREB influences cellulase production of Penicillium decumbens. In generation, this study provides information that can be helpful for constructing cellulase hyper-producing strain.
Cellulase ; biosynthesis ; Endopeptidases ; genetics ; metabolism ; Gene Knockout Techniques ; Lignin ; metabolism ; Mutant Proteins ; metabolism ; Penicillium ; enzymology ; genetics ; Recombination, Genetic ; Ubiquitinated Proteins ; genetics ; Ubiquitination

Diabetes mellitus is characterized by decreased insulin secretion and action. Decreased insulin secretion results from a reduction in mass and/or function of pancreatic beta-cells. Apoptosis, oxidative stress, mitochondrial dysfunction, and endoplasmic reticulum (ER) stress responses have been suggested as mechanisms for the changes in beta-cells in type 2 diabetes; however, the underlying causes have not been clearly elucidated. Autophagy is an intracellular process that maintains cellular homeostasis through degradation and recycling of organelles. Recently, we reported reduction of beta-cell mass in autophagy-deficient mice. Pancreatic insulin content was also decreased due to the decreased beta-cell mass and the reduced number of insulin granules. Morphological analysis of these beta-cells revealed an accumulation of ubiquitinated proteins, swollen mitochondria, and distended ER. Insulin secretory function ex vivo was also impaired. As a result, autophagy-deficient mice showed hypoinsulinemia and hyperglycemia. These results suggested that autophagy is necessary to maintain the structure, mass and function of beta-cells. In addition, as autophagy may play a protective role against ER stress and rejuvenate organelle function, impaired autophagy may lead to mitochondrial dysfunction and ER stress, which have been implicated as causes of insulin resistance. Therefore, in addition to beta-cell homeostasis, dysregulated autophagy may possibly be involved in insulin resistance.
Animals ; Apoptosis ; Autophagy ; Diabetes Mellitus ; Endoplasmic Reticulum ; Homeostasis ; Hyperglycemia ; Insulin ; Insulin Resistance ; Insulin-Secreting Cells ; Mice ; Mitochondria ; Organelles ; Oxidative Stress ; Recycling ; Ubiquitinated Proteins

Glucosamine, a naturally occurring amino monosaccharide, has been reported to play a role in the regulation of apoptosis more than half century. However the effect of glucosamine on tumor cells and the involved molecular mechanisms have not been thoroughly investigated. Glucosamine enters the hexosamine biosynthetic pathway (HBP) downstream of the rate-limiting step catalyzed by the GFAT (glutamine:fluctose-6-phosphate amidotransferase), providing UDP-GlcNAc substrates for O-linked beta-N-acetylglucosamine (O-GlcNAc) protein modification. Considering that O-GlcNAc modification of proteasome subunits inhibits its activity, we examined whether glucosamine induces growth inhibition via affecting proteasomal activity. In the present study, we found glucosamine inhibited proteasomal activity and the proliferation of ALVA41 prostate cancer cells. The inhibition of proteasomal activity results in the accumulation of ubiquitinated proteins, followed by induction of apoptosis. In addition, we demonstrated that glucosamine downregulated proteasome activator PA28gamma and overexpression of PA28gamma rescued the proteasomal activity and growth inhibition mediated by glucosamine. We further demonstrated that inhibition of O-GlcNAc abrogated PA28gamma suppression induced by glucosamine. These findings suggest that glucosamine may inhibit growth of ALVA41 cancer cells through downregulation of PA28gamma and inhibition of proteasomal activity via O-GlcNAc modification.
Acetylglucosamine/chemistry/metabolism ; Alloxan/pharmacology ; Apoptosis/*drug effects ; Autoantigens/genetics/*metabolism ; Cell Line, Tumor ; Cell Proliferation/*drug effects ; Gene Expression Regulation, Neoplastic ; Glucosamine/*pharmacology ; Humans ; Male ; Phosphorylation ; Prostatic Neoplasms/*enzymology ; Proteasome Endopeptidase Complex/*antagonists & inhibitors/genetics/metabolism ; RNA, Small Interfering/genetics ; Ubiquitinated Proteins/metabolism