Gong W, Roth S, Michel K, Gressner A M
Department of Clinical Chemistry, Philipps University, Marburg, Germany.
Gastroenterology. 1998 Feb;114(2):352-63. doi: 10.1016/s0016-5085(98)70488-3.
BACKGROUND & AIMS: Hepatic stellate cells (HSCs) are one important source for transforming growth factor beta (TGF-beta). They produce TGF-beta in a latent form associated with latency-associated peptide and latent TGF-beta-binding protein (LTBP). This study was designed to investigate, on RNA and protein levels, which isoforms of LTBP and TGF-beta are expressed in HSCs and myofibroblasts.
HSCs isolated from rat liver were analyzed for LTBP and TGF-beta at various times of culture during transdifferentiation into myofibroblasts using immunocytochemical staining, metabolic labeling and immunoprecipitation, reverse-transcription polymerase chain reaction (RT-PCR), and sequencing.
Alkaline phosphatase-anti-alkaline phosphatase staining and fluorescence immunostainings indicated the expression of all three components of the large latent TGF-beta complex in HSCs and myofibroblasts. Transcripts of three TGF-beta and LTBP isoforms were detected by RT-PCR and confirmed by sequence analyses. A new LTBP-1 splice form was found lacking part of the hinge region with a potential proteinase cleavage site. Metabolic labeling followed by immunoprecipitation with LTBP antiserum confirmed the synthesis and secretion of various LTBP-related proteins.
The existence of different LTBP isoforms and splice variants in HSCs and myofibroblasts suggests multiple functions of the LTBP family in rat liver, which might not be restricted to the maintenance of TGF-beta latency.
肝星状细胞（HSCs）是转化生长因子β（TGF-β）的一个重要来源。它们以与潜伏期相关肽和潜伏TGF-β结合蛋白（LTBP）相关的潜伏形式产生TGF-β。本研究旨在从RNA和蛋白质水平研究LTBP和TGF-β的哪些异构体在肝星状细胞和成肌纤维细胞中表达。
使用免疫细胞化学染色、代谢标记和免疫沉淀、逆转录聚合酶链反应（RT-PCR）和测序，对从大鼠肝脏分离的肝星状细胞在向成肌纤维细胞转分化的不同培养时间进行LTBP和TGF-β分析。
碱性磷酸酶-抗碱性磷酸酶染色和荧光免疫染色表明，大潜伏TGF-β复合物的所有三个组分在肝星状细胞和成肌纤维细胞中均有表达。通过RT-PCR检测到三种TGF-β和LTBP异构体的转录本，并经序列分析证实。发现一种新的LTBP-1剪接形式，其铰链区的一部分缺失，具有潜在的蛋白酶切割位点。代谢标记后用LTBP抗血清进行免疫沉淀，证实了各种LTBP相关蛋白的合成和分泌。
肝星状细胞和成肌纤维细胞中存在不同的LTBP异构体和剪接变体，提示LTBP家族在大鼠肝脏中具有多种功能，可能不限于维持TGF-β的潜伏状态。
