Lin David Tse Shen, Conibear Elizabeth
Centre for Molecular Medicine and Therapeutics, University of British Columbia, Vancouver, Canada.
Department of Medical Genetics, University of British Columbia, Vancouver, Canada.
Elife. 2015 Dec 23;4:e11306. doi: 10.7554/eLife.11306.
Dynamic changes in protein S-palmitoylation are critical for regulating protein localization and signaling. Only two enzymes - the acyl-protein thioesterases APT1 and APT2 - are known to catalyze palmitate removal from cytosolic cysteine residues. It is unclear if these enzymes act constitutively on all palmitoylated proteins, or if additional depalmitoylases exist. Using a dual pulse-chase strategy comparing palmitate and protein half-lives, we found knockdown or inhibition of APT1 and APT2 blocked depalmitoylation of Huntingtin, but did not affect palmitate turnover on postsynaptic density protein 95 (PSD95) or N-Ras. We used activity profiling to identify novel serine hydrolase targets of the APT1/2 inhibitor Palmostatin B, and discovered that a family of uncharacterized ABHD17 proteins can accelerate palmitate turnover on PSD95 and N-Ras. ABHD17 catalytic activity is required for N-Ras depalmitoylation and re-localization to internal cellular membranes. Our findings indicate that the family of depalmitoylation enzymes may be substantially broader than previously believed.
蛋白质S-棕榈酰化的动态变化对于调节蛋白质定位和信号传导至关重要。已知只有两种酶——酰基蛋白硫酯酶APT1和APT2——可催化从胞质半胱氨酸残基上去除棕榈酸。目前尚不清楚这些酶是否对所有棕榈酰化蛋白都持续起作用，或者是否存在其他去棕榈酰化酶。通过使用比较棕榈酸和蛋白质半衰期的双脉冲追踪策略，我们发现敲低或抑制APT1和APT2可阻断亨廷顿蛋白的去棕榈酰化，但不影响突触后致密蛋白95（PSD95）或N-Ras上的棕榈酸周转。我们利用活性分析来鉴定APT1/2抑制剂Palmostatin B的新型丝氨酸水解酶靶点，并发现一个未表征的ABHD17蛋白家族可加速PSD95和N-Ras上的棕榈酸周转。N-Ras去棕榈酰化和重新定位于细胞内膜需要ABHD17的催化活性。我们的研究结果表明，去棕榈酰化酶家族可能比之前认为的要广泛得多。
