Schacher S, Wu F, Sun Z Y, Wang D
Center for Neurobiology and Behavior, Columbia University College of Physicians and Surgeons, New York State Psychiatric Institute, 722 West 168th Street, New York, New York 10032, USA.
J Neurobiol. 2000 Nov 15;45(3):152-61. doi: 10.1002/1097-4695(20001115)45:3<152::aid-neu3>3.0.co;2-0.
Aplysia neurons express several splice variants of apCAM, a member of the Ig superfamily of cell adhesion molecules. The major transmembrane isoform is endocytosed in sensory neurons (SNs) during the early phases of long-term facilitation (LTF) of SN synapses evoked by serotonin (5-HT) or in the motor neuron L7 during the early phases of long-term depression (LTD) of SN synapses evoked by Phe-Met-Arg-Phe-amide (FMRFa). We used single cell RT-PCR to evaluate whether expression of mRNAs encoding for different apCAM isoforms in SNs and L7 is regulated during LTF produced by 5-HT, and LTD produced by FMRFa. Single SNs and L7s express mRNAs encoding for all major isoforms, but the proportion of each isoform expressed differs for the two cells. SN expresses more mRNA encoding for GPI-linked isoforms, while L7 expresses more mRNA encoding for the major transmembrane isoform. The neuromodulators produced significant changes in the proportional levels of mRNAs encoding for specific apCAM isoforms during the first 4 h after treatments without affecting overall levels of apCAM mRNA. 5-HT evoked changes that exaggerated cell-specific differences in isoform expression. FMRFa evoked changes that reduced cell-specific differences in isoform expression. The effects of the neuromodulators on apCAM mRNA expression were not detected when cells were cultured alone or when SNs were cocultured with another motor cell that failed to induce synapse formation (L11). The results suggest that rapid cell-specific regulation of splice variant expression may contribute to different forms of long-term synaptic plasticity.
海兔神经元表达apCAM的几种剪接变体，apCAM是免疫球蛋白超家族细胞粘附分子的成员。主要的跨膜异构体在5-羟色胺（5-HT）诱发的感觉神经元（SNs）突触长期易化（LTF）早期阶段被内吞，或者在苯丙氨酸-甲硫氨酸-精氨酸-苯丙氨酸酰胺（FMRFa）诱发的SNs突触长期抑制（LTD）早期阶段在运动神经元L7中被内吞。我们使用单细胞逆转录聚合酶链反应（RT-PCR）来评估在5-HT产生的LTF和FMRFa产生的LTD过程中，SNs和L7中编码不同apCAM异构体的mRNA表达是否受到调控。单个SNs和L7表达编码所有主要异构体的mRNA，但两种细胞中每种异构体表达的比例不同。SN表达更多编码糖基磷脂酰肌醇（GPI）连接异构体的mRNA，而L7表达更多编码主要跨膜异构体的mRNA。在处理后的前4小时内，神经调质使编码特定apCAM异构体的mRNA比例水平发生显著变化，而不影响apCAM mRNA的总体水平。5-HT引起的变化夸大了异构体表达中的细胞特异性差异。FMRFa引起的变化减少了异构体表达中的细胞特异性差异。当细胞单独培养或SNs与另一个未能诱导突触形成的运动细胞（L11）共培养时，未检测到神经调质对apCAM mRNA表达的影响。结果表明，剪接变体表达的快速细胞特异性调控可能有助于不同形式的长期突触可塑性。
