Pascall John C, Brown Kenneth D
Signalling Programme, Babraham Institute, Babraham Hall, Cambridge CB2 4AT, UK.
Biochem Biophys Res Commun. 2004 Apr 23;317(1):244-52. doi: 10.1016/j.bbrc.2004.03.039.
Rhomboid-1 is a serine protease that cleaves the membrane domain of the Drosophila EGF-family protein, Spitz, to release a soluble growth factor. Several vertebrate rhomboid-like proteins have been identified, although their substrates and functions remain unknown. The human rhomboid, RHBDL2, cleaves the membrane domain of Drosophila Spitz when the proteins are co-expressed in mammalian cells. However, the membrane domains of several mammalian EGF-family proteins were not cleaved by RHBDL2, suggesting that the endogenous targets of the human protease are not EGF-related factors. We demonstrate that the amino acid sequence at the luminal face of the membrane domain of a substrate protein determines whether it is cleaved by RHBDL2. Based on this finding, we predicted B-type ephrins as potential RHBDL2 substrates. We found that one of these, ephrinB3, was cleaved so efficiently by the protease that little ephrinB3 was detected on the surface of cells co-expressing RHBDL2. These results raise the possibility that RHBDL2-mediated proteolytic processing may regulate intercellular interactions between ephrinB3 and eph receptors.
类菱形蛋白酶-1是一种丝氨酸蛋白酶，可切割果蝇表皮生长因子（EGF）家族蛋白“斯皮茨”（Spitz）的膜结构域，以释放可溶性生长因子。尽管其底物和功能尚不清楚，但已鉴定出几种脊椎动物类菱形蛋白酶样蛋白。当人类类菱形蛋白酶RHBDL2与果蝇Spitz在哺乳动物细胞中共表达时，它会切割果蝇Spitz的膜结构域。然而，几种哺乳动物EGF家族蛋白的膜结构域并未被RHBDL2切割，这表明该人类蛋白酶的内源性靶点不是EGF相关因子。我们证明，底物蛋白膜结构域腔面的氨基酸序列决定了它是否会被RHBDL2切割。基于这一发现，我们预测B型 Ephrin 蛋白是RHBDL2的潜在底物。我们发现，其中一种EphrinB3被该蛋白酶高效切割，以至于在共表达RHBDL2的细胞表面几乎检测不到EphrinB3。这些结果增加了一种可能性，即RHBDL2介导的蛋白水解过程可能调节EphrinB3与Eph受体之间的细胞间相互作用。
