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)

The lysosomal alpha-mannosidase gene in Dictyostelium discoideum is representative of a small group of genes that are expressed under two different conditions: 1) immediately upon removal of the bacterial food source from exponentially growing cells at < 5 x 10(5) cells/ml (which also initiates the developmental cycle), and 2) when the concentration of a secreted glycoprotein termed the prestarvation response factor (PSF) reaches a critical threshold in cultures growing at densities > 5 x 10(5) cells/ml. In this report we show that transcription of the alpha-mannosidase gene induced by starvation did not require protein synthesis in axenic wild-type strains, whereas protein synthesis was required for the transcriptional induction observed in response to PSF. Northern blot analysis was also done using mRNA from G alpha 1 and G alpha 2 gene disruption mutants. These genes encode subunits of heterotrimeric G proteins found at the cell surface in growing cells and cells early in development. The pattern of alpha-mannosidase gene expression was normal in these mutants as well as in mutants unable to produce the secreted glycoprotein conditioned medium factor or the cAMP receptor-1 protein. These genes have been shown to regulate the expression of many genes during early development. Promoter analysis studies identified a 145-base pair sequence element containing a TTG box which was required for alpha-mannosidase transcriptional induction under both starvation conditions and in response to PSF. The TTG box identified is an important regulatory element in the promoter of another prestarvation response gene, the discoidin I gamma gene. A ts mutant was found to misregulate the expression of both discoidin I and alpha-mannosidase expression at restrictive temperatures. Taken together these results suggest that the prestarvation response genes may be coordinately regulated possibly through the TTG box.
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PMID:Characterization of the signal transduction pathways and cis-acting DNA sequence responsible for the transcriptional induction during growth and development of the lysosomal alpha-mannosidase gene in Dictyostelium discoideum. 836 7

The role of myosin Is in endosomal trafficking and the lysosomal system was investigated in a Dictyostelium discoideum myosin I double mutant myoB-/C-, that has been previously shown to exhibit defects in fluid-phase endocytosis during growth in suspension culture (Novak et al., 1995). Various properties of the endosomal pathway in the myoB-/C- double mutant as well as in the myoB- and myoC- single mutants, including intravesicular pH, and intracellular retention time and exocytosis of a fluid phase marker, were found to be indistinguishable from wild-type parental cells. The intimate connection between the contractile vacuole complex and the endocytic pathway in Dictyostelium, and the localization of a myosin I to the contractile vacuole in Acanthamoeba, led us to also examine the structure and function of this organelle in the three myosin I mutants. No alteration in contractile vacuole structure or function was observed in the myoB-, myoC- or myoB-/C- cell lines. The transport, processing, and localization of a lysosomal enzyme, alpha-mannosidase, were also unaltered in all three mutants. However, the myoB- and myoB-/C- cell lines, but not the myoC- cell line, were found to oversecrete the lysosomal enzymes alpha-mannosidase and acid phosphatase, during growth and starvation. None of the mutants oversecreted proteins following the constitutive secretory pathway. Two additional myosin I mutants, myoA- and myoA-/B-, were also found to oversecrete the lysosomally localized enzymes alpha-mannosidase and acid phosphatase. Taken together, these results suggest that these myosins do not play a role in the intracellular movement of vesicles, but that they may participate in controlling events that occur at the actin-rich cortical region of the cell. While no direct evidence has been found for the association of myosin Is with lysosomes, we predict that the integrity of the lysosomal system is tied to the fidelity of the actin cortex, and changes in cortical organization could influence lysosomal-related membrane events such as internalization or transit of vesicles to the cell surface.
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PMID:Examination of the endosomal and lysosomal pathways in Dictyostelium discoideum myosin I mutants. 890 11

Saccharomyces cerevisiae alpha-mannosidase (Ams1) is a cargo protein that is transported to the vacuole by the cytoplasm-to-vacuole targeting (Cvt) pathway during conditions of growth and by autophagy during conditions of starvation. After transport to the vacuole, Ams1 functions as a resident hydrolase. Ams1 has been overexpressed in the methylotrophic yeast Pichia pastoris, purified and crystallized in two crystal forms. Form I belongs to space group P2(1), with unit-cell parameters a = 145.7, b = 127.7, c = 164.0 A, beta = 101.5 degrees . Form II belongs to space group I222 or I2(1)2(1)2(1), with unit-cell parameters a = 127.9, b = 163.7, c = 291.5 A. Diffraction data were collected from these crystals to a resolution of 3.3 A for form I and of 2.6 A for form II using synchrotron radiation.
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PMID:Crystallization of Saccharomyces cerevisiae alpha-mannosidase, a cargo protein of the Cvt pathway. 1947 33


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