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Abstract：
The NAD-synthesizing enzyme nicotinamide mononucleotide adenylyltransferase 2 (NMNAT2) is a critical survival factor for axons and its constant supply from neuronal cell bodies into axons is required for axon survival in primary culture neurites and axon extension in vivo. Recently, we showed that palmitoylation is necessary to target NMNAT2 to post-Golgi vesicles, thereby influencing its protein turnover and axon protective capacity. Here we find that NMNAT2 is a substrate for cytosolic thioesterases APT1 and APT2 and that palmitoylation/depalmitoylation dynamics are on a time scale similar to its short half-life. Interestingly, however, depalmitoylation does not release NMNAT2 from membranes. The mechanism of palmitoylation-independent membrane attachment appears to be mediated by the same minimal domain required for palmitoylation itself. Furthermore, we identify several zDHHC palmitoyltransferases that influence NMNAT2 palmitoylation and subcellular localization, among which a role for zDHHC17 (HIP14) in neuronal NMNAT2 palmitoylation is best supported by our data. These findings shed light on the enzymatic regulation of NMNAT2 palmitoylation and highlight individual thioesterases and palmitoyltransferases as potential targets to modulate NMNAT2-dependent axon survival.
摘要：
NAD合成酶烟酰胺单核苷酸腺苷酰转移酶2（NMNAT2）是轴突的关键存活因子，并且其从神经元细胞体到轴突的恒定供应是轴突在原代培养神经突和体内轴突延伸中的存活所必需的。最近,我们表明，棕榈酰化是必要的目标NMNAT2后高尔基囊泡，从而影响其蛋白质周转和轴突保护能力。在这里，我们发现NMNAT2是胞质硫酯酶APT1和APT2的底物，并且棕榈酰化/脱棕榈酰化动力学的时间尺度与其短半衰期相似。有趣的是,然而,脱棕榈酰化不会从膜中释放NMNAT2。棕榈酰化非依赖性膜附着的机制似乎是由棕榈酰化本身所需的相同最小结构域介导的。此外，我们鉴定了几种影响NMNAT2棕榈酰化和亚细胞定位的zDHHC棕榈酰转移酶，其中zDHHC17（HIP14）在神经元NMNAT2棕榈酰化中的作用得到了我们数据的最好支持。这些发现阐明了NMNAT2棕榈酰化的酶促调节，并强调了单个硫酯酶和棕榈酰转移酶是调节NMNAT2依赖性轴突存活的潜在靶标。
