Serine/Arginine-Protein Kinase 1 Co-Phosphorylation Signatures Uncover Splicing-Driven Mechanisms in Oncogenic Pathway Modulation.

Serine/arginine-protein kinase 1 (SRPK1) is a central regulator of alternative splicing whose overexpression drives oncogenic reprogramming in multiple cancers. To understand the phosphorylation dynamics of SRPK1 activity, we performed a systematic integrative phosphoproteomic meta-analysis of 798 profiling and 232 differential human datasets. We identified S51, S309, and S311 as the three predominant Class I phosphosites on SRPK1. High-confidence co-phosphoregulated proteins (Fisher's Exact Test p < 0.05, ≥3 independent studies, ≥3 experimental conditions) revealed an extensive network of splicing factors (SRRM1, SRRM2, GPATCH8) and noncanonical RS-domain proteins (LBR) that function as both substrates and binary interactors, preferentially linked to S309 and S311. Proteogenomic interrogation via cProSite demonstrated significant upregulation of phosphorylation at these sites in breast, ovarian cancer and lung adenocarcinoma cohorts. Downstream substrates and co-regulated proteins further intersected with apoptosis regulators like SIRT2, BAD, FOXO3, and PI3K/Akt pathway components, mechanistically hinting at SRPK1 phosphorylation in apoptosis suppression and uncontrolled proliferation. These co-phosphorylation signatures therefore position SRPK1 as a potential orchestrator of splicing condensates that rewire oncogenic pathways, offering a phosphosite-specific blueprint for targeted splicing modulators and combination immunotherapies in splicing-related malignancies.