Center for Research in Reproductive Physiology, Department of Cell Biology and Molecular Physiology, Magee-Womens Research Institute, University of Pittsburgh, Pittsburgh, PA 15261, USA.
Biol Reprod. 2013 Mar 7;88(3):59. doi: 10.1095/biolreprod.112.104414. Print 2013 Mar.
The blood-testis barrier (BTB) is a large junctional complex composed of tight junctions, adherens junctions, and gap junctions between adjacent Sertoli cells in the seminiferous tubules of the testis. Maintenance of the BTB as well as the controlled disruption and reformation of the barrier is essential for spermatogenesis and male fertility. Tyrosine phosphorylation of BTB proteins is known to regulate the integrity of adherens and tight junctions found at the BTB. SHP2 is a nonreceptor protein tyrosine phosphatase (PTP) and a key regulator of growth factor-mediated tyrosine kinase signaling pathways. We found that SHP2 is localized to Sertoli-Sertoli cell junctions in rat testis. The overexpression of a constitutive active SHP2 mutant, SHP2 Q79R, up-regulated the BTB disruptor ERK1/2 via Src kinase in primary rat Sertoli cells in culture. Furthermore, focal adhesion kinase (FAK), which also supports BTB integrity, was found to interact with SHP2 and constitutive activation of SHP2 decreased FAK tyrosine phosphorylation. Expression of the SHP2 Q79R mutant in primary cultured Sertoli cells also resulted in the loss of tight junction and adherens junction integrity that corresponded with the disruption of the actin cytoskeleton and mislocalization of adherens junction and tight junction proteins N-cadherin, β-catenin, and ZO-1 away from the plasma membrane. These results suggest that SHP2 is a key regulator of BTB integrity and Sertoli cell support of spermatogenesis and fertility.
血睾屏障（BTB）是由紧密连接、黏附连接和缝隙连接组成的大型连接复合体，位于睾丸生精小管的相邻支持细胞之间。BTB 的维持以及屏障的受控破坏和再形成对于精子发生和男性生育力是至关重要的。已知 BTB 蛋白的酪氨酸磷酸化调节 BTB 处黏附连接和紧密连接的完整性。SHP2 是一种非受体蛋白酪氨酸磷酸酶（PTP），也是生长因子介导的酪氨酸激酶信号通路的关键调节剂。我们发现 SHP2 定位于大鼠睾丸的支持细胞-支持细胞连接。在培养的原代大鼠支持细胞中，组成型激活的 SHP2 突变体 SHP2 Q79R 的过表达通过Src 激酶上调 BTB 破坏剂 ERK1/2。此外，还发现支持 BTB 完整性的粘着斑激酶（FAK）与 SHP2 相互作用，而 SHP2 的组成型激活会降低 FAK 酪氨酸磷酸化。在原代培养的支持细胞中表达 SHP2 Q79R 突变体也导致紧密连接和黏附连接完整性的丧失，这与肌动蛋白细胞骨架的破坏以及黏附连接和紧密连接蛋白 N-钙黏蛋白、β-连环蛋白和 ZO-1 从质膜的定位错误相对应。这些结果表明，SHP2 是 BTB 完整性和支持细胞支持精子发生和生育力的关键调节剂。
