β3GnT2 maintains adenylyl cyclase-3 signaling and axon guidance molecule expression in the olfactory epithelium.
β3GnT2 maintains adenylyl cyclase-3 signaling and axon guidance molecule expression in the olfactory epithelium.
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DOI：
10.1523/jneurosci.0224-11.2011
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发表时间：
2011-04-27
期刊：
影响因子：
--
通讯作者：
Schwarting GA
中科院分区：
文献类型：
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作者：
Henion TR;Faden AA;Knott TK;Schwarting GA
在嗅上皮（OE）中，气味受体刺激产生cAMP信号，其在气味检测和轴突引导分子表达的调节中起作用。合成cAMP的酶腺苷酸环化酶3（AC 3）在嗅觉感觉神经元（OSN）中与聚-N-乙酰乳糖胺（PLN）寡糖共表达，通过糖基转移酶β 3GnT 2确定。任何一种酶的缺失都会导致嗅球（OB）神经支配和OSN存活的类似缺陷，这表明糖基化对AC 3功能可能很重要。我们在这里表明，AC 3是广泛修改与N-连接的PLN，这是必不可少的AC 3的活动和本地化。在Western印迹上，来自野生型OE的AC 3作为与PLN结合凝集素莱亚相互作用的高度糖基化的200 kDa条带扩散迁移。来自β 3GnT 2 −/− OE的AC 3失去了这些PLN修饰，而是作为140 kDa的糖蛋白迁移。此外，在β 3GnT 2 −/− OE中，基础和毛喉素刺激的cAMP产生减少了80-90%。尽管AC 3正常运输以使OSN纤毛无效，但它不存在于异常靶向OB的轴突投射中。cAMP依赖性导向受体neuropilin-1也从β 3GnT 2 −/− OSN和轴突中丢失，而semaphorin-3A配体表达上调。此外，kirrel 2是一种嵌合表达的粘附分子，在轴突分选中起作用，在β 3GnT 2 −/− OB投射中不存在。这些结果表明，PLN聚糖在OSN中对于适当的AC 3定位和功能是必需的。我们认为，cAMP依赖性引导信号的丢失也是在β 3GnT 2 −/−小鼠中观察到的严重轴突引导缺陷的关键因素。
In the olfactory epithelium (OE), odorant receptor stimulation generates cAMP signals that function in both odor detection and the regulation of axon guidance molecule expression. The enzyme that synthesizes cAMP, adenylyl cyclase 3 (AC3), is coexpressed in olfactory sensory neurons (OSNs) with poly-N-acetyllactosamine (PLN) oligosaccharides determined by the glycosyltransferase β3GnT2. The loss of either enzyme results in similar defects in olfactory bulb (OB) innervation and OSN survival, suggesting that glycosylation may be important for AC3 function. We show here that AC3 is extensively modified with N-linked PLN, which is essential for AC3 activity and localization. On Western blots, AC3 from the wildtype OE migrates diffusely as a heavily glycosylated 200 kDa band that interacts with the PLN-binding lectin LEA. AC3 from the β3GnT2−/− OE loses these PLN modifications, migrating instead as a 140 kDa glycoprotein. Furthermore, basal and forskolin-stimulated cAMP production is reduced 80–90% in the β3GnT2−/− OE. Although AC3 traffics normally to null OSN cilia, it is absent from axon projections that aberrantly target the OB. The cAMP-dependent guidance receptor neuropilin-1 is also lost from β3GnT2−/− OSNs and axons, while semaphorin-3A ligand expression is upregulated. In addition, kirrel2, a mosaically expressed adhesion molecule that functions in axon sorting, is absent from β3GnT2−/− OB projections. These results demonstrate that PLN glycans are essential in OSNs for proper AC3 localization and function. We propose that the loss of cAMP-dependent guidance cues is also a critical factor in the severe axon guidance defects observed in β3GnT2−/− mice.