Yang Yan, Udayasankar Sangeetha, Dunning James, Chen Peng, Gillis Kevin D
Departments of Biological Engineering, Electrical Engineering, and Physiology, and Dalton Cardiovascular Research Center, University of Missouri, Research Park Drive, Columbia, MO 65211, USA.
Proc Natl Acad Sci U S A. 2002 Dec 24;99(26):17060-5. doi: 10.1073/pnas.242624699. Epub 2002 Nov 21.
We have used flash photolysis of caged Ca2+ and membrane capacitance measurements to probe exocytosis in chromaffin cells at low concentrations of intracellular Ca2+ ([Ca2+]i) (<10 microM). We observed a small pool of granules that is more sensitive to [Ca2+]i than the previously described "readily releasable pool." Upon activation of PKC, this "highly Ca2+-sensitive pool" is enhanced in size to a greater extent than the readily releasable pool but is eliminated upon expression of a C-terminal deletion mutant (Delta9) of synaptosome-associated protein of 25 kDa (SNAP-25). Thus, in chromaffin cells, PKC enhances exocytosis both by increasing the number of readily releasable vesicles and by shifting vesicles to a highly Ca2+-sensitive state, enabling exocytosis at sites relatively distant from Ca2+ channels.
我们利用笼锁Ca2+的闪光光解和膜电容测量，在低细胞内Ca2+浓度（[Ca2+]i）（<10 microM）下探测嗜铬细胞中的胞吐作用。我们观察到一小部分颗粒，其对[Ca2+]i的敏感性高于先前描述的“易释放池”。蛋白激酶C（PKC）激活后，这个“高度Ca2+敏感池”的大小增加程度大于易释放池，但在表达25 kDa突触体相关蛋白（SNAP-25）的C末端缺失突变体（Delta9）后被消除。因此，在嗜铬细胞中，PKC通过增加易释放囊泡的数量以及将囊泡转变为高度Ca2+敏感状态来增强胞吐作用，从而使胞吐作用能够在离Ca2+通道相对较远的位点发生。
