Abstract
BACKGROUND/AIM: Acute myocardial infarction (AMI) triggers systemic biochemical responses, including dynamic changes in the phosphorylation status of circulating proteins. However, the phosphoproteomic profile of serum in the context of AMI remains insufficiently characterized. This study aimed to investigate serum phosphoproteomic alterations associated with AMI and to explore potential correlations with markers of cardiac injury. MATERIALS AND METHODS: A comparative phosphoproteomic analysis was performed on serum samples obtained from eight patients with AMI and pooled healthy control samples. High-abundance serum proteins were depleted, and phosphopeptides were enriched using TiO(2) phosphopeptide enrichment kit. Samples were analyzed by liquid chromatography-tandem mass spectrometry using a Q Exactive HF-X Orbitrap mass spectrometer. Data were searched against the Homo sapiens database using Sequest HT with a 1% false discovery rate and were quantified by label-free quantification using Proteome Discoverer version 2.4. RESULTS: A total of 46 phosphoproteins were confidently identified, revealing distinct phosphorylation profiles between AMI and control samples. Increased phosphorylation levels were observed for solute carrier family 12 member 5, apolipoprotein L1, the low-molecular-weight isoform of kininogen-1, and osteopontin in AMI serum. Conversely, phosphorylated inter-alpha-trypsin inhibitor heavy chain H2, antithrombin III, histidine-rich glycoprotein, peroxiredoxin-4, GTPase ERas, and the 26S proteasome non-ATPase regulatory subunit 1 were reduced or undetectable. A strong negative correlation was found between apolipoprotein L1 phosphorylation and cardiac troponin I concentrations (r = -0.91; p = 0.0016). CONCLUSION: These findings demonstrate that serum phosphoproteomics can provide valuable insights into the molecular events associated with AMI. The inverse relationship between apolipoprotein L1 phosphorylation and cardiac troponin I levels suggests that phosphoproteomic profiling may aid in understanding myocardial injury mechanisms.