Unknown

Dataset Information

0

Low tetrahydrobiopterin biosynthetic capacity of human monocytes is caused by exon skipping in 6-pyruvoyl tetrahydropterin synthase.


ABSTRACT: Biosynthesis of (6 R )-5,6,7,8-tetrahydro-L-biopterin (H(4)-biopterin), an essential cofactor for aromatic amino acid hydroxylases and NO synthases, is effectively induced by cytokines in most of the cell types. However, human monocytes/macrophages form only a little H(4)-biopterin, but release neopterin/7,8-dihydroneopterin instead. Whereas 6-pyruvoyl tetrahydropterin synthase (PTPS) activity, the second enzyme of H(4)-biopterin biosynthesis, is hardly detectable in these cells, PTPS mRNA levels were comparable with those of cell types containing intact PTPS activity. By screening a THP-1 cDNA library, we identified clones encoding the entire open reading frame (642 bp) as well as clones lacking the 23 bp exon 3, which results in a premature stop codon. Quantification of the two mRNA species in different cell types (blood-derived cells, fibroblasts and endothelial cells) and cell lines showed that the amount of exon-3-containing mRNA is correlated closely to PTPS activity. The ratio of exon-3-containing to exon-3-lacking PTPS mRNA is not affected by differential mRNA stability or nonsense-mediated mRNA decay. THP-1 cells transduced with wild-type PTPS cDNA produced H(4)-biopterin levels and expressed PTPS activities and protein amounts comparable with those of fibroblasts. We therefore conclude that exon 3 skipping in transcription rather than post-transcriptional mechanisms is a major cause of the low PTPS protein expression observed in human macrophages and related cell types.

SUBMITTER: Leitner KL 

PROVIDER: S-EPMC1223526 | biostudies-other | 2003 Aug

REPOSITORIES: biostudies-other

Similar Datasets

| S-EPMC7304350 | biostudies-literature
| S-EPMC7145592 | biostudies-literature
| S-EPMC4719003 | biostudies-literature
| S-EPMC6831832 | biostudies-literature
| S-EPMC8673534 | biostudies-literature
| S-EPMC5063410 | biostudies-literature
| S-EPMC7564355 | biostudies-literature
| S-EPMC8922962 | biostudies-literature
| S-EPMC152795 | biostudies-literature
| S-EPMC3892928 | biostudies-literature