Receptor for extracellular adenine nucleotides such as ADP (PubMed:25822790, PubMed:9038354, PubMed:9442040). In platelets, binding to ADP leads to mobilization of intracellular calcium ions via activation of phospholipase C, a change in platelet shape, and ultimately platelet aggregation (PubMed:9442040). {ECO:0000269|PubMed:25822790, ECO:0000269|PubMed:9038354, ECO:0000269|PubMed:9442040}. This is the function of P2RY1 (purinergic receptor P2Y1, ENSG00000169860).