Ivarsson Rosita, Jing Xingjun, Waselle Laurent, Regazzi Romano, Renström Erik
Department of Experimental Medical Science, Lund University, Lund, Sweden.
Traffic. 2005 Nov;6(11):1027-35. doi: 10.1111/j.1600-0854.2005.00342.x.
We have examined the importance of the actin-based molecular motor myosin 5a for insulin granule transport and insulin secretion. Expression of myosin 5a was downregulated in clonal INS-1E cells using RNAinterference. Stimulated hormone secretion was reduced by 46% and single-cell exocytosis, measured by capacitance recordings, was inhibited by 42% after silencing. Silencing of Slac-2c/MYRIP, which links insulin granules to myosin 5a, resulted in similar inhibition of single-cell exocytosis. Antibody inhibition of the myosin 5a-Slac-2c/MYRIP interaction significantly reduced the recruitment of insulin granules for release. The pool of releasable granules independent of myosin 5a activity was estimated to approximately 550 granules. Total internal reflection microscopy was then applied to directly investigate granule recruitment to the plasma membrane. Silencing of myosin 5a inhibited granule recruitment during late phase of insulin secretion. In conclusion, we propose a model where insulin granules are transported through the actin network via both myosin 5a-mediated transport and via passive diffusion, with the former playing the major role during stimulatory conditions.
我们研究了基于肌动蛋白的分子马达肌球蛋白5a在胰岛素颗粒运输和胰岛素分泌中的重要性。使用RNA干扰在克隆的INS-1E细胞中下调肌球蛋白5a的表达。沉默后，刺激后的激素分泌减少了46%，通过电容记录测量的单细胞胞吐作用受到了42%的抑制。连接胰岛素颗粒与肌球蛋白5a的Slac-2c/MYRIP的沉默导致单细胞胞吐作用受到类似抑制。对肌球蛋白5a-Slac-2c/MYRIP相互作用的抗体抑制显著减少了用于释放的胰岛素颗粒的募集。估计不依赖于肌球蛋白5a活性的可释放颗粒池约为550个颗粒。然后应用全内反射显微镜直接研究颗粒向质膜的募集。肌球蛋白5a的沉默在胰岛素分泌后期抑制了颗粒募集。总之，我们提出了一个模型，其中胰岛素颗粒通过肌球蛋白5a介导的运输和被动扩散两种方式通过肌动蛋白网络运输，前者在刺激条件下起主要作用。
