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At least 1,243 records · Page 69Linked to original sources
PubMed2000

Biogenesis of endoplasmic reticulum proteins involved in Ca2+ signalling during megakaryocytic differentiation: an in vitro study.

The endoplasmic reticulum (ER) plays a key role in Ca(2+) signalling through Ca(2+) release via inositol 1,4,5-trisphosphate receptors (InsP(3)-Rs) and Ca(2+) uptake by sarco/endoplasmic reticulum Ca(2+)-ATPases (SERCAs). Here, we investigated the organization of platelet ER and its biogenesis during megakaryocytopoiesis. First, erythro/megakaryoblastic MEG 01, UT7, M-O7e and CHRF 288-11 cell lines, platelets and thrombopoietin-induced UT7-Mpl cells were selected for the study of SERCA2b and SERCA3 proteins by Western blotting using the antibodies IID8 and PL/IM430, respectively. As judged by platelet glycoprotein IIIa (GPIIIa) expression, an increase in SERCA3 proteins was observed while that of SERCA2b remained unchanged throughout maturation. Second, these studies were extended to the newly described alternatively spliced SERCA3a-c RNAs and InsP(3)-Rs using the in vitro model of PMA-induced differentiation of MEG 01 cells. Time-course and dose-response studies showed a maximal approx. 4-fold up-regulation of SERCA3 proteins using 10(-8) M PMA for 3 days, which paralleled induction of GPIIIa expression. SERCA3 induction was found to occur at the level of mRNA. The modulation of the different SERCA3 species (i.e. 3a, 3b and 3c) was isoform-specific: while SERCA3a was slightly increased, an approx. 3-fold induction of SERCA3b, and a 4-fold induction of SERCA3c, was observed after 24 h of PMA treatment. Isoform-specific Western blotting and/or reverse transcriptase PCR studies showed that InsP(3)-R types I, II and III are expressed in MEG 01 cells, as well as in platelets. Study of the expression of these InsP(3)-R types in PMA-induced MEG 01 cells revealed that: (i) InsP(3)-RI protein and mRNA showed no changes; (ii) InsP(3)-RII mRNA was up-regulated and peaked at hour 48 and (iii) InsP(3)-RIII mRNA and protein showed a transitory maximal 3- and 2.3-fold increase at hours 6 and 30, respectively. Upon PMA treatment of CHRF 288-11 cells, in which GPIIIa is not induced upon treatment, a similar pattern of regulation of InsP(3)-R types II and III was seen, but a distinct pattern of SERCA3 regulation was observed. These results suggest a profound reorganization of ER-protein patterns during megakaryocytopoiesis and underline the role of SERCA3 gene regulation in the control of Ca(2+)-dependent platelet functions.

Calcium Signaling↗
PubMed1978

Cell wall biogenesis in Oocystis: experimental alteration of microfibril assembly and orientation.

Cell wall biogenesis in the unicellular green alga Oocystis apiculata has been studied. Under normal growth conditions, a cell wall with ordered microfibrils is synthesized. In each layer there are rows of parallel microfibrils. Layers are nearly perpendicular to each other. Terminal linear synthesizing complexes are located in the plasma membrane, and they are capable of bidirectional synthesis of cellulose microfibrils. Granule bands associated with the inner leaflet of the plasma membrane appear to control the orientation of newly synthesized microfibrils. Subcortical microtubules also are present during wall synthesis. Patterns of cell wall synthesis were studied after treatment with EDTA and EGTA as well as divalent cations (MgSO4, CaSO4, Cacl2). 0.1 M EDTA treatment for 15 min results in the disassociation of the terminal complexes from the ends of microfibrils. EDTA-treated cells followed by 15 min treatment with MgSO4 results in reaggregation of the linear complexes into a paired state, remote from the original ends to which they were associated. After 90 min treatment with MgSO4, normal synthesis resumes. EGTA and calcium salts do not affect the linear complexes or microfibril orientation. Treatments with colchicine and vinblastine sulphate do not depolymerize the microtubles, but the wall microfibril orientation is altered. With colchicine or vinblastine, the change in orientation from layer to layer is inhibited. The process is reversible upon removal of the drugs. Lumicolchicine has no effect upon microfibril orientation, but granule bands are disorganized. Treatment with coumarin, a known inhibitor of cellulose synthesis, causes the loss of visualization of subunits of the terminal complexes. The possibility of the existence of a membrane-associated colchicine-sensitive orientation protein for cellulose microfibrils is discussed. Transmembrane modulation of microfibril synthesis and orientation is presented.

Calcium↗
PubMed2001

lyc1, a transgenic mutant of Lactuca sativa (lettuce) tightly linked to chloroplast biogenesis.

A T-DNA tagging mutant of lettuce was studied. The transgenic lettuce mutant, designated light yellowish cotyledon1 (lyc1), exhibited a chloroplast mutant phenotype in which the chloroplast development was arrested at the cotyledon stage and the cotyledon became a light yellowish due to the reduced level of chlorophyll content. A microscopic observation of the mutant showed that the chloroplasts failed to position along the cell wall, but were scattered in the cytoplasm. The number of chloroplasts in the mutant was reduced to 66% compared to that in the wild-type plant. These results suggest that the lyc1 mutation is due to a defect in the biogenesis of chloroplasts. Also, the homozygous lyc1 mutant became lethal in a T2 and F1 progeny analysis, indicating that the mutation is recessive.

Chlorophyll↗
PubMed1977

Localization of the interference of ascorbic acid deficiency with bile acid biogenesis.

The catabolism of 26-14C-cholesterol and of 26-14C-7alpha-hydroxycholesterol, the first stage in the transformation of cholesterol to bile acids, was studied in guinea-pigs with chronic latent vitamin C deficiency. Vitamin C deficiency markedly inhibited the oxidation of 26-14C-cholesterol to 14CO2, but did not significantly affect the catabolism of 26-14C-7alpha-hydroxycholesterol. The distribution of 14C in the tissues and body fluids of control and vitamin-deficient guinea pigs injected with labelled 7alpha-hydroxycholesterol was likewise the same. Ascorbic acids is probably needed only for 7alpha-hydroxylation of cholesterol, while the other stages of bile acid biogenesis are independent of vitamin C.

Animals↗
PubMed2004

[Isolation and primary identification of methylotrophic yeast Hansenula polymorpha mutants for peroxisome biogenesis].

After exposure of cells of the methylotrophic yeast Hansenula polymorpha HF246 leu1-1 to N-nitro-N-nitrosoguanidine, a collection of 227 mutants unable to grow on methanol at elevated temperature (45 degrees C) was obtained. Ninety four ts mutants (35% of the total number of mutants), which were unable to grow on methanol only at 45 degrees C but could grow at optimal temperature (37 degrees C), were isolated. Complementation analysis of mutants using 12 deletion mutants for genes of peroxisome biogenesis (PEX) (available in this yeast species by the beginning of our work) allowed to assign 51 mutants (including 16 ts) to the separate group of mutants unable to complement deletion mutants with defects in eight PEX genes. These mutants were classified into three groups: group 1 contained 10 pex10 mutants (4 ts mutants among them); group 2 included 19 mutants that failed to complement other pex testers: 1 pex1; 2 pex4 (1 ts); 6 pex5 (5 ts); 3 pex8; 6 (3ts)- pex19; group 3 contained 22 "multiple" mutants. In mutants of group 3, hybrids with several testers do not grow on methanol. All mutants (51) carried recessive mutations, except for mutant 108, in which the mutation was dominant only at 30 degrees C, which suggests that it is ts-dominant. Recombination analysis of mutants belonging to group 2 revealed that only five mutants (two pex5 and three pex8) carried mutations for the corresponding PEX genes. The remaining 14 mutants yielded methanol-utilizing segregants in an arbitrarily chosen sample of hybrids with the pex tester, which indicates mutation location in other genes. In 19 mutants, random analysis of ascospores from hybrids obtained upon crossing mutants of group 3 with a strain lacking peroxisomal disorders (ade11) revealed a single mutation causing the appearance of a multiple phenotype. A more detailed study of two mutants from this group allowed the localization of this mutation in the only PEX gene (PEX or PEX2). The revealed disorder of complementation interactions between nonallelic genes is under debate.

Adenosine Triphosphatases↗
PubMed2006

[Mutagenesis, screening and characterization of mutants known as peroxisome biogenesis disorders in yeast].

Peroxisomes are essential for organisms' development and physiology. This fact is underscored by the lethality of a group of genetic disorders collectively known as the peroxisome biogenesis disorders (PBDs), such as Zellweger syndrome, in which peroxisomes fail to assemble properly. Defining the molecular bases of the PBDs has been the impetus behind the identification of the genes controlling peroxisome assembly, the PEX genes, from various modern organisms. Here as a original strain, Yarrowia lipolytica E122 was mutated by diethyl sulfate (DES) treatment and two mutants including temperature sensitive one were obtained. Compared to the initial strain, the two mutants showed more diffuse pattern of fluorescence characteristic of a cytosolic localization in immunofluorescence analysis, and showed no morphologically recognizable peroxisomes in electron micrographs. The two mutants arose from new gene mutation characterized by transformation and will be very useful in identification of new gene controlling peroxisome assembly from yeast.

Cytosol↗
PubMed1991

Effect of different hypolipemic agents on rat liver peroxisomal and mitochondrial functions and biogenesis.

The effect of four fibrate analogues (i.e. clofibrate, ciprofibrate, clobuzarit and 2,4-dichlorophenoxyacetic acid (2,4-D), an active herbicide molecule) were tested on the biogenesis of liver mitochondrial and peroxisomal proteins by rat in vivo treatment at 100 ppm for 26 weeks. The evaluations were done at different levels: somatic index, histochemistry electron microscopy, enzymatic activities on purified peroxisomes and mitochondria, polypeptides electrophoresis and immunolabeling, and finally mRNA hybridization with specific DNA probes. This work shows that the tested hypolipemic agents are strong peroxisomal proliferators especially ciprofibrate, while mitochondria are weakly affected. However, the four fibrates gave different effects, especially 2,4-D which modifies mitochondrial polypeptide pattern. Post-transcriptional study of mRNAs level shows a slight increase in catalase mRNA despite the potential of hypolipemic agents. The peroxisomal acyl-CoA oxidase mRNA content is enhanced with ciprofibrate treatment as well as mitochondrial R-3-hydroxybutyrate dehydrogenase (BDH) mRNA level. Finally, the dual action of ciprofibrate on content and on enzymatic activity of BDH (a lipid metabolism related enzyme) reveals that such a molecule may have differential regulatory effects (positive on gene transcription or mRNA stability and negative on catalytic enzyme activity).

Animals↗
PubMed1991

Discovery and sequence analysis of bacterial genes involved in the biogenesis of c-type cytochromes.

We report the DNA sequence and mutational analysis of a novel cluster of six Bradyrhizobium japonicum genes of which at least three (designated cycV, cycW, and cycX) are essential for the formation of all cellular c-type cytochromes. Mutants having insertions in these genes were completely devoid of any soluble (periplasmic) or membrane-bound c-type cytochromes; even the apo form of cytochrome c1 was not detectable, neither in the membrane nor in the soluble fraction. As a consequence, the mutants had pleiotropic phenotypes such as defects in nitrate respiration, H2 oxidation, electron transport to cytochrome alpha alpha 3, and microaerobic respiration during symbiosis. A fourth open reading frame (ORF132) encoded a protein that might also be concerned with cytochrome c formation, but perhaps only indirectly. The other two open reading frames did not appear to function in this process. The predicted amino acid sequences of the cycW and cycX gene products suggested that these proteins were membrane-bound. The cycV gene product showed extensive similarity to the ATP-binding subunit of a superfamily of membrane-associated transport systems. The predicted ORF132 product was strikingly similar to bacterial thioredoxins and eukaryotic protein disulfide isomerase. Based on these findings it is possible that these proteins are members of a complex transport system involved in the biogenesis of all cytochromes c.

Adenosine Triphosphate↗
PubMedDate not supplied

Regulation of ribosome biogenesis in differentiated rat myotubes.

The rate of ribosome biogenesis is closely coupled with cell proliferation, representing a unique model system for studying gene regulation. Terminal differentiation of rat L6 myoblasts, an example of a rapidly proliferating population of cells being converted into a non-dividing syncytial population, results in an 80% decline in the rate of ribosome accumulation. Ribosome production during myogenesis is regulated by a down-shift in the rate of rRNA accumulation, controlled at the level of transcription by specific trans-acting factors. The synthesis of both ribosomal proteins and 5S rRNA remains unchanged in myotubes, however, resulting in an over-production of these precursors. The excess molecules are rapidly degraded, preventing the accumulation of a static pool of ribosome components.

Animals↗
PubMed1991

[Membrane biogenesis].

The literary data on the problem of the membrane biogenesis are generalized. The mechanisms of formation, possible ways of metabolism of biomembrane structure in cells and the ways of their degradation are considered. A conclusion has been made on the existence in the cells several types of movement as for the separate components and membrane fragments as well.

Animals↗
PubMed1990

Cell-type control of membrane biogenesis induced by HMG-CoA reductase.

Quantitative increases in HMG-CoA reductase, the rate-limiting enzyme in sterol biosynthesis, induce membrane biogenesis in both yeast and mammalian cells. The subcellular organization of the resulting membrane differs in the two cell types: mammalian cells generate crystalloid endoplasmic reticulum whereas yeast cells assemble karmellae. We examined the consequences of heterologous expression of HMG-CoA reductase to distinguish features of this response that were cell-type specific from those that were isozyme-specific. This analysis demonstrated that membrane proliferation was induced in both mammalian and yeast cells by HMG-CoA reductase from either organism. However, the morphology of the induced membranes was determined by the cell type rather than the particular isozyme. Thus, both yeast and mammalian HMG-CoA reductase contained functional signals for membrane proliferation that were operational in either cell type, but the qualitative response to those signals was cell-type specific.

Animals↗
PubMed1990

Biogenesis of peroxisomes: sequential biosynthesis of the membrane and matrix proteins in the course of hepatic regeneration.

The biogenesis of peroxisomes was investigated in the model of regenerating rat liver after partial hepatectomy (PH), using analytical differential centrifugation in combination with immunoblotting and in vivo pulse labeling as well as immunoelectron microscopy. The total activity of catalase decreased sharply after PH, returning gradually over several days to normal levels. In the 16 to 32-h period the enzyme activity started to increase first in the heavy mitochondrial fraction, shifting at 28 h to the crude peroxisomal and at 32 h to the microsomal fraction, suggesting de novo formation of peroxisomes by budding or fragmentation from larger aggregates. Whereas most peroxisomal matrix proteins were reduced during the 16 to 32-h period after PH, the 26 and 70 kDa peroxisomal membrane proteins were increased. Moreover, in vivo pulse labeling studies with radioactive leucine showed significantly higher levels of specific activity in the peroxisomal membrane than in the matrix subfractions at 16 h with increasing labeling of the matrix at 32 h after PH. These findings suggest that de novo formation of peroxisomes in regenerating rat liver is initiated by the synthesis of membrane proteins and is followed by that of the matrix components.

Animals↗
PubMed1990

Glycogen biogenesis in the adipocyte and mammary adenocarcinoma and the influence of insulin.

3T3 LI P-3 adipocytes and a rat mammary carcinoma each contain a protein (or proteins) of Mr 400 kDa approx. that undergoes glucosylation when incubated with UDPglucose and Mn2+. In each case, the product of glucosylation is a protein-bound maltosaccharide containing up to 14 glucose residues, and therefore capable of priming glycogen synthesis. The proteins bear a formal similarity to the self-glucosylating protein of Mr 37 kDa that primes muscle glycogen synthesis, but do not cross-react with an antibody that cross-reacts with the muscle protein. The extent of protein glucosylation in the adipocyte is rapidly and markedly stimulated when the cells are bathed in insulin, suggesting that this initial step in glycogen biogenesis, protein glucosylation, is under the influence of the hormone.

Adenocarcinoma↗
PubMed1990

Matrix vesicle biogenesis in vitro by rachitic and normal rat chondrocytes.

Calcifying matrix vesicles (MVs) are released from chondrocytes and osteoblasts in monolayer culture. In the present studies, we tested the ability of rachitic versus normal rat growth plate chondrocytes in micromass or monolayer primary cultures to produce MVs. Unlike earlier reports of in vitro MV biogenesis by chicken chondrocytes in which most MVs were released into the medium, we found that most of the released rat matrix vesicles were entrapped in a newly formed cartilaginous matrix enveloping the cells. These matrix-associated MVs could be isolated by mild collagenase treatment and concentrated by differential centrifugation. Vesicle production slowed in the older 2- to 4-week-old cultures and, unlike vesicle release from cultured chicken chondrocytes, active vesicle production did not show a second burst of activity at 3 to 4 weeks. Alkaline phosphatase (ALP) activity diminished with time in culture in cells and matrix vesicles, suggesting a decrease in differentiative expression. Protein profiles on SDS polyacrylamide gels of native matrix vesicles and culture-derived MVs from rachitic and normal cells were quite similar and showed a typical simplified protein pattern as compared to chondrocyte plasma membrane proteins. There were distinctive proteins migrating at 130, 80 to 95, 66, 43, 20, and 14 kd. Culture-derived MVs showed vigorous in vitro calcifying activity that was ALP related. We conclude that 1) rachitic chondrocytes are essentially normal in their matrix vesicle production; 2) matrix entrapment of MVs is a characteristic of rat chondrocyte cultures; and 3) culture-produced MVs are similar to native MVs in protein profile and calcifiability, and thus can be studied as a model for normal MV composition and calcification.

Animals↗
PubMed1989

Biogenesis of cytochrome c1. Role of cytochrome c1 heme lyase and of the two proteolytic processing steps during import into mitochondria.

The biogenesis of cytochrome c1 involves a number of steps including: synthesis as a precursor with a bipartite signal sequence, transfer across the outer and inner mitochondrial membranes, removal of the first part of the presequence in the matrix, reexport to the outer surface of the inner membrane, covalent addition of heme, and removal of the remainder of the presequence. In this report we have focused on the steps of heme addition, catalyzed by cytochrome c1 heme lyase, and of proteolytic processing during cytochrome c1 import into mitochondria. Following translocation from the matrix side to the intermembrane-space side of the inner membrane, apocytochrome c1 forms a complex with cytochrome c1 heme lyase, and then holocytochrome c1 formation occurs. Holocytochrome c1 formation can also be observed in detergent-solubilized preparations of mitochondria, but only after apocytochrome c1 has first interacted with cytochrome c1 heme lyase to produce this complex. Heme linkage takes place on the intermembrane-space side of the inner mitochondrial membrane and is dependent on NADH plus a cytosolic cofactor that can be replaced by flavin nucleotides. NADH and FMN appear to be necessary for reduction of heme prior to its linkage to apocytochrome c1. The second proteolytic processing of cytochrome c1 does not take place unless the covalent linkage of heme to apocytochrome c1 precedes it. On the other hand, the cytochrome c1 heme lyase reaction itself does not require that processing of the cytochrome c1 precursor to intermediate size cytochrome c1 takes place first. In conclusion, cytochrome c1 heme lyase catalyzes an essential step in the import pathway of cytochrome c1, but it is not involved in the transmembrane movement of the precursor polypeptide. This is in contrast to the case for cytochrome c in which heme addition is coupled to its transport directly across the outer membrane into the intermembrane space.

Chromatography, High Pressure Liquid↗
PubMed1989

Light-harvesting pigment-proteins of photosystem I in maize. Subunit composition and biogenesis.

Three different pigment-binding proteins of the light-harvesting complex (LHC I) of maize photosystem I (PS I) have been isolated. Absorption and fluorescence excitation spectral analyses showed that each pigment-protein can transfer absorbed energy from its carotenoid and/or chlorophyll b components to chlorophyll alpha. Their apoproteins with apparent sizes of 24 (LHC Ia), 21 (LHC Ib), and 17 (LHC Ic) kDa have been purified to homogeneity. Differences in their pigment and amino acid compositions and in their reactions with antibodies demonstrate that the two smaller pigment-proteins are not proteolytically derived from the largest one. LHC Ib's apoprotein is particularly enriched in cysteine residues. None of the three apoproteins cross-reacted with antibodies raised against the major light-harvesting chlorophyll a/b-protein of photosystem II (LHC IIb) or against the PS I core complex (CC I) subunits. Studies of the biogenesis of PS I during greening of etiolated plants showed that all of the CC I subunits accumulated to a detectable level prior to the appearance of the 17-kDa subunit of LHC I, the accumulation of which preceded those of the 24- and 21-kDa subunits of LHC I. In addition, subunit VI of CC I is shown to be differentially expressed in mesophyll and bundle sheath cells; a slightly larger form of it accumulates in mesophyll than in bundle sheath thylakoids during plastid development.

Apoproteins↗
PubMed1987

Effects of castanospermine and 1-deoxynojirimycin on insulin receptor biogenesis. Evidence for a role of glucose removal from core oligosaccharides.

The insulin proreceptor is a 190-kDa glycoprotein that is processed to mature alpha (135-kDa) and beta (95-kDa) subunits. In order to determine the role of carbohydrate chain processing in insulin receptor biogenesis, we investigated the effect of inhibiting glucose removal from core oligosaccharides of the insulin proreceptor with glucosidase inhibitors, castanospermine and 1-deoxynojirimycin. Cultured IM-9 lymphocytes treated with inhibitors had 50% reduction in surface insulin receptors as demonstrated by ligand binding, affinity cross-linking with 125I-insulin, and lactoperoxidase/Na 125I labeling studies. Degradation rates of surface labeled receptors were similar in both control and inhibitor-treated cells (t1/2 = 5 h); thus, accelerated receptor degradation could not account for this reduction. Biosynthetic labeling experiments with [3H]leucine and [3H]mannose identified an apparently higher molecular size proreceptor (approximately 205 kDa) that failed to show the characteristic decline with time as seen in the normal 190-kDa proreceptor. Along with this finding, the biosynthetic label appearing in the mature subunits was reduced in these inhibitor-treated cells. Endoglycosidase H treatment of both precursors produced identical 170-kDa bands. Carbohydrate chains released from the 205-kDa precursor by endoglycosidase H migrated in the same position as the Glc2-3Man9GlcNAc standards when separated by high performance liquid chromatography, whereas the 190-kDa proreceptor oligosaccharides migrated similar to the Man7-9GlcNAc chains. Although the mature subunits of control and inhibitor-treated cells demonstrated equal electrophoretic mobility, the endoglycosidase H-sensitive oligosaccharides of the mature subunits in treated cells also contained residues that migrated similar to the Glc2-3Man9GlcNAc standards. Thus, glucose removal from core oligosaccharides is apparently not necessary for the cleavage of the insulin proreceptor, but does delay processing of this precursor, which probably accounts for the reduction in cell-surface receptors.

1-Deoxynojirimycin↗
PubMed1986

The nuclear-coded subunits of yeast cytochrome c oxidase. The amino acid sequences of subunits VII and VIIa, structural similarities between the three smallest polypeptides of the holoenzyme, and implications for biogenesis.

The complete amino acid sequences of subunits VII and VIIa from yeast cytochrome c oxidase are reported. Subunits VII and VIIa are 57 residues (Mr = 6603) and 54 residues (Mr = 6303) in length, respectively. Both polypeptides are amphiphilic, have an internal hydrophobic section and hydrophilic NH2 and COOH termini, and terminate at their COOH termini with a basic amino acid. This structural motif is similar to that possessed by subunit VIII of yeast cytochrome c oxidase. All three polypeptides have hydrophobic sections which are long enough to span the inner membrane; all three polypeptides lack methionine at their NH2 termini; and all three polypeptides have COOH termini which could result from proteolysis by a protease with trypsin or cathepsin B-like activity. These observations raise the interesting possibility that subunits VII, VIIa, and VIII are transmembranous polypeptides which are processed at both their NH2 and COOH termini during their biogenesis.

Amino Acid Sequence↗