Fig 2: Effect of gene silencing of Rab11a and Rab11b, respectively on FN1 secretion. (A) Effect of gene silencing of Rab11 isoforms on mRNA level of Rab11 isoforms and FN1 by specific siRNAs. mRNA expression was examined by qPCR analysis. siCON, control siRNA; siRab11a, Rab11a specific siRNA; siRab11b, Rab11b specific siRNA. *** p < 0.001 vs. siCon. ns, not significant (n = 3, mean ± SD). (B) Effect of Rab11 gene silencing on Rab11 protein expression level in cell lysate. Top, representative Western blot; Bottom, statistical representation of the Western blot signal (n = 3, mean ± SD). *** p < 0.001 vs. siCon. Full-length blots were presented in Supplementary Figure S3. (C) Effect of Rab11 isoform KD on FN1 secretion. Representative image of Western blot analysis of FN1 protein amount in cell lysate and culture media. Control siRNA and Rab11a or Rab11b specific siRNA transfected HPMCs were serum starved for 16 h and cells were then treated as described in the legend for Figure 5. Full-length blots were presented in Supplementary Figure S3. (D) Statistical representation of normalized secreted level of FN1 after TGF-ß stimulation (n = 3, mean ± SD). *** p < 0.001. ns, not significant. The red spots in bar graphs display the distribution of data points.

Fig 3: T-DM1 and RAB GTPase in vitro correlations.Linear regression analysis curves between RAB5A (A), RAB4A (B), and RAB11A (C) protein expression (average of N = 3 as presented in Fig. 2) and T-DM1 sensitivity (1/IC50(T-DM1)) (average of N = 3 as presented in Fig. 1 and Table 1) in the five cell lines. D The linear regression curve between HER2 (average of N = 3 as presented in Fig. 2) × RAB5A protein expression and T-DM1 response. Each data point represents one cell line. Source data are provided as a Source Data file.

Fig 4: Structure of the SH3BP5–Rab11a complex.(A) Overall view of the SH3BP5–Rab11a complex. Rab11a is colored in pink, except that switch I, switch II, interswitch, and P loop are colored in red, orange, grey, and yellow, respectively. SH3BP5 is colored in blue. The phosphate ion bound to the P loop is shown as light green sticks. (B) Structure of the GDP-bound Rab11a. The coloring scheme is the same as that in (A). GDP is shown as light green sticks. (C) Structure of the GTP?S-bound Rab11a. The coloring scheme is the same as that in (A). GTP?S and Mg2+ are shown as light green sticks and a purple sphere, respectively.

Fig 5: Semiquantification of GEF activities.(A) GEF activities for Rab11a (1–173) and Rab11a (1–211). The kobs values for the indicated conditions are shown in dot plots. The bars represent the average values. (B) GEF activities of the SH3BP5 mutants shown in Figs 3 and 4. The kobs values for the indicated SH3BP5 mutants are shown in dot plots. The bars represent the average values. (C) GEF activities for the Rab11a mutants shown in Figs 3 and 4. The kobs values for the indicated Rab11a mutants are shown in dot plots. The bars represent the average values.