HORMONAL REGULATION OF CELLULAR METABOLISM

蛋白质的磷酸化-去磷酸化是最重要的 调节细胞功能的机制。蛋白激酶C (PKC)，一种钙/磷脂依赖的蛋白激酶，已经成为一种 细胞生长、分化、基因的关键调控元件 表达、激素分泌、细胞表面受体功能和细胞 新陈代谢。这种蛋白激酶可以被二酰甘油激活，a 信号诱导的击穿产生的第二信使 磷脂酰肌醇。此外，它还被认为是一种受体。 诱导多效性反应的促肿瘤佛波醇酯 可与许多激素和生长因子刺激的细胞相媲美。三 已经从哺乳动物的脑中发现了同工酶形式的PKC。 制备了抗这些酶的多克隆抗体和单抗。 他们的免疫化学特征。这些酶被发现具有 不同的组织、细胞和亚细胞分布，并 在发育过程中表达的差异。PKC在调解中的作用 神经递质的作用通过培养神经元来研究。 文化。这些细胞在类似的生长调控下表达PKCII和III 形态与出生后大鼠完整的小脑相同。对人的刺激 用兴奋性氨基酸、谷氨酸或 佛波酯导致两种PKC与颗粒物的结合 然而，只有PKCII而不是PKCIII被发现与 膜骨架。细胞内PKC的膜结合是一种 激活的必备步骤。几种含肌醇的磷脂 被发现与PKC有很高的亲和力，特别是 中枢神经系统特异性PKCI。PKC与这些磷脂的相互作用使 与二酰甘油相近的酶，由酶的激活产生 磷脂酶C。这类磷脂可以作为锚定部位。 膜上PKC的表达。蛋白激酶C在基因表达调控中的激活 是通过研究转录因子的磷酸化来研究的， CCAAT/增强子结合蛋白(CEBP)，它含有一个亮氨酸重复序列 二聚界面和DNA结合的上游碱性区域。 截短形式的CEBP在两个Ser残基上的磷酸化 碱性区域会导致DNA结合的减弱。其中一个基因的突变 半胱氨酸的丝氨酸残基排除了PKC介导的反应，提示了一种作用 PKC在转录调控中的作用。PKC I基因的基因组结构为 分析的目的是定义组织特异性和 该激酶在发育过程中的表达。基因组片段 包含5‘侧翼区、第一外显子和第一内含子， 已经被分离和测序。几种潜在的转录因子 通过足迹分析确定了结合位点。

Phosphorylation-dephosphorylation of proteins is one of the most important mechanisms for the regulation of cellular functions. Protein kinase C (PKC), a Ca2+/phospholipid-dependent protein kinase, has emerged as a pivotal regulatory element for cell growth, differentiation, gene expression, hormone secretion, cell surface receptor function, and cellular metabolism. This protein kinase can be activated by diacylglycerol, a second messenger generated by signal-induced breakdown of phosphoinositides. In addition, it has been identified as a receptor for tumor-promoting phorbol esters which elicit pleiotropic responses comparable to those stimulated by many hormones and growth factors. Three isozymic forms of PKC have been identified from mammalian brains. Polyclonal and monoclonal antibodies against these enzymes were prepared for their immunochemical characterization. These enzymes were found to have distinct tissue, cellular, and subcellular distributions and were differentially expressed during development. The role of PKC in mediating the action of neurotransmitter was investigated with neurons grown in culture. These cells express PKCII and III in a similar growth-regulated pattern as in intact cerebella of postnatal rats. Stimulation of the cultured granule cells with the excitatory amino acid, glutamate, or phorbol ester causes the association of both PKCs with the particulate fraction; however, only PKCII, but not PKCIII, was found to associate with the membrane skeleton. Membrane association of PKC in the cell is an obligatory step for activation. Several inositol-containing phospholipids were found to interact with PKC with high affinity, in particular, the CNS-specific PKCI. Interaction of PKC with these phospholipids places the enzyme in close proximity to diacylglycerol generated by the activation of phospholipase C. This class of phospholipids may serve as anchoring sites of PKC at the membrane. Activation of PKC in the control of gene expression was investigated by studying the phosphorylation of a transcription factor, CCAAT/enhancer-binding protein (CEBP), which contains a leucine-repeat dimerization interface and an upstream basic region for DNA binding. Phosphorylation of a truncated form of CEBP at two Ser residues within the basic region results in attenuation of DNA binding. Mutation of one of the Ser residues to Cys obviates the PKC-mediated response, suggesting a role of PKC in transcriptional control. The genomic structure of PKC I gene was analyzed for the purpose of defining tissue-specific and development-regulated expression of this kinase. A genomic fragment containing the 5'-flanking region, the first exon, and the first intron, has been isolated and sequenced. Several potential transcriptional factor binding sites have been identified by footprint analysis.