Nucleoporin TPR integrates MAPK signaling with mitogen-induced transcriptional programs.

The nuclear pore complex (NPC) component TPR has emerged as a multifunctional scaffold implicated in mitosis, chromatin organization, mRNA export, and genome stability. However, TPR's role in mitogenic signal transduction remains largely unexplored. Here, we investigate whether nucleoporin TPR functions as a MAPK-regulated nuclear component that modulates mitogenic signals initiated at the plasma membrane-including EGFR activation-and their transcriptional output. Transcriptomic profiling reveals that TPR depletion reshapes EGF-induced, MAPK-responsive gene expression, including altered expression of MAPK pathway components and enhanced induction of the immediate-early gene FOS. Functionally, TPR-depleted cells exhibit increased FOS induction upon EGF stimulation and altered EGF-driven cell-cycle progression. Using a novel phospho-specific monoclonal antibody, we show that TPR is phosphorylated at Ser2155 following EGFR activation via the canonical RAS-RAF-MEK-ERK MAPK cascade, placing TPR downstream of MAPK pathway activation. This phosphorylation is suppressed by clinically used EGFR and BRAF inhibitors and, conversely, is constitutively induced by oncogenic RAS and BRAF, indicating that Ser2155 phosphorylation reflects MAPK pathway activity. In vivo, CRISPR/Cas9-engineered Tpr haploinsufficient mice show changes in MAPK pathway regulatory gene expression in bulk spleen RNA-seq, consistent with findings in human cells, and enhanced Fos induction in splenocytes upon CD3/CD28 stimulation, together suggesting a conserved association between TPR levels and altered MAPK-related transcriptomic profiles. Finally, immunohistochemical analysis reveals elevated TPR phosphorylation in serous ovarian carcinoma and heterogeneous phosphorylation patterns in triple-negative breast cancer, two tumor types frequently characterized by MAPK pathway hyperactivation. Together, these findings uncover a previously unappreciated role for TPR as a MAPK-responsive nuclear factor and support a model in which NPC-associated components fine-tune mitogen-induced transcriptional responses.