LAMTOR2 (p14) is a core component of the Ragulator complex that functions as a critical regulator of mTORC1 signaling and cellular nutrient sensing. As part of the pentameric Ragulator complex, LAMTOR2 acts as a guanine nucleotide exchange factor (GEF) and adapter protein that activates Rag GTPases and recruits them to the lysosomal membrane 1. This positioning enables mTORC1 assembly and activation in response to amino acid availability, facilitating cell growth regulation 2. LAMTOR2 plays dual roles in immune defense: it mediates TAX1BP1-dependent xenophagy against bacterial pathogens like Group A Streptococcus and Salmonella by enabling autolysosome formation 3, and it enhances macrophage antimicrobial responses through SCFA-GPR43 signaling, promoting phagosome-lysosome fusion and ERK phosphorylation 4. Beyond immunity, LAMTOR2 participates in disease pathogenesis: it interacts with BCLAF1 to regulate osteoarthritic cartilage degradation 5, serves as a scaffold enabling VSIG2-mediated mTOR hyperactivation in pancreatic cancer 6, and is elevated in ankylosing spondylitis where it promotes pathogenic TH17 cell differentiation 7. Genetic deficiency of LAMTOR2 causes primary immunodeficiency with hypopigmentation 8, underscoring its essential role in immune homeostasis and melanocyte biology.