scholarly journals Induction of calreticulin expression in response to amino acid deprivation in Chinese hamster ovary cells

1998 ◽  
Vol 329 (2) ◽  
pp. 389-394 ◽  
Author(s):  
Richard HEAL ◽  
John McGIVAN
Keyword(s):  
Amino Acid ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Fold Increase ◽  
Asparagine Synthetase ◽  
Mrna Levels ◽  
Amino Acid Deprivation ◽  
Ovary Cells ◽  
Protein Levels

The role of calreticulin as a stress-induced molecular chaperone protein of the endoplasmic reticulum is becoming more apparent. We characterize here the induction of calreticulin in response to complete amino acid deprivation in Chinese hamster ovary cells. Amino acid deprivation caused a 4-fold increase in calreticulin protein levels over a period of 4-10 h. In addition to an overall increase in protein levels, the glycosylation of calreticulin was increased. This glycosylation event was blocked by tunicamycin and was not required for the increase in calreticulin protein levels. Immunofluorescence studies localized calreticulin to the ER of CHO cells, and no significant change was observed after amino acid deprivation. Northern-blot analysis showed that calreticulin mRNA levels were increased approx. 10-fold in response to complete amino acid deprivation. The response was sensitive to actinomycin D and α-amanitin, implying that regulation is primarily at the level of transcription. These results are similar to the large increases in asparagine synthetase mRNA observed in response to amino acid deprivation, but the amino acid-deprivation-response element identified to be involved in asparagine synthetase induction is absent from the calreticulin promoter.

Spontaneous splicing mutations at the dihydrofolate reductase locus in Chinese hamster ovary cells

1986 ◽  
Vol 6 (6) ◽  
pp. 1926-1935
Author(s):  
P J Mitchell ◽  
G Urlaub ◽  
L Chasin
Keyword(s):  
Amino Acid ◽  
Dihydrofolate Reductase ◽  
Splice Site ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Splice Sites ◽  
Ovary Cells ◽  
Splicing Mutations ◽  
Intron 4

We isolated and characterized three spontaneous mutants of Chinese hamster ovary cells that were deficient in dihydrofolate reductase activity. All three mutants contained no detectable enzyme activity and produced dihydrofolate reductase mRNA species that were shorter than those of the wild type by about 120 bases. Six exons are normally represented in this mRNA; exon 5 was missing in all three mutant mRNAs. Nuclease S1 analysis of the three mutants indicated that during the processing of the mutant RNA, exon 4 was spliced to exon 6. The three mutant genes were cloned, and the regions around exons 4 and 5 were sequenced. In one mutant, the GT dinucleotide at the 5' end of intron 5 had changed to CT. In a second mutant, the first base in exon 5 had changed from G to T. In a revertant of this mutant, this base was further mutated to A, a return to a purine. Approximately 25% of the mRNA molecules in the revertant were spliced correctly to produce an enzyme with one presumed amino acid change. In the third mutant, the AG at the 3' end of intron 4 had changed to AA. A mutation that partially reversed the mutant phenotype had changed the dinucleotide at the 5' end of intron 4 from GT to AT. The splicing pattern in this revertant was consistent with the use of cryptic donor and acceptor splice sites close to the original sites to produce an mRNA with three base changes and a protein with two amino acid changes. These mutations argue against a scanning model for the selection of splice site pairs and suggest that only a single splice site need be inactivated to bring about efficient exon skipping (a regulatory mechanism for some genes). The fact that all three mutants analyzed exhibited exon 5 splicing mutations indicates that these splice sites are hot spots for spontaneous mutation.

scholarly journals Prolonged activation of phospholipase D in Chinese hamster ovary cells expressing platelet-activating-factor receptor lacking cytoplasmic C-terminal tail

1997 ◽  
Vol 327 (1) ◽  
pp. 239-244 ◽  
Author(s):  
Bo LIU ◽  
Shigeru NAKASHIMA ◽  
Takahito ADACHI ◽  
Yuzuru ITO ◽  
Tomoko TAKANO ◽  
...  
Keyword(s):  
Phospholipase D ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Platelet Activating Factor ◽  
Chinese Hamster ◽  
Mrna Levels ◽  
Primary Role ◽  
Ovary Cells ◽  
Protein Kinase Cα ◽  
Paf Receptor

The mechanism and role of phospholipase D (PLD) activation by platelet-activating factor (PAF) were examined with Chinese hamster ovary cells stably expressing wild-type PAF receptor (WT-H cells) and truncated PAF receptor lacking the C-terminal cytoplasmic tail (D-H cells). Treatment of D-H cells with PAF resulted in the rapid formation of Ins(1,4,5)P3, which was followed by a sustained phase for more than 10 min. In these cells, PAF-induced PLD activation lasted for more than 20 min. In contrast, PLD activation in WT-H cells was transient. PAF stimulation caused the biphasic formation of 1,2-diacylglycerol (DG) in both types of cell. The first phase was rapid and transient, coinciding with the Ins(1,4,5)P3 peak. The second sustained phase of DG formation was attenuated by butanol, which produces phosphatidylbutanol at the expense of phosphatidic acid (PA) by transphosphatidylation activity of PLD, and by propranolol, a selective inhibitor for PA phosphohydrolase catalysing the conversion of PA into DG. The DG level returned nearly to basal at 20 min after PAF stimulation in WT-H cells, whereas in D-H cells the elevated DG level was sustained for more than 20 min. The profile of translocation of protein kinase Cα (PKCα) to membrane was similar to that of DG formation. In WT-H cells, PKCα was transiently associated with membranes and then returned to the cytosol. However, in D-H cells PKCα was rapidly translocated to and remained in membranes for more than 20 min. Butanol suppressed this sustained translocation of PKCα. Furthermore the mRNA levels of c-fos and c-jun by PAF in WT-H cells were much lower than those in D-H cells. Propranolol and butanol at concentrations that inhibited the formation of DG suppressed the PAF-induced mRNA expression of c-fos and c-jun. Taken together, the prolonged PLD activation in D-H cells confirmed a primary role for phospholipase C/PKC in PLD activation by PAF. Furthermore the results obtained here suggest that sustained PLD activation in turn leads to chronic activation and membrane translocation of PKCα, which might play an important role in the expression of c-fos and c-jun.

Purification of phosphatidylglycerophosphate synthase from Chinese hamster ovary cells

2001 ◽  
Vol 354 (1) ◽  
pp. 9-15 ◽  
Author(s):  
Kiyoshi KAWASAKI ◽  
Osamu KUGE ◽  
Yoshio YAMAKAWA ◽  
Masahiro NISHIJIMA
Keyword(s):  
Chinese Hamster Ovary ◽  
Mammalian Cells ◽  
Polyclonal Antibodies ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Mitochondrial Fraction ◽  
Ovary Cells ◽  
Protein Levels ◽  
Defective Mutant ◽  
Sds Page

Phosphatidylglycerophosphate (PGP) synthase catalyses the committed step in the biosynthesis of phosphatidylglycerol and cardiolipin in mammalian cells. Recently we isolated a Chinese hamster ovary (CHO) PGS1 cDNA encoding PGP synthase. In the present study we purified this PGP synthase to near-homogeneity from the mitochondrial fraction of CHO-K1 cells; the final enzyme preparation gave a single 60kDa protein on SDS/PAGE. Polyclonal antibodies raised against a recombinant CHO PGS1 protein cross-reacted with the purified 60kDa protein and with CHO membrane proteins of 60kDa and 62kDa that increased after transfection with the PGS1 cDNA. The 60 and 62kDa protein levels in a PGP synthase-defective mutant of CHO-K1 cells were markedly lower than those in CHO-K1 cells. These results indicated that the purified 60kDa protein was PGP synthase encoded by the PGS1 gene. In addition we found that the purified PGP synthase had no PGP phosphatase activity, indicating that phosphatidylglycerol was produced from CDP-diacylglycerol through two steps catalysed by distinct enzymes, PGP synthase and PGP phosphatase.

N-terminal residues in murine P-selectin glycoprotein ligand-1 required for binding to murine P-selectin

Blood ◽  
2003 ◽  
Vol 101 (2) ◽  
pp. 552-559 ◽  
Author(s):  
Lijun Xia ◽  
Vishwanath Ramachandran ◽  
J. Michael McDaniel ◽  
Kiem N. Nguyen ◽  
Richard D. Cummings ◽  
...  
Keyword(s):  
Amino Acid ◽  
Amino Acid Sequence ◽  
Chinese Hamster Ovary ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Fluid Phase ◽  
Terminal Region ◽  
Wild Type ◽  
Ovary Cells ◽  
N Terminus

P-selectin binds to the N-terminal region of human P-selectin glycoprotein ligand-1 (PSGL-1). For optimal binding, this region requires sulfation on 3 tyrosines and specific core-2O-glycosylation on a threonine. P-selectin is also thought to bind to the N terminus of murine PSGL-1, although it has a very different amino acid sequence than human PSGL-1. Murine PSGL-1 has potential sites for sulfation at Tyr13 and Tyr15 and for O-glycosylation at Thr14 and Thr17. We expressed murine PSGL-1 or constructs with substitutions of these residues in transfected Chinese hamster ovary cells that coexpressed the glycosyltransferases required for binding to P-selectin. The cells were assayed for binding to fluid-phase P-selectin and for tethering and rolling on P-selectin under flow. In both assays, substitution of Tyr13 or Thr17 markedly diminished, but did not eliminate, binding to P-selectin. In contrast, substitution of Tyr15 or Thr14 did not affect binding. Substitution of all 4 residues eliminated binding. Treatment of cells with chlorate, an inhibitor of sulfation, markedly reduced binding of wild-type PSGL-1 to P-selectin but did not further decrease binding of PSGL-1 with substitutions of both tyrosines. These data suggest that sulfation of Tyr13 andO-glycosylation of Thr17 are necessary for murine PSGL-1 to bind optimally to P-selectin. Because it uses only one tyrosine, murine PSGL-1 may rely more on other peptide components andO-glycosylation to bind to P-selectin than does human PSGL-1.

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