(a) Relative levels of markers of late endosomes (Rab7a, Rab11a/b), lysosomes (Lamp1/2, M6pr) and early endosomes (Eea1, Rab5a) among endosome fractions of BBB cells, measured using LC-SRM. Peptides identified for Rab11 are common between Rab11a and Rab11b. M6pr is cation-dependent mannose-6-phosphate receptor. Shown are relative abundance (mean ± SD) of protein-specific peptides values from at least three endosome preparations. (b) Percentage of the same makers in LDFs and HDFs relative to total fractions as analyzed by LC-SRM. Shown are mean ± SD from at least three independent endosome preparations.