A High-Affinity Peptide Ligand Targeting Syntenin Inhibits Glioblastoma

Despite the recent advances in cancer therapeutics, highly aggressive cancer forms, such as glioblastoma (GBM), still have very low survival rates. The intracellular scaffold protein syntenin, comprising two postsynaptic density protein-95/discs-large/zona occludens-1 (PDZ) domains, has emerged as a novel therapeutic target in highly malignant phenotypes including GBM. Here, we report the development of a novel, highly potent, and metabolically stable peptide inhibitor of syntenin, KSL-128114, which binds the PDZ1 domain of syntenin with nanomolar affinity. KSL-128114 is resistant toward degradation in human plasma and mouse hepatic microsomes and displays a global PDZ domain selectivity for syntenin. An X-ray crystal structure reveals that KSL-128114 interacts with syntenin PDZ1 in an extended noncanonical binding mode. Treatment with KSL-128114 shows an inhibitory effect on primary GBM cell viability and significantly extends survival time in a patient-derived xenograft mouse model. Thus, KSL-128114 is a novel promising candidate with therapeutic potential for highly aggressive tumors, such as GBM.

The effect of nutrient limitation on styrene metabolism in Pseudomonas putida CA-3

Styrene degradation in Pseudomonas putida CA-3 has previously been shown to be subject to catabolite repression in batch culture. We report here on the catabolite-repressing effects of succinate and glutamate and the effects of a limiting inorganic-nutrient concentration on the styrene degradation pathway of P. putida CA-3 in a chemostat culture at low growth rates (0.05 h-1). Oxidation of styrene and the presence of styrene oxide isomerase and phenylacetaldehyde dehydrogenase activities were used as a measure of the expression of the styrene degradation pathway. Both glutamate and succinate failed to repress the styrene degradation ability under growth conditions of carbon and energy limitation. Lower levels of enzyme activities of the styrene degradation pathway were seen in cells grown on styrene or phenylacetic acid (PAA) under conditions of both ammonia and sulfate limitation than were seen under carbon and energy limitation. Cells grown on PAA under continuous culture oxidize styrene and styrene oxide and possess styrene oxide isomerase and NAD(+)-dependent phenylacetaldehyde dehydrogenase activities. Catabolite repression of styrene metabolism was observed in cells grown on styrene or PAA in the presence of growth-saturating (nonlimiting) concentrations of succinate or glutamate under sulfate limitation.

Catabolite repression of the toluene degradation pathway in Pseudomonas putida harboring pWW0 under various conditions of nutrient limitation in chemostat culture

In earlier studies, the pathway of toluene and m- and p-xylene degradation (TOL pathway) in Pseudomonas putida (pWW0) was found to be subject to catabolite repression when the strain was grown at the maximal rate on glucose or succinate in the presence of an inducer. This report describes catabolite repression of the TOL pathway by succinate in chemostat cultures run at a low dilution rate (D = 0.05 h-1) under different conditions of inorganic-nutrient limitation. The activity of benzylalcohol dehydrogenase (BADH) in cell extracts was used as a measure of the expression of the TOL upper pathway. When cells were grown in the presence of 10 to 15 mM succinate under conditions of phosphate or sulfate limitation, the BADH activity in response to the nonmetabolizable inducer o-xylene was less than 2% of that of cells grown under conditions of succinate limitation. Less repression was found under conditions of ammonium or oxygen limitation (2 to 10% and 20 to 35%, respectively, of the BADH levels under succinate limitation). The BADH expression levels determined under the different growth conditions appeared to correlate well with the mRNA transcript levels from the upper pathway promoter (Pu), which indicates that repression was due to a blockage at the transcriptional level. The meta-cleavage pathway was found to be less susceptible to catabolite repression. The results obtained suggest that the occurrence of catabolite repression is related to a high-energy status of the cells rather than to a high growth rate or directly to the presence of growth-saturating concentrations of a primary carbon and energy source.