Lu/BCAM membrane localization. (A) FRAP of biotin-labeled erythrocytes (top row; original magnification ×40) and Lu/BCAM-labeled, neuraminidase-treated, erythrocytes (bottom row). Alexa Fluor 488 was bleached at 70% output power for 3 iterations for a duration of 1.29 seconds. (B) FRAP quantification of biotin-labeled erythrocytes (dotted line), untreated Lu/BCAM-labeled erythrocytes (thin line), and neuraminidase-treated Lu/BCAM-labeled erythrocytes (thick line). (C) Lu/BCAM western blot of DSM and DRM either treated with neuraminidase (+) or not treated (−). Membrane was separated using 1% Triton X-100. Flotillin was used as a positive control to show successful isolation of lipid rafts (DRM). (D) Depicted is how GpC-derived sialic acid residues interact with arginine 338 on the third domain of Lu/BCAM, inhibiting the interaction with laminin-α5. Upon loss of sialic acid residues, through either erythrocyte aging or removal of sialic acid by neuraminidase, this interaction is lost, leading exposure of the sialic acid binding domain of Lu/BCAM, facilitating an interaction with laminin-α5–derived sialic acid residues.