Study of New Roles in AMP Metabolism by Using Gene Modified Animals

AMP脱氨酶(AMPD)催化AMP转化为IMP，被认为在嘌呤代谢中起重要作用，但AMPD在体内的具体功能尚不清楚。因此，我们建立了针对每个AMPD基因的基因敲除小鼠，以阐明三个AMPD基因在体内的功能。此外，我们试图通过交配这些AMPD基因敲除的小鼠来制造AMPD联合缺乏症的模型小鼠。AMPD2基因敲除小鼠表现出肌肉特异性AMPD缺乏，骨骼肌AMP/ATP比值增加，肌肉中AMP激活的激酶磷酸化程度增加。AMPD2基因敲除小鼠出现蛋白尿，肾脏和肝脏AMPD活性降低。肝组织中AMP升高，磷酸化AMPK和ACC升高。AMPD3基因敲除小鼠的红细胞和心脏中的AMPD活性降低，红细胞中的ATP活性升高，但没有其他明显的表型。在AMPD复合缺陷方面，虽然建立了AMPD1/AMPD2双缺陷小鼠和AMPD1/AMPD3双缺陷小鼠，但发现AMPD2/AMPD3双缺陷小鼠在出生后3周内死亡。这些研究揭示了AMPD在肾脏和肝脏中的功能相关性。

AMP deaminase (AMPD) catalyzes AMP to IMP and is thought to play an important role in purine metabolism, though detailed function of AMPD in vivo has not been understood. Therefore, we established gene knock-out mice for each AMPD gene to elucidate in vivo function of three AMPD genes. Furthermore, we tried to produce model mice for combined AMPD deficiency by mating these AMPD knock-out mice. AMPD2 knockout mice showed muscle specific deficiency of AMPD and increased AMP/ATP ratio in skeletal muscle as well as more phophorylation of AMP-activated kinase in muscle. AMPD2 knockout mice exhibited proteinuria along with decreased AMPD activity in kidney and liver. Also, they showed increased AMP and increase of phophorylated AMPK and ACC in liver. AMPD3 knockout mice exhibited decreased AMPD acitivity in red cells and heart, and they showed increased ATP in red cells without other prominent phenotype. About combined AMPD deficiency, AMPD2/AMPD3 double deficient mice were found to die before 3 weeks after birth, though AMPD1/AMPD2 double deficient mice as well as AMPD1/AMPD3 double deficient mice were established. These studies revealed the functional relevance of AMPD in kidney as well as liver.