PTH SECRETORY PROTEIN-I PROCESSING & SECRETION

甲状旁腺及其荷尔蒙甲状旁腺激素(PTH)起着关键作用。 在钙离子动态平衡。最近甲状旁腺的第二种主要蛋白质 腺体已被识别，命名为分泌蛋白-I(SP-I)，其 与甲状旁腺激素一样，细胞的分泌也受到钙离子的密切调控。SP-I是 糖基化，分子量约70kD。它的化学成分是 类似于肾上腺髓质的主要蛋白质--嗜铬粒蛋白A(CGA) 这与嗜铬粒含量有关。它已被检测到 通过免疫学手段在包括甲状腺在内的其他几个内分泌细胞中 有降钙素的C细胞，有SRIF的胰岛和有垂体的 扶轮基金会。SP-I可能在血管内皮细胞的加工和/或分泌中发挥特定作用 在检测到它的那些细胞中的多肽激素。这 假说将在甲状旁腺中检验，通过关联 SP-I的合成、糖基化及其他共价修饰 甲状旁腺素的细胞内加工和分泌。我们将确定a)如果 与甲状旁腺素共存的“新”颗粒池中的SP-I在化学上有所不同 如果这样的差异可以解释 两种荷尔蒙池被差异化地引出的能力 分泌物；b)如果纯化的SP-I的蛋白分解活性 准备是与生俱来的，如果它参与了钙依赖 和非钙依赖性甲状旁腺素的细胞内降解；以及c)如果SP-I 对骨骼、肾脏和血管系统产生生理作用--这些组织 是PTH的目标。牛、猪和大鼠甲状旁腺将孵化成 不同的时间和条件(例如促分泌剂、高钙和低钙， 呼吸、蛋白质合成、糖基化的抑制剂)与 放射性氨基酸、糖、磷酸和脂肪酸标记甲状旁腺素和 SP-I在其处理的不同阶段。PTH、SP-I及相关 碎片将从介质、粗膜馏分和 纯化的分泌颗粒，并测定其数量、大小、结构、程度 糖基化等。在颗粒的情况下，插层 SP-I与颗粒膜，并可能突出通过，将是 测试，因为这可以解释PtH和SP-I在 多个分泌池。为了将这一概念扩展到其他 内分泌组织，我们将确定垂体腺的哪些颗粒 含有SP-I；如果SP-I是从大鼠胰岛细胞和 使用哪种激素；如果在这些和其他 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.