Trichosporin-B-III, an alpha-aminoisobutyric acid-containing peptide, causes Ca(2+)-dependent catecholamine secretion from adrenal medullary chromaffin cells.
Trichosporin-B-III, an alpha-aminoisobutyric acid-containing peptide, causes Ca(2+)-dependent catecholamine secretion from adrenal medullary chromaffin cells.
复制标题
Trichosporin-B-III 是一种含有 α-氨基异丁酸的肽，可导致肾上腺髓质嗜铬细胞分泌 Ca(2) 依赖性儿茶酚胺。
作者：
E. Tachikawa;S. Takahashi;K. Furumachi;T. Kashimoto;A. Iida;Y. Nagaoka;T. Fujita;Y. Takaishi
我们研究了丝孢菌素-B-III，一种α-氨基异丁酸的抗生素肽，由19个氨基酸残基和苯丙氨酸组成，对培养的牛肾上腺嗜铬细胞分泌儿茶酚胺的影响。用丝孢菌素-B-III（3-20 μ M）孵育细胞引起儿茶酚胺分泌的增加。在低浓度（3和5 μ M）的丝孢菌素-B-III诱导的分泌是完全依赖于外部的Ca 2+，而较高浓度（10和20 μ M）诱导的部分是独立的Ca 2+。低浓度（5 μ M）的丝孢菌素-B-III不增加乳酸脱氢酶（细胞质的标记酶）从细胞中的释放。相反，较高浓度（10 μ M）的肽增加了酶的释放。Trichosporin-B-III还引起细胞内~（45）Ca ~（2+）内流和细胞内游离Ca ~（2+）浓度的增加。儿茶酚胺分泌和45 Ca 2+内流的增加与丝孢菌素-B-III浓度（3-10 μ M）的关系相似。毛孢菌素-B-Ⅲ引起的分泌、~（45）Ca ~（2+）内流和细胞内游离Ca ~（2+）浓度增加的时间过程也非常相似。丝孢菌素-B-III诱导的分泌（在5 μ M）不受Na+从孵育介质中消除或添加河豚毒素，高选择性电压依赖性Na+通道的阻滞剂，或六甲双铵，烟碱乙酰胆碱受体的阻滞剂的影响。另一方面，电压依赖性Ca 2+通道阻断剂地尔硫卓（2-200 μ M）和尼卡地平（1-200 μ M）均以浓度依赖性方式抑制丝孢菌素-B-III（5 μ M）诱导的分泌。丝孢菌素-B-III诱导的（在5 μ M）分泌也被抑制的Mn 2+（5 mM）的培养基中添加。地尔硫卓（20 μ M）对丝孢菌素-B-III诱导的（5 μ M）分泌的抑制作用可通过增加外部Ca 2+浓度来逆转。这些结果表明，毛孢菌素-B-III导致牛肾上腺嗜铬细胞分泌的儿茶酚胺通过两种机制，钙离子依赖性和钙离子非依赖性（仅在高浓度的毛孢菌素-B-III）。此外，这些结果有力地表明，丝孢菌素-B-III，在Ca（2+）依赖性分泌，激活内源性电压依赖性Ca（2+）通道，或本身在膜上形成的通道，并诱导Ca（2+）流入细胞。
We examined the effect of trichosporin-B-III, an alpha-aminoisobutyric acid-containing antibiotic peptide consisting of 19 amino acid residues and a phenylalaninol, on catecholamine secretion from cultured bovine adrenal chromaffin cells. Incubation of the cells with trichosporin-B-III (3-20 microM) caused an increase in the secretion of catecholamines. The secretion induced by trichosporin-B-III at low concentrations (3 and 5 microM) was completely dependent on external Ca2+, whereas that induced by higher concentrations (10 and 20 microM) was partly independent of Ca2+. Trichosporin-B-III at low concentration (5 microM) did not increase the release of lactate dehydrogenase, a marker enzyme of cytoplasm, from the cells. In contrast, the peptide at higher concentration (10 microM) increased the release of the enzyme. Trichosporin-B-III also caused both 45Ca2+ influx into the cells and an increase in the intracellular free Ca2+ concentration. The increases in catecholamine secretion and 45Ca2+ influx behaved similarly in relation to trichosporin-B-III concentration (3-10 microM). The time courses of the increases in secretion, 45Ca2+ influx, and intracellular free Ca2+ concentration induced by trichosporin-B-III were also quite similar. Trichosporin-B-III-induced (at 5 microM) secretion was not affected by the elimination of Na+ from the incubation medium or by the addition of tetrodotoxin, a blocker of highly selective voltage-dependent Na+ channels, or hexamethonium, a blocker of nicotinic acetylcholine receptors. On the other hand, both diltiazem (2-200 microM) and nicardipine (1-200 microM), blockers of voltage-dependent Ca2+ channels, inhibited the secretion induced by trichosporin-B-III (5 microM) in a concentration-dependent manner. Trichosporin-B-III-induced (at 5 microM) secretion also was suppressed by the addition of Mn2+ (5 mM) to the medium. The diltiazem (20 microM) inhibition of trichosporin-B-III-induced (at 5 microM) secretion was reversed by increasing the external Ca2+ concentration. These results indicate that trichosporin-B-III causes the secretion of catecholamines from bovine adrenal chromaffin cells by two mechanisms, Ca2+ dependent and Ca2+ independent (only at high concentrations of trichosporin-B-III). Furthermore, these results strongly suggest that trichosporin-B-III, in Ca(2+)-dependent secretion, activates endogenous voltage-dependent Ca2+ channels, or itself forms the channels in the membranes, and induces Ca2+ influx into the cells.