Characterization of a transneuronal cytokine family Cbln - regulation of secretion by heteromeric assembly
Characterization of a transneuronal cytokine family Cbln - regulation of secretion by heteromeric assembly
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DOI：
10.1111/j.1460-9568.2007.05361.x
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发表时间：
2007-02-01
影响因子：
3.4
通讯作者：
Yuzaki, Michisuke
中科院分区：
文献类型：
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作者：
Iijima, Takatoshi;Miura, Eriko;Yuzaki, Michisuke
Cbln 1是C1 q和肿瘤坏死因子超家族的成员，在浦肯野细胞中作为小脑颗粒细胞源性突触完整性和可塑性的跨神经元调节因子起着至关重要的作用。尽管其他Cbln家族成员Cbln 2-Cbln 4在整个CNS中具有不同的空间和时间表达模式，但它们的生化和生物学特性在很大程度上仍未被表征。在这里，我们证明了在哺乳动物异源细胞中，Cbln 2和Cbln 4作为N-连接的糖蛋白分泌，如Cbln 1。相反，尽管存在功能性信号序列，但Cbln 3单独表达时不分泌，而是由于其N-末端结构域而保留在内质网（ER）或顺式高尔基体中。Cbln家族的所有成员在体外不仅形成同聚体，而且形成异聚体复合物。因此，当Cbln 1和Cbln 3在异源细胞中共表达时，一部分Cbln 1蛋白保留在ER或顺式高尔基体中;相反，一些Cbln 3蛋白与Cbln 1一起分泌。类似地，在表达Cbln 1和Cbln 3的野生型颗粒细胞中，Cbln 3蛋白部分分泌并到达浦肯野细胞树突上的突触后位点，而Cbln 3在cbln 1无效颗粒细胞中几乎完全降解。这些结果表明，像Cbln 1，Cbln 2和Cbln 4也可以作为跨神经元的调节突触功能在不同的大脑区域。此外，小脑颗粒细胞中Cbln 1和Cbln 3之间的异聚体形成可能调节彼此的运输和信号传导途径;类似地，其他Cbln家族蛋白的异聚化也可能在其他神经元中具有生物学意义。
Cbln1, a member of the C1q and tumor necrosis factor superfamily, plays crucial roles as a cerebellar granule cell-derived transneuronal regulator of synapse integrity and plasticity in Purkinje cells. Although other Cbln family members, Cbln2-Cbln4, have distinct spatial and temporal patterns of expression throughout the CNS, their biochemical and biological properties have remained largely uncharacterized. Here, we demonstrated that in mammalian heterologous cells, Cbln2 and Cbln4 were secreted as N-linked glycoproteins, like Cbln1. In contrast, despite the presence of a functional signal sequence, Cbln3 was not secreted when expressed alone but was retained in the endoplasmic reticulum (ER) or cis-Golgi because of its N-terminal domain. All members of the Cbln family formed not only homomeric but also heteromeric complexes with each other in vitro. Accordingly, when Cbln1 and Cbln3 were co-expressed in heterologous cells, a proportion of the Cbln1 proteins was retained in the ER or cis-Golgi; conversely, some Cbln3 proteins were secreted together with Cbln1. Similarly, in wild-type granule cells expressing Cbln1 and Cbln3, Cbln3 proteins were partially secreted and reached postsynaptic sites on Purkinje cell dendrites, while Cbln3 was almost completely degraded in cbln1-null granule cells. These results indicate that like Cbln1, Cbln2 and Cbln4 may also serve as transneuronal regulators of synaptic functions in various brain regions. Furthermore, heteromer formation between Cbln1 and Cbln3 in cerebellar granule cells may modulate each other's trafficking and signaling pathways; similarly, heteromerization of other Cbln family proteins may also have biological significance in other neurons.