Disease relevance of PCT1

• E. coli MM294/pUCK3 and MM294/pCC41 cells, which express a choline kinase from Saccharomyces cerevisiae (CKIase; encoded by the CKI gene) and a cholinephosphate cytidylyltransferase from S. cerevisiae (CCTase; encoded by the CCT gene) respectively, were added to this CTP-producing reaction system [1].
• Expression of yeast CCT in a baculovirus system as a 6x-His-tag fusion protein was higher and was used to purify yeast CCT by a procedure that included delipidation [2].
• Based on the specificity of the Htt-CCT1 interaction, the CCT1 substrate-binding domain may provide a versatile scaffold for therapeutic inhibitors of neurodegenerative disease [3].
• Conversely, overexpression of a single TRiC subunit, CCT1, is sufficient to remodel Htt-aggregate morphology in vivo and in vitro, and reduces Htt-induced toxicity in neuronal cells [3].
• Furthermore, it shows less, but significant, similarity to yeast ET as well as to other cytidylyltransferases, including rat CTP:phosphocholine cytidylyltransferase and Bacillus subtilis glycerol-3-phosphate cytidylyltransferase [4].

High impact information on PCT1

• In vivo, CCT is essential for Cdc20-dependent cell cycle events such as sister chromatid separation and exit from mitosis [5].
• Here, we show that the hetero-oligomeric chaperonin TRiC (also known as CCT) physically interacts with polyglutamine-expanded variants of huntingtin (Htt) and effectively inhibits their aggregation [3].
• The role in protein folding of the eukaryotic chaperonin TRiC/CCT is only partially understood [6].
• During plant evolution, the number of genes encoding HAP proteins was greatly amplified, and these proteins may have acquired novel functions, such as mediating the effect of CCT domain proteins on gene expression [7].
• The CCT (for CONSTANS, CONSTANS-LIKE, TOC1) domain is found in 45 Arabidopsis thaliana proteins involved in processes such as photoperiodic flowering, light signaling, and regulation of circadian rhythms [7].

Chemical compound and disease context of PCT1

• The recombinant CCT expressed in E. coli is catalytically active, as evidenced by the conversion of phosphocholine to CDP-choline [8].
• Investigation of a choline phosphate synthesis pathway in Streptococcus pneumoniae: evidence for choline phosphate cytidylyltransferase activity [9].

Biological context of PCT1

• In this study, we have used both nutritional deprivation as well as a conditional temperature sensitive allele of PCT1 (CTP:phosphocholine cytidylyltransferase) coupled with an inactivated phosphatidylethanolamine methylation pathway to determine how cells respond to inactivation of phosphatidylcholine synthesis [10].
• Pct1p activity is regulated by Sec14p, a cytoplasm/Golgi localized phosphatidylcholine/phosphatidylinositol binding protein that regulates Golgi-derived vesicle transport partially through its ligand-dependent regulation of PCT1 derived enzyme activity [10].
• The plasmid directed the synthesis of an active cholinephosphate cytidylyltransferase in Escherichia coli, confirming that CCT is the structural gene for this enzyme [11].
• 1. The structural gene for cholinephosphate cytidylyltransferase (CCT) was isolated from a Saccharomyces cerevisiae genomic library by means of complementation in a mutant of the yeast defective in the enzyme [12].
• The nucleotide sequence which contained CCT was determined by the dideoxy chain-termination method [12].

Anatomical context of PCT1

• The CTP: phosphocholine cytidylyltransferase (CT) gene from yeast and cDNA from rat liver were over-expressed 20-30-fold in COS cells [13].
• Dark-grown transgenic Arabidopsis seedlings expressing the C-terminal domains (CCT) of the cryptochrome (CRY) blue light photoreceptors exhibit features that are normally associated only with light-grown seedlings, indicating that the signaling mechanism of Arabidopsis CRY is mediated through CCT [14].
• Thus, the loss of cross-linking efficiency suggested that contact sites at the dimer interface had increased distance or reduced flexibility upon binding of CCT to membranes [15].
• We propose that the antagonistic actions of PhLP3 and prefoldin serve to modulate CCT activity and play a key role in establishing a functional cytoskeleton in vivo [16].
• Among the group II chaperonins, CCT proteins provide crucial machinery for the stabilization and proper folding of several proteins in the cytosol of eukaryotic cells through interactions that are subunit-specific and geometry-dependent [17].

Associations of PCT1 with chemical compounds

• Metabolic studies determined that phosphatidylcholine biosynthesis decreased to negligible levels within 1 h upon shift to the nonpermissive temperature for the temperature-sensitive PCT1 allele [10].
• We now report that SEC14p effects an in vivo depression of CDP-choline pathway activity by inhibiting choline-phosphate cytidylyltransferase (CCTase; EC 2.7.7.15), the rate-determining enzyme of the CDP-choline pathway [18].
• The concentration optima for the activation of Y-CT by oleic acid or anionic phospholipids were 5-10-fold lower than those for R-CT [13].
• Y-CT activity was insensitive to PC vesicles containing the neutral lipids diacylglycerol, monoacylglycerol or oleyl alcohol [13].
• The positively charged aminolipid sphingosine antagonized the stimulation by oleic acid of both Y-CT and R-CT [13].

Other interactions of PCT1

• This CCT/CKI fused protein retained both activities and the thermal stability of its cholinephosphate cytidylyltransferase activity was nearly the same as the native CCT enzyme [19].
• Three genes had already been cloned and sequenced: CCT, ADE3 and TR-I [20].

Analytical, diagnostic and therapeutic context of PCT1

• The yeast CCT gene was isolated from genomic DNA using the polymerase chain reaction and was found to encode tyrosine at position 192 instead of histidine, as originally reported [2].
• Molecular cloning of CTP:phosphocholine cytidylyltransferase from Plasmodium falciparum [8].
• Southern blot analysis of restricted S. pneumoniae genomic DNA probed with the gene coding for the choline phosphate cytidylyltransferase of Saccharomyces cerevisiae demonstrated that there is homology between the S. cerevisiae cct gene and genomic DNA of S. pneumoniae [9].
• We observed subcellular localization of expressed products of the mutant CT-ICL genes by immunoelectron microscopy [21].

References