PTH SECRETORY PROTEIN-I PROCESSING & SECRETION

甲状旁腺及其激素甲状旁腺素（PTH）起着关键作用 Ca++稳态。 最近，甲状旁腺的第二种主要蛋白质 分泌蛋白-I（Secretory Protein-I，SP-I）是一种分泌蛋白， 与PTH一样，PTH的分泌受Ca++的密切调节。 SP-I是 糖基化的并且具有约70 kD的分子量。 它是化学 类似于嗜铬粒蛋白A（CGA）-肾上腺髓质的主要蛋白质 与嗜铬颗粒内容物共同分泌。 已经检测 通过免疫学手段在其他几种内分泌细胞中，包括甲状腺， C细胞与降钙素、胰岛与SRIF和垂体与 扶轮基金会。 SP-I可能在蛋白质的加工和/或分泌中发挥特定作用， 在那些检测到它的细胞中的肽激素。 这 假设将在甲状旁腺中进行检验， 合成、糖基化和其他共价修饰 细胞内加工和分泌PTH。 我们将确定a）如果 与PTH共存于“新”颗粒池中的SP-I在化学上不同， 与“成熟”颗粒池中的差异，如果这种差异可以解释 对于两种激素库的能力， B）如果在纯化的细胞中观察到SP-I的蛋白水解活性， 准备是固有的，如果它参与钙依赖性 和PTH的钙非依赖性细胞内降解;和c）如果SP-I 对骨骼、肾脏和脉管系统--这些组织 是PTH的目标。 牛、猪和大鼠甲状旁腺将孵育 各种时间和条件（例如，促分泌素，高钙和低钙， 呼吸、蛋白质合成、糖基化的抑制剂）， 放射性氨基酸、糖、磷酸盐和脂肪酸来标记PTH， SP-I在其处理的各个阶段。 PTH、SP-I及相关 将从培养基、粗膜级分中分离片段， 纯化分泌颗粒并测定其数量、大小、结构、程度 在颗粒的情况下， SP-I与颗粒膜，并可能通过颗粒膜突出， 测试，因为这可以解释PTH和SP-I的“编码”， 多个分泌池。 为了将这一概念推广到其他领域， 内分泌组织，我们将确定哪些颗粒的垂体 含有SP-I;如果SP-I由大鼠胰岛细胞共分泌， 与激素;如果免疫活性SP-I检测在这些和其他 内分泌组织在物理上等同于SP-I和CGA。

The parathyroid gland and its hormone, parathormone (PTH), play a key role in Ca++ homeostasis. Recently a second major protein of the parathyroid gland has been recognized, named secretory protein-I (SP-I), whose secretion, as that of PTH, is closely regulated by Ca++. SP-I is glycosylated and has a molecular weight of about 70 kD. It is chemically similar to chromogranin A (CGA)--a major protein of the adrenal medulla that is cosecreted with chromaffin granule contents. It has been detected by immunological means in several other endocrine cells including thyroid C-cells with calcitonin, pancreatic islets with SRIF and pituitary with TRF. SP-I may play a specific role in the processing and/or secretion of peptide hormones in those cells in which it has been detected. This hypothesis will be tested in the parathyroid gland by correlating the synthesis, glycosylation and other covalent modifications to SP-I with the intracellular processing and secretion of PTH. We will determine a) if the SP-I that coexists with PTH in the "new" granule pool differs chemically from that in the "mature" granule pool and if such a difference can account for the ability of the two hormone pools to be differentially elicited for secretion; b) if the proteolytic activity of SP-I noted in purified preparations is inherent, and if it participates in the calcium-dependent and calcium-independent intracellular degradation of PTH; and c), if SP-I exerts a physiological action on bone, kidney and vasculature--tissues that are targets of PTH. Cow, pig and rat parathyroids will be incubated for various times and conditions (e.g., secretagogues, high and low calcium, inhibitors of respiration, protein synthesis, glycosylation) with radioactive amino acids, sugars, phosphate and fatty acids to label PTH and SP-I at various stages of their processing. PTH, SP-I and related fragments will be isolated from medium, crude membrane fractions and purified secretory granules and assayed for amount, size, structure, degree of glycosylation, etc. In the case of the granules, the intercalation of SP-I with, and possible protrusion through, the granule membrane will be tested since this could account for the "coding" of the PTH and SP-I in multiple secretory pools. In order to extend this concept to other endocrine tissues, we will determine which granules of the pituitary contain SP-I; if SP-I is cosecreted from rat pancreatic islet cells and with which hormones; and if immunoactive SP-I detected in these and other endocrine tissues is physically equivalent to SP-I and CGA.