Paizis K, Kirkland G, Polihronis M, Katerelos M, Kanellis J, Power D A
Department of Clinical Immunology, St. Vincent's Hospital, Fitzroy, Victoria, Australia.
Kidney Int. 1998 May;53(5):1162-71. doi: 10.1046/j.1523-1755.1998.00846.x.
Heparin-binding epidermal growth factor-like growth factor (HB-EGF) is a recently described member of the epidermal growth factor (EGF) family. It binds to heparan sulfate proteoglycans via a cationic domain and is a potent mitogen for epithelial cells, fibroblasts and vascular smooth muscle cells. In the present study we have attempted to identify changes in quantity and distribution of HB-EGF in two models of acute glomerular epithelial cell injury, using Western blotting, immunohistochemistry and in situ hybridization. Prior to disease induction, Western blots showed some expression of HB-EGF protein within glomeruli. Within the first three days in the acute puromycin aminonucleoside (PAN) and passive Heymann nephritis (PHN) models, immunohistochemistry and in situ hybridization demonstrated an up-regulation of HB-EGF mRNA and protein in glomerular epithelial cells (GEC). In both cases, increased protein and mRNA was found prior to the onset of proteinuria and continued until day 21 post-induction, the last time point studied. Early in the course of the models, HB-EGF was localized to the cytoplasm of glomerular epithelial cells. At day 21, however, HB-EGF protein was distributed in a nodular pattern within GEC and along the glomerular basement membrane (GBM) in both models, suggesting that the secreted form might bind to the membrane. The increase in HB-EGF protein within glomeruli was confirmed by Western blots of glomerular membrane protein which, however, demonstrated a single 29 kDa species, consistent with the transmembrane form. These data are not consistent with binding of the secreted form of HB-EGF to the GBM. The transmembrane form of HB-EGF is able to signal in a juxtracrine fashion, so increased expression of HB-EGF mRNA and protein by GEC might contribute to the genesis of proteinuria through the initiation of abortive GEC mitogenesis.
肝素结合表皮生长因子样生长因子（HB-EGF）是表皮生长因子（EGF）家族中最近被描述的成员。它通过一个阳离子结构域与硫酸乙酰肝素蛋白聚糖结合，是上皮细胞、成纤维细胞和血管平滑肌细胞的一种强效促有丝分裂原。在本研究中，我们试图通过蛋白质免疫印迹法、免疫组织化学和原位杂交技术，确定在两种急性肾小球上皮细胞损伤模型中HB-EGF的数量和分布变化。在疾病诱导之前，蛋白质免疫印迹显示肾小球内有一些HB-EGF蛋白表达。在急性嘌呤霉素氨基核苷（PAN）和被动型Heymann肾炎（PHN）模型的头三天内，免疫组织化学和原位杂交显示肾小球上皮细胞（GEC）中HB-EGF mRNA和蛋白上调。在这两种情况下，蛋白尿发作前就发现蛋白质和mRNA增加，并持续到诱导后第21天，即研究的最后一个时间点。在模型病程早期，HB-EGF定位于肾小球上皮细胞的细胞质中。然而，在第21天，两种模型中HB-EGF蛋白均以结节状分布于GEC内并沿着肾小球基底膜（GBM）分布，这表明分泌形式可能与膜结合。肾小球膜蛋白的蛋白质免疫印迹证实了肾小球内HB-EGF蛋白的增加，然而，其显示为单一的29 kDa条带，与跨膜形式一致。这些数据与HB-EGF的分泌形式与GBM结合不一致。HB-EGF的跨膜形式能够以旁分泌方式发出信号，因此GEC中HB-EGF mRNA和蛋白表达的增加可能通过引发流产性GEC有丝分裂而导致蛋白尿的发生。
