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Biochem Biophys Res Commun. 2006 Aug 18;347(1):76-82. Epub 2006 Jun 16.

Silence of synaptotagmin I in INS-1 cells inhibits fast exocytosis and fast endocytosis.

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  • 1Institute of Biophysics and Biochemistry, HuaZhong University of Science and Technology, Wuhan, PR China.


Synaptotagmin I (Syt I) is a Ca(2+) sensor for triggering fast synchronized release of neurotransmitters. However, controversy remains whether Syt I is also obligatory for the exocytosis and endocytosis of larger dense core vesicles (LDCVs) in endocrine cells. In this study, we used a short hairpin RNA (shRNA) to silence the expression of Syt I and investigated the roles of Syt I on exocytosis and endocytosis in INS-1 cells. Our results demonstrated that expression of Syt I is remarkably reduced by the Syt I gene targeting shRNA. Using high-time resolution capacitance measurement, we found that the silence of Syt I decreased the calcium sensitivity of fusion of insulin granules and therefore reduced the exocytotic burst triggered by step-like [Ca(2+)](i) elevation. In addition, the occurrence frequency and amplitude of fast endocytosis were remarkably reduced in the silenced cells. We conclude that Syt I not only participates in the Ca(2+)-sensing of LDCV fusion with plasmalemma, but also plays a crucial role in fast endocytosis in INS-1 cells.

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