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Decreased Protein Levels (decreased + protein_level)

Distribution by Scientific Domains

Medical Sciences	50%

Selected Abstracts

Scanning mutagenesis of regions in the G, protein Gpa1 that are predicted to interact with yeast mating pheromone receptors

FEMS YEAST RESEARCH, Issue 1 2008
Douglas P. Gladue
Abstract The mechanism by which receptors activate heterotrimeric G proteins was examined by scanning mutagenesis of the Saccharomyces cerevisiae pheromone-responsive G, protein (Gpa1). The juxtaposition of high-resolution structures for rhodopsin and its cognate G protein transducin predicted that at least six regions of G, are in close proximity to the receptor. Mutagenesis was targeted to residues in these domains in Gpa1, which included four loop regions (,2,,3, ,2,,4, ,3,,5, and ,4,,6) as well as the N and C termini. The mutants displayed a range of phenotypes from nonsignaling to constitutive activation of the pheromone pathway. The constitutive activity of some mutants could be explained by decreased production of Gpa1, which permits unregulated signaling by G,,. However, the constitutive activity caused by the F344C and E335C mutations in the ,2,,4 loop and F378C in the ,3,,5 loop was not due to decreased protein levels, and was apparently due to defects in sequestering G,,. The strongest loss of the function mutant, which was not detectably induced by a pheromone, was caused by a K314C substitution in the ,2,,3 loop. Several other mutations caused weak signaling phenotypes. Altogether, these results suggest that residues in different interface regions of G, contribute to activation of signaling. [source]

Cyclooxygenase-2 inhibitor celecoxib augments chemotherapeutic drug-induced apoptosis by enhancing activation of caspase-3 and -9 in prostate cancer cells

INTERNATIONAL JOURNAL OF CANCER, Issue 3 2005
Devendra S. Dandekar
Abstract Many tumors constitutively express high levels of the inducible form of proinflammatory enzyme, cyclooxygenase-2 (COX-2). Increased COX-2 expression is associated with tumor cell resistance to many cytotoxic chemotherapy drugs. Furthermore, increased resistance to cytotoxic antitumor drugs is also known to be dependent on associated stromal cells in many tumors. We investigated whether prostate tumor-associated stromal cells, marrow-derived osteoblasts, affect cytotoxicity of 2 antitumor drugs, COL-3 and docetaxel (TXTR), and whether it is dependent on COX-2 activity. We further examined whether inhibiting the activity of COX-2 negate the stroma-induced decrease in drug sensitivity in tumor cells. COX-2-specific inhibitor celecoxib (CXB) was used to inhibit COX-2 activity and associated alteration in cell death signaling was investigated. Coculturing PC-3ML cells with osteoblasts decreased the cytotoxicity of the tested antitumor drugs and was associated with increased COX-2 activity in PC-3ML cells. A significant decrease in drug-induced PGE2 increase and an increase in cytotoxicity were observed when cells were treated with COL-3 or TXTR combined with CXB. Cytotoxicity of single or combination treatment increased apoptosis, which was associated with caspase-3 and -9 activation, PARP cleavage, increased BAD protein, but decreased protein levels of XIAP and BCL- xL. Oral administration of CXB (40 mg/kg) to mice with PC-3ML tumors for 42 days increased tumor latency, decreased tumor growth and enhanced tumor control with COL-3 or TXTR. Overall, a synergistic enhancement of antitumor activity in combination treatment was observed in vitro and an additive effect in vivo. These observations suggest a potential clinical use of combined dosing of COX-2 inhibitors and cytotoxic drugs at lower, nontoxic dose than currently used to treat advanced prostate cancer. © 2005 Wiley-Liss, Inc. [source]

Proteomic and SAGE profiling of murine melanoma progression indicates the reduction of proteins responsible for ROS degradation

PROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 5 2006
Gustavo A. de Souza
Abstract Using 2-DE of total cell protein extracts, we compared soluble proteins from murine melanoma lines Tm1 and Tm5 with proteins from the nontumoral cell melan-a from which they were derived. Seventy-one of the 452 spots (average) detected with CBB were differentially accumulated, i.e., increased or decreased twofold. Forty-four spots were identified by PMF/MALDI-TOF, 15 with increased and 29 with decreased protein levels. SAGE showed that 17/34 (50%) of the differentially accumulated proteins, pI range 4,7, presented similar differences at the mRNA level. Major reductions in protein were observed in tumor cells of proteins that degrade reactive oxygen species (ROS). Decreases of , twofold in GST, superoxide dismutase, aldehyde dehydrogenase, thioredoxin, peroxiredoxin 2, and peroxiredoxin 6 protein were observed. SAGE indicated the reduction of other proteins involved in ROS degradation. As expected, the accumulation of exogenous peroxides was significantly higher in the tumor cells while the levels of glutathionylation were two times lower in the tumor cells compared to melan-a. The differential accumulation of proteins involved in oncogene/tumor suppressor pathways was observed. Melanoma cells can favor survival pathways activated by ROS by inhibiting p53 pathways and activation of Ras and c-myc pathways. [source]

Inhibition of Matrix Metalloproteinase-9 Attenuates Acute Small-for-Size Liver Graft Injury in Rats

AMERICAN JOURNAL OF TRANSPLANTATION, Issue 4 2010
Z. Y. Ma
Ischemia/reperfusion (I/R) and portal hypertension have been implicated in small-for-size liver graft dysfunction. Matrix metalloproteinases-2 and -9 (MMP-2/9) are critically proposed to involve in hepatic I/R injury and activated by hemodynamic force. We hypothesized that MMP-2/9 overexpression played a crucial role in acute graft injury following small-for-size liver transplantation (LT). Rats were randomly assigned into four groups: 75% partial hepatectomy (PH); 100% LT; 25% LT and 25% LT treated with CTT peptide (MMP-2/9 inhibitor). ELISA, real-time PCR, gelatin zymography and immunohistochemistry were used to determine the expression pattern of MMP-2/9 in liver tissue. MMP-9 expression was significantly increased 6 h after reperfusion and reached a peak 12 h in the 25% LT group, whereas MMP-2 was expressed in all groups invariably. Compared with the 25% LT group, rats from CTT-treated group exhibited markedly decreased alanine aminotransferase and total bilirubin values, downregulated proinflammatory cytokines, attenuated malondialdehyde (MDA) and myeloperoxidase (MPO) activities, and improved liver histology. Likewise, MMP-9 inhibition significantly reduced number of TUNEL-positive cells and caspase-3 activity, along with decreased protein levels of Fas and Fas-L. Specifically, rat survival was also improved in the CTT-treated group. These results support critical function of MMP-9 involved in acute small-for-size livergraft injury. [source]