Rosenthal J J, Liu T I, Gilly W F
Hopkins Marine Station, Department of Biological Sciences, Stanford University, Pacific Grove, California 93950, USA.
J Neurosci. 1997 Jul 1;17(13):5070-9. doi: 10.1523/JNEUROSCI.17-13-05070.1997.
Squid giant axons are formed by giant fiber lobe (GFL) neurons of the stellate ganglion (SG). Other large motoneurons in the SG form a parallel system. A small family of cDNAs (SqKv1A-D) encoding Kv1 alpha-subunits was identified in a squid (Loligo opalescens) SG/GFL library. Members have distinct 5' untranslated regions (UTRs) and initial coding regions, but beyond a certain point (nucleotide 34 of SqKv1A) only nine differences exist. 3' UTRs are identical. Predicted alpha-subunits are nearly identical, and only the N termini differ significantly, primarily in length. RNase protection assays that use RNA isolated from specific SG regions show that SqKv1A mRNA is expressed prominently in the GFL but not in the SG proper. SqKv1B yields the opposite pattern. SqKv1D also is expressed only in the SG. SqKv1C expression was not detectable. In situ hybridizations confirm these results and reveal that SqKv1B mRNA is abundant in many large neurons of the SG, whereas SqKv1D expression is limited to small isolated clusters of neurons. SqKv1A and B are thus the predominant Kv1 mRNAs in the SG/GFL complex. Activation properties of SqKv1A and B channels expressed in oocytes are very similar to one another and compare favorably with properties of native delayed rectifier channels in GFL neurons and large SG neurons. The Kv1 complement in these squid neurons thus seems to be relatively simple. Several differences exist between cloned and native channels, however, and may reflect differences in the cellular environments of oocytes and neurons.
鱿鱼的巨轴突由星状神经节（SG）的巨纤维叶（GFL）神经元形成。SG中的其他大型运动神经元形成一个平行系统。在鱿鱼（加州双柔鱼）的SG/GFL文库中鉴定出一小家族编码Kv1α亚基的cDNA（SqKv1A - D）。这些成员具有不同的5'非翻译区（UTR）和起始编码区，但在某一点之后（SqKv1A的第34个核苷酸）仅存在九个差异。3'UTR是相同的。预测的α亚基几乎相同，仅N端有显著差异，主要是长度不同。使用从特定SG区域分离的RNA进行的核糖核酸酶保护试验表明，SqKv1A mRNA在GFL中大量表达，但在SG本身中不表达。SqKv1B呈现相反的模式。SqKv1D也仅在SG中表达。未检测到SqKv1C的表达。原位杂交证实了这些结果，并揭示SqKv1B mRNA在SG的许多大型神经元中丰富，而SqKv1D的表达仅限于小的孤立神经元簇。因此，SqKv1A和B是SG/GFL复合体中主要的Kv1 mRNA。在卵母细胞中表达的SqKv1A和B通道的激活特性彼此非常相似，并且与GFL神经元和大型SG神经元中天然延迟整流通道的特性相比具有优势。因此，这些鱿鱼神经元中的Kv1互补体似乎相对简单。然而，克隆通道和天然通道之间存在一些差异，这可能反映了卵母细胞和神经元细胞环境的差异。
