Journal: Cellular and Molecular Life Sciences: CMLS
Article Title: A regulatory circuit operated by KDELR1 and KDELR3 fine-tunes the composition of the early secretory pathway
doi: 10.1007/s00018-025-06049-1
Figure Lengend Snippet: Different roles of human KDELRs. A Seventy-two hours after silencing with the indicated KDELR-specific duplexes, the supernatants of cells cultured for six hours were harvested and analysed by WB. Aliquots of the lysates and supernatants (the latter tenfold concentrated) of HeLa Milano cells were resolved under reducing conditions on a 4–12% pre-casted polyacrylamide gel run in MOPS buffer. After transfer to nitrocellulose, the membrane was first stained with anti-KDEL antibodies (clone 10C3, Enzo Life Sciences) and subsequently with anti-ERp44 and anti-AGR2, as indicated. Tubulin was used as a loading control. The simultaneous KD of all KDELRs (lanes 3 and 9) induced the extracellular release of all the ER-resident proteins visualized intracellularly. The identity of the two upper bands recognized by anti-KDEL (denoted X and Y) remains to be established. The intracellular signal corresponding to ERp44 and ERp46 (IN) disappeared almost completely upon downregulation of all KDELRs (lane 3), and partially under KDELR2 KD (lane 5). Noteworthy, instead, AGR2 increased dramatically upon downregulation of ERp44 or KDELR3 (lanes 2 and 6, respectively). See panel C for the relative quantifications. B Visual pulse-chase assays [ , ] (see also Materials and Methods for details) were used to compare the secretion rate of Halo-ERp44ΔRDEL (Halo-ERp44Δ), Halo-ERp46ΔKDEL (Halo-ERp46Δ), Halo-PDIΔKDEL (Halo-PDIΔ) and spHalo . The left panel shows the WB image of one representative experiment out of three, highlighting the signal of the fluorescent Halo-TMR used for the pulse (and visualized with a 532 nm laser). Densitometric quantifications are reported in the right panel (average of three independent experiments). The ratio of secreted/intracellular TMR-labelled signals was calculated for each time point (OUT/IN) and normalized to the ratio obtained for spHalo CTRL at 120 min time point, assumed to represent unassisted secretion . Statistical significance was calculated by Two-way ANOVA. The colours of the asterisks refer to the samples against which the comparison was performed. C Densitometric quantification of four independent WBs like the one shown in panel A. The bands specifically decorated by anti-AGR2 antibodies were quantified and normalized against tubulin. The ratios obtained were normalized to untreated cells. Statistical significance was calculated by an unpaired Student's t-test. D HeLa Milano cells were treated with duplexes specific for silencing ERp44 (44) ERp46 (46), or with control reagents (-) as indicated. Aliquots of their lysates were separated on 4–12% polyacrylamide gels under reducing conditions, blotted onto nitrocellulose and decorated with the antibodies indicated on the right-hand margin. Tubulin was used as loading control. Note the increase of AGR2 upon ERp44 KD but not ERp46 KD (compare lanes 2 and 3). The red asterisk points at a background band recognized by anti-ERp46 antibodies in this experiment. E HeLa Milano (left panel) and mucin-producing Caco-2 cells (right panel) were treated with ERp44- or AGR2- specific duplexes, or with control reagents (-) as indicated. Aliquots of their lysates (IN) and of their culture supernatants (OUT) ten-fold concentrated were separated on 4–12% polyacrylamide gels under reducing conditions, blotted onto nitrocellulose and decorated with the indicated antibodies. Ponceau signals provided loading controls
Article Snippet: AGR2 , Rabbit (Proteintech) , 1:500 in PBS 0.1% Tween.
Techniques: Cell Culture, Membrane, Staining, Control, Pulse Chase, Comparison