MOB1A (MOB kinase activator 1A) is a critical regulatory protein in the Hippo signaling pathway that controls organ size, tissue homeostasis, and tumor suppression. MOB1A functions as a scaffold protein that activates LATS1/2 kinases, which subsequently phosphorylate and inactivate the YAP1 oncoprotein, preventing its nuclear translocation and suppressing cell proliferation 1. MOB1A also cooperates with MST1/2 kinases to activate STK38 family kinases in Hippo pathway signaling 2. MOB1A loss results in severe pathological consequences. Double knockout of MOB1A/B in keratinocytes causes hyperproliferation, apoptotic resistance, and trichilemmal carcinoma development, demonstrating its essential tumor suppressor role 3. Similarly, MOB1A/B depletion in intestinal epithelium leads to loss of stem cells and epithelial degeneration through dysregulation of YAP, Wnt, and BMP/TGF-β signaling 4. Conversely, MOB1A overexpression promotes malignant behavior in ovarian cancer through aberrant activation of the PI3K/AKT/mTOR pathway, indicating context-dependent oncogenic activity 5. MOB1A has also been identified as a tumor-associated antigen recognized by tumor-infiltrating lymphocytes in high-grade serous ovarian cancer 6. Additionally, MOB1A participates in immune regulation through the Hippo pathway 1 and serves as a substrate for bacterial manipulation during Legionella infection 7. Recent multi-ancestry GWAS identified MOB1A variants associated with Alzheimer's disease risk 8.