Chaudhry A, Granneman J G
Center for Cell Biology, Sinai Research Institute, Detroit, MI 48235.
Metabolism. 1991 Apr;40(4):432-7. doi: 10.1016/0026-0495(91)90156-q.
The subcellular distribution of Gs alpha (the alpha-subunit of guanine nucleotide-binding stimulatory protein of adenylyl cyclase) was examined in interscapular brown adipose tissue (IBAT) to determine (1) if Gs alpha is completely colocalized with adenylyl cyclase in the plasma membrane, and (2) whether cold exposure, which increases adenylyl cyclase activity, changes the subcellular distribution of Gs alpha. Subcellular fractions were prepared from IBAT by differential centrifugation and analyzed for Gs alpha by immunoblotting. Adenylyl cyclase activity and Gs alpha were detected in all the subcellular fractions except the cytosol. The plasma membrane fraction showed the greatest enrichment of adenylyl cyclase and Gs alpha. However, the enrichment of adenylyl cyclase in the plasma membrane fraction was greater than that for Gs alpha, which was also associated to a large degree with the mitochondrial fraction. Thus, compared with the mitochondrial fraction, both 5' nucleotidase and adenylyl cyclase were enriched by over 200% in the plasma membrane fraction, but Gs alpha was enriched by only 50%. Exposure of rats to 4 degrees C for 3 days increased fluoride-stimulated adenylyl cyclase activity, but did not increase the amount of immunoreactive Gs alpha in any of the subcellular fractions examined. The above results demonstrate that not all Gs alpha in IBAT is colocalized with adenylyl cyclase in the plasma membrane. The finding that cold exposure did not change the subcellular distribution of Gs alpha indicates that the cold-induced increase in adenylyl cyclase activity is not due to translocation of Gs alpha from subcellular compartments to the plasma membrane.
研究了Gsα（腺苷酸环化酶的鸟嘌呤核苷酸结合刺激蛋白的α亚基）在肩胛间棕色脂肪组织（IBAT）中的亚细胞分布，以确定：（1）Gsα是否与腺苷酸环化酶在质膜上完全共定位；（2）增加腺苷酸环化酶活性的冷暴露是否会改变Gsα的亚细胞分布。通过差速离心从IBAT制备亚细胞组分，并通过免疫印迹分析Gsα。除细胞质外，在所有亚细胞组分中均检测到腺苷酸环化酶活性和Gsα。质膜组分显示腺苷酸环化酶和Gsα的富集程度最高。然而，质膜组分中腺苷酸环化酶的富集程度高于Gsα，Gsα在很大程度上也与线粒体组分相关。因此，与线粒体组分相比，质膜组分中5'核苷酸酶和腺苷酸环化酶的富集程度均超过200%，但Gsα仅富集50%。将大鼠暴露于4℃3天可增加氟化物刺激的腺苷酸环化酶活性，但在所检测的任何亚细胞组分中均未增加免疫反应性Gsα的量。上述结果表明，IBAT中的并非所有Gsα都与质膜中的腺苷酸环化酶共定位。冷暴露未改变Gsα的亚细胞分布这一发现表明，冷诱导的腺苷酸环化酶活性增加并非由于Gsα从亚细胞区室转运至质膜所致。
