Kikuchi Shota, Odashima Koki, Yasui Tadashi, Torii Seiji, Hosaka Masahiro, Gomi Hiroshi
Department of Veterinary Anatomy, College of Bioresource Sciences, Nihon University, Fujisawa, Japan.
Laboratory of Molecular Life Sciences, Department of Biotechnology, Akita Prefectural University, Akita, Japan.
J Histochem Cytochem. 2025 Jan-Feb;73(1-2):29-53. doi: 10.1369/00221554241311965. Epub 2025 Jan 10.
SummaryPrevious studies have suggested that chromogranin A (CgA) is a partner molecule of secretogranin III (SgIII). In mouse pituitary corticotroph-derived AtT-20 cells, SgIII plays a role in sorting CgA/hormone aggregates into secretory granules (SGs). Although CgA expression is equivocal, CgB is clearly detectable in the rat pituitary corticotrophs. Therefore, we hypothesized that CgB shares a function with CgA in pituitary corticotrophs. In the binding assays, CgB, similar to CgA, showed binding activity to SgIII under weakly acidic conditions and in the presence of Ca. Considering the differences in animal species, the different abilities of antibodies, and the conditions of tissue fixation and thin sectioning in immunofluorescence histochemistry, we found that CgA was expressed in a small population (approximately 10%), and its expression intensity was weaker than that of CgB (>98%) in rodent pituitary corticotrophs. In addition, similar to CgA, CgB and SgIII were colocalized in adrenocorticotropic hormone (ACTH) granules. The labeling of CgA and CgB was not completely consistent, and CgB colocalized with SgIII in many granules. These results suggest that there are multiple sorting systems for ACTH granules in pituitary corticotrophs and that the SgIII/CgB complex behaves more dominantly than the SgIII/CgA complex, which has somewhat different properties.
摘要
先前的研究表明，嗜铬粒蛋白A（CgA）是分泌粒蛋白III（SgIII）的伴侣分子。在小鼠垂体促肾上腺皮质激素细胞衍生的AtT-20细胞中，SgIII在将CgA/激素聚集体分选到分泌颗粒（SGs）中发挥作用。虽然CgA的表达不明确，但在大鼠垂体促肾上腺皮质激素细胞中可清楚检测到CgB。因此，我们推测CgB在垂体促肾上腺皮质激素细胞中与CgA具有共同功能。在结合试验中，与CgA相似，CgB在弱酸性条件下且存在Ca的情况下显示出与SgIII的结合活性。考虑到动物物种的差异、抗体的不同能力以及免疫荧光组织化学中组织固定和薄切片的条件，我们发现在啮齿动物垂体促肾上腺皮质激素细胞中，CgA在一小部分细胞（约10%）中表达，其表达强度弱于CgB（>98%）。此外，与CgA相似，CgB和SgIII共定位于促肾上腺皮质激素（ACTH）颗粒中。CgA和CgB的标记并不完全一致，并且CgB在许多颗粒中与SgIII共定位。这些结果表明，垂体促肾上腺皮质激素细胞中ACTH颗粒存在多种分选系统，并且SgIII/CgB复合物的行为比具有 somewhat不同特性的SgIII/CgA复合物更占主导地位。
