SH2B1 is a multifunctional adaptor protein that serves as a critical regulator of energy homeostasis and cellular signaling. Mechanistically, SH2B1 enhances kinase activity of JAK2 and multiple receptor tyrosine kinases including insulin, IGF1, and BDNF receptors 1. In leptin signaling, SH2B1 binds simultaneously to JAK2 and IRS1/IRS2, promoting formation of signaling complexes that activate PI3-kinase pathways 2. SH2B1 localizes to plasma membranes, cytoplasm, and focal adhesions, where it regulates actin cytoskeletal reorganization and promotes cell motility 3. Genetically, SH2B1 mutations are strongly associated with early-onset obesity, leptin resistance, insulin resistance, and type 2 diabetes in humans 4. Global Sh2b1 deletion in mice produces severe obesity, insulin resistance, and hyperphagia 2, while neuron-specific restoration rescues obesity phenotypes 5. A paraventricular hypothalamus→dorsal raphe nucleus neurocircuit expressing SH2B1 regulates energy balance through BDNF/TrkB signaling 5. Beyond metabolic disease, SH2B1 expression is downregulated in Parkinson's disease brains, and neuronal SH2B1 protects against MPTP-induced dopaminergic neurodegeneration through HSC70-mediated PLIN4 degradation 6. SH2B1 has also been implicated in cancer progression across multiple tissue types 7, demonstrating pleiotropic functions in disease pathogenesis.