Studies on calcium-sensitive regulators of signal transduction in central nervous system.

钙结合蛋白将钙信息转化为各种生理反应。从大鼠脑中分离出一种新的23 kDa钙结合蛋白。基于部分氨基酸序列，我们从大鼠脑cDNA文库中分离出多个不同的克隆，提示大脑中存在多个同工蛋白，形成了一个新的钙敏感调节蛋白家族。其中一个克隆被发现编码一个钙结合蛋白，具有三个EF-hand结构，由193个氨基酸残基组成。在成年大鼠脑中，该蛋白仅在海马锥体细胞中表达，命名为hippocalcin。希波钙素以钙依赖的方式与质膜结合。Hippocalcin在其氨基末端甘氨酸残基上发生肉豆蔻酰化，这是其膜结合特性的关键事件。这些结果提示海马蛋白参与突触后神经功能。在发育中的大鼠脑中，海马中海马蛋白的表达随着年龄的增长而增加，而大脑皮层和小脑中的表达在出生后早期高于老年，提示海马蛋白的表达受到细胞类型和发育过程的严格控制，并在发育早期的神经元分化中发挥作用。人希波calcin cDNA的分离将有助于研究该蛋白在人脑中的功能和表达以及该蛋白与神经系统疾病的可能关系。我们以大鼠海马钙蛋白cDNA为探针，筛选了一个人海马cDNA文库，获得了5个不同的克隆。其中一个克隆体被发现编码人类希波calcin。人希波calcin序列与大鼠相应序列的氨基酸同源性为100%，核苷酸同源性为92%。人类希波calcin基因定位在1号染色体上。

Calcium-binding proteins transduce the calcium messages into a variety of physiological responses. We have isolated a novel 23 kDa calcium-binding protein from rat brain. Based on the partial amino acid sequences, we have isolated several different clones from rat brain cDNA library, suggesting that multiple isoproteins are exist in the brain and form a new family of calcium-sensitive regulator. One of these clones was found to encode a calcium-binding protein with three EF-hand structures, consisting of 193 amino acid residues. In adult rat brain, this protein was expressed exclusively in the pyramidal cells of the hippocampus and was designated hippocalcin. Hippocalcin associates the plasma membrane in a calcium-dependent manner. Hippocalcin is myristoylated at its amino-terminal glycine residue, a key event in terms of its membrane-association property. These results suggest the involvement of hippocalcin in postsynaptic neural function. In developing rat brain, hippocalcin expression in the hippocampus increases with age, whereas the expression in the cerebral cortex and cerebellum is higher in early postnatal ages than in older ages, suggesting that the expression of hippocalcin is strictly controlled by both cell type and developmental process and that hippocalcin plays a role in neuronal differentiation in early stages of development.Isolation of the cDNA for human hippocalcin should be useful to investigate the function and expression of this protein in human brain and the possible relationship of this protein to neurological disorders. We have screened a human hipplcampus cDNA library using rat hippocalcin cDNA as a probe and obtained five different clones. One of these clones was found to encode human hippocalcin. Comparison of the human hippocalcin sequence with the corresponding rat sequence revealed an amino acid identity of 100% and nucleotide identity of 92%. The human hippocalcin gene was mapped to chromosome 1.