CELL BIOLOGY Correction for “Shear stress-dependent regulation of apical endocytosis in renal proximal tubule cells mediated by primary cilia,” by Venkatesan Raghavan, Youssef Rbaibi, Núria M. Pastor-Soler, Marcelo D. Carattino, and Ora A. Weisz, which appeared in issue 23, June 10, 2014, of Proc Natl Acad Sci USA (111:8506–8511; first published May 27, 2014; 10.1073/pnas.1402195111).
The authors wish to note: “We recently discovered an error in our calculation of fluid shear stress (FSS) in our endocytosis experiments performed in ibidi 6-chamber slides. Based on the manufacturer’s guidelines, the endocytosis studies in Figs. 2, 3, and 5 and in Figs. S3 B and C were performed using a FSS of 0.1 dyne/cm2 instead of the intended 1 dyne/cm2. The x axis in Fig. 2C should accordingly be scaled tenfold lower that in the original publication. This discrepancy in FSS does not alter the primary conclusions of our work. However, our suggestion based on the data in Fig. 2C that proximal tubule (PT) cells tune their internalization capacity in response to altered glomerular filtration rates (GFRs) within the normal physiologic range is now in question, as it appears that endocytosis in proximal tubule cells is activated even by exposure to very low fluid shear stress. We apologize for the error.” The corrected Fig. 2 and its corrected legend appear below.
Fig. 2.
Time course, reversibility, and FSS threshold of FSS-stimulated apical endocytosis. (A) Time course of onset of FSS-stimulated endocytosis. OK cells plated in Ibidi μ-slide chambers were incubated under static conditions or exposed to 0.1-dyne/cm2 FSS in the presence of 40 µg/mL Alex Fluor 647-albumin for the indicated time periods, then fixed, and average internalized fluorescence quantified from 15 to 20 fields per condition. *P < 0.04 vs. paired static control by Student t test. (Inset) Albumin uptake over a 1–3-h time course. *P < 0.02 vs. static control by t test. (B) Reversibility of FSS-stimulated endocytosis. OK cells were exposed to 0.1-dyne/cm2 FSS for 1 h in the presence (1) or absence (2–4) of 40 µg/mL Alexa Fluor 647-albumin. Cells were then fixed immediately (1) or incubated under static conditions for 15 min (2), 30 min (3), or 60 min (4) before addition of 40 µg/mL Alex Fluor 647-albumin for 1 h. As controls, Alexa Fluor 647-albumin was added to cells incubated under static conditions for 1 h at the start of the time course (5) or after 2 h (6) to coincide with the uptake period for sample 4. Internalized fluorescence was quantified for five fields per condition. The average fluorescence ± range from two independent experiments is plotted. *P < 0.05 vs. static control (sample 6) by ANOVA with Bonferroni correction. All other pairwise comparisons are not significantly different. (C) OK cells were incubated with 40 μg/mL Alexa Fluor 647-albumin for 1 h under static conditions (0 dyne/cm2) or during exposure to the indicated FSS. Average internalized fluorescence was quantified from four wells for each time point. *P < 0.05 vs. all other conditions by ANOVA, except endocytosis measured at 0.10 vs. 0.15 dyne/cm2 are not significantly different from each other.