Division of Pulmonary Biology, Cincinnati Children's Hospital Medical Center, and Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, Ohio, United States of America.
PLoS One. 2011 Jan 26;6(1):e16482. doi: 10.1371/journal.pone.0016482.
Pulmonary surfactant is a complex mixture of lipids and proteins that is essential for postnatal function. Surfactant is synthesized in alveolar type II cells and stored as multi-bilayer membranes in a specialized secretory lysosome-related organelle (LRO), known as the lamellar body (LB), prior to secretion into the alveolar airspaces. Few LB proteins have been identified and the mechanisms regulating formation and trafficking of this organelle are poorly understood. Lamellar bodies were isolated from rat lungs, separated into limiting membrane and core populations, fractionated by SDS-PAGE and proteins identified by nanoLC-tandem mass spectrometry. In total 562 proteins were identified, significantly extending a previous study that identified 44 proteins in rat lung LB. The lung LB proteome reflects the dynamic interaction of this organelle with the biosynthetic, secretory and endocytic pathways of the type II epithelial cell. Comparison with other LRO proteomes indicated that 60% of LB proteins were detected in one or more of 8 other proteomes, confirming classification of the LB as a LRO. Remarkably the LB shared 37.8% of its proteins with the melanosome but only 9.9% with lamellar bodies from the skin. Of the 229 proteins not detected in other LRO proteomes, a subset of 34 proteins was enriched in lung relative to other tissues. Proteins with lipid-related functions comprised a significant proportion of the LB unique subset, consistent with the major function of this organelle in the organization, storage and secretion of surfactant lipid. The lung LB proteome will facilitate identification of molecular pathways involved in LB biogenesis, surfactant homeostasis and disease pathogenesis.
肺表面活性剂是一种复杂的脂质和蛋白质混合物，对出生后的功能至关重要。肺表面活性剂由肺泡 II 型细胞合成，并以多层膜的形式储存在一个特殊的分泌溶酶体相关细胞器（LRO）中，称为板层小体（LB），然后分泌到肺泡气腔中。已经鉴定出少数 LB 蛋白，而调节该细胞器形成和运输的机制知之甚少。从大鼠肺中分离出板层小体，分为限制膜和核心群体，通过 SDS-PAGE 分离，并用纳升液相色谱-串联质谱鉴定蛋白质。总共鉴定出 562 种蛋白质，大大扩展了之前在大鼠肺 LB 中鉴定出 44 种蛋白质的研究。肺 LB 蛋白质组反映了该细胞器与 II 型上皮细胞的生物合成、分泌和内吞途径的动态相互作用。与其他 LRO 蛋白质组的比较表明，LB 蛋白中有 60%在 8 种其他蛋白质组中的一种或多种中被检测到，这证实了 LB 被归类为 LRO。值得注意的是，LB 与黑素体共享 37.8%的蛋白质，但与皮肤的板层小体仅共享 9.9%。在其他 LRO 蛋白质组中未检测到的 229 种蛋白质中，有 34 种蛋白质子集在肺中比其他组织更丰富。具有脂质相关功能的蛋白质构成了 LB 独特亚组的重要部分，这与该细胞器在组织、储存和分泌表面活性剂脂质方面的主要功能一致。肺 LB 蛋白质组将有助于鉴定与 LB 发生、表面活性剂动态平衡和疾病发病机制相关的分子途径。
