VPS33B deficiency results in degradation of α-granule cargo in lysosomes. (A) Both wild-type (WT) and VPS33B-KO imMKCLs were differentiated after the standard 5-day protocol and treated with bafilomycin A1 (BafA1) or the vehicle dimethyl sulfoxide during the last 24 hours. Total cell extracts were prepared, and the overall VWF and PF4 protein levels were analyzed by immunoblotting (2 independent replicates are shown). (B) The bar graph shows the quantification of independent replicates normalized to the amount of actin that was used as a loading control (WT, n = 3; VPS33B-KO, n = 5). *P ≤ .05.