1. Inositol pyrophosphates inhibit synaptotagmin-dependent exocytosis
- Author
-
Yeon-Kyun Shin, Jooyoung Lee, Igor Pavlovic, Seung Ju Park, Jae Won Kyung, Seyun Kim, Tae-Young Yoon, Henning J. Jessen, Yong Seok Jho, Sung Hyun Kim, Tae-Sun Lee, Seulgi Lee, Yoosoo Yang, Dae-Hyuk Kweon, and Byoungjae Kong
- Subjects
0301 basic medicine ,Vesicle fusion ,Inositol Phosphates ,Biology ,Hippocampus ,PC12 Cells ,Corrections ,Exocytosis ,Synaptotagmin 1 ,Rats, Sprague-Dawley ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Animals ,Inositol ,Neurons ,Multidisciplinary ,Phosphotransferases (Phosphate Group Acceptor) ,SNAP25 ,Munc-18 ,Kiss-and-run fusion ,Biological Sciences ,Cell biology ,Rats ,Synaptic vesicle exocytosis ,030104 developmental biology ,chemistry ,Synaptotagmin I ,030217 neurology & neurosurgery - Abstract
Inositol pyrophosphates such as 5-diphosphoinositol pentakisphosphate (5-IP7) are highly energetic inositol metabolites containing phosphoanhydride bonds. Although inositol pyrophosphates are known to regulate various biological events, including growth, survival, and metabolism, the molecular sites of 5-IP7 action in vesicle trafficking have remained largely elusive. We report here that elevated 5-IP7 levels, caused by overexpression of inositol hexakisphosphate (IP6) kinase 1 (IP6K1), suppressed depolarization-induced neurotransmitter release from PC12 cells. Conversely, IP6K1 depletion decreased intracellular 5-IP7 concentrations, leading to increased neurotransmitter release. Consistently, knockdown of IP6K1 in cultured hippocampal neurons augmented action potential-driven synaptic vesicle exocytosis at synapses. Using a FRET-based in vitro vesicle fusion assay, we found that 5-IP7, but not 1-IP7, exhibited significantly higher inhibitory activity toward synaptic vesicle exocytosis than IP6 Synaptotagmin 1 (Syt1), a Ca(2+) sensor essential for synaptic membrane fusion, was identified as a molecular target of 5-IP7 Notably, 5-IP7 showed a 45-fold higher binding affinity for Syt1 compared with IP6 In addition, 5-IP7-dependent inhibition of synaptic vesicle fusion was abolished by increasing Ca(2+) levels. Thus, 5-IP7 appears to act through Syt1 binding to interfere with the fusogenic activity of Ca(2+) These findings reveal a role of 5-IP7 as a potent inhibitor of Syt1 in controlling the synaptic exocytotic pathway and expand our understanding of the signaling mechanisms of inositol pyrophosphates.
- Published
- 2016