Copines are a family of cytosolic proteins that associate with membranes in a calcium‐dependent manner and are found in many eukaryotic organisms. Dictyostelium discoideum has six copine genes (cpnA‐cpnF), and cells lacking cpnA(cpnA⁻) have defects in cytokinesis, chemotaxis, adhesion, and development. CpnA has also been shown to associate with the plasma membrane, contractile vacuoles (CV), and organelles of the endolysosomal pathway. Here, we use cpnA⁻ cells to investigate the role of CpnA in CV function and endocytosis. When placed in water, cpnA⁻ cells made abnormally large CVs that took longer to expel. Visualization of CVs with the marker protein GFP‐dajumin indicated that cpnA⁻ cells had fewer CVs that sometimes refilled before complete emptying. In endocytosis assays, cpnA⁻ cells took up small fluorescent beads by macropinocytosis at rates similar to parental cells. However, cpnA⁻ cells reached a plateau sooner than parental cells and had less fluorescence at later time points. p80 antibody labeling of postlysosomes (PL) indicated that there were fewer and smaller PLs in cpnA⁻ cells. In dextran pulse‐chase experiments, the number of PLs peaked earlier in cpnA⁻ cells, and the PLs did not become as large and disappeared sooner as compared to parental cells. PLs in cpnA⁻ cells were also shown to have more actin coats, suggesting CpnA may play a role in actin filament disassembly on PL membranes. Overall, these results indicate that CpnA is involved in the regulation of CV size and expulsion, and the maturation, size, and exocytosis of PLs.

中文翻译：

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Copine A调节小球藻中收缩液泡和溶酶体的大小和胞吐作用。

pine树是一个以钙依赖的方式与细胞膜结合的胞质蛋白家族，存在于许多真核生物中。粘菌有六个COPINE基因（cpnA - cpnF）和细胞缺乏cpnA（cpnA ^- ）在胞质分裂，趋化，黏附和发育缺陷。CpnA还显示与内膜溶酶体途径的质膜，收缩液泡（CV）和细胞器相关。在这里，我们使用cpnA ^-细胞研究CpnA的CV功能和内吞作用。当放置在水中，cpnA ^-细胞产生异常大的CV，需要更长的时间才能排出。与标记蛋白GFP-dajumin简历的可视化表示，cpnA ^-细胞具有较少的简历是完全排空之前有时补充。在细胞内吞试验，cpnA ^-细胞巨胞以类似于亲本细胞率拿起小荧光珠。然而，cpnA ^-细胞达到平台期比亲本细胞更快，曾在稍后的时间点较少的荧光。P80 postlysosomes（PL）的抗体标记指出，有较少的及较小的PL cpnA ^-细胞。在右旋糖酐脉冲追踪实验中，PLs的数量在cpnA中较早达到峰值^-与亲本细胞相比，PL并没有那么大，消失得更快。PL内的cpnA ^-细胞也显示有更多的肌动蛋白的大衣，这CpnA可以在PL膜发挥作用的肌动蛋白丝拆卸。总体而言，这些结果表明CpnA参与了CV大小和排泄以及PL的成熟，大小和胞吐作用的调节。