Lin L F, Kao L S, Westhead E W
Program in Molecular and Cellular Biology, University of Massachusetts, Amherst.
J Neurochem. 1994 Nov;63(5):1941-7. doi: 10.1046/j.1471-4159.1994.63051941.x.
The Na+/Ca2+ exchanger is an important element in the maintenance of calcium homeostasis in bovine chromaffin cells. The Na+/Ca2+ exchanger from other cell types has been extensively studied, but little is known about its regulation in the cell. We have investigated the role of reversible protein phosphorylation in the activity of the Na+/Ca2+ exchanger of these cells. Cells treated with 1 mM dibutyryl cyclic AMP (dbcAMP), 1 microM phorbol 12,13-dibutyrate, 1 microM okadaic acid, or 100 nM calyculin A showed lowered Na+/Ca2+ exchange activity and prolonged cytosolic Ca2+ transients caused by depolarization. A combination of 10 nM okadaic acid and 1 microM dbcAMP synergistically inhibited Na+/Ca2+ exchange activity. Conversely, 50 microM 1-(5-isoquinolinyl-sulfonyl)-2-methylpiperazine, a protein kinase inhibitor, enhanced Na+/Ca2+ exchange activity. Moreover, we used cyclic AMP-dependent protein kinase and calcium phospholipid-dependent protein kinase catalytic subunits to phosphorylate isolated membrane vesicles and found that the Na+/Ca2+ exchange activity was inhibited by this treatment. These results indicate that reversible protein phosphorylation modulates the activity of the Na+/Ca2+ exchanger and suggest that modulation of the exchanger may play a role in the regulation of secretion.
钠钙交换体是维持牛嗜铬细胞钙稳态的重要因素。来自其他细胞类型的钠钙交换体已得到广泛研究，但对其在细胞内的调节机制却知之甚少。我们研究了可逆性蛋白磷酸化在这些细胞钠钙交换体活性中的作用。用1 mM二丁酰环磷腺苷（dbcAMP）、1 μM佛波酯12,13 -二丁酸酯、1 μM冈田酸或100 nM花萼海绵诱癌素A处理的细胞，其钠钙交换活性降低，去极化引起的胞质钙瞬变延长。10 nM冈田酸和1 μM dbcAMP联合使用可协同抑制钠钙交换活性。相反，50 μM 1 -（5 -异喹啉磺酰基）- 2 -甲基哌嗪（一种蛋白激酶抑制剂）可增强钠钙交换活性。此外，我们使用环磷腺苷依赖性蛋白激酶和钙磷脂依赖性蛋白激酶催化亚基对分离的膜囊泡进行磷酸化，发现这种处理可抑制钠钙交换活性。这些结果表明，可逆性蛋白磷酸化调节钠钙交换体的活性，并提示交换体的调节可能在分泌调节中发挥作用。
