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Identification of prolyl hydroxylation modifications in mammalian cell proteins.

ABSTRACT: Prolyl hydroxylation is a PTM that plays an important role in the formation of collagen fibrils and in the oxygen-dependent regulation of hypoxia inducible factor-? (HIF-?). While this modification has been well characterized in the context of these proteins, it remains unclear to what extent it occurs in the remaining mammalian proteome. We explored this question using MS to analyze cellular extracts subjected to various fractionation strategies. In one strategy, we employed the von Hippel Lindau tumor suppressor protein, which recognizes prolyl hydroxylated HIF-?, as a scaffold for generating hydroxyproline capture reagents. We report novel sites of prolyl hydroxylation within five proteins: FK506-binding protein 10, myosin heavy chain 10, hexokinase 2, pyruvate kinase, and C-1 Tetrahydrofolate synthase. Furthermore, we show that identification of prolyl hydroxylation presents a significant technical challenge owing to widespread isobaric methionine oxidation, and that manual inspection of spectra of modified peptides in this context is critical for validation.

SUBMITTER: Arsenault PR

PROVIDER: S-EPMC4438755 | biostudies-literature | 2015 Apr

REPOSITORIES: biostudies-literature

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Identification of prolyl hydroxylation modifications in mammalian cell proteins.

Arsenault Patrick R PR Heaton-Johnson Katherine J KJ Li Lin-Sheng LS Song Daisheng D Ferreira Vinicius S VS Patel Nish N Master Stephen R SR Lee Frank S FS

Proteomics 20150119 7

Prolyl hydroxylation is a PTM that plays an important role in the formation of collagen fibrils and in the oxygen-dependent regulation of hypoxia inducible factor-α (HIF-α). While this modification has been well characterized in the context of these proteins, it remains unclear to what extent it occurs in the remaining mammalian proteome. We explored this question using MS to analyze cellular extracts subjected to various fractionation strategies. In one strategy, we employed the von Hippel Lind ...[more]

PMID: 25421965

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Project description:Mutations in the genes encoding cartilage associated protein (CRTAP) and prolyl 3-hydroxylase 1 (P3H1 encoded by LEPRE1) were the first identified causes of recessive Osteogenesis Imperfecta (OI). These proteins, together with cyclophilin B (encoded by PPIB), form a complex that 3-hydroxylates a single proline residue on the α1(I) chain (Pro986) and has cis/trans isomerase (PPIase) activity essential for proper collagen folding. Recent data suggest that prolyl 3-hydroxylation of Pro986 is not required for the structural stability of collagen; however, the absence of this post-translational modification may disrupt protein-protein interactions integral for proper collagen folding and lead to collagen over-modification. P3H1 and CRTAP stabilize each other and absence of one results in degradation of the other. Hence, hypomorphic or loss of function mutations of either gene cause loss of the whole complex and its associated functions. The relative contribution of losing this complex's 3-hydroxylation versus PPIase and collagen chaperone activities to the phenotype of recessive OI is unknown. To distinguish between these functions, we generated knock-in mice carrying a single amino acid substitution in the catalytic site of P3h1 (Lepre1(H662A) ). This substitution abolished P3h1 activity but retained ability to form a complex with Crtap and thus the collagen chaperone function. Knock-in mice showed absence of prolyl 3-hydroxylation at Pro986 of the α1(I) and α1(II) collagen chains but no significant over-modification at other collagen residues. They were normal in appearance, had no growth defects and normal cartilage growth plate histology but showed decreased trabecular bone mass. This new mouse model recapitulates elements of the bone phenotype of OI but not the cartilage and growth phenotypes caused by loss of the prolyl 3-hydroxylation complex. Our observations suggest differential tissue consequences due to selective inactivation of P3H1 hydroxylase activity versus complete ablation of the prolyl 3-hydroxylation complex.

Project description:The hydroxylation of proline residues to 4-trans-hydroxyproline (Hyp) is a common post-translational protein modification in plants, mediated by prolyl 4-hydroxylases (P4Hs). Hyps predominantly occur in a group of cell wall proteins, the Hydroxyproline-rich glycoproteins (HRGPs), where they are frequently O-glycosylated. While prolyl-hydroxylation and O-glycosylation are important, e.g. for cell wall stability, they are not desirable in plant-made pharmaceuticals. Sequence motifs recognized for prolyl-hydroxylation derived from vascular plants were proposed but did not include data from mosses, such as Physcomitrella. Here, a phylogenetic reconstruction of plant P4Hs identified six P4Hs in four subfamilies in mosses. We analysed the amino acid sequences and structural environments around Hyps in Physcomitrella utilizing 73 Hyp sites in 24 secretory proteins from multiple MS/MS datasets, and found that prolines in close proximity to other prolines, alanine, serine, threonine and valine were preferentially hydroxylated. About 95 % of the Hyp sites were predictable with a combination of previously defined motifs and methods. In our data, AOV (Ala-Hyp-Val) was the most frequent prolyl-hydroxylation pattern. Additionally, short arabinose chains were attached to Hyps in two cell-wall pectinesterases. A combination of 443 AlphaFold structure models and our MS data of peptides with nearly 3000 proline sites found Hyps predominantly on protein surfaces in disordered regions. Moss-produced human erythropoietin (EPO) exhibited plant-specific O-glycosylation with arabinose chains on two Hyps. This modification was significantly reduced in a P4H1 single knock-out (KO) Physcomitrella mutant. Quantitative proteomics after isotope labelling with different P4H-KO moss mutants revealed specific changes in the amount of proteins, including HRGPs, and a modified prolyl-hydroxylation pattern from the mutants, suggesting a differential function of the six Physcomitrella P4Hs. Quantitative RT-PCR proved a differential effect of single P4H KOs on the expression of the other five p4h genes, suggesting a partial compensation of the mutation. AlphaFold-Multimer models for Physcomitrella P4H1 and its target EPO peptide superposed with the crystal structure of Chlamydomonas P4H1 and a peptide substrate suggested significant amino acids in the active centre of the enzyme that form H-bonds with the peptide substrate, and revealed differences between P4H1 and the other five Physcomitrella P4Hs.

Project description:Protein hydroxylases are oxygen- and ?-ketoglutarate-dependent enzymes that catalyse hydroxylation of amino acids such as proline, thus linking oxygen and metabolism to enzymatic activity. Prolyl hydroxylation is a dynamic post-translational modification that regulates protein stability and protein-protein interactions; however, the extent of this modification is largely uncharacterized. The goals of this study are to investigate the biological consequences of prolyl hydroxylation and to identify new targets that undergo prolyl hydroxylation in human cardiomyocytes.We used human induced pluripotent stem cell-derived cardiomyocytes in combination with pulse-chase amino acid labelling and proteomics to analyse the effects of prolyl hydroxylation on protein degradation and synthesis. We identified 167 proteins that exhibit differences in degradation with inhibition of prolyl hydroxylation by dimethyloxalylglycine (DMOG); 164 were stabilized. Proteins involved in RNA splicing such as serine/arginine-rich splicing factor 2 (SRSF2) and splicing factor and proline- and glutamine-rich (SFPQ) were stabilized with DMOG. DMOG also decreased protein translation of cytoskeletal and sarcomeric proteins such as ?-cardiac actin. We searched the mass spectrometry data for proline hydroxylation and identified 134 high confidence peptides mapping to 78 unique proteins. We identified SRSF2, SFPQ, ?-cardiac actin, and cardiac titin as prolyl hydroxylated. We identified 29 prolyl hydroxylated proteins that showed a significant difference in either protein degradation or synthesis. Additionally, we performed next-generation RNA sequencing and showed that the observed decrease in protein synthesis was not due to changes in mRNA levels. Because RNA splicing factors were prolyl hydroxylated, we investigated splicing ± inhibition of prolyl hydroxylation and detected 369 alternative splicing events, with a preponderance of exon skipping.This study provides the first extensive characterization of the cardiac prolyl hydroxylome and demonstrates that inhibition of ?-ketoglutarate hydroxylases alters protein stability, translation, and splicing.

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Identification of prolyl hydroxylation modifications in mammalian cell proteins.

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Identification of prolyl hydroxylation modifications in mammalian cell proteins.

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