In the article “HIV Nef-mediated Major Histocompatibility Complex Class I Down-Modulation Is Independent of Arf6 Activity,” by Jakob E. Larsen, Ramiro H. Massol, Thomas J.F. Nieland, and Tomas Kirchhausen (Mol. Biol. Cell [2004] 15, 323-331; 10.1091/mbc.E03-08-0578), the caption for Figure 1 should read as follows:

Figure 1. Down-modulation of MHC-I molecules induced by Nef in Jurkat T-cells and U373mg astrocytoma cells. (A) Jurkat T-cells were transduced with retroviral constructs to express either EGFP, or the chimera proteins Nef, NefM20A, NefAxxA, or NefAAAA fused to EGFP for 48 h. (B) The extent of downregulation of MHC-I and CD4 molecules at the cell surface and the expression level of EGFP were determined by flow cytometry and are plotted on a logarithmic scale. For each experiment, 25,000 cells were analyzed. (C) MHC-I rates of internalization in Jurkat T-cells in the absence of Nef or expressing wild-type and mutant Nef proteins, determined as the percent fraction of cell surface MHC-I molecules internalized as a function of time. (D) Uptake of MHC-I in U373mg astrocytoma cells expressing wild-type or mutants forms of Nef. 72 h after Transduction, cells were incubated at 37°C with Alexa594-anti-MHC-I for 4 h and with Alexa647-transferrin during the last 30 min. Each image corresponds to single confocal sections of randomly selected fields of cells. Bar, 20μm

Also, on page 326, col. 2, line 13, the first full sentence should read as follows:

Similar expansion of the tubular notwork was observed with Jurkat T-cells (Figure 3C). The online version of the article has been corrected. The authors apologize for the errors.

The figure captions in the article “HIV Nef-mediated Major Histocompatibility Complex Class I Down-Modulation Is Independent of Arf6 Activity”, by Jakob E. Larsen, Ramiro H. Massol, Thomas J. F. Nieland, and Tomas Kirchhausen (Mol. Biol. Cell [2004], 15, 323-331; 10.1091/mbc.E03-08-0578), were published in error. The online version of the article has been corrected.