OS4 Activators

OS4, known for its role in lipid trafficking and signaling, primarily functions in phosphatidylinositol 4-phosphate (PI4P)/diacylglycerol (DAG) counter-transport at the Golgi. The activity of this protein can be enhanced by chemicals that increase DAG concentration, such as 1-Oleoyl-2-acetyl-sn-glycerol (OAG) and a diacylglycerol kinase inhibitor, R59022. Also, Phorbol 12-myristate 13-acetate (PMA), an activator of protein kinase C (PKC), can enhance OS4's function through its effects on DAG levels. On the other hand, PIK-93, a PI4KIIIβ inhibitor, can indirectly activate OS4 by reducing PI4P levels, thus influencing the counter-transport process.

OS4's activity in vesicular transport can be enhanced by Phenylarsine oxide (PAO), which disrupts vesicular traffic. Lipid homeostasis agents like Progesterone, Cerulenin, and U18666A can augment OS4's lipid transport function by altering lipid composition and intracellular cholesterol transport. Further, the protein's localization to the ER-Golgi interface allows it to be activated by chemicals that induce ER stress, such as Thapsigargin. Filipin III, a cholesterol-binding compound, can enhance OS4's role in cholesterol homeostasis, while Wortmannin, a phosphoinositide 3-kinase (PI3K) inhibitor, can affect OS4's activity by influencing phosphoinositide metabolism.