Kempaiah Prakasha, Chand Hitendra S, Kisiel Walter
Department of Pathology, University of New Mexico Health Sciences Center, Albuquerque, NM 87131-0001, USA.
Arch Biochem Biophys. 2009 Feb;482(1-2):58-65. doi: 10.1016/j.abb.2008.11.028. Epub 2008 Dec 10.
Tissue factor pathway inhibitor-2 (TFPI-2) is a serine proteinase inhibitor that induces caspase-mediated apoptosis when offered to a variety of tumor cells. In order to investigate the mechanism of TFPI-2-induced apoptosis, we initially studied the uptake and trafficking of TFPI-2 by HT-1080 cells. Exogenously offered TFPI-2 was rapidly internalized and distributed in both the cytosolic and nuclear fractions. Nuclear localization of TFPI-2 was also detected in a variety of endothelial cells constitutively expressing TFPI-2. Nuclear localization of TFPI-2 required a NLS sequence located in its Lys/Arg-rich C-terminal tail comprising residues 191-211, as a TFPI-2 construct lacking the C-terminal tail failed to localize to the nucleus. Complexes of TFPI-2 and importin-alpha were co-immunoprecipitated from cell lysates of HT-1080 cells either offered or overexpressing this protein, providing evidence that TFPI-2 was shuttled to the nucleus by the importin system. Our results provide the initial description of TFPI-2 internalization and translocation to the nucleus in a number of cells.
组织因子途径抑制剂-2（TFPI-2）是一种丝氨酸蛋白酶抑制剂，当作用于多种肿瘤细胞时可诱导半胱天冬酶介导的细胞凋亡。为了研究TFPI-2诱导细胞凋亡的机制，我们首先研究了HT-1080细胞对TFPI-2的摄取和转运。外源提供的TFPI-2迅速内化并分布于胞质和核组分中。在组成性表达TFPI-2的多种内皮细胞中也检测到了TFPI-2的核定位。TFPI-2的核定位需要位于其富含赖氨酸/精氨酸的C末端尾巴（包含191-211位残基）中的一个核定位信号序列，因为缺少C末端尾巴的TFPI-2构建体无法定位到细胞核。从提供或过表达该蛋白的HT-1080细胞裂解物中共同免疫沉淀出TFPI-2与输入蛋白α的复合物，这表明TFPI-2是通过输入蛋白系统穿梭至细胞核的。我们的结果首次描述了TFPI-2在多种细胞中的内化及向细胞核的转运。
