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Abstract：
Transglutaminase 2 (TGase2) has been shown to contribute to the mesangial IgA1 deposition in a humanized mouse model of IgA nephropathy (IgAN), but the mechanism is not fully understood. In this study, we found that inhibition of TGase2 activity could dramatically decrease the amount of polymeric IgA1 (pIgA1) isolated from patients with IgAN that interacts with human mesangial cells (HMC). TGase2 was expressed both in the cytosol and on the membrane of HMC. Upon treatment with pIgA1, there were more TGase2 recruited to the membrane. Using a cell model of mesangial deposition of pIgA1, we identified 253 potential TGase2-associated proteins in the cytosolic fraction and observed a higher concentration of cellular vesicles and increased expression of Ras homolog family member A (RhoA) in HMC after pIgA1 stimulation. Both the amount of pIgA1 deposited on HMC and membrane TGase2 level were decreased by inhibition of the vesicle trafficking pathway. Mechanistically, TGase2 was found to be coprecipitated with RhoA in the cellular vesicles. Membrane TGase2 expression was greatly increased by overexpression of RhoA, while it was reduced by knockdown of RhoA. Our in vitro approach demonstrated that TGase2 was transported from the cytosol to the membrane through a RhoA-mediated vesicle-trafficking pathway that can facilitate pIgA1 interaction with mesangium in IgAN.
摘要：
转谷氨酰胺酶2（TGase2）已被证明有助于IgA肾病（IgAN）的人源化小鼠模型中的系膜IgA1沉积，但机制还不完全清楚。在这项研究中,我们发现抑制TGase2活性可以显著降低从IgAN患者中分离出的与人肾小球系膜细胞(HMC)相互作用的多聚IgA1(pIgA1)的量.TGase2在HMC的胞质溶胶和膜上均有表达。在用pIgA1处理后,有更多的TGase2募集到膜。使用pIgA1系膜沉积的细胞模型，我们在胞质部分中鉴定了253种潜在的TGase2相关蛋白，并观察到pIgA1刺激后HMC中更高浓度的细胞囊泡和Ras同源家族成员A（RhoA）的表达增加。通过抑制囊泡运输途径，沉积在HMC上的pIgA1量和膜TGase2水平均降低。机械上,发现TGase2在细胞囊泡中与RhoA共沉淀。膜TGase2表达通过RhoA的过表达而大大增加,虽然它被击倒了RhoA。我们的体外方法表明，TGase2通过RhoA介导的囊泡运输途径从细胞质转运到膜，该途径可以促进IgAN中pIgA1与系膜的相互作用。
