MAP3K19 is a serine/threonine kinase that functions as a mitogen-activated protein kinase kinase kinase, activating downstream MAPK signaling cascades. Mechanistically, MAP3K19 directly phosphorylates MEK and MKK7, thereby activating ERK and JNK kinases 1. The kinase operates in a RAF-independent manner to sustain ERK pathway activation 1. MAP3K19 plays critical roles in multiple pathological contexts. In idiopathic pulmonary fibrosis (IPF), MAP3K19 is upregulated and essential for TGF-β pathway-mediated myofibroblast differentiation and extracellular matrix deposition; targeting MAP3K19 attenuates fibroblast activation both in vitro and in humanized models 2. In chr2 obstructive pulmonary disease (COPD), MAP3K19 is overexpressed in alveolar macrophages and bronchial epithelium, where it activates NF-κB and pro-inflammatory chemokines (CXCL-8, CCL-20, CCL-7) in response to cigarette smoke; MAP3K19 inhibition reduces pulmonary inflammation and emphysematous changes 3. In oncology, MAP3K19 is essential for KRAS-mutant lung cancer cell survival through sustained ERK/JNK activation 1. Additionally, MAP3K19 genetic variants are associated with keratoconus, a progressive corneal disorder 45, and have been identified in bicuspid aortic valve patients 6. These findings establish MAP3K19 as a therapeutic target in fibrotic, inflammatory, and neoplastic lung diseases.