Processing of hydrophobic pulmonary surfactant protein B in rat type II cells.
Processing of hydrophobic pulmonary surfactant protein B in rat type II cells.
复制标题
大鼠 II 型细胞中疏水性肺表面活性蛋白 B 的加工。
DOI：
10.1152/ajplung.1989.257.2.l100
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Whitsett,JA
中科院分区：
文献类型：
--
作者：
Weaver,TE;Whitsett,JA
表面活性剂蛋白 B (SP-B) 的氨基酸序列源自人类基因组和 cDNA 序列，表明活性多肽包含在 381 个残基的前蛋白原序列中。在大鼠肺泡 II 型上皮细胞的原代培养物中研究了成熟 SP-B 的合成，该合成需要在前蛋白的 NH2 末端和 COOH 末端进行蛋白水解加工。 II型细胞用[35S]甲硫氨酸-半胱氨酸脉冲标记15-30分钟并追踪0-18小时。 SP-B 蛋白原 (Mr = 42,000) 在早期时间点在培养基中积累，但在后期时间点下降，表明蛋白原发生细胞外蛋白水解。相反，表面活性剂蛋白A (SP-A)，另一种表面活性剂蛋白，在此期间继续在细胞外积累。 SP-B (Mr = 25,000) 的蛋白水解片段在培养基中积累，时间进程稍慢，与前蛋白的细胞外蛋白水解一致。还检测到了 SP-B 的细胞内加工。在较晚时间点在细胞内和培养基中检测到Mr 8,000和12,000的SP-B多肽。这些形式的 SP-B（Mr = 8,000 和 12,000）在二维等电聚焦十二烷基硫酸钠-聚丙烯酰胺凝胶电泳中与从大鼠肺泡灌洗液中分离出的成熟 SP-B 共迁移。在从大鼠肺匀浆中分离的层状体中也检测到了 SP-B 的成熟形式 (Mr = 8,000)，但没有检测到 Mr 42,000 和 25,000 SP-B 前体。这些实验证明 II 型上皮细胞在体外将 prepro-SP-B 完全蛋白水解加工成肺泡 Mr 8,000 形式。（摘要截断为 250 字）
The amino acid sequence of surfactant protein B (SP-B), derived from human genomic and cDNA sequences, indicates that the active polypeptide is contained within the sequence of a preproprotein of 381 residues. Synthesis of mature SP-B, which requires proteolytic processing at both the NH2- and COOH-termini of the proprotein, was studied in primary cultures of rat alveolar type II epithelial cells. Type II cells were pulse labeled with [35S]methionine-cysteine for 15-30 min and chased for 0-18 h. SP-B proprotein (Mr = 42,000) accumulated in the medium at early time points but declined at later time points suggesting extracellular proteolysis of the proprotein. In contrast, surfactant protein A (SP-A), another surfactant protein, continued to accumulate extracellularly during this time period. A proteolytic fragment of SP-B (Mr = 25,000) accumulated in the medium with a slightly slower time course, consistent with extracellular proteolysis of the proprotein. Intracellular processing of SP-B was also detected. SP-B polypeptides of Mr 8,000 and 12,000 were detected intracellularly and in the medium at late time points. These forms of SP-B (Mr = 8,000 and 12,000) comigrated in two-dimensional isoelectric-focusing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with mature SP-B isolated from rat alveolar lavage fluid. The mature form of SP-B (Mr = 8,000), but not the Mr 42,000 and 25,000 SP-B precursors, was also detected in lamellar bodies isolated from rat lung homogenates. These experiments demonstrate complete proteolytic processing of prepro-SP-B to the alveolar Mr 8,000 form by type II epithelial cells in vitro.(ABSTRACT TRUNCATED AT 250 WORDS)