CALCIUM METABOLISM AND PROTEIN PHOSPHORYLATION IN NEURONAL SYSTEMS

神经丝蛋白（NFP）仅在神经系统中发现 并含有（尤其是在中，NF-M和高，NF-H亚基）大 丝氨酸磷酸化位点的数量。 多激酶系统是 在磷酸化这些位点中起作用。 我们最初的目标是确定 神经系统中的这些特定激酶。 我们已就此 有以下三种不同类型的第二信使 来自大鼠脊髓的磷酸化NFP的独立激酶：1） 酪蛋白激酶I（CKI）样活性似乎与NF 从大鼠脊髓中分离的制剂。 CKI，从大鼠中纯化 脊髓，磷酸化所有三个NF-亚基，优先选择 NF-H 另一方面，酪蛋白激酶II（CKII）磷酸化较差 NF-H，但对NF-M和NF-L具有更高的亲和力; 2）微管相关的 蛋白激酶（MAP激酶）样活性，磷酸化所有三个 亚单位。 然而，这些激酶不磷酸化去磷酸化， NFs，也不是含有lys-ser-pro（KSP）的串联重复序列基序 存在于NF-H和NF-M中，其中这些丝氨酸残基广泛存在于 磷酸化; 3）P34 cdc 2样激酶（KSP）激酶）：该激酶出现于 磷酸化存在的KSP序列的一些多重重复 NF-M和NF-H。 该激酶识别的共有序列是 XS/TPXK。 这种激酶的性质表明它与 P34 cdc 2激酶，已知其参与调节 细胞周期 这一观察结果意味着神经元cdc 2的不同作用。 就像神经系统中的激酶，细胞分裂最小。 我们 还采用分子生物学方法研究了CDC 2样 神经系统中的激酶，并已克隆和结构 其特征在于P34 cdc 2样激酶。 低严格性筛选 使用小鼠筛选大鼠脑cDNA文库 P34 cdc 2 cDNA作为探针。 鉴定了一个cDNA，命名为神经元cdc 2- 基于其与P34 cdc 2的序列相似性， 主要是神经元表达。

Neurofilament proteins (NFPs) are found exclusively in the nervous system and contain (especially in middle, NF-M and high, NF-H subunits) large numbers of serine phosphorylation sites. Multiple kinase systems are operative in phosphorylating these sites. Our initial aim is to identify these specific kinases in the nervous system. In this regard, we have characterized the following three different classes of second messenger- independent kinases from rat spinal cord which phosphorylate NFPs: 1) casein kinase I (CKI)-like activity appears to be associated with NF preparations isolated from rat spinal cord. CKI, purified from rat spinal cord, phosphorylates all three NF-subunits with a preference for NF-H. Casein kinase II (CKII), on the other hand, poorly phosphorylates NF-H but has higher affinity for NF-M and NF-L; 2) Microtubule-associated protein kinase (MAP kinase)-like activity, phosphorylates all three subunits. However, these kinases do not phosphorylate dephosphorylated NFs, nor a tandemly repeated sequence motif containing lys-ser-pro (KSP) present in NF-H and NF-M where these serine residues are extensively phosphorylated; 3) P34cdc2-like kinase (KSP) kinase): this kinase appears to phosphorylate some of the multiple repeats of KSP sequences present in NF-M and NF-H. The consensus sequence recognized by this kinase is XS/TPXK. The properties of this kinase show that it is closely related to P34cdc2 kinase which is known to be involved in the regulation of the cell cycle. This observation implies a different role for neuronal cdc2- like kinase in the nervous system where cell division is minimal. We have also taken a molecular biological approach to study the cdc2-like kinase in the nervous system and have cloned and structurally characterized a P34cdc2-like kinase. A low stringency screening procedure was used to screen a rat brain cDNA library using a mouse P34cdc2 cDNA as a probe. A cDNA was identified and named neuronal cdc2- like kinase (nclk) based on its sequence similarity to P34cdc2 and its predominantly neuronal expression.