Restriction of secretory granule motion near the plasma membrane of chromaffin cells.
Restriction of secretory granule motion near the plasma membrane of chromaffin cells.
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DOI：
10.1083/jcb.153.1.177
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发表时间：
2001-04-02
影响因子：
7.8
通讯作者：
Axelrod, D
中科院分区：
文献类型：
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作者：
Johns, L M;Levitan, E S;Shelden, E A;Holz, R W;Axelrod, D
用全内反射荧光显微镜定量研究了牛嗜铬细胞质膜附近分泌颗粒的运动和分布。在由全内反射产生的倏逝场可测量地照射的100 - 300 nm区域内，颗粒优先集中在PM附近。垂直于基材的颗粒运动（z方向）比自由布朗运动所预期的要慢得多，在数十纳米的距离上受到强烈限制，并且倾向于在0.5秒内反转方向。颗粒的z方向扩散系数随着颗粒接近颗粒而在小于颗粒直径的范围内连续减小两个数量级。这些分析表明，系链或异质基质系统严重限制了颗粒运动的PM附近。破伤风毒素和肉毒杆菌毒素A的轻链的瞬时表达没有破坏PM附近颗粒的受限运动，表明SNARE蛋白SNAP-25和VAMP对于降低的流动性是不必要的。然而，在这些细胞中，质膜或颗粒膜上缺乏功能性SNARE减少了一些颗粒紧邻PM的时间。
We used total internal reflection fluorescence microscopy to study quantitatively the motion and distribution of secretory granules near the plasma membrane (PM) of living bovine chromaffin cells. Within the ∼300-nm region measurably illuminated by the evanescent field resulting from total internal reflection, granules are preferentially concentrated close to the PM. Granule motion normal to the substrate (the z direction) is much slower than would be expected from free Brownian motion, is strongly restricted over tens of nanometer distances, and tends to reverse directions within 0.5 s. The z-direction diffusion coefficients of granules decrease continuously by two orders of magnitude within less than a granule diameter of the PM as granules approach the PM. These analyses suggest that a system of tethers or a heterogeneous matrix severely limits granule motion in the immediate vicinity of the PM. Transient expression of the light chains of tetanus toxin and botulinum toxin A did not disrupt the restricted motion of granules near the PM, indicating that SNARE proteins SNAP-25 and VAMP are not necessary for the decreased mobility. However, the lack of functional SNAREs on the plasma or granule membranes in such cells reduces the time that some granules spend immediately adjacent to the PM.