We thank Cheng Xue, for his interest in our work and their thoughtful and constructive comments on our recent article published in the British Journal of Pharmacology (Duan et al., 2026). The reader raises several important mechanistic questions regarding the GRK2-NOX4 regulatory axis. We welcome this scientific discourse and provide our responses below, which we believe will further the understanding of cisplatin-induced nephrotoxicity. The reader first notes that our study utilized a pan-phospho-serine/threonine antibody to detect NOX4 phosphorylation and did not identify the specific residue(s) targeted by GRK2. We agree that identification of the precise phosphorylation site is essential to confirm direct regulation. In our original study, we used pan-phospho-serine/threonine antibodies to demonstrate that GRK2 promotes NOX4 phosphorylation and verified this effect using a kinase-dead GRK2 mutant (K220R). As suggested, we will perform mass spectrometry and site-directed mutagenesis to identify the exact residue (s) phosphorylated by GRK2. These experiments will be included in follow-up studies to fully validate direct interaction and modification. The reader also points out that we did not identify the specific E3 ligase responsible for NOX4 ubiquitination or elucidate how phosphorylation interferes with this degradation pathway. We agree that this mechanism requires further clarification. Our original data confirmed that GRK2 suppresses NOX4 ubiquitination and increases its protein stability, which is consistent with published reports that NOX4 is regulated by ubiquitin–proteasome degradation (Tsubouchi et al., 2017). As recommended, we plan to screen candidate E3 ubiquitin ligases for NOX4 and explore how GRK2-dependent phosphorylation interferes with ligase binding, protein conformation or subcellular localization. These mechanistic details will be further elucidated in our extended research. Regarding the interpretation of epithelial–mesenchymal transition (EMT), the reader suggests that interpreting tubular epithelial cell EMT as a primary source of myofibroblasts may be an oversimplification and recommends distinguishing between ‘partial EMT’ and complete fibroblast conversion. We appreciate this important clarification. In our study, EMT markers were used to indicate tubular cell dysfunction, maladaptive repair and pro-fibrotic signalling, rather than complete transition to myofibroblasts. In fact, the term “EMT” in this article was employed to describe the process by which cells acquire a mesenchymal phenotype, rather than to confirm direct conversion into fibroblasts. We agree with the reader that recent evidence highlights the role of “partial EMT” in driving fibrogenic signalling and maladaptive repair (Grande et al., 2015; Lovisa et al., 2016; Lu et al., 2025; Shi et al., 2023). We will revise and clarify this interpretation in future publications to align with current academic consensus. We greatly appreciate the positive recognition and insightful perspectives provided in the letter, as well as the valuable suggestions for strengthening the mechanistic basis of the GRK2–NOX4 regulatory axis. We fully agree that further mechanistic clarification will help consolidate our findings and inspire more in-depth investigations toward optimizing reno-protective strategies during cisplatin-based chemotherapy. We thank the reader and the journal for the opportunity to respond to these valuable comments. Key protein targets and ligands in this article are hyperlinked to corresponding entries in https://www.guidetopharmacology.org and are permanently archived in the Concise Guide to PHARMACOLOGY 2025/26 (Alexander et al., 2025). Fei Duan: Writing—review and editing; writing—original draft. Bingfa Xu: Conceptualization. Wei Wei: Conceptualization. Chun Wang: Conceptualization; writing—review and editing. The authors declare no conflicts of interest.
Duan et al. (Wed,) studied this question.