Department of Biology, University of Fribourg, Fribourg, Switzerland.
Department of Biology, University of Fribourg, Fribourg, Switzerland.
J Biol Chem. 2023 Dec;299(12):105384. doi: 10.1016/j.jbc.2023.105384. Epub 2023 Oct 28.
Perilipins (PLINs) constitute an evolutionarily conserved family of proteins that specifically associate with the surface of lipid droplets (LDs). These proteins function in LD biogenesis and lipolysis and help to stabilize the surface of LDs. PLINs are typically composed of three different protein domains. They share an N-terminal PAT domain of unknown structure and function, a central region containing 11-mer repeats that form amphipathic helices, and a C-terminal domain that adopts a 4-helix bundle structure. How exactly these three distinct domains contribute to PLIN function remains to be determined. Here, we show that the N-terminal PAT domain of PLIN3 binds diacylglycerol (DAG), the precursor to triacylglycerol, a major storage lipid of LDs. PLIN3 and its PAT domain alone bind liposomes with micromolar affinity and PLIN3 binds artificial LDs containing low concentrations of DAG with nanomolar affinity. The PAT domain of PLIN3 is predicted to adopt an amphipathic triangular shaped structure. In silico ligand docking indicates that DAG binds to one of the highly curved regions within this domain. A conserved aspartic acid residue in the PAT domain, E86, is predicted to interact with DAG, and we found that its substitution abrogates high affinity binding of DAG as well as DAG-stimulated association with liposome and artificial LDs. These results indicate that the PAT domain of PLINs harbor specific lipid-binding properties that are important for targeting these proteins to the surface of LDs and to ER membrane domains enriched in DAG to promote LD formation.
脂肪滴（LDs）表面特异性结合的蛋白家族，称为 perilipins（PLINs）。这些蛋白在 LD 的生物发生和脂解中发挥作用，并有助于稳定 LD 的表面。PLINs 通常由三个不同的蛋白结构域组成。它们共享一个未知结构和功能的 N 端 PAT 结构域，一个包含 11 个重复的中心区域，这些重复形成两性螺旋，以及一个采用 4 螺旋束结构的 C 端结构域。这三个不同的结构域如何确切地发挥作用仍有待确定。在这里，我们表明 PLIN3 的 N 端 PAT 结构域与二酰基甘油（DAG）结合，DAG 是三酰基甘油（LDs 的主要储存脂质）的前体。PLIN3 及其 PAT 结构域单独以微摩尔亲和力结合脂质体，PLIN3 以纳摩尔亲和力结合含有低浓度 DAG 的人工 LD。PLIN3 的 PAT 结构域预计采用具有两亲性三角形的结构。计算机配体对接表明 DAG 结合到该结构域的一个高度弯曲区域内。PAT 结构域中的保守天冬氨酸残基 E86 预测与 DAG 相互作用，我们发现其取代会破坏 DAG 的高亲和力结合以及 DAG 刺激与脂质体和人工 LD 的结合。这些结果表明 PLINs 的 PAT 结构域具有特定的脂质结合特性，对于将这些蛋白靶向 LD 表面以及富含 DAG 的 ER 膜结构域以促进 LD 形成至关重要。
