Selbi Wisam, Day Anthony J, Rugg Marilyn S, Fülöp Csaba, de la Motte Carol A, Bowen Timothy, Hascall Vincent C, Phillips Aled O
Institute of Nephrology, University of Cardiff School of Medicine, Heath Park, Cardiff, Wales, CF14 4XN, UK.
J Am Soc Nephrol. 2006 Jun;17(6):1553-67. doi: 10.1681/ASN.2005080879. Epub 2006 May 10.
The functional consequences of increased renal cortical hyaluronan that is associated with both acute injury and progressive scarring are unclear. The aim of this study was to characterize hyaluronan synthase-2 (HAS2)-driven HA synthesis and determine its effect on renal proximal tubular epithelial cell (PTC) function, because this is known to be the inducible form of HA synthase in this cell type. Overexpression of HAS2 mRNA increased HA generation, which in the supernatant predominantly was HA of large molecular weight, whereas there was an increase in low molecular weight HA in cell-associated fractions. This was associated with increased expression of hyaluronidases, inhibition of HA cable formation concurrent with reduction in HA-dependent monocyte binding, and increased pericellular HA matrix. Overexpression of HAS2 led to enhanced cell migration. HA can be modified by the covalent attachment of heavy chains that are derived from the serum protein inter-alpha-inhibitor (IalphaI), a process that is known to be catalyzed by TNF-alpha-stimulated gene 6 (TSG-6; an inflammation-associated protein). Enhanced migration was abrogated by blocking antibodies to either IalphaI or TSG-6. Addition of recombinant full-length TSG-6 (TSG-6Q) or TSG-6Q_Y94F, a mutant variant with impaired HA binding, increased cell migration. Both of these proteins were able to mediate the covalent transfer of heavy chains, from IalphaI and pre-alpha-inhibitor, onto HA. Addition of the isolated TSG-6-Link module (Link_TSG-6), which binds HA but is unable to form covalent complexes with IalphaI/pre-alpha-inhibitor, had no effect on migration, suggesting that TSG-6-mediated formation of heavy chain-HA complexes is critical in the formation of a pericellular HA matrix.
与急性损伤和进行性瘢痕形成相关的肾皮质透明质酸增加的功能后果尚不清楚。本研究的目的是表征透明质酸合酶-2（HAS2）驱动的HA合成，并确定其对肾近端小管上皮细胞（PTC）功能的影响，因为已知这是该细胞类型中HA合酶的可诱导形式。HAS2 mRNA的过表达增加了HA的生成，在上清液中主要是高分子量的HA，而在细胞相关部分中低分子量HA增加。这与透明质酸酶表达增加、HA电缆形成的抑制以及HA依赖性单核细胞结合的减少同时发生，并且细胞周围HA基质增加有关。HAS2的过表达导致细胞迁移增强。HA可以通过与源自血清蛋白α-间抑制因子（IαI）的重链共价连接而被修饰，这一过程已知由TNF-α刺激基因6（TSG-6；一种炎症相关蛋白）催化。针对IαI或TSG-6的阻断抗体消除了增强的迁移。添加重组全长TSG-6（TSG-6Q）或HA结合受损的突变变体TSG-6Q_Y94F增加了细胞迁移。这两种蛋白质都能够介导重链从IαI和前α-抑制因子共价转移到HA上。添加分离的TSG-6连接模块（Link_TSG-6），它能结合HA但不能与IαI/前α-抑制因子形成共价复合物，对迁移没有影响，这表明TSG-6介导的重链-HA复合物形成在细胞周围HA基质的形成中至关重要。
