Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0038187 (starvation)
 24,951 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mevalonate starvation of hamster fibroblasts resulted in a shift of rab1b from the membrane to the cytosolic fraction, suggesting that rab1b depends upon an isoprenoid modification for its membrane localization. rab1b and rab3a proteins expressed in insect cells incorporated a product of [3H]mevalonate, and gas chromatography analysis of material released by Raney nickel cleavage demonstrated that rab1b and rab3a are modified by geranylgeranyl groups. Additionally, in vitro prenylation analysis demonstrated farnesyl modification of H-ras but geranylgeranyl modification of five rab proteins (1a, 1b, 2, 3a, and 6). Together, these results suggest that the carboxyl-terminal CC/CXC motifs (X = any amino acid) specifically signal for addition of geranylgeranyl, but not farnesyl, groups. A rab1b mutant protein lacking the two carboxyl-terminal cysteine residues was not prenylated in vitro. However, since a mutant H-ras protein that terminates with tandem cysteine residues was also not modified, the CC motif may be essential, but not sufficient, to signal prenylation of rab1b. Finally, rab1b and rab3a proteins were not efficient substrates for either farnesyl- or geranylgeranyltransferase activities that modify CAAX-containing proteins (A = any aliphatic amino acid). Therefore, rab proteins may be modified by a prenyltransferase(s) distinct from the prenyltransferases that modify carboxyl-terminal CAAX proteins.
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PMID:Isoprenoid modification of rab proteins terminating in CC or CXC motifs. 164 36

The Saccharomyces cerevisiae genes FAS1 and FAS2 encoding the beta and alpha subunit of yeast fatty acid synthetase (FAS), respectively, were individually deleted by one-step gene disruption. Northern blot analysis of RNA from the resulting fas null allele mutants indicated that deletion of FAS2 did not influence the transcription of FAS1, while FAS2 transcription was significantly reduced in the delta fas1 strain. These data suggest an activating role of subunit beta on FAS2 gene expression or, alternatively, a repression of FAS2 by an excess of its own gene product. Compared to the intact alpha 6 beta 6 complex, the individual FAS subunits synthesized in the delta fas1 or delta fas2 strains exhibit a considerably increased sensitivity towards the proteinases present in the yeast cell homogenate. Using yeast mutants specifically defective in the vacuolar proteinases yscA (PRA1/ PEP4 gene product) and/or yscB (PRB1 gene product), it was shown that in vitro, subunit alpha is efficiently degraded by proteinase yscA while for degradation of subunit beta, the combined action of proteinases yscA and yscB is necessary. In vivo, besides the vacuolar proteinases, an additional proteolytic activity specifically affecting free FAS subunit alpha becomes increasingly apparent in cells entering the stationary growth phase. In contrast, under similar conditions uncomplexed FAS subunit beta is stable in strains lacking the vacuolar proteinases yscA and yscB. The reduced FAS subunit levels, at the stationary phase, were independent of the corresponding FAS transcript concentrations. Thus, differential degradation pathways are obviously removing an excess of either FAS subunit, at least under starvation conditions. A combination of both regulation of FAS gene expression and proteolysis of free FAS polypeptides may therefore explain the equimolar amounts of both FAS subunits observed in yeast wild-type cells.
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PMID:Differential proteolytic sensitivity of yeast fatty acid synthetase subunits alpha and beta contributing to a balanced ratio of both fatty acid synthetase components. 173 46

The activation process of vacuolar proteinases in the yeast Saccharomyces cerevisiae via precursor maturation is initiated by the PRA1/PEP4 gene product, proteinase yscA. Chromosomal deletion of the PRA1/PEP4 locus leads to accumulation of inactive pro-proteinases in the vacuole. Nine active-site mutations of proteinase yscA have been constructed in vitro. All these mutations lead to the expression of proteinase yscA species in vivo that are inactive against the in vitro substrate hemoglobin and the in vivo substrates pro-proteinase yscB and pro-carboxypeptidase yscY. However, three active-site mutations in proteinase yscA sustained the precursor maturation of proteinase yscB and carboxypeptidase yscY after exchange of the genomic wild-type allele with the respective proteinase yscA mutant alleles. In contrast to yeast strains deleted in proteinase yscA, the respective mutants carry out all cellular functions that rely on a proteolytically active vacuole. This wild-type behaviour of proteinase yscA mutant cells is dependent on the presence of active proteinase yscB. Proteinase yscA and proteinase yscB are equally able to fulfil essential cellular functions. For instance, either proteinase is able to maintain viability under starvation. However, mature proteinase yscB is not stable in the absence of proteinase yscA. The wild-type-like conformation of proteolytically inactive mutant proteinase yscA proteins stabilizes mature proteinase yscB and thus enables continuous maturation of pro-proteinase yscB by active proteinase yscB. After inhibition of the proteolytic activity of proteinase yscB in these proteinase yscA mutants with phenylmethysulfonyl fluoride or deletion of the PRB1 gene, maturation of all zymogens investigated in the vacuole, including the proteinase yscA mutant proteins, is blocked. The proteolytic activities of the vacuole in such a strain can be regained, however, by introduction of a wild-type proteinase yscA gene allowing subsequent autocatalytic maturation of wild-type pro-proteinase yscA. This indicates that an initial self-activation process of proteinase yscA is necessary for the activation of vacuolar zymogens.
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PMID:Biogenesis of the yeast vacuole (lysosome). The use of active-site mutants of proteinase yscA to determine the necessity of the enzyme for vacuolar proteinase maturation and proteinase yscB stability. 762 61

The ability of Ras proteins to initiate eukaryotic cell proliferation requires the post-translational attachment of a farnesyl group, an isoprenoid lipid moiety derived from mevalonate, to the carboxyl-terminus of the protein. This modification is essential for the subsequent processing and intracellular targeting of the Ras protein. Here we report that mevalonate is also required for the efficient synthesis of Ras proteins in Saccharomyces cerevisiae. Depletion of intracellular mevalonate resulted in decreased steady-state levels of Ras1p and Ras2p, an effect that was mediated at the level of mRNA accumulation. The sequences controlling the response of RAS2 mRNA level to mevalonate availability, mapped to the coding region of the RAS2 gene. Mevalonate starvation also had a significant effect on the expression of some, but not all, genes encoding prenylated proteins. The regulatory effect on RAS2 mRNA did not require a functional farnesyl transferase. These results uncover a novel regulatory role for mevalonate-derived products and expand the potential for inhibitors of mevalonate metabolism as anti-cancer agents.
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PMID:Control of RAS mRNA level by the mevalonate pathway. 774 95

Human pancreatic cancer cell lines have remarkable tolerance to nutrition starvation, which enables them to survive under a tumor microenvironment. A novel antiausterity strategy in anticancer drug discovery led to the discovery of agents that preferentially inhibit the survival of cancer cells under low nutrient conditions. Artocarpus altilis (Family: Moraceae) is commonly referred to as breadfruit, traditionally for the treatment of many diseases. Many prenylated flavonoid and prenylated chalocones together with their cancer cell cytotoxicity were reported from this plant. This chapter briefly summarizes the constituents, biosynthesis, cytotoxicity, and antiausterity activity on PANC-1 human pancreatic cancer cell line of A. altilis.
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PMID:Prenylated Dihydrochalcones from Artocarpus altilis as Antiausterity Agents. 2629 57

The opportunistic fungal pathogen Candida albicans acquires essential metals from the host, yet the host can sequester these micronutrients through a process known as nutritional immunity. How the host withholds metals from C. albicans has been poorly understood; here we examine the role of calprotectin (CP), a transition metal binding protein. When CP depletes bioavailable Zn from the extracellular environment, C. albicans strongly upregulates ZRT1 and PRA1 for Zn import and maintains constant intracellular Zn through numerous cell divisions. We show for the first time that CP can also sequester Cu by binding Cu(II) with subpicomolar affinity. CP blocks fungal acquisition of Cu from serum and induces a Cu starvation stress response involving SOD1 and SOD3 superoxide dismutases. These transcriptional changes are mirrored when C. albicans invades kidneys in a mouse model of disseminated candidiasis, although the responses to Cu and Zn limitations are temporally distinct. The Cu response progresses throughout 72 h, while the Zn response is short-lived. Notably, these stress responses were attenuated in CP null mice, but only at initial stages of infection. Thus, Zn and Cu pools are dynamic at the host-pathogen interface and CP acts early in infection to restrict metal nutrients from C. albicans.
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PMID:Role of Calprotectin in Withholding Zinc and Copper from Candida albicans. 2913 49