MAP3K1 is a serine/threonine protein kinase that functions as a crucial hub in mitogen-activated protein kinase signal transduction cascades 1. The protein activates both ERK and JNK kinase pathways through phosphorylation of MAP2K1 and MAP2K4, and may directly phosphorylate MAPK8/JNK1 12. Additionally, MAP3K1 activates CHUK and IKBKB, central kinases in the NF-κB inflammatory pathway 1. Mechanistically, MAP3K1 operates within a phospho-regulatory module balanced by the PPP2R3C phosphatase at centrosomes, where dysregulation impairs microtubule organization and centrosome function 3. Clinically, MAP3K1 mutations are associated with 46,XY gonadal dysgenesis through gain-of-function mechanisms that increase ERK1/ERK2 and p38 phosphorylation, interfering with testis determination 4. In breast cancer, MAP3K1 mutations drive tumor immune heterogeneity in HR+/HER2- tumors by suppressing MHC-I antigen presentation through TAP1/2 degradation, enabling immune escape 5. Germline MAP3K1 polymorphisms (rs889312) predict poor overall survival across multiple cancer types 6, and sex-specific variants associate with gastric cancer risk, particularly in men with low soy product intake 7. MAP3K1 genetic variation also associates with acute respiratory distress syndrome outcomes, with variants correlating to heightened inflammatory cytokine production 8.