Sago H, Kitagawa M, Obata S, Mori N, Taketani S, Rochelle J M, Seldin M F, Davidson M, St John T, Suzuki S T
Doheny Eye Institute, Los Angeles, CA 90033, USA.
Genomics. 1995 Oct 10;29(3):631-40. doi: 10.1006/geno.1995.9956.
To study the diversity of the protocadherin family, the cDNA clones for a novel protocadherin were isolated by screening rat brain cDNA libraries with a cDNA fragment obtained by PCR, and some of the properties were then characterized. The overall structure of the protein defined by the clone is similar to that of previously identified protocadherins; however, the cytoplasmic domain is distinct from those of previously cloned protocadherins or any other protein sequences in the data bank. We named this protocad herin-3 (Pcdh3) since this is the third protocadherin of which the entire coding sequence has been determined. Most of the deduced amino acid sequences of other cDNA clones obtained by the screening show high homology with but are distinct from that of Pcdh3, indicating that most of these sequences correspond to homologous but different protocadherins. These results demonstrate that Pcdh3 and the protocadherins defined by these clones constitute a protocadherin subfamily. Chromosome mapping indicates that mouse Pcdh3 is located in a specific region of mouse chromosome 18, close to the location of previously cloned protocadherins, suggesting that various protocadherins form a cluster in this region. In situ hybridization results showed that Pcdh3 and its related proteins were expressed at various areas in brain. The expressed Pcdh3 protein from the cDNA in mouse L cells was about 100 kDa in molecular weight and was localized at cell-cell contact sites. In contrast to the classical cadherins, however, the expressed Pcdh3 was sensitive to trypsin even in the presence of Ca2+, and the transfectants did not show strong Ca(2+)-dependent cell aggregation activity. These results indicate the structural and possibly functional diversity of the protocadherin family and suggest a distinctive biological role for Pcdh3.
为了研究原钙黏蛋白家族的多样性，通过用PCR获得的cDNA片段筛选大鼠脑cDNA文库，分离出一种新型原钙黏蛋白的cDNA克隆，然后对其一些特性进行了表征。该克隆所定义的蛋白质的整体结构与先前鉴定的原钙黏蛋白相似；然而，其胞质结构域与先前克隆的原钙黏蛋白或数据库中的任何其他蛋白质序列不同。我们将这种原钙黏蛋白命名为原钙黏蛋白-3（Pcdh3），因为这是第三个其完整编码序列已被确定的原钙黏蛋白。通过筛选获得的其他cDNA克隆的大多数推导氨基酸序列与Pcdh3具有高度同源性，但又与之不同，这表明这些序列中的大多数对应于同源但不同的原钙黏蛋白。这些结果表明，Pcdh3和由这些克隆所定义的原钙黏蛋白构成了一个原钙黏蛋白亚家族。染色体定位表明，小鼠Pcdh3位于小鼠18号染色体的一个特定区域，靠近先前克隆的原钙黏蛋白的位置，这表明各种原钙黏蛋白在该区域形成一个簇。原位杂交结果显示，Pcdh3及其相关蛋白在脑中的各个区域表达。从小鼠L细胞中的cDNA表达的Pcdh3蛋白分子量约为100 kDa，并且定位于细胞 - 细胞接触位点。然而，与经典钙黏蛋白不同的是，即使在存在Ca2+的情况下，表达的Pcdh3对胰蛋白酶敏感，并且转染细胞没有显示出强烈的Ca(2+)依赖性细胞聚集活性。这些结果表明了原钙黏蛋白家族的结构和可能的功能多样性，并暗示了Pcdh3具有独特的生物学作用。
