Lipid Droplet-Associated Hydrolase Promotes Lipid Droplet Fusion and Enhances ATGL Degradation and Triglyceride Accumulation.
Lipid Droplet-Associated Hydrolase Promotes Lipid Droplet Fusion and Enhances ATGL Degradation and Triglyceride Accumulation.
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DOI：
10.1038/s41598-017-02963-y
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发表时间：
2017-06-02
影响因子：
4.6
通讯作者：
Paul A
中科院分区：
文献类型：
--
作者：
Goo YH;Son SH;Paul A
脂滴（LD）相关水解酶（LDAH）是一种新发现的LD蛋白，在主要储存三酰基甘油（TAG）的组织中大量表达。然而，LDAH如何调节TAG代谢仍然未知。我们发现油酸负载后，LDAH从内质网转定位到新形成的LD，并以微管蛋白依赖的方式诱导LD聚结。HEK293细胞中LDAH过表达和下调分别升高和降低TAG水平。脉冲和追逐实验表明，LDAH促进了TAG的生物生成，但也降低了TAG的周转率和脂肪酸从细胞中释放。预测的催化基序和酰基转移酶基序的突变不影响TAG水平，这表明这种影响与LDAH的酶活性无关。然而，在c端缺失90个氨基酸的LDAH选择性剪接变体不会促进LD融合或TAG积累，但它仍然定位于LD。有趣的是，LDAH增强了脂肪甘油三酯脂肪酶（ATGL）的多泛素化和蛋白酶体降解，ATGL是TAG水解的限速酶。ATGL的共表达逆转了LDAH诱导的LD表型变化，两种蛋白抵消了它们对TAG储存的影响。综上所述，这些研究表明，在TAG储存在ldh中的条件下，LDAH主要起致脂作用，诱导LD生长并促进ATGL的降解。
Lipid droplet (LD)-associated hydrolase (LDAH) is a newly identified LD protein abundantly expressed in tissues that predominantly store triacylglycerol (TAG). However, how LDAH regulates TAG metabolism remains unknown. We found that upon oleic acid loading LDAH translocalizes from the ER to newly formed LDs, and induces LD coalescence in a tubulin-dependent manner. LDAH overexpression and downregulation in HEK293 cells increase and decrease, respectively, TAG levels. Pulse and chase experiments show that LDAH enhances TAG biogenesis, but also decreases TAG turnover and fatty acid release from cells. Mutations in predicted catalytic and acyltransferase motifs do not influence TAG levels, suggesting that the effect is independent of LDAH’s enzymatic activity. However, a LDAH alternative-splicing variant missing 90 amino acids at C-terminus does not promote LD fusion or TAG accumulation, while it still localizes to LDs. Interestingly, LDAH enhances polyubiquitination and proteasomal degradation of adipose triglyceride lipase (ATGL), a rate limiting enzyme of TAG hydrolysis. Co-expression of ATGL reverses the changes in LD phenotype induced by LDAH, and both proteins counterbalance their effects on TAG stores. Together, these studies support that under conditions of TAG storage in LDs LDAH plays a primarily lipogenic role, inducing LD growth and enhancing degradation of ATGL.