Everett A D, Xue C, Stoops T
Department of Pediatrics, University of Virginia Health Sciences Center, Charlottesville 22908, USA.
J Am Soc Nephrol. 1999 Aug;10(8):1737-45. doi: 10.1681/ASN.V1081737.
Although a number of growth and transcription factors are known to regulate renal growth and development, the signal transduction molecules necessary to mediate these developmental signals are relatively unknown. Therefore, the activity and mRNA and protein expression of the signal transduction molecule protein phosphatase 2A (PP2A) were examined during rat kidney development. Northern analysis of total kidney RNA or Western analysis of kidney protein homogenates from embryonic day 15 to 90-d-old adults demonstrated developmental regulation of the catalytic, major 55-kD B regulatory subunit and A structural subunit with the highest levels of expression in late embryonic and newborn kidneys. Similarly, okadaic acid-inhibitable phosphatase enzyme activity was highest in the embryonic and newborn kidney. To map cell-specific expression of PP2A in the developing kidney, in situ hybridization with a catalytic subunit digoxigenin-labeled cRNA was performed on embryonic day 20 and newborn kidneys. PP2A was found predominately in the nephrogenic cortex and particularly in the developing glomeruli and non-brush border tubules in the embryonic day 20 and newborn kidneys. Similarly, immunocytochemistry with a specific PP2A catalytic subunit polyclonal anti-peptide antibody demonstrated catalytic subunit protein particularly concentrated in the podocytes of glomeruli in the newborn kidney. In the adult kidney, PP2A protein was no longer detectable except in the nuclei of distal tubular cells. Therefore, the developmental regulation of PP2A activity and protein during kidney development and its mapping to the nephrogenic cortex, developing glomeruli, and tubules suggests a role for PP2A in the regulation of nephron growth and differentiation.
尽管已知多种生长和转录因子可调节肾脏的生长和发育，但介导这些发育信号所需的信号转导分子相对尚不明确。因此，我们检测了信号转导分子蛋白磷酸酶2A（PP2A）在大鼠肾脏发育过程中的活性以及mRNA和蛋白质表达。对胚胎第15天至90日龄成年大鼠的肾脏总RNA进行Northern分析，或对肾脏蛋白质匀浆进行Western分析，结果表明催化性、主要的55-kD B调节亚基和A结构亚基在发育过程中受到调控，在胚胎后期和新生肾脏中的表达水平最高。同样，冈田酸抑制的磷酸酶活性在胚胎和新生肾脏中最高。为了绘制PP2A在发育中肾脏的细胞特异性表达图谱，我们在胚胎第20天和新生肾脏上进行了与催化亚基地高辛标记cRNA的原位杂交。在胚胎第20天和新生肾脏中，PP2A主要存在于肾皮质，特别是在发育中的肾小球和无刷状缘的肾小管中。同样，用特异性PP2A催化亚基多克隆抗肽抗体进行免疫细胞化学检测显示，催化亚基蛋白在新生肾脏的肾小球足细胞中尤其集中。在成年肾脏中，除了远端肾小管细胞的细胞核外，不再能检测到PP2A蛋白。因此，PP2A活性和蛋白质在肾脏发育过程中的发育调控及其在肾皮质、发育中的肾小球和肾小管中的定位表明，PP2A在肾单位生长和分化的调节中发挥作用。
