Physiological function of acylated proteins in salivary gland

近年来，受体的功能和各种细胞外信号的胞内传递机制已逐渐阐明，而与这种传递机制有关的独特蛋白质（酰化蛋白; AP）尚未见报道。因此，为了确定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，而且分析其脂肪酰基部分。萃取AP的结果表明，非离子去污剂，特别是Triton X-114，是非常有价值的使用相分离法。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，线粒体和微粒体膜组分中富含棕榈酸、肉豆蔻酸和硬脂酸。这种趋势在线粒体中比在微粒体中更强。由于膜蛋白的脂肪酸组成与先前观察到的膜磷脂的脂肪酸组成非常不同，因此分析了常见的酰基供体，即转化为酰基辅酶A的游离脂肪酸。这种脂肪酸组成与磷脂的脂肪酸组成相似，因此，提示酰化蛋白质的酶可能对酰基辅酶A具有非常严格的特异性。为了阐明AP在唾液腺中的生理功能，观察AP在刺激唾液分泌细胞中的蛋白质谱和脂肪酰基部分的变化是有效的。尽管使用苯乙醯胺和佛波醇酯（PMA）作为刺激物和放射性标记的脂肪酸对它们进行分析，但是在所使用的条件下，不仅膜结合蛋白质，而且它们的脂肪酸都没有观察到显著的改变。今后我们将进行实验以纯化AP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.