Guanidinoacetate methyltransferase in the mouse: extensive expression in Sertoli cells of testis and in microvilli of caput epididymis.
Guanidinoacetate methyltransferase in the mouse: extensive expression in Sertoli cells of testis and in microvilli of caput epididymis.
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DOI：
10.1095/biolreprod50.1.152
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发表时间：
1994
影响因子：
3.6
通讯作者：
Hang Lee;Hirofumi Ogawa;Motoji Fujioka;G. Gerton
中科院分区：
文献类型：
--
作者：
Hang Lee;Hirofumi Ogawa;Motoji Fujioka;G. Gerton
胍基乙酸甲基转移酶（GAMT）催化肌酸（Cr）生物合成途径的最后一步，即甲基从S-腺苷甲硫氨酸转移到胍基乙酸。尽管这种甲基化反应在细胞能量代谢和甲基代谢中的重要性，但缺乏对这种酶的表达和细胞定位的系统研究。作为一种手段，以确定为什么睾丸和精囊含有高水平的铬，我们分析了GAMT蛋白和mRNA水平在小鼠组织中的Western和北方印迹分析。结果表明，GAMT在组织特异性水平上受到调节;该酶在睾丸、附睾头、卵巢和肝脏中表达最高。性别之间也存在差异; GAMT mRNA和蛋白质水平在雌性肝脏中高于雄性肝脏。此外，随着雄性小鼠从新生期发育到性成熟，GAMT蛋白水平在睾丸中增加，但在肝脏中降低。免疫组织化学标记显示GAMT主要定位于睾丸支持细胞和附睾头上皮细胞的微绒毛中。通过对纯化的睾丸细胞、不同年龄青春期前小鼠的睾丸和生殖细胞缺陷突变小鼠睾丸的生化和分子分析，证实了支持细胞中GAMT的表达。这些结果表明，铬合成广泛的曲细精管和附睾头的上皮细胞，这表明GAMT或代谢途径相关的铬生物合成可能是重要的生殖细胞的发育或功能。
Guanidinoacetate methyltransferase (GAMT) catalyzes the last step of the biosynthetic pathway to creatine (Cr), the transfer of a methyl group from S-adenosylmethionine to guanidinoactate. Despite the importance of this methylation reaction in cellular energy metabolism and in methyl group metabolism, a systematic study of the expression and cellular localization of this enzyme is lacking. As a means for determining why the testis and seminal vesicles contain high levels of Cr, we analyzed GAMT protein and mRNA levels in mouse tissues by Western and Northern blot analyses. The results show that GAMT was regulated at tissue-specific levels; the enzyme was most highly expressed in testis, caput epididymis, ovary, and liver. Differences were also noted between sexes; the levels of GAMT mRNA and protein were higher in female liver than in male liver. Furthermore, as the male mouse developed from neonatal stages through sexual maturity, the GAMT protein level increased in testis but decreased in liver. Immunohistochemical labeling showed that GAMT was localized primarily in Sertoli cells of the testis and in microvilli of the epithelial cells lining the caput epididymis. GAMT expression in Sertoli cells was confirmed by biochemical and molecular analyses of purified testicular cells, testes from prepubertal mice of different ages, and germ cell-deficient mutant mouse testes. These results indicate that Cr is synthesized extensively in the epithelia of seminiferous tubules and caput epididymis, suggesting that GAMT or metabolic pathways related to Cr biosynthesis may be important for germ cell development or function.