Perez J L, Jing S Q, Wong T W
Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854, USA.
Oncogene. 1996 Apr 4;12(7):1469-77.
The Cak receptor kinase is a member of a novel family of receptors that are characterized by the unique structure of the ectodomains. We have identified a new isoform of Cak that differs from the original isolate by the deletion of 37 amino acids in the cytoplasmic juxtamembrane sequence. Analysis of the genomic sequence suggests that the two isoforms arise by exon skipping. The isoform-specific insert contains the motif NPXY, which was previously shown to be involved in diverse signaling function in a number of receptors. By RNase protection analyses, we found that the long isoform, Cak I is expressed at three- to sevenfold the abundance of the short isoform (Cak II). By Western blotting, Cak I receptor was found to be expressed in mouse embryos and in adult brain. Cak II protein was not detected in mouse embryos or adult tissues, but is abundantly expressed in some breast tumor cell lines. The expression profile of Cak suggests that its primary function is likely to be in developmental regulation. The coexpression of the Cak isoforms in some epithelial cell lines suggests that heterodimer formation may be a key feature in the function of the receptor.
Cak受体激酶是一类新型受体家族的成员，其特点是胞外结构域具有独特结构。我们鉴定出一种新的Cak异构体，它与原始分离物的不同之处在于其胞质近膜序列中缺失了37个氨基酸。对基因组序列的分析表明，这两种异构体是通过外显子跳跃产生的。异构体特异性插入片段包含NPXY基序，此前已证明该基序在许多受体的多种信号功能中发挥作用。通过核糖核酸酶保护分析，我们发现长异构体Cak I的表达丰度是短异构体（Cak II）的三到七倍。通过蛋白质免疫印迹法，发现Cak I受体在小鼠胚胎和成年大脑中表达。在小鼠胚胎或成年组织中未检测到Cak II蛋白，但在一些乳腺肿瘤细胞系中大量表达。Cak的表达谱表明其主要功能可能在于发育调控。Cak异构体在一些上皮细胞系中的共表达表明，异二聚体的形成可能是该受体功能的一个关键特征。
