Mer Proteins

Mer, also known as MerTK or c-Mer, is the third TAM receptor tyrosine kinase and a central executor of efferocytosis, the phagocytic clearance of apoptotic cells. Through Gas6 and PROS1 ligation, MerTK triggers cytoskeletal remodeling in macrophages and retinal pigment epithelium while inducing anti-inflammatory gene programs. In the retina, daily MerTK-mediated engulfment of photoreceptor outer segments is indispensable, and loss-of-function mutations cause a form of retinitis pigmentosa. The receptor is broadly expressed in myeloid cells and upregulated in tumors, where it fosters immune evasion; both MerTK-blocking antibodies and small molecules are being explored to restore antitumor immunity.