Lipid transfer by ORP3 is required for the regulation of PI4P and PI(4,5)P2 at the plasma membrane in mitosis

Abstract

During mitosis, cellular contents including the genetic material and membrane-bound organelles must be faithfully distributed between the two daughter cells. Regulation of PI(4,5)P2 levels at the plasma membrane is essential for mitotic progression, including anchoring of the mitotic spindle, recruitment of the actomyosin cytoskeleton at the cleavage furrow, and abscission. Here, we demonstrate that the ORP3 lipid transfer protein, which transfers PI4P from the plasma membrane to the endoplasmic reticulum (ER) at ER-plasma membrane contacts, plays a crucial role in the regulation of PI4P and PI(4,5)P2 levels at the plasma membrane in mitosis. We show that defects in ORP3 function alter PI4P and PI(4,5)P2 distributions, distribution of the actin cytoskeleton at the plasma membrane, mitotic spindle geometry, chromosome segregation, abscission, and lead to the accumulation of multinucleated cells. The function of ORP3 in mitosis is dependent on its ER-partner VAPA and phosphorylation of the ORP3 VAPA-binding motif strongly recruits ORP3 to the ER, priming it for PI4P transfer from the plasma membrane to the ER. Finally ORP3 is required to prevent PI4P accumulation at the cytoplasmic bridge as a result of PI(4,5)P2 hydrolysis for abscission and successful completion of cell division. Altogether, ORP3 plays a key role in PI4P and PI(4,5)P2 regulation during mitosis. Impairment of ORP3 function results in multiple cell division phenotypes, leading to genetic instability and aneuploidy.