Physiological function of acylated proteins in salivary gland

近年来，受体的功能和各种细胞外信号在细胞内传递的机制逐渐被阐明，目前还没有报道有一种独特的蛋白质(酰化蛋白；AP)与这种传递机制有关。因此，为了明确AP的生理意义，我们试图以大鼠唾液腺为模型细胞，不仅分析AP的蛋白质，还分析其脂肪酰基部分。对AP的萃取结果表明，非离子洗涤剂，特别是Triton X-114，在相分离方法中是非常有价值的。对大鼠腮腺膜结合蛋白的脂肪酸组成进行了分析，结果表明，棕榈酸、肉豆蔻酸和硬脂酸在线粒体和微米体膜部分中含量丰富。这种趋势在线粒体中比在微生物体中更强。由于膜蛋白的脂肪酸组成与以前观察到的膜磷脂的脂肪酸组成有很大的不同，因此分析了常见的酰基供体--转化为酰基-COAs的游离脂肪酸。这一脂肪酸组成与磷脂相似，因此，该酶对酰基辅酶A可能具有很强的粘附性。为了阐明唾液腺对AP的生理作用，观察唾液分泌刺激细胞中AP的蛋白质模式和脂肪酰基的变化是有效的。尽管用苯肾上腺素和佛波酯(PMA)刺激和放射性标记的脂肪酸进行了分析，但在所使用的条件下，不仅膜结合蛋白和脂肪酸没有显著变化。在今后的实验中，我们将对AP进行纯化，并阐明其生化和生理特性。

Recently, the mechanisms for receptor's function and intracellular transmission of various extracellular signals have been gradually clarified and it is no reported that the unique protein (acylated protein; AP) is related to this transmission mechanism. Therefore, in order to define the physiological significance of AP, we tried to analyze not only AP's protein but also its fatty acyl moiety using rat salivary gland as a model cell. The obtained results for the extraction of AP suggest AP that non-ionic detergent, especially Triton X-114, is very valuable using the phase separation method. The composition of fatty acids in membrane-bound proteins from rat parotid gland were analyzed and it was shown that palmitic, myristic and stearic acids were rich in mitochondrial and microsomal membrane fractions. This tendency was stronger in mitochondria than in microsomes. Since the fatty acid composition of membrane proteins was very different from that of membrane phospholipids which was observed previously, the common acyl donors, free fatty acids converted to acyl-CoAs, were analyzed. This fatty acid composition was similar to that of phospholipids and therefore, it is suggested that the enzyme to acylate protein may have very stict specificity for acyl-CoA. in order to clarify the physiological function of AP using salivary gland, it is effective to observe the changes of AP's protein pattern and fatty acyl moiety in the stimulated cells for saliva secretion. although they were analyzed suing phenylephrine and phorbol ester(PMA) for stimuli and radio-labeled fatty acids, the significant alterations in not only membranebound proteins, hoever, but also their fatty acids were not observed under the conditions used. In future, we will experiment to purify AP and clarify its biochemical and physiological characteristics.