Organic anion transporter polypeptide 4C1 or OATP4C1 is a human protein. It is also known as "solute carrier organic anion transporter family member 4A1". OATP4C1 is coded for by the gene SLCO4C1, which is located on chromosome 5q21. The OATP4C1 protein is expressed in the basolateral membrane of the nephron of the human kidney, where it is involved in the uptake of organic anions for elimination in the urine. The drug digoxin is an important substrate of this transporter.