Endoplasmic Reticulum Localization of DHHC Palmitoyltransferases Mediated by Lysine-based Sorting Signals
Endoplasmic Reticulum Localization of DHHC Palmitoyltransferases Mediated by Lysine-based Sorting Signals
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DOI：
10.1074/jbc.m111.272369
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发表时间：
2011-11-11
影响因子：
4.8
通讯作者：
Chamberlain, Luke H.
中科院分区：
文献类型：
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作者：
Gorleku, Oforiwa A.;Barns, Anna-Marie;Chamberlain, Luke H.
细胞内棕榈酰化动力学由24个DHHC（天冬氨酸-组氨酸-组氨酸-半胱氨酸）棕榈酰转移酶家族调节，这些酶以室特异性方式定位。大多数DHHC蛋白定位于内质网（ER）和高尔基膜，少数靶向后高尔基膜。迄今为止，还没有关于哺乳动物DHHC蛋白中分选信号精细定位的报道；因此，目前尚不清楚DHHC家族的空间分布是如何实现的。在这里，我们已经确定并表征了基于赖氨酸的分选信号，这些信号决定了DHHC4和DHHC6在ER膜上的受限定位。DHHC6中的ER靶向信号符合KKXX基序，而DHHC4中的信号则是一个独特的KXX基序。通过将DHHC4或DHHC6中含有KXX和KKXX基元的C端五肽序列添加到DHHC3的C端，将棕榈酰转移酶从高尔基体重新分配到内质网膜上，所鉴定的二赖氨酸信号足以确定内质网定位。最近的研究表明，新合成的外周膜蛋白棕榈酰化主要发生在高尔基体上。事实上，之前对外周膜蛋白SNAP25和半胱氨酸串蛋白的分析完全符合它们最初的棕榈酰化是由高尔基定位的DHHC蛋白介导的。有趣的是，在共表达研究中，er定位的DHHC3能够将SNAP25和半胱氨酸串蛋白棕榈酰化到与野生型高尔基定位的DHHC3相似的水平。这些结果表明，内在活性DHHC蛋白靶向特定的膜区室是导致底物棕榈酰化的空间限制模式的重要因素。
Intracellular palmitoylation dynamics are regulated by a family of 24 DHHC (aspartate-histidine-histidine-cysteine) palmitoyltransferases, which are localized in a compartment-specific manner. The majority of DHHC proteins localize to endoplasmic reticulum (ER) and Golgi membranes, and a small number target to post-Golgi membranes. To date, there are no reports of the fine mapping of sorting signals in mammalian DHHC proteins; thus, it is unclear how spatial distribution of the DHHC family is achieved. Here, we have identified and characterized lysine-based sorting signals that determine the restricted localization of DHHC4 and DHHC6 to ER membranes. The ER targeting signal in DHHC6 conforms to a KKXX motif, whereas the signal in DHHC4 is a distinct KXX motif. The identified dilysine signals are sufficient to specify ER localization as adding the C-terminal pentapeptide sequences from DHHC4 or DHHC6, which contain these KXX and KKXX motifs, to the C terminus of DHHC3, redistributes this palmitoyltransferase from Golgi to ER membranes. Recent work proposed that palmitoylation of newly synthesized peripheral membrane proteins occurs predominantly at the Golgi. Indeed, previous analyses of the peripheral membrane proteins, SNAP25 and cysteine string protein, are fully consistent with their initial palmitoylation being mediated by Golgi-localized DHHC proteins. Interestingly, ER-localized DHHC3 is able to palmitoylate SNAP25 and cysteine string protein to a similar level as wild-type Golgi-localized DHHC3 in co-expression studies. These results suggest that targeting of intrinsically active DHHC proteins to defined membrane compartments is an important factor contributing to spatially restricted patterns of substrate palmitoylation.