Functional analysis for signal transducsion via GPI-anchord neural cell adhesion molecules of contactin subgroup

Contactin亚群分子包括Contactin、Tag-1、Nb-2、Nb-3、BIG-1和BIG-2，是属于免疫球蛋白超家族(IGSF)的GPI锚定的神经黏附分子。已知的GPI锚定分子归因于洗涤剂不溶的低密度组分(脂筏)，其中许多信号转导分子是共定位的。在这项研究中，我研究了这些分子在脑组织形成和高级脑功能中的功能，特别是通过突触传递的信号转导。结果如下：1)Contact n和Nb-3以及与Contact n在同一侧质膜上顺式相互作用的Contact n相关蛋白(CASPR 1)分布于大鼠大脑皮层突触体脂筏部分(突触后密度，PSD)。2)PSD-95是PSD特有的折叠蛋白，与Contact n和Nb-3免疫共沉淀。(3)30月龄大鼠皮质突触体内共定位的蛋白质总量低于6月龄的PSD。相比之下，与年轻人的PSD相比，老年PSD中的胆固醇含量要高得多。4)CASPR家族中的Caspr2和4也定位于脂筏中。通过EAST双杂交系统分析，发现一些有趣的蛋白质与Caspr2和Caspr4的胞内部分相互作用。我目前正在对这些蛋白质进行鉴定。这些结果表明，Contact n和NB-3可能与CASPR家族顺式相互作用，并可能参与突触后功能。

Contactin subgroup molecules including contactin, TAG-1, NB-2, NB-3, BIG-1 and BIG-2 are GPI-anchored neural adhesion molecules belonged in immunoglobulin-superfamily(IGSF). A GPI-anchored molecule is known to attribute to detergent insoluble low-density fractions (lipid rafts) in which many signal transducing molecules are co-localized. In this study, I have investigated the functions of these molecules on the formation of brain organization and higher brain functions, especially focusing on signal transduction via synaptic transmission. Results were as follows.1)Contactin and NB-3 as well as contactin associated protein (Caspr 1) which is cis-interacted with contactin on the same side of plasma membrane were distributed in lipid raft fraction derived from synaptosome (postsynaptic density, PSD) of rat cerebral cortex.2)PSD-95 that is one of folding protein specifically localized in PSD was immunoprecipitated with both contactin and NB-3. And Caspr1 was detected in the precipitants with contactin, but not in that with NB-3.3)Total amount of proteins co-localized in the PSD derived from 30 month-old rat cortical synaptosome was less than that in PSD from 6 month-old. In contrast, cholesterol was much more contained in old PSD compared from young adult PSD. I have currently analyzed what kind of proteins were fluctuated by aging in cortical PSD fraction.4)Caspr2 and 4 belonging to the Caspr family were also localized in lipid raft. Analysis by East two-hybrid system, some interesting proteins were found to interact with the intracellular portion of either Caspr2 and 4. I have currently characterizing those proteins.These results suggested that contactin and NB-3 may cis-interact with caspr family and possibly involve in the postsynaptic functions.