Phosphatidic acid at the crossroads of membrane dynamics: from molecular specificity to synthetic innovation

Phosphatidic acid (PA) has emerged as a central regulator of membrane dynamics, vesicle trafficking, exocytosis, and intracellular signaling. Building on recent advances, including subspecies-specific functions of PA in neuroendocrine exocytosis, the primacy of PLD1-derived PA in vivo, and the development of natural-mimetic PA analogues, this review integrates biochemical, biophysical, and systems-level insights across eukaryotes. We contextualize the role of PA in vesicular trafficking, delineate how acyl-chain composition encodes molecular specificity, summarize enzymatic sources and sinks sculpting spatiotemporal control of PA pools within cells, and examine emerging tools used for measuring and disturbing PA in living cells to unravel its function. Given the pleiotropic roles of PA among numerous experimental contexts such as the nervous, endocrine, immune, and metabolic systems, mapping mechanistic connections to disease through mTOR and RAF/MEK/ERK signaling, autophagy, and organelle contact-site biology. Finally, we outline future directions spanning single-cell lipidomics, imaging mass spectrometry, and therapeutic lipid engineering. Together, available evidence positions PA as a conserved, tunable molecular switch that coordinates membrane mechanics with signal transduction to enable realisation of a wide range of function within cells.