Synthesis and Intracellular Transport of Common Antigens of Secretory Granule Membrane.

分别对大鼠和兔腮腺分泌颗粒膜产生单克隆抗体（mab）。单抗可识别位于具有n -连接碳水化合物的分泌颗粒管腔侧的整体膜糖蛋白：分子量；大鼠98 ~ 65kd，家兔55 ~ 65kd。免疫组织化学研究表明，在大鼠和家兔的外分泌细胞和内分泌细胞的分泌颗粒以及各种细胞的溶酶体中都发现了分泌颗粒膜抗原。这些结果表明，共同抗原存在于分泌颗粒膜。免疫金电镜显示，AR-42J大鼠胰腺肿瘤细胞和腮腺腺泡细胞的分泌颗粒、溶酶体、高尔基囊泡和凝聚液泡的膜上存在抗原；高尔基体无免疫反应。在家兔中，抗原仅沿腮腺腺泡细胞、外分泌胰腺细胞和腺垂体细胞的分泌颗粒膜定位。采用HRP标记的单抗，我们在AR42J细胞胞排后对抗原进行了检索。单抗通过抗原介导的内吞作用特异性内化。它被运输到核内体，随后进入反式高尔基网络，然后包装成分泌颗粒。然而，高尔基堆积显示没有摄取标记抗体。这些结果表明，分泌颗粒膜的共同抗原在胞吐后被重复使用，并提示抗原池可能存在于反式高尔基网络中。

Monoclonal antibodies (mAbs) were generated to the secretory granule membrane of rat and rabbit parotid gland, respectively. The mAbs recognized integral membrane glycoproteins localized on the luminal side of the secretory granules with N-linked carbohydrates : molecular weight ; 98-65 kD in the rat, 55-65 kD in the rabbit.Immunohistochemical studies indicated that both the secretory granule membrane antigens were found in the secretory granules of both exocrine and endocrine cells, and in the lysosomes of various cells in the rat and rabbit. These results indicated that common antigens are present in the secretory granule membranes. Immunoelectron microscopy with immunogold revealed that antigen was present on the membrane of the secretory granules, lysosomes, the Golgi vesicles and condensing vacuoles in pancreatic and parotid acinar cells and AR-42J rat pancreatic tumor cells ; the Golgi stacks exhibited no immunoreaction. In the rabbit, the antigen was localized exclusively along the membranes of secretory granules in the parotid acinar cells, exocrine pancreatic cells and adenohypophyseal cells.Employing HRP labeled mAb, we followed the retrieval of the antigen after exocytosis in AR42J cells. The mAb was internalized specifically with antigen-mediated endocytosis. It was transported to endosomes, subsequently to the trans-Golgi network, and then packaged into secretory granules. However, the Golgi stacks revealed no uptake of the labeled antibody. These results indicated that the common antigen of secretory granule memrane is reused after exocytosis, and suggested that the pool of the antigen might present in the trans-Golgi network.