Nowroozi N, Kawata T, Liu P, Rice D, Zernik J H
Department of Orthodontics, School of Dentistry, University of Southern California, 925 W 34th St, Los Angeles, CA 90089-0641, USA.
Arch Otolaryngol Head Neck Surg. 2001 Nov;127(11):1381-4. doi: 10.1001/archotol.127.11.1381.
Ganglioside G(M1) is a membrane glycolipid typical of nerve cell membranes, where it partakes in neurotransmitter release and is catabolized by the lysosomal beta-galactosidase (GM1ase) (EC 3.2.1.23). After demonstrating a novel degenerative disease of the parotid gland in mice deficient in GM1ase, mimicking the human storage disease GM(1) gangliosidosis, we studied GM1ase and ganglioside G(M1) content in the human parotid glands.
Levels of GM1ase and ganglioside G(M1) were determined in samples of parotid tissues and neighboring muscle (as a negative control) for 3 subjects. Tissues were also processed for histochemical demonstration of GM1ase.
The mean specific activity of GM1ase was more than 6-fold higher in the healthy human parotid tissues (1.4 +/- 0.5 nmol of 4-methylumbelliferone per minute per milligram of protein) relative to the neighboring muscle tissue (0.23 +/- 0.07 nmol of 4-methylumbelliferone per minute per milligram of protein). Activity of GM1ase was histochemically localized mainly to striated duct and acinar cells of the parotid gland. Ganglioside G(M1) content in the parotid gland was on average 30-fold higher relative to muscle.
Our results are consistent with previous findings reported in the mouse and the rabbit, and probably reflect a general property of the mammalian parotid glands. The novel mechanism we previously proposed for the mouse parotid saliva secretion, mimicking neurotransmitter release in ganglioside G(M1)-containing nerve cells, is probably applicable also to the human parotid gland. Similarly, the human parotid gland is probably also severely affected in GM(1) gangliosidosis.
神经节苷脂G(M1)是神经细胞膜特有的一种膜糖脂，它参与神经递质释放，并由溶酶体β-半乳糖苷酶（GM1酶）（EC 3.2.1.23）进行分解代谢。在证实GM1酶缺陷的小鼠出现一种新型腮腺退行性疾病，类似于人类储存疾病GM(1)神经节苷脂贮积症后，我们研究了人腮腺中GM1酶和神经节苷脂G(M1)的含量。
测定了3名受试者腮腺组织和相邻肌肉（作为阴性对照）样本中GM1酶和神经节苷脂G(M1)的水平。组织还进行了GM1酶的组织化学检测。
健康人腮腺组织中GM1酶的平均比活性（每分钟每毫克蛋白质1.4±0.5 nmol 4-甲基伞形酮）比相邻肌肉组织（每分钟每毫克蛋白质0.23±0.07 nmol 4-甲基伞形酮）高6倍以上。GM1酶的活性在组织化学上主要定位于腮腺的纹状管和腺泡细胞。腮腺中神经节苷脂G(M1)的含量平均比肌肉高30倍。
我们的结果与之前在小鼠和兔子中报道的结果一致，可能反映了哺乳动物腮腺的一般特性。我们之前提出的模拟含神经节苷脂G(M1)的神经细胞中神经递质释放的小鼠腮腺唾液分泌新机制，可能也适用于人类腮腺。同样，GM(1)神经节苷脂贮积症可能也会严重影响人类腮腺。
