The effects of secreted forms of beta-amyloid-precursor proteins (APP(S)s) on the intracellular Ca2+ concentration ([Ca2+]i) were investigated in rat cultured hippocampal neurones. APP695S, a secretory form of APP695, attenuated the increase in [Ca2+]i evoked by glutamate. In addition, APP695S itself evoked an increase in [Ca2+]i in 1 or 2 day-cultured hippocampal cells, but not in 7 to 13 day-cultured cells. 2. Eighty-one percent of neurones which were immunocytochemically positive for microtubule-associated protein 2 responded to APP695S with an increase in [Ca2+]i. 3. APP695S induced a transient rise in [Ca2+]i even in the absence of extracellular Ca2+ and produced an elevation in inositol-1,4,5-trisphosphate (IP3) in a concentration-dependent manner from 100 to 500 ng ml(-1). In the presence of extracellular Ca2+, APP695S caused a transient rise in [Ca2+]i followed by a sustained phase at high [Ca2+]i, suggesting Ca2+ entry from the extracellular space. 4. The [Ca2+]i elevation was mimicked by amino terminal peptides of APPs, but not by carboxy terminal peptides. 5. These results taken together suggest that APP695S induces an increase in [Ca2+]i in hippocampal neurones through an IP3-dependent mechanism that changes according to the stage of development.
摘要
在大鼠海马神经元培养物中研究了β-淀粉样前体蛋白分泌形式（APP(S)s）对细胞内钙离子浓度（[Ca2+]i）的影响。APP695S是APP695的一种分泌形式，它减弱了谷氨酸引起的[Ca2+]i升高。此外，APP695S本身在培养1或2天的海马细胞中引起[Ca2+]i升高，但在培养7至13天的细胞中则没有。2. 免疫细胞化学检测微管相关蛋白2呈阳性的神经元中，81%对APP695S产生反应，[Ca2+]i升高。3. 即使在没有细胞外钙离子的情况下，APP695S也能诱导[Ca2+]i短暂升高，并以浓度依赖的方式（从100至500 ng ml(-1)）使肌醇-1,4,5-三磷酸（IP3）升高。在存在细胞外钙离子的情况下，APP695S导致[Ca2+]i短暂升高，随后在高[Ca2+]i水平维持，提示钙离子从细胞外空间内流。4. APPs的氨基末端肽可模拟[Ca2+]i升高，但羧基末端肽则不能。5. 综合这些结果表明，APP695S通过一种依赖IP3的机制诱导海马神经元[Ca2+]i升高，该机制随发育阶段而变化。
