The MAS1L antibody targets the MAS1L (MAS1 proto-oncogene-like) protein, a class A G protein-coupled receptor (GPCR) and a paralogue of the MAS1 oncogene. MAS1L is encoded by the *MAS1L* gene in humans and shares partial homology with MAS1. though its physiological role remains less characterized. It is implicated in tissue development, inflammatory responses, and vascular regulation, potentially interacting with ligands like angiotensin-(1-7), albeit through distinct signaling pathways compared to MAS1. Structurally, MAS1L contains seven transmembrane domains typical of GPCRs, with extracellular and intracellular loops critical for ligand binding and downstream signaling. Research using MAS1L antibodies primarily focuses on detecting endogenous expression levels, subcellular localization, and functional studies in model systems. These antibodies are vital tools for elucidating MAS1L's role in pathologies such as cancer, cardiovascular diseases, and fibrosis. However, challenges persist due to limited knowledge of its precise ligand-receptor interactions, tissue-specific expression patterns, and cross-reactivity concerns with related GPCRs. Validation via knockout controls or siRNA knockdown is often recommended to ensure antibody specificity in applications like Western blotting, immunohistochemistry, or immunofluorescence.