Vido Michael J, Rock Justin, Aplin Andrew E
Department of Cancer Biology, Thomas Jefferson University, Philadelphia, PA, USA.
Jefferson College of Life Sciences, Thomas Jefferson University, Philadelphia, PA, USA.
Pigment Cell Melanoma Res. 2021 Jul;34(4):696-702. doi: 10.1111/pcmr.12932. Epub 2020 Oct 14.
The serine-threonine kinase, BRAF, is an upstream regulator of the MEK-ERK1/2 pathway and is commonly mutated in cancer. 14-3-3 proteins bind to two sites in BRAF, N-terminal S365, and C-terminal S729. 14-3-3 binding modulates the activity and dimerization of both wild-type and non-V600 mutant forms of BRAF. In BRAF V600E mutants, the C-terminal S729 site affects dimerization of truncated splice variants. The N-terminal, S365, is removed in BRAF V600E splice variants but its importance in full-length BRAF V600 mutants remains uncertain. We tested the role of S365 in dimerization and RAF inhibitor resistance in full-length BRAF V600E. Mutating BRAF S365 site to an alanine (S365A) reduced 14-3-3 association and increased BRAF V600E homodimerization. BRAF V600E S365A displayed reduced sensitivity to RAF inhibitor at the level of MEK-ERK1/2 signaling, cell growth, and cell viability. These data suggest that alteration or removal of the S365 14-3-3 binding site may contribute to RAF inhibitor resistance.
丝氨酸 - 苏氨酸激酶BRAF是MEK - ERK1/2信号通路的上游调节因子，在癌症中常发生突变。14 - 3 - 3蛋白与BRAF的两个位点结合，即N端的S365和C端的S729。14 - 3 - 3的结合调节野生型和非V600突变型BRAF的活性和二聚化。在BRAF V600E突变体中，C端的S729位点影响截短剪接变体的二聚化。在BRAF V600E剪接变体中，N端的S365被去除，但其在全长BRAF V600突变体中的重要性仍不确定。我们测试了S365在全长BRAF V600E二聚化和RAF抑制剂抗性中的作用。将BRAF的S365位点突变为丙氨酸（S365A）可减少14 - 3 - 3的结合并增加BRAF V600E的同源二聚化。BRAF V600E S365A在MEK - ERK1/2信号传导、细胞生长和细胞活力水平上对RAF抑制剂的敏感性降低。这些数据表明，S365的14 - 3 - 3结合位点的改变或去除可能导致RAF抑制剂抗性。
