Large-Scale Cellular Phosphoproteomic Analysis Reveals a Putative Role for LPIN1 S162 in Metabolic Signaling

Lipin-1 (LPIN1) is a nucleocytoplasmic phosphatidate phosphatase and transcriptional coregulator that plays essential roles in lipid metabolism, insulin signaling, and energy homeostasis. Although LPIN1 function is extensively regulated by phosphorylation, the biological significance of individual phosphosites remains poorly understood. Here, we systematically assembled and analyzed LPIN1 phosphosite information from 99 differential cellular phosphoproteomics datasets to identify functionally relevant regulatory sites. Among 20 differentially regulated phosphosites, S162 emerged as the most frequently and consistently perturbed site across diverse cellular contexts. Co-occurrence analysis revealed that S162 exhibits a phosphoregulation pattern distinct from the canonical insulin-responsive phosphosite cluster of LPIN1, suggesting a unique regulatory role. To define its signaling context, phosphosite coregulation analysis identified extensive associations between LPIN1 S162 and phosphosites involved in insulin signaling, AMPK signaling, autophagy, and metabolic adaptation. Notably, S162 phosphorylation was consistently associated with inhibitory phosphorylation events within insulin receptor substrate signaling and with phosphosites linked to compensatory metabolic stress-response pathways. These signaling patterns suggest that LPIN1 S162 phosphorylation is potentially associated with attenuation of canonical insulin-responsive signaling and the emergence of stress-adaptive metabolic programs. Based on its unique evolutionary conservation, signaling associations, and structural position adjacent to the polybasic membrane-binding domain, we propose that S162 represents a previously unrecognized regulatory phosphosite that may contribute to LPIN1-dependent metabolic adaptation and warrants direct experimental investigation.