Sivakamasundari P, Kalaiselvi P, Sakthivel R, Selvam R, Varalakshmi P
Department of Medical Biochemistry, University of Madras, Taramani, Chennai-113, India.
Clin Chim Acta. 2004 Sep;347(1-2):111-9. doi: 10.1016/j.cccn.2004.04.008.
Urolithiasis is a multifactorial process that starts with the formation of microcrystals in the urine and terminates as mature renal calculi. The oxalate binding protein plays a vital role in the transport of oxalate. The physiological significance of the presence of oxalate binding protein in the nuclear pore complex is not well understood.
The nuclear envelope was extracted from human cadaver kidneys. 14C oxalate was labeled, nuclear pore complex proteins were extracted and loaded onto Sephadex G-200, and further purified in DEAE-Sephadex A-50 column. The radioactive protein peak was pooled, concentrated and checked for purity in SDS-PAGE. The purified protein showed cross-reactivity with the monoclonal antibody (MAb 414) and was homogeneous. Urine samples of healthy individuals with no history of kidney disease served as control. Blood and urine samples were collected from kidney and autoimmune disorder patients and checked for the expression of p62 protein by ELISA.
Extracted and purified nuclear pore complex oxalate binding protein had a molecular weight of 62 kDa. A threefold increase in oxalate excretion was observed in hyperoxaluric patients compared to control subjects. The protein expression was found to be higher in hyperoxaluric patients vs. controls, chronic renal failure (CRF) and acute renal failure (ARF), whereas decreased expression was observed in nephrotic syndrome (NS) patients. p62 autoantibodies was observed in hyperoxaluria (HO), systemic lupus erythematosus (SLE) and primary biliary cirrhosis (PBC), whereas it was absent in controls.
Increased expression of p62 may be due to membrane damage induced by oxalate stress, and may be used as a diagnostic marker. This study also confirms the presence of p62 autoantibodies in HO patients.
尿路结石是一个多因素过程，始于尿液中微晶的形成，最终形成成熟的肾结石。草酸结合蛋白在草酸转运中起重要作用。核孔复合物中存在草酸结合蛋白的生理意义尚不清楚。
从人尸体肾脏中提取核膜。用14C标记草酸，提取核孔复合物蛋白并加载到Sephadex G - 200上，然后在DEAE - Sephadex A - 50柱上进一步纯化。收集放射性蛋白峰，浓缩并在SDS - PAGE中检查纯度。纯化后的蛋白与单克隆抗体（MAb 414）显示交叉反应且均一。无肾脏疾病史的健康个体的尿液样本作为对照。从肾脏和自身免疫性疾病患者中采集血液和尿液样本，通过ELISA检测p62蛋白的表达。
提取并纯化的核孔复合物草酸结合蛋白分子量为62 kDa。与对照受试者相比，高草酸尿症患者的草酸排泄量增加了三倍。发现高草酸尿症患者的蛋白表达高于对照组、慢性肾衰竭（CRF）和急性肾衰竭（ARF）患者，而肾病综合征（NS）患者的表达降低。在高草酸尿症（HO）、系统性红斑狼疮（SLE）和原发性胆汁性肝硬化（PBC）患者中观察到p62自身抗体，而在对照组中未观察到。
p62表达增加可能是由于草酸应激诱导的膜损伤，可作为诊断标志物。本研究还证实了HO患者中存在p62自身抗体。
