GTP Concentration Bursts Locally at Endocytic Sites for Dynamin-Dependent Membrane Fisson

Abstract

Endocytosis is a basic property of cells and is required for a variety of cellular processes including migration, hormone signaling, and neurotransmission. During endocytosis, a part of plasma membrane is buckled inwards to form a vesicle. These vesicles are severed from the plasma membrane by dynamin GTPases. However, this reaction requires a large amount of GTP. The global elevation in the GTP level within cytoplasm would be toxic to the cells, and thus, how its level is regulated for dynamin activity during endocytosis remains enigmatic. Here, we measure the GTP concentrations around endocytic sites using GTP sensors and show that the GTP concentration increases acutely around endocytic pits to provide a sufficient amount of GTP for the dynamin activity. This local enrichment of GTP precedes dynamin recruitment by ∼500 ms, suggesting that GTP bursting is prerequisite for dynamin assembly. The generated GTP does not diffuse out from endocytic sites, indicating that GTP is constantly consumed by dynamin. GTP bursting is most likely regulated by nucleoside-diphosphate kinases, which convert ATP to GTP. Our results demonstrate that GTP concentration is spatiotemporally regulated to provide sufficient energy for dynamin-mediated membrane fission.