Fig. 5.

Upregulation of Rab8B induced by VCR resulted in the increase of ABCB1-enriched EVs secretion. A Human Rab GTPase family members targeting trafficking of vesicles were screened using real-time quantitative PCR. The Rabs that were significantly upregulated or downregulated (P < 0.01, > 5 fold change) by the treatment of VCR in KBv200 cells were identified and consider for further validation. B-D The treatment with VCR led to a significant increase in Rab8B protein expression level in KBv200 cells. E-F The silence of Rab8B by three different shRNAs was validated by Western blotting and qPCR, respectively. Scramble shRNA sequence was used as a control (termed as s.c.). G-H Inhibition of Rab8B reduced the rate of ABCB1 intercellular transfer.  I-J Inhibition of Rab8B resulted in a reduction in the secretion of MVs. K-L Silencing of Rab8B dramatically reduced the secretion of ABCB1 proteins. M-N  Immunoblot shows VCR suppresses the expression of Rab5 in KB cells.  O Endogenous Rab5 in KB cells is knockdown by specific siRNA against Rab5 as compared to control scramble sequence. P-Q The transfer rate of ABCB1 is increased when the expression of Rab5 is suppressed in KB cells. * = P < 0.05, ** = P < 0.01