scholarly journals THE BIOGENESIS OF MITOCHONDRIA

1968 ◽  
Vol 37 (2) ◽  
pp. 207-220 ◽  
Author(s):  
P. G. Wallace ◽  
M. Huang ◽  
Anthony W. Linnane
Keyword(s):  
Growth Medium ◽  
Mitochondrial Membrane ◽  
Plasma Membranes ◽  
Unsaturated Fatty Acids ◽  
Glucose Repression ◽  
Tween 80 ◽  
Vacuolar Membrane ◽  
Yeast Cells ◽  
Complex Spectrum ◽  
Nutritive Medium

Yeast cells grown anaerobically have been shown to vary in their ultrastructure and absorption spectrum depending upon the composition of the growth medium. The changes observed in the anaerobically grown cells are governed by the availability of unsaturated fatty acids and ergosterol and a catabolite or glucose repression. All the cells contain nuclear and plasma membranes, but the extent of the occurrence of vacuolar and mitochondrial membranes varies greatly with the growth conditions. Cells grown anaerobically on the least nutritive medium, composed of 0.5% Difco yeast extract-5% glucose-inorganic salts (YE-G), appear to contain little vacuolar membrane and no clearly recognizable mitochondrial profiles. Cells grown anaerobically on the YE-G medium supplemented with Tween 80 and ergosterol contain clearly recognizable vacuolar membrane and some mitochondrial profiles, albeit rather poorly defined. Cells grown on YE-G medium supplemented only with Tween 80 are characterized by the presence of large amounts of cytoplasmic membrane in addition to vacuolar membrane and perhaps some primitive mitochondrial profiles. When galactose replaces glucose as the major carbon source in the medium, the mitochondrial profiles within the cytoplasm become more clearly recognizable and their number increases. In aerobically grown cells, the catabolite repression also operates to reduce the total number of mitochondrial profiles. The possibility is discussed that cells grown anaerobically on the YE-G medium may not contain mitochondrial membrane and, therefore, that such cells, on aeration, form mitochondrial membrane from nonmitochondrial sources. A wide variety of absorption compounds is observed in anaerobically grown cells which do not correspond to any of the classical aerobic yeast cytochromes. The number and relative proportions of these anaerobic compounds depend upon the composition of the growth medium, the most complex spectrum being found in cells grown in the absence of lipid supplements.

scholarly journals Membrane recruitment of Atg8 by Hfl1 facilitates turnover of vacuolar membrane proteins in yeast cells approaching stationary phase

BMC Biology ◽  
2021 ◽  
Vol 19 (1) ◽  
Author(s):  
Cheng-Wen He ◽  
Xue-Fei Cui ◽  
Shao-Jie Ma ◽  
Qin Xu ◽  
Yan-Peng Ran ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Membrane Protein ◽  
Stationary Phase ◽  
Molecular Mechanisms ◽  
Multivesicular Body ◽  
Degradation Process ◽  
Vacuolar Membrane ◽  
Yeast Cells ◽  
Membrane Structures ◽  
Membrane Recruitment

Abstract Background The vacuole/lysosome is the final destination of autophagic pathways, but can also itself be degraded in whole or in part by selective macroautophagic or microautophagic processes. Diverse molecular mechanisms are involved in these processes, the characterization of which has lagged behind those of ATG-dependent macroautophagy and ESCRT-dependent endosomal multivesicular body pathways. Results Here we show that as yeast cells gradually exhaust available nutrients and approach stationary phase, multiple vacuolar integral membrane proteins with unrelated functions are degraded in the vacuolar lumen. This degradation depends on the ESCRT machinery, but does not strictly require ubiquitination of cargos or trafficking of cargos out of the vacuole. It is also temporally and mechanistically distinct from NPC-dependent microlipophagy. The turnover is facilitated by Atg8, an exception among autophagy proteins, and an Atg8-interacting vacuolar membrane protein, Hfl1. Lack of Atg8 or Hfl1 led to the accumulation of enlarged lumenal membrane structures in the vacuole. We further show that a key function of Hfl1 is the membrane recruitment of Atg8. In the presence of Hfl1, lipidation of Atg8 is not required for efficient cargo turnover. The need for Hfl1 can be partially bypassed by blocking Atg8 delipidation. Conclusions Our data reveal a vacuolar membrane protein degradation process with a unique dependence on vacuole-associated Atg8 downstream of ESCRTs, and we identify a specific role of Hfl1, a protein conserved from yeast to plants and animals, in membrane targeting of Atg8.

GRR1 of Saccharomyces cerevisiae is required for glucose repression and encodes a protein with leucine-rich repeats

1991 ◽  
Vol 11 (10) ◽  
pp. 5101-5112
Author(s):  
J S Flick ◽  
M Johnston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Protein Interactions ◽  
Tandem Repeats ◽  
Glucose Repression ◽  
Molecular Data ◽  
Primary Response ◽  
Yeast Cells ◽  
Cell Fractionation ◽  
Protein Protein Interactions ◽  
Yeast Saccharomyces Cerevisiae

Growth of the yeast Saccharomyces cerevisiae on glucose leads to repression of transcription of many genes required for alternative carbohydrate metabolism. The GRR1 gene appears to be of central importance to the glucose repression mechanism, because mutations in GRR1 result in a pleiotropic loss of glucose repression (R. Bailey and A. Woodword, Mol. Gen. Genet. 193:507-512, 1984). We have isolated the GRR1 gene and determined that null mutants are viable and display a number of growth defects in addition to the loss of glucose repression. Surprisingly, grr1 mutations convert SUC2, normally a glucose-repressed gene, into a glucose-induced gene. GRR1 encodes a protein of 1,151 amino acids that is expressed constitutively at low levels in yeast cells. GRR1 protein contains 12 tandem repeats of a sequence similar to leucine-rich motifs found in other proteins that may mediate protein-protein interactions. Indeed, cell fractionation studies are consistent with this view, suggesting that GRR1 protein is tightly associated with a particulate protein fraction in yeast extracts. The combined genetic and molecular data are consistent with the idea that GRR1 protein is a primary response element in the glucose repression pathway and is required for the generation or interpretation of the signal that induces glucose repression.

scholarly journals CBMT-17. DEFECTIVE QKI-DEPENDENT LIPID METABOLISM INDUCES GENOMIC INSTABILITY AND SENSITIZES GLIOBLASTOMA TO IMMUNOTHERAPY

2019 ◽  
Vol 21 (Supplement_6) ◽  
pp. vi36-vi36
Author(s):  
Takashi Shingu ◽  
Jian Hu
Keyword(s):  
Genomic Instability ◽  
Mitochondrial Membrane ◽  
Rna Binding ◽  
Cytoplasmic Membrane ◽  
Unsaturated Fatty Acids ◽  
Rna Stability ◽  
Membrane Integrity ◽  
Immune Checkpoints ◽  
Mitochondrial Defects ◽  
And Function

Abstract Despite transformative effects on the therapy of cancers such as melanoma and lung adenocarcinoma, blockade of the T cell immune checkpoints has generated limited impact on glioblastoma. Identifying genetic/genomic alterations that could potentially sensitize the patients to immunotherapy will significantly improve the efficacy of immunotherapy on glioblastoma patients. As part of our effort to identify novel glioma suppressors that affect the interaction of GSCs with their microenvironment, we discovered that the RNA-binding protein Quaking (QKI) is a key regulator of cellular endocytosis. QKI is mutated or deleted in ~34% of human glioblastomas. Supporting QKI’s tumor suppresser function, 92% of the Nestin-CreERT2;QkiL/L;PtenL/L;p53L/L mice developed glioblastoma with a median survival of 105 days, however, the Nestin-CreERT2;PtenL/L;p53L/L mice did not develop any glioma up to a year. Mechanistically, QKI regulates the RNA stability and alternative splicing of numerous protein and lipid components of endolysosomes, particularly the unsaturated fatty acids (UFAs). Functionally, deletion of Qki and inhibition of UFA biosynthesis both decrease endolysosome-mediated receptor degradation, thereby enriching receptors on the cytoplasmic membrane (e.g., Frizzled and Notch1) that are essential for maintaining stemness. This enrichment of receptor signaling enables GSCs to cope with the low ligand levels during their invasion. On the other hand, lower lysosomal activity induced by Qki deletion and UFA loss led to defective mitophagy. We also found that insufficient UFAs in mitochondrial membrane significantly compromised mitochondrial membrane integrity and function. These two mechanisms concomitantly led to accumulation of damaged mitochondria and higher levels of reactive oxygen species (ROS), and consequently genomic instability. Lastly, we found that the higher level of genomic instability induced by Qki loss rendered cells more sensitive to anti-CTLA4 and anti-PD1 antibodies. Taken together, our data suggest that Qki/UFA loss-induced endolysosomal and mitochondrial defects promote gliomagenesis yet render cells vulnerabilities that could be harnessed for therapeutic purposes.

Quantitative effects of unsaturated fatty acids in microbial mutants. VI. Selective growth responses of yeast and bacteria to cis-octadecenoate isomers

1976 ◽  
Vol 54 (8) ◽  
pp. 736-745 ◽  
Author(s):  
John B. Ohlrogge ◽  
Eugene D. Barber ◽  
William E. M. Lands ◽  
F. D. Gunstone ◽  
I. A. Ismail
Keyword(s):  
Fatty Acids ◽  
Unsaturated Fatty Acids ◽  
Ethylenic Bond ◽  
Yeast Cells ◽  
Nutritional Requirement ◽  
Bacterial Cells ◽  
Growth Responses ◽  
Cellular Lipids ◽  
Acyl Chains ◽  
Extensive Growth

The full series of positional isomers of cis-octadecenoate were tested for their suitability in meeting the nutritional requirement for unsaturated fatty acids by mutants of Escherichia coli and Saccharomyces cerevisiae that were unable to synthesize unsaturated fatty acids.Quantitative comparisons of the efficiencies of the various isomers showed a range from 0–48 cells per femtomole for the prokaryotic cells and 0–5 for eukaryotic cells. The Δ5 isomer was much more effective than the Δ6 isomer with the bacterial cells whereas the reverse was true with the yeast cells. In general, isomers containing a cis ethylenic bond between carbons 7 and 12 were able to support extensive growth of either type of mutant.Since all of the various isomers were incorporated into cellular lipids by both types of microorganism, the different efficiencies observed in supporting growth were not a simple reflection of the inability of an acid to be esterified. The differences may reflect the suitability of the resultant esterified product to function as a normal membrane lipid.The contents of various fatty acids in the cellular phospholipids when growth ceases may have a linearly cumulative relationship to the degree of expansion of the acyl chains.

scholarly journals Molecular analysis of GPH1, the gene encoding glycogen phosphorylase in Saccharomyces cerevisiae.

1989 ◽  
Vol 9 (4) ◽  
pp. 1659-1666 ◽  
Author(s):  
P K Hwang ◽  
S Tugendreich ◽  
R J Fletterick
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Glycogen Phosphorylase ◽  
Glucose Repression ◽  
Essential Gene ◽  
Yeast Cells ◽  
Exponential Growth Phase ◽  
Phosphorylase Activity ◽  
Glycogen Accumulation ◽  
Multiple Copies ◽  
Diploid Cells

In yeast cells, the activity of glycogen phosphorylase is regulated by cyclic AMP-mediated phosphorylation of the enzyme. We have previously cloned the gene for glycogen phosphorylase (GPH1) in Saccharomyces cerevisiae. To assess the role of glycogen and phosphorylase-catalyzed glycogenolysis in the yeast life cycle, yeast strains lacking a functional GPH1 gene or containing multiple copies of the gene were constructed. GPH1 was found not to be an essential gene in yeast cells. Haploid cells disrupted in GPH1 lacked phosphorylase activity and attained higher levels of intracellular glycogen but otherwise were similar to wild-type cells. Diploid cells homozygous for the disruption were able to sporulate and give rise to viable ascospores. Absence of functional GPH1 did not impair cells from synthesizing and storing trehalose. Increases in phosphorylase activity of 10- to 40-fold were detected in cells carrying multiple copies of GPH1-containing 2 microns plasmid. Northern (RNA) analysis indicated that GPH1 transcription was induced at the late exponential growth phase, almost simultaneous with the onset of intracellular glycogen accumulation. Thus, the low level of glycogen in exponential cells was not primarily maintained through regulating the phosphorylation state of a constitutive amount of phosphorylase. GPH1 did not appear to be under formal glucose repression, since transcriptional induction occurred well in advance of glucose depletion from the medium.

scholarly journals Tissue- and paralogue-specific functions of acyl-CoA-binding proteins in lipid metabolism in Caenorhabditis elegans

2011 ◽  
Vol 437 (2) ◽  
pp. 231-241 ◽  
Author(s):  
Ida C. Elle ◽  
Karina T. Simonsen ◽  
Louise C. B. Olsen ◽  
Pernille K. Birck ◽  
Sidse Ehmsen ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Unsaturated Fatty Acids ◽  
Expression Patterns ◽  
High Specificity ◽  
Tissue Expression ◽  
Yeast Cells ◽  
Loss Of Function ◽  
C Elegans ◽  
Eukaryotic Species ◽  
Quadruple Mutant

ACBP (acyl-CoA-binding protein) is a small primarily cytosolic protein that binds acyl-CoA esters with high specificity and affinity. ACBP has been identified in all eukaryotic species, indicating that it performs a basal cellular function. However, differential tissue expression and the existence of several ACBP paralogues in many eukaryotic species indicate that these proteins serve distinct functions. The nematode Caenorhabditis elegans expresses seven ACBPs: four basal forms and three ACBP domain proteins. We find that each of these paralogues is capable of complementing the growth of ACBP-deficient yeast cells, and that they exhibit distinct temporal and tissue expression patterns in C. elegans. We have obtained loss-of-function mutants for six of these forms. All single mutants display relatively subtle phenotypes; however, we find that functional loss of ACBP-1 leads to reduced triacylglycerol (triglyceride) levels and aberrant lipid droplet morphology and number in the intestine. We also show that worms lacking ACBP-2 show a severe decrease in the β-oxidation of unsaturated fatty acids. A quadruple mutant, lacking all basal ACBPs, is slightly developmentally delayed, displays abnormal intestinal lipid storage, and increased β-oxidation. Collectively, the present results suggest that each of the ACBP paralogues serves a distinct function in C. elegans.

scholarly journals Multicopy suppressors of phenotypes resulting from the absence of yeast VDAC encode a VDAC-like protein.

1997 ◽  
Vol 17 (10) ◽  
pp. 5727-5738 ◽  
Author(s):  
E Blachly-Dyson ◽  
J Song ◽  
W J Wolfgang ◽  
M Colombini ◽  
M Forte
Keyword(s):  
Outer Membrane ◽  
Mitochondrial Membrane ◽  
Genomic Library ◽  
Carbon Sources ◽  
Yeast Cells ◽  
Growth Defect ◽  
Outer Mitochondrial Membrane ◽  
Voltage Dependent Anion Channel ◽  
Yeast Saccharomyces Cerevisiae ◽  
Yeast Vdac

The permeability of the outer mitochondrial membrane to most metabolites is believed to be based in an outer membrane, channel-forming protein known as VDAC (voltage-dependent anion channel). Although multiple isoforms of VDAC have been identified in multicellular organisms, the yeast Saccharomyces cerevisiae has been thought to contain a single VDAC gene, designated POR1. However, cells missing the POR1 gene (delta por1) were able to grow on yeast media containing a nonfermentable carbon source (glycerol) but not on such media at elevated temperature (37 degrees C). If VDAC normally provides the pathway for metabolites to pass through the outer membrane, some other protein(s) must be able to partially substitute for that function. To identify proteins that could functionally substitute for POR1, we have screened a yeast genomic library for genes which, when overexpressed, can correct the growth defect of delta por1 yeast grown on glycerol at 37 degrees C. This screen identified a second yeast VDAC gene, POR2, encoding a protein (YVDAC2) with 49% amino acid sequence identity to the previously identified yeast VDAC protein (YVDAC1). YVDAC2 can functionally complement defects present in delta por1 strains only when it is overexpressed. Deletion of the POR2 gene alone had no detectable phenotype, while yeasts with deletions of both the POR1 and POR2 genes were viable and able to grow on glycerol at 30 degrees C, albeit more slowly than delta por1 single mutants. Like delta por1 single mutants, they could not grow on glycerol at 37 degrees C. Subcellular fractionation studies with antibodies which distinguish YVDAC1 and YVDAC2 indicate that YVDAC2 is normally present in the outer mitochondrial membrane. However, no YVDAC2 channels were detected electrophysiologically in reconstituted systems. Therefore, mitochondrial membranes made from wild-type cells, delta por1 cells, delta por1 delta por2 cells, and delta por1 cells overexpressing YVDAC2 were incorporated into liposomes and the permeability of resulting liposomes to nonelectrolytes of different sizes was determined. The results indicate that YVDAC2 does not confer any additional permeability to these liposomes, suggesting that it may not normally form a channel. In contrast, when the VDAC gene from Drosophila melanogaster was expressed in delta por1 yeast cells, VDAC-like channels could be detected in the mitochondria by both bilayer and liposome techniques, yet the cells failed to grow on glycerol at 37 degrees C. Thus, channel-forming activity does not seem to be either necessary or sufficient to restore growth on nonfermentable carbon sources, indicating that VDAC mediates cellular functions that do not depend on the ability to form channels.

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