In RPE cells, MCT1/CD147 is polarized to the apical and MCT3/CD147 to the basolateral membrane. In wild-type MDCK cells, all MCT/CD147 complexes are sorted basolaterally. When rCD147-L252A is expressed in MDCK cells, MCT1/ rCD147-L252A complexes are localized to the apical membrane while MCT1/CD147 complexes are basolateral. In contrast, endogenously expressed MCT4 or exogenously expressed MCT3 remain basolateral whether they are complexed with endogenous CD147 or with exogenously expressed rCD147-L252A, indicating that MCT3 and MCT4 both harbor BLSS.