Institute of General Physiology, Ulm University, Albert-Einstein-Allee 11, 89081 Ulm, Germany.
Cells. 2021 Dec 24;11(1):45. doi: 10.3390/cells11010045.
The lamellar body (LB) of the alveolar type II (ATII) cell is a lysosome-related organelle (LRO) that contains surfactant, a complex mix of mainly lipids and specific surfactant proteins. The major function of surfactant in the lung is the reduction of surface tension and stabilization of alveoli during respiration. Its lack or deficiency may cause various forms of respiratory distress syndrome (RDS). Surfactant is also part of the innate immune system in the lung, defending the organism against air-borne pathogens. The limiting (organelle) membrane that encloses the LB contains various transporters that are in part responsible for translocating lipids and other organic material into the LB. On the other hand, this membrane contains ion transporters and channels that maintain a specific internal ion composition including the acidic pH of about 5. Furthermore, P2X receptors, ligand gated ion channels of the danger signal ATP, are expressed in the limiting LB membrane. They play a role in boosting surfactant secretion and fluid clearance. In this review, we discuss the functions of these transporting pathways of the LB, including possible roles in disease and as therapeutic targets, including viral infections such as SARS-CoV-2.
板层小体（LB）是肺泡 II 型（ATII）细胞的溶酶体相关细胞器（LRO），其中包含表面活性剂，这是一种主要由脂质和特定表面活性剂蛋白组成的复杂混合物。表面活性剂在肺部的主要功能是降低呼吸过程中的表面张力并稳定肺泡。其缺乏或不足可能导致各种形式的呼吸窘迫综合征（RDS）。表面活性剂也是肺部固有免疫系统的一部分，可保护机体免受空气传播病原体的侵害。包围 LB 的限制（细胞器）膜包含各种转运蛋白，部分负责将脂质和其他有机物质转运到 LB 中。另一方面，该膜包含离子转运蛋白和通道，可维持特定的内部离子组成，包括约 5 的酸性 pH 值。此外，P2X 受体，即危险信号 ATP 的配体门控离子通道，在限制的 LB 膜中表达。它们在促进表面活性剂分泌和液体清除方面发挥作用。在这篇综述中，我们讨论了 LB 的这些转运途径的功能，包括在疾病中的可能作用以及作为治疗靶点，包括 SARS-CoV-2 等病毒感染。
