Xiong W C, Macklem M, Parsons J T
Department of Microbiology and Cancer Center, University of Virginia Health Sciences Center, Charlottesville, Virginia 22908, USA.
J Cell Sci. 1998 Jul 30;111 ( Pt 14):1981-91. doi: 10.1242/jcs.111.14.1981.
Focal adhesion kinase and the recently identified proline-rich tyrosine kinase 2 (PYK2), also known as cell adhesion kinase &bgr ;, related adhesion focal tyrosine kinase or calcium-dependent protein tyrosine kinase, define a new family of non-receptor protein tyrosine kinases. Activation of PYK2 has been implicated in multiple signaling events, including modulation of ion channels, T- and B-cell receptor signaling and cell death. Mechanisms underlying the functional diversity of PYK2 are unclear. Here, we provide evidence for two novel alternatively expressed isoforms of PYK2. One isoform, designated PYK2s (PYK2 splice form), appears to be a splice variant of PYK2 lacking 42 amino acids within the C-terminal domain. A second isoform, referred to as PRNK (PYK2-related non-kinase), appears to be specified by mRNAs that encode only part of the C-terminal domain of PYK2. Northern blot analysis indicates that the unspliced PYK2 is expressed at high levels in the brain and poorly expressed in the spleen, whereas PYK2s and PRNK are expressed in the spleen. In situ hybridization studies of rat brain demonstrate that the unspliced PYK2 is selectively expressed at high levels in hippocampus, cerebral cortex and olfactory bulb, whereas PYK2s and PRNK are expressed at low levels in all regions of rat brain examined. Immunofluorescence analysis of ectopically expressed PRNK protein shows that PRNK, in contrast to full-length PYK2, is localized to focal adhesions by sequences within the focal adhesion targeting domain. In addition, PYK2, but not PRNK, interacts with p130(cas )and Graf. These results imply that PRNK may selectively regulate PYK2 function in certain cells by binding to some but not all PYK2 binding partners, and the functional diversity mediated by PYK2 may be due in part to complex alternative splicing.
粘着斑激酶以及最近发现的富含脯氨酸的酪氨酸激酶2（PYK2），也被称为细胞粘着激酶β、相关粘着斑酪氨酸激酶或钙依赖性蛋白酪氨酸激酶，它们定义了一个新的非受体蛋白酪氨酸激酶家族。PYK2的激活涉及多种信号转导事件，包括离子通道的调节、T细胞和B细胞受体信号转导以及细胞死亡。PYK2功能多样性的潜在机制尚不清楚。在此，我们提供了两种新的PYK2可变表达异构体的证据。一种异构体，命名为PYK2s（PYK2剪接形式），似乎是PYK2的剪接变体，在C末端结构域内缺少42个氨基酸。第二种异构体，称为PRNK（PYK2相关非激酶），似乎由仅编码PYK2 C末端结构域一部分的mRNA所指定。Northern印迹分析表明，未剪接的PYK2在脑中高水平表达，在脾中低水平表达，而PYK2s和PRNK在脾中表达。对大鼠脑的原位杂交研究表明，未剪接的PYK2在海马、大脑皮层和嗅球中选择性高水平表达，而PYK2s和PRNK在所检查的大鼠脑的所有区域中低水平表达。对异位表达的PRNK蛋白的免疫荧光分析表明，与全长PYK2不同，PRNK通过粘着斑靶向结构域内的序列定位于粘着斑。此外，PYK2与p130（cas）和Graf相互作用，而PRNK不与它们相互作用。这些结果表明，PRNK可能通过与部分而非全部PYK2结合伙伴结合，在某些细胞中选择性调节PYK2功能，并且PYK2介导的功能多样性可能部分归因于复杂的可变剪接。
