Journal
BIOCHEMICAL AND BIOPHYSICAL RESEARCH COMMUNICATIONS
Volume 347, Issue 1, Pages 76-82Publisher
ACADEMIC PRESS INC ELSEVIER SCIENCE
DOI: 10.1016/j.bbrc.2006.06.045
Keywords
INS-1 cell; synaptotagmin I; shRNA; RNAi; exocytosis; endocytosis
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Synaptotagmin I (Syt I) is a Ca2+ 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-I 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 [Ca2+](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 Ca2+-sensing of LDCV fusion with plasmalemma, but also plays a crucial role in fast endocytosis in INS-I cells. (c) 2006 Elsevier Inc. All rights reserved.
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