Phosphatidylinositol 4-phosphate (PI4P) is a phospholipid found in cell membranes, particularly in the endoplasmic reticulum and plasma membrane. It plays a crucial role in cellular signaling and membrane dynamics, acting as a precursor for other important lipids and signaling molecules. PI4P is involved in various cellular processes, including vesicle trafficking and cytoskeletal organization. It serves as a docking site for proteins that contain specific binding domains, facilitating communication and transport within the cell. Its regulation is essential for maintaining cellular functions and responding to external signals.