FITM1, FITM2 bind TAGs

Lipid droplets (LDs) are cytosolic structures found in cells of all eukaryotes, comprising a monolayer of phospholipids surrounding a core of uncharged lipids such as triglyceride (TAG) and sterol esters. They play an important role in both cellular physiology and disease. LD formation involves the partitioning of neutral lipids from their site of synthesis at the endoplasmic reticulum (ER) to the cytosol. The fat storage-inducing transmembrane proteins 1 and 2 (FITM1 and FITM2) belong to an evolutionarily-conserved gene family which mediates LD formation (Kadereit et al. 2008, Gross et al. 2011). FITM1 and FITM2 are ER membrane associated proteins that mediate binding and partitioning of TAGs into LDs (Gross et al. 2011, Miranda et al. 2014). In mammals, FITM1 is expressed primarily in skeletal muscle whereas FITM2 is expressed primarily in adipose tissue, suggesting these proteins may have unique functions (Gross et al. 2011).

脂滴（LDs）是存在于真核细胞质中的细胞器结构，由一层磷脂单分子层包围着由中性脂质如甘油三酯（TAG）和甾醇酯组成的中心核心。脂滴在细胞生理和疾病过程中扮演着至关重要的角色。脂滴的形成涉及中性脂质从内质网（ER）的合成位点向细胞质的分配。诱导脂肪储存的跨膜蛋白1和2（FITM1和FITM2）属于一个在进化上保守的基因家族，该家族介导脂滴的形成（Kadereit等，2008，Gross等，2011）。FITM1和FITM2是内质网膜相关蛋白，它们介导TAGs结合并分配到脂滴中（Gross等，2011，Miranda等，2014）。在哺乳动物中，FITM1主要在骨骼肌中表达，而FITM2主要在脂肪组织中表达，这表明这些蛋白质可能具有独特的功能（Gross等，2011）。