Speaker: XIONG Ding (Graduate Student, MBI, NUS)
Date: 5 December 2016, Monday
Time: 10am
Venue: MBI, T-lab, level 5 seminar rooms

Supervisor(s): Prof Wu Min

Abstract: Dynamic patterns, such as oscillations and waves, of signaling factors are of great importance to cell physiology in many single and multicellular systems. Currently, majority of the studies focus primarily on cytoskeleton-dependent feedbacks. In contrast, information on signaling mechanisms upstream of the actin cytoskeleton remains unclear.

In this study, I report phosphoinositides traveling waves on plasma membrane of rat basophilic leukemia (RBL) mast cells (Xiong et al. 2016). Sequential waves of phosphoinositides are generated by two phase-shifted phosphoinositide phosphatases namely synaptojanin 2 and SHIP1. By perturbing phosphoinositides using optogenetic methods and chemical drugs, I demonstrate that the pulses of PtdIns(4,5)P2 regulate the amplitude of cyclic membrane waves while PtdIns(3,4)P2 sets the frequency. Class I PI3Kδ is the main functional PI3K involved in regulating the frequency through phosphatase-dependent inhibitory action. Besides, dynamic patterns of global oscillations have been observed on plasma membrane and ER membrane coupling with calcium oscillations. Cyclic recruitment of calcium channel STIM1 on ER membrane is synchronized with the PtdIns(4)P dynamics. Collectively, the spatiotemporal dynamics of lipid metabolism have a key role in efficiently directing signals on plasma membrane and ER membrane.

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