Isoform 3 of Heterogeneous nuclear ribonucleoprotein K

Heterogeneous nuclear ribonucleoprotein K (hnRNP K) is an RNA-binding protein involved in post-transcriptional gene regulation, including mRNA processing, stability, and translation (UniProt: P61978-3). The protein localizes to the nucleus and cytoplasm where it participates in multiple cellular pathways controlling gene expression at the RNA level. No specific tissue distribution or baseline disease associations are documented in the UniProt record.

hnRNP K isoform 3 is upregulated in Alzheimer's Disease brain tissue compared to age-matched controls (Chaparral AD proteomics). In a quantitative proteomics study of post-mortem AD brain samples analyzed across four subcellular fractions using tandem mass tag labeling and data-dependent acquisition mass spectrometry, this isoform showed a mean log2 fold-change of +0.28, indicating modest elevation in AD pathology. The upregulation was detected in at least one subcellular fraction, suggesting altered hnRNP K expression or localization may contribute to AD-related molecular changes, though the biological significance of this modest increase requires further investigation.