CYTOSOLIC MODULATION OF PLASMA MEMBRANE ION TRANSPORT

这项研究的长期目标是阐明一些 离子运输的机制，以确定如何变化的 细胞溶质里程碑调节离子转运，并确定 细胞环境的变化如何改变转运速率。 的 本项目的重点是红细胞钙调素激活钙泵 细胞，这是一个模型，质膜钙泵在其他 细胞 最近的证据表明，钙泵介导Ca/II 交换和钙运输没有H的运动。 现款车型 的钙泵，同时包括ATP，ADP，磷酸盐， Ca，不要明确考虑质子。 这项补助金的具体目的是审查 细胞外质子和ATP对红细胞钙泵的影响。 一些 将审查的问题包括： L. 质子对于重置泵机制重要吗？ 半周期？ 2. Ho必须在ATP结合之前结合 加快下泵前的运输站点返回 循环可以发生？3. 当质子不被传输时， 被转移了吗 实验方案是检查ATP和H对 Ca泵的几个部分反应，包括Ca/Ca交换， 泵，包括Ca/Ca交换逆转和磷酸化中间体 分解 动力学研究的目标之一是确定 其构象变化是速率限制的。 调控 这些构象变化的速度由膜的改变 环境会调节泵的活动。 在红细胞中， 可以确定细胞内的单独影响， 质子、钙离子、核苷酸浓度和细胞外 质子和钙离子。 这一点很重要，因为，例如，蔡和 Ho是基质，但Cao和Hi是前向泵浦的产物 周期 钙的瞬时升高对于这种细胞内信号传导是重要的。 心肌、骨骼肌和平滑肌收缩、细胞 分化和细胞增殖。 钙泵将钙恢复到 因此有助于终止信号。 钙泵活性的缺陷会导致钙的增加， 随后增加Na和K。 这些变化将改变关键 细胞质功能 这种离子的变化 在包括肾衰竭和心力衰竭的几种疾病状态中， 高血压和肌肉萎缩症。 红细胞的改变 钙泵在镰状细胞病中有报道。

The long-term objectives of this research are to elucidate some of the mechanisms of ion transport, to determine how changes of the cytosolic mileau modulate ion transport, and to determine how changes of the cellular environment alter transport rate. The focus of this project is the calmodulin activated Ca pump of red cells, which Is a model for plasma membrane Ca pumps in other cells. Recent evidence indicates that the Ca pump mediates Ca/ll exchange and also Ca transport without H movement. Current models of the Ca pump, while including roles for ATP, ADP, phosphate, and Ca, do not explicitly consider protons. The specific aims of this grant are to examine the effects of extracellular protons and ATP on the red cell Ca pump. Some of the questions to be examined are: l. Are protons important for resetting the pump mechanism after the Ca half cycle? 2. Must Ho bind before ATP can bind to accelerate the return of the transport sites before the next pump cycle can occur? 3. When protons are not transported, what is transported instead? The experimental protocol is to examine the effect of ATP and H on several partial reactions of the Ca pump, including Ca/Ca exchange, pump, including Ca/Ca exchange reversal and phosphointermediate decomposition. One of the goals of a kinetic study is to determine which conformational changes are rate limiting. Regulation of the rate of these conformational changes by alterations in the membrane environment would modulate pump activity. In the red cell it is possible to determine the separate effects of intracellular protons, calcium ions, nucleotide concentrations, and extracellular protons and calcium ions. This is important since, e.g., Cai and Ho are substrates but Cao and Hi are products of the forward pump cycle. A transient rise in Ca is important for signalling in such processes as cardiac, skeletal, and smooth muscle contraction, cell differentiation and cell poliferation. The Ca pump restores Ca to basal levels and therefore assists in terminating the signal. Defects in Ca pump activity would lead to an increase in Ca with subsequent increases in Na and K. These changes would alter key cytoplasmic functions. Such ionic alterations have been implicated in several disease states including renal and cardiac failure, hypertension, and muscular dystrophy. Alterations of the red cell Ca pump have been reported in sickle cell disease.