Wiest D L, Burkhardt J K, Hester S, Hortsch M, Meyer D I, Argon Y
Department of Microbiology and Immunology, Duke University Medical Center, Durham, North Carolina 27710.
J Cell Biol. 1990 May;110(5):1501-11. doi: 10.1083/jcb.110.5.1501.
The induction of high-rate protein secretion entails increased biogenesis of secretory apparatus organelles. We examined the biogenesis of the secretory apparatus in the B cell line CH12 because it can be induced in vitro to secrete immunoglobulin (Ig). Upon stimulation with lipopolysaccharide (LPS), CH12 cells increased secretion of IgM 12-fold. This induced secretion was accompanied by preferential expansion of the ER and the Golgi complex. Three parameters of the rough ER changed: its area and volume increased 3.3- and 3.7-fold, respectively, and the density of membrane-bound ribosomes increased 3.5-fold. Similarly, the area of the Golgi stack increased 3.3-fold, and its volume increased 4.1-fold. These changes provide sufficient biosynthetic capacity to account for the increased secretory activity of CH12. Despite the large increase in IgM synthesis, and because of the expansion of the ER, the concentration of IgM within the ER changed less than twofold during the differentiation process. During the amplification of the rough ER, the expression of resident proteins changed according to one of two patterns. The majority (75%) of rough microsomal (RM) proteins increased in proportion to the increase in rough ER size. Included in this group were both lumenal proteins such as Ig binding protein (BiP), and membrane proteins such as ribophorins I and II. In addition, the expression of a minority (approximately 9%) of RM polypeptides increased preferentially, such that their abundance within the RM of secreting CH12 cells was increased. Thus, the expansion of ER during CH12 differentiation involves preferential increases in the abundance of a few resident proteins, superimposed upon proportional increases in most ER proteins.
高速率蛋白质分泌的诱导需要分泌细胞器生物合成的增加。我们研究了B细胞系CH12中分泌细胞器的生物合成，因为它可以在体外被诱导分泌免疫球蛋白（Ig）。在用脂多糖（LPS）刺激后，CH12细胞的IgM分泌增加了12倍。这种诱导分泌伴随着内质网（ER）和高尔基体复合体的优先扩张。粗面内质网的三个参数发生了变化：其面积和体积分别增加了3.3倍和3.7倍，膜结合核糖体的密度增加了3.5倍。同样，高尔基体堆叠的面积增加了3.3倍，其体积增加了4.1倍。这些变化提供了足够的生物合成能力来解释CH12分泌活性的增加。尽管IgM合成大幅增加，并且由于内质网的扩张，内质网内IgM的浓度在分化过程中变化不到两倍。在粗面内质网扩增过程中，驻留蛋白的表达根据两种模式之一发生变化。大多数（75%）的粗面微粒体（RM）蛋白与粗面内质网大小的增加成比例增加。这一组包括腔内蛋白如Ig结合蛋白（BiP）和膜蛋白如核糖体结合蛋白I和II。此外，少数（约9%）RM多肽的表达优先增加，使得它们在分泌性CH12细胞的RM中的丰度增加。因此，CH12分化过程中内质网的扩张涉及少数驻留蛋白丰度的优先增加，叠加在大多数内质网蛋白的成比例增加之上。
