Fig. 6: Loss of FKBPL and CKAP4 facilitates protein secretion.

a, b HeLa/ssRFP-EGFP-KDEL WT, FKBPL KO, CKAP4 KO, and FKBPL-CKAP4 DKO cells were incubated in full medium containing 1 μg/ml doxycycline for 16 h and analyzed by immunoblotting (a). Signal intensities of full-length ssRFP-EGFP-KDEL relative to TUBA were quantified (b). c–e HeLa/ssRFP-EGFP-KDEL WT, FKBPL KO, CKAP4 KO, and FKBPL-CKAP4 DKO cells were incubated in full medium containing 1 μg/ml doxycycline for 12 h, doxycycline-free medium for another 24 h, and analyzed by immunoblotting (c). Signal intensities of full-length ssRFP-EGFP-KDEL (d) and cleaved ssRFP-EGFP-KDEL (e) relative to TUBA were quantified. f–i HeLa/ssRFP-EGFP-KDEL WT, FKBPL-CKAP4 DKO, TEX264 KO, and FIP200 KO cells were incubated in full medium containing 1 μg/ml doxycycline for 12 h, doxycycline-free medium for another 24 h, and cell extracts (CELL) and conditioned medium (CM) were analyzed by immunoblotting (f). Signal intensities of full-length ssRFP-EGPF-KDEL (g) and the cleaved ssRFP (h) in cell extracts (CELL), and ssRFP-EGFP-KDEL (i) in CM relative to TUBA were quantified. j–m Cell extracts (CELL) and CM of HeLa/WT and FKBPL-CKAP4 DKO were analyzed by immunoblotting (j). Signal intensities of COL1A2 (k), SERPINA1 (l), and GAPDH (m) in CM relative to TUBA were quantified. Data represents the mean ± SEM of four independent experiments in (b, d, e) and four independent experiments in (g–i, k, l, and m). Differences were statistically analyzed by one-way ANOVA followed by Dunnett’s multiple comparisons test in (b, d, e, g, h, i, k, l, and m). Arbitrary units, arb. units.