Han Ki-Hwan, Lee U-Young, Jang Yoon-Seong, Cho Yoon Mi, Jang Young Min, Hwang In-A, Ghee Jung Yeon, Lim Sun-Woo, Kim Wan-Young, Yang Chul Woo, Kim Jin, Kwon Oh-Joo
Department of Anatomy, College of Medicine, Ewha Womans University, Korea.
Am J Physiol Renal Physiol. 2007 Jan;292(1):F100-6. doi: 10.1152/ajprenal.00009.2006. Epub 2006 Aug 8.
Brain/kidney (B/K) protein is a novel double C2-like-domain protein that is highly expressed in rat brain and kidney, but its cellular localization and functional role in the kidney are still undetermined. We examined the cellular localization of B/K protein in the rat kidney under normal and ischemic conditions. Ischemia-reperfusion (I/R) injury was induced by clamping both renal arteries for 45 min, and animals were killed at 1 and 6 h and 1, 2, 3, 5, 7, 14, and 28 days after the reperfusion. Kidney tissues were processed for immunohistochemistry and immunoblot analyses using rabbit anti-B/K polyclonal antibodies. In control kidneys, B/K protein was expressed primarily in distal tubules including the thick ascending limb, distal convoluted and connecting tubules, and collecting duct. Notably, B/K protein was also expressed in the straight portion (S3 segment), but not in the S1 or S2, of proximal tubules, and podocytes of the glomerulus. In rat kidneys with I/R injury, expression of B/K protein was differentially regulated according to the anatomic location. In distal tubules, overall expression of B/K protein was markedly decreased. On the other hand, I/R injury significantly increased B/K protein expression in the S3 segment of the outer medulla as well as in the rat proximal tubular epithelial cell line NRK-52E in vitro. Furthermore, B/K protein was strongly expressed in many exfoliated cells in the lumen and urine. These findings suggest that B/K protein is closely associated with cell death in proximal tubules, which are vulnerable to I/R injury in the kidney.
脑/肾（B/K）蛋白是一种新型的双C2样结构域蛋白，在大鼠脑和肾中高表达，但其在肾脏中的细胞定位和功能作用仍未明确。我们研究了正常和缺血条件下大鼠肾脏中B/K蛋白的细胞定位。通过夹闭双侧肾动脉45分钟诱导缺血再灌注（I/R）损伤，在再灌注后1小时、6小时以及1天、2天、3天、5天、7天、14天和28天处死动物。使用兔抗B/K多克隆抗体对肾组织进行免疫组织化学和免疫印迹分析。在对照肾脏中，B/K蛋白主要表达于远端小管，包括髓袢升支粗段、远曲小管和连接小管以及集合管。值得注意的是，B/K蛋白也表达于近端小管的直部（S3段），但不表达于S1或S2段，以及肾小球的足细胞。在发生I/R损伤的大鼠肾脏中，B/K蛋白的表达根据解剖位置受到不同调节。在远端小管中，B/K蛋白的总体表达明显降低。另一方面，I/R损伤显著增加了外髓质S3段以及体外培养的大鼠近端肾小管上皮细胞系NRK-52E中B/K蛋白的表达。此外，B/K蛋白在管腔和尿液中的许多脱落细胞中强烈表达。这些发现表明，B/K蛋白与近端小管中的细胞死亡密切相关，近端小管在肾脏中易受I/R损伤。
