The NADPH oxidase 2 (NOX2) complex is a critical regulator of immune homeostasis. It is utilized by phagocytic leukocytes including neutrophils, monocytes, and macrophages to generate reactive oxygen species (ROS) that drive microbe clearance and modulate inflammatory responses. Within NOX2, the essential scaffold protein p47phox plays a pivotal role in orchestrating enzyme activation and facilitating the assembly and membrane translocation of cytosolic components of the complex. Tight regulation of p47phox activity is crucial, and its disruption is linked to a number of pathological conditions. Conversely, its hyperactivity contributes to oxidative stress, tissue damage, the progression of cardiovascular diseases, neurodegenerative disorders, inflammatory conditions, metabolic syndromes, and cancer. In this review, we detail the structural and functional roles of p47phox, mechanisms of its regulation, and its multifaceted contributions to disease pathogenesis. We explore the latest advances in p47phox-targeted therapeutic strategies, discuss current challenges in the field, highlight p47phox’s potential as a transformative target in redox biology and propose future directions to unlock its clinical utility.

Clear cell renal cell carcinoma (ccRCC) is the most prevalent form of RCC and is defined by loss of von Hippel–Lindau (VHL) function and dysregulated hypoxia signaling. Hyperactivation of the mTOR pathway is also frequently observed. These factors increase anabolic and protein-synthetic demand leading to proteotoxic stress. To survive under these conditions, ccRCC cells rely on adaptive endoplasmic reticulum (ER) stress responses and autophagy to maintain proteostasis. Regulated in Development and DNA Damage Response 1 (REDD1, also known as DDIT4) is a key stress response protein that integrates hypoxic, metabolic, and ER stress signals to regulate mechanistic target of rapamycin (mTOR) complex 1 (mTORC1) activity and redox homeostasis. REDD1 can either suppress tumor growth through mTOR inhibition or promote survival by facilitating oxidative stress tolerance and autophagy depending on the specific context. In ccRCC, REDD1 expression is driven by VHL loss and HIF stabilization. Yet, mTORC1 activity frequently persists due to dysregulation of upstream repressors such as TSC1/TSC2, direct activating mutations in mTOR, and enhanced growth factor signaling. This paradox underscores the complex interplay between REDD1 and the oncogenic signaling landscape of RCC. Here, we review emerging evidence positioning REDD1 as a pivotal link between hypoxia, mTOR signaling, and ER stress in ccRCC and discuss how therapeutic modulation of this pathway through ER stress inducers, proteasome inhibitors, and p97/valosin-containing protein (VCP) inhibitors may overcome adaptive resistance and improve patient outcomes.