Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:6.3.2.19 (ubiquitin-protein ligase)
 799 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have previously shown that stress-induced protein degradation requires a functional ubiquitin-activating enzyme and the autophagic-lysosomal pathway. In this study, we examined the occurrence of ubiquitin-protein conjugates that form during nutrient starvation. Kidney and liver epithelial cells respond to nutrient stress by enhancing autophagy and protein degradation. We have shown that this degradative response was more dramatic in nondividing cultures. In addition, the onset of autophagy was suppressed by pactamycin, cycloheximide, and puromycin. We observed an accumulation of ubiquitinated proteins coincident with the degradative response to amino acid starvation. The stress-induced protein ubiquitination was not affected by cycloheximide, indicating that protein synthesis was not required. The ubiquitinated proteins were localized to the cytosol and subcellular fractions enriched with autophagosomes and lysosomes. The incorporation of the ubiquitinated proteins into autolysosomes was dramatically reduced by 3-methyladenine, an inhibitor of autophagy. The evidence suggests that ubiquitinated proteins are sequestered by autophagy for degradation. We next set out to identify those primary ubiquitinated proteins at 60 kDa and 68 kDa. Polyclonal antibodies were prepared against these proteins that had been immunopurified from rat liver lysosomes. The antibodies prepared against those 68 kDa proteins also recognized a 40 kDa protein in cytosolic fractions. Internal amino acid sequences obtained from two cyanogen bromide fragments of this 40 kDa protein were shown to be identical to sequences in liver fructose1,6-bisphosphate aldolase B. Anti-Ub68 antibodies recognized purified aldolase A and aldolase B. Conversely, antibodies prepared against aldolase B recognized the 40 kDa aldolase as well as four to five high molecular weight forms, including a 68 kDa protein. Finally, we have shown that the degradation of aldolase B was enhanced during amino acid and serum starvation. This degradation was suppressed by chloroquine and 3-methyladenine, suggesting that aldolase B was being degraded within autolysosomes. We propose that aldolase B is ubiquitinated within the cytosol and then transported into autophagosomes and autolysosomes for degradation during nutrient stress.
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PMID:Ubiquitinated aldolase B accumulates during starvation-induced lysosomal proteolysis. 988 86

The present study was undertaken to investigate the anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit and to explore the molecular mechanisms of action in MCF-7 cells. Cytotoxic properties of hexane, ethyl acetate and methanol extracts were carried out against MCF-7 cells using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assay. Ethyl acetate extract showed good cytototoxic activities compared to hexane and methanol extracts. Methyl caffeate was isolated from the ethyl acetate extract using column chromatography. Cytotoxic properties of methyl caffeate was investigated against MCF-7, A549, COLO320, HepG-2 and Vero cells. The compound showed potent cytotoxic properties against MCF-7 cells compared to A549, COLO320 and HepG-2 cells. Methyl caffeate significantly reduced cell proliferation and increased formation of fragmented DNA and apoptotic body in MCF-7 cells. Bcl-2, Bax, Bid, p53, caspase-3, PARP and cytochrome c release were detected by western blot analysis. The activities of caspases-3 and PARP gradually increased after the addition of isolated compound. Bcl-2 protein was down regulated; Bid and Bax were up regulated after the treatment with methyl caffeate. Molecular docking studies showed that the compound bound stably to the active sites of poly (ADP-ribose) polymerase-1 (PARP1), B cell CLL/lymphoma-2 (BCL-2), E3 ubiquitin-protein ligase (MDM2) and tubulin. The results strongly suggested that methyl caffeate induced apoptosis in MCF-7 cells via caspase activation through cytochrome c release from mitochondria.
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PMID:In vitro anticancer activity of methyl caffeate isolated from Solanum torvum Swartz. fruit. 2641 18