Department of Materials Science and Engineering, Johns Hopkins University, 3400 Charles Street, Baltimore, MD 21218, United States.
Program in Molecular Biophysics, Johns Hopkins University, 3400 Charles street, Baltimore, MD 21218, United States.
Biochim Biophys Acta Mol Cell Res. 2017 Jan;1864(1):31-38. doi: 10.1016/j.bbamcr.2016.10.011. Epub 2016 Oct 21.
All members of the Eph receptor family of tyrosine kinases contain a SAM domain near the C terminus, which has been proposed to play a role in receptor homotypic interactions and/or interactions with binding partners. The SAM domain of EphA2 is known to be important for receptor function, but its contribution to EphA2 lateral interactions in the plasma membrane has not been determined. Here we use a FRET-based approach to directly measure the effect of the SAM domain on the stability of EphA2 dimers on the cell surface in the absence of ligand binding. We also investigate the functional consequences of EphA2 SAM domain deletion. Surprisingly, we find that the EphA2 SAM domain inhibits receptor dimerization and decreases EphA2 tyrosine phosphorylation. This role is dramatically different from the role of the SAM domain of the related EphA3 receptor, which we previously found to stabilize EphA3 dimers and increase EphA3 tyrosine phosphorylation in cells in the absence of ligand. Thus, the EphA2 SAM domain likely contributes to a unique mode of EphA2 interaction that leads to distinct signaling outputs.
Eph 受体家族的所有酪氨酸激酶成员在 C 端附近都含有一个 SAM 结构域，该结构域被认为在受体同源相互作用和/或与结合伴侣的相互作用中发挥作用。EphA2 的 SAM 结构域对于受体功能很重要，但它对 EphA2 质膜中侧向相互作用的贡献尚未确定。在这里，我们使用基于 FRET 的方法直接测量 SAM 结构域在没有配体结合的情况下对细胞表面 EphA2 二聚体稳定性的影响。我们还研究了 EphA2 SAM 结构域缺失的功能后果。令人惊讶的是，我们发现 EphA2 SAM 结构域抑制受体二聚化并降低 EphA2 酪氨酸磷酸化。这一作用与我们之前发现的相关 EphA3 受体的 SAM 结构域的作用截然不同，我们发现 EphA3 受体的 SAM 结构域在没有配体的情况下稳定 EphA3 二聚体并增加 EphA3 酪氨酸磷酸化。因此，EphA2 SAM 结构域可能有助于 EphA2 相互作用的独特模式，从而产生不同的信号输出。
