Plasma proteins containing damaged l-isoaspartyl residues are increased in uremia: Implications for mechanism

These authors equally contributed to this work.Keywords: cystic fibrosis, CFTR, autophagy, cysteamine, epigallocatechin gallate, sweat chloride Abbreviations: BECN1/Beclin 1, autophagy-related; CF, cystic fibrosis; CFTR, cystic fibrosis transmembrane conductance regulator; CHX, cycloheximide; CSNK2, casein kinase 2; CXCL2, chemokine (C-X-C motif) ligand 2; CXCL8, chemokine (C-X-C motif) ligand 8; EGCG, epigallocatechin gallate; FEV, forced expiratory volume; PM, plasma membrane; RPD, rectal potential difference; SQSTM1, sequestosome 1; TGM2, transglutaminase 2; TNF, tumor necrosis factor.Restoration of BECN1/Beclin 1-dependent autophagy and depletion of SQSTM1/p62 by genetic manipulation or autophagy-stimulatory proteostasis regulators, such as cystamine, have positive effects on mouse models of human cystic fibrosis (CF). These measures rescue the functional expression of the most frequent pathogenic CFTR mutant, F508del, at the respiratory epithelial surface and reduce lung inflammation in Cftr F508del homozygous mice. Cysteamine, the reduced form of cystamine, is an FDA-approved drug. Here, we report that oral treatment with cysteamine greatly reduces the mortality rate and improves the phenotype of newborn mice bearing the F508del-CFTR mutation. Cysteamine was also able to increase the plasma membrane expression of the F508del-CFTR protein in nasal epithelial cells from F508del homozygous CF patients, and these effects persisted for 24 h after cysteamine withdrawal. Importantly, this cysteamine effect after washout was further sustained by the sequential administration of epigallocatechin gallate (EGCG), a green tea flavonoid, both in vivo, in mice, and in vitro, in primary epithelial cells from CF patients. In a pilot clinical trial involving 10 F508del-CFTR homozygous CF patients, the combination of cysteamine and EGCG restored BECN1, reduced SQSTM1 levels and improved CFTR function from nasal epithelial cells in vivo, correlating with a decrease of chloride concentrations in sweat, as well as with a reduction of the abundance of TNF/ TNF-alpha (tumor necrosis factor) and CXCL8 (chemokine [C-X-C motif] ligand 8) transcripts in nasal brushing and TNF and CXCL8 protein levels in the sputum. Altogether, these results suggest that optimal schedules of cysteamine plus EGCG might be used for the treatment of CF caused by the F508del-CFTR mutation.

show abstract

“…The methodologies of the analyses for plasma cysteamine levels were performed 69 as described in Supplemental Materials. …”

Section: Pharmacokinetic and Pharmacodynamic Analysesmentioning

confidence: 99%

Restoration of CFTR function in patients with cystic fibrosis carrying the F508del-CFTR mutation

et al. 2014

View full text Add to dashboard Cite

show abstract

“…In a previous paper, we showed that in uremic patients on hemodialysis, plasma protein damage is significantly increased, as measured by an assay using human recombinant PCMT (4). This damage involves all plasma proteins, but in particular, albumin is the most affected plasma protein.…”

Section: Discussionmentioning

confidence: 93%

“…Free homocysteine is in dynamic equilibrium with other forms, such as AdoHcy, and homocysteine thiolactone, not considering the capability of free homocysteine to elicit oxidative stress. We have previously shown that AdoHcy is able, through transmethylation inhibition, to induce erythrocyte membrane protein damage (5,6) and is at least partly involved in plasma protein damage (4) and in alterations of the allelic expression of imprinted genes in uremia (9). The formation of homocysteine thiolactone, a highly reactive homocysteine derivative, is another plausible mechanism of homocysteine toxicity, which depends on the cyclization of free homocysteine, as a result of methionyl tRNA synthetase proofreading activity, a process that is able to prevent homocysteine misincorporation into proteins (34).…”

Section: Discussionmentioning

confidence: 99%

“…Methylation of plasma proteins was performed in vitro as described previously (4). Results are expressed as picomoles of incorporated methyl groups per milligram of protein.…”

Section: In Vitro Transmethylation Assay Of Plasma Proteinsmentioning

confidence: 99%

“…The presence of damaged residues interferes with normal protein structure and function. We previously demonstrated that in chronic renal failure patients who undergo hemodialysis therapy, these residues significantly accumulate in plasma and that the most affected protein is albumin (4). Under normal conditions, these residues are repaired by a mechanism that involves an enzymatic step catalyzed by a methyltransferase (protein isoaspartyl carboxyl-O-methyltransferase [PCMT]; EC 2.1.1.77).…”

mentioning

confidence: 99%

See 2 more Smart Citations

Plasma Protein Aspartyl Damage Is Increased in Hemodialysis Patients

Perna¹,

Ingrosso²,

Satta³

et al. 2004

Journal of the American Society of Nephrology

View full text Add to dashboard Cite

Abstract. Plasma proteins in hemodialysis patients display a significant increase in deamidated/isomerized Asx (asparagine and aspartic acid) content, a marker of protein fatigue damage. This has been linked to the toxic effects of hyperhomocysteinemia in uremic erythrocytes; however, treatment aimed at abating homocysteine levels did not lead to significant reductions in plasma protein damage. The hypothesis that lack of reduction in protein damage could be due to protein increased intrinsic instability, as result of interference with the uremic milieu rather than to hyperhomocysteinemia, was put forward. The deamidated/isomerized Asx content of normal plasma incubated with several uremic toxins for 24 h, 72 h, and 7 d was measured, identifying a group of toxins that were able to elicit this kind of damage. Uremic toxins were also incubated with purified human albumin, and dose-response experiments with the two most toxic agents in terms of protein damage (guanidine and guanidinopropionic acid) were carried out. The effect of the hemodialysis procedure on protein damage was evaluated. For investigating also the consequences of these alterations, human albumin was treated in vitro to produce an increase in deamidated/isomerized Asx residues, and the effects of albumin deamidation on protein binding were evaluated.

show abstract

Differential expression of microRNAs associated with neurodegenerative diseases and diabetic nephropathy in protein l‐isoaspartyl methyltransferase‐deficient mice

Ren

Ling

et al. 2021

Cell Biology International

View full text Add to dashboard Cite

Protein l‐isoaspartyl methyltransferase (PIMT/PCMT1), an enzyme repairing isoaspartate residues in peptides and proteins that result from the spontaneous decomposition of normal l‐aspartyl and l‐asparaginyl residues during aging, has been revealed to be involved in neurodegenerative diseases (NDDs) and diabetes. However, the molecular mechanisms for a putative association of PIMT dysfunction with these diseases have not been clarified. Our study aimed to identify differentially expressed microRNAs (miRNAs) in the brain and kidneys of PIMT‐deficient mice and uncover the epigenetic mechanism of PIMT‐involved NDDs and diabetic nephropathy (DN). Differentially expressed miRNAs by sequencing underwent target prediction and enrichment analysis in the brain and kidney of PIMT knockout (KO) mice and age‐matched wild‐type (WT) littermates. Sequence analysis revealed 40 differentially expressed miRNAs in the PIMT KO mouse brain including 25 upregulated miRNAs and 15 downregulated miRNAs. In the PIMT KO mouse kidney, there were 80 differentially expressed miRNAs including 40 upregulated miRNAs and 40 downregulated miRNAs. Enrichment analysis and a systematic literature review of differentially expressed miRNAs indicated the involvement of PIMT deficiency in the pathogenesis in NDDs and DN. Some overlapped differentially expressed miRNAs between the brain and kidney were quantitatively assessed in the brain, kidney, and serum‐derived exosomes, respectively. Despite being preliminary, these results may aid in investigating the pathological hallmarks and identify the potential therapeutic targets and biomarkers for PIMT dysfunction‐related NDDs and DN.

show abstract

Plasma proteins containing damaged l-isoaspartyl residues are increased in uremia: Implications for mechanism

Abstract: Plasma protein damage, as determined by protein L-isoaspartyl content, is increased in uremia. This alteration is to be ascribed to an increased protein structural instability, rather than the effect of hyperhomocysteinemia.

Cited by 12 publications

References 0 publications

Restoration of CFTR function in patients with cystic fibrosis carrying the F508del-CFTR mutation

Restoration of CFTR function in patients with cystic fibrosis carrying the F508del-CFTR mutation

Plasma Protein Aspartyl Damage Is Increased in Hemodialysis Patients

Differential expression of microRNAs associated with neurodegenerative diseases and diabetic nephropathy in protein l‐isoaspartyl methyltransferase‐deficient mice

Contact Info

Product

Resources

About