MDM2 Protein, Human

MDM2 Protein, an E3 ubiquitin-protein ligase, plays a central role in the intricate regulation of cellular processes by mediating the ubiquitination and subsequent proteasomal degradation of the tumor suppressor p53/TP53, leading to its downregulation. Beyond its interaction with p53/TP53, MDM2 inhibits p53/TP53- and p73/TP73-mediated cell cycle arrest and apoptosis by binding to their transcriptional activation domain, highlighting its role as a negative regulator of these critical cellular responses. Not limited to its interactions with p53/TP53, MDM2 functions as a ubiquitin ligase E3 toward itself and ARRB1, permitting the nuclear export of p53/TP53 and promoting the proteasome-dependent ubiquitin-independent degradation of retinoblastoma RB1 protein. Additionally, MDM2 inhibits DAXX-mediated apoptosis by inducing its ubiquitination and degradation, demonstrating its versatile involvement in apoptotic pathways. As a component of various complexes, including TRIM28/KAP1-MDM2-p53/TP53 and TRIM28/KAP1-ERBB4-MDM2, MDM2 links growth factor and DNA damage response pathways. It further mediates ubiquitination and proteasome degradation of DYRK2, IGF1R, SNAI1, DCX, and DLG4, influencing diverse cellular functions such as dendritic spine density, receptor endocytosis, and mitochondrial respiration. Through its interactions with NDUFS1, MDM2 negatively regulates mitochondrial respiration, leading to increased oxidative stress and commitment to the mitochondrial pathway of apoptosis. These multifaceted roles underscore the intricate regulatory functions of MDM2 in cellular homeostasis and stress responses.