Journal: The Journal of Biological Chemistry
Article Title: MARCH8-mediated ubiquitination regulates expression of the antiviral protein IFITM3
doi: 10.1016/j.jbc.2025.110879
Figure Lengend Snippet: MARCH8 leads to IFITM3 degradation in lysosomes through the K63-linked polyubiquitylation . A and B, MARCH8 WT and knockdown (KD) HeLa cells were treated by CHX (100 μM) for 0, 2, 4, and 6 h followed by Western blot. Lanes shown are nonadjacent but from the same immunoblot. The quantification is shown on the right ( B ). Quantifications derive from three independent experiments (mean ± SD). C, HEK293T cells were cotransfected with FLAG-IFITM3 and MARCH8 WT or empty vector. Cells were then treated with DMSO, MG132 (50 μM), bafilomycin (1 μM), CQ (50 μM), and 3-MA (100 μM) for 4 h and processed for Western blot. D, HEK293T cells were cotransfected with FLAG-IFITM3 and WT MARCH8 (WT), the W114A mutant MARCH8 (W114A), or the Y222A mutant MARCH8 (Y222A) followed by Western blot. E, statistical results of the Western blot ( D ). Values are means ± SD from three independent experiments (n = 3). Statistical differences were determined by two-sided Student’s t test; ∗∗∗ p < 0.0001. ns, nonsignificant. F , HEK293T cells were cotransfected for 24 h with HA-Ub, FLAG-IFITM3, and vector, MARCH8, or NEDD4. Cells were treated with CQ (50 μM) for 4 h. Cells were harvested for co-IP using anti-FLAG Ab-coated agarose beads and analyzed by Western blot. G, HEK293T cells were cotransfected for 24 h with HA-Ub, FLAG-IFITM3, and vector, MARCH8 WT, or MARCH8 W114A. Cells were treated with CQ (50 μM) for 4 h. Cells were harvested for co-IP using anti-FLAG beads and analyzed by Western blot. H, HEK293T cells were transfected with HA-tagged ubiquitin mutants, FLAG-IFITM3 and MARCH8. Cells were treated with CQ (50 μM) for 4 h. Cell lysates were subject to IP with anti-FLAG antibody, and the IP and input samples were analyzed by Western blot with antibodies against the indicated protein targets. Ab, antibody; CHX, cycloheximide; co-IP, coimmunoprecipitation; CQ, chloroquine; DMSO, dimethyl sulfoxide; HEK293T, human embryonic kidney 293T cell line; IFITM3, interferon-induced transmembrane protein 3; K63, lysine 63; MARCH, Membrane-Associated RING-CH; Ub, ubiquitin.
Article Snippet: Antibodies used for Western blot are as follows: MARCH8 (Proteintech; catalog no.: 14119-1-AP; 1:1000 dilution), IFITM3 (Proteintech; catalog no.: 11714-1-AP; 1:1000dilution), FLAG (Sigma–Aldrich; catalog no.: F7425; 1:2000 dilution), Myc (Sigma–Aldrich; catalog no.: C3956; 1:2000 dilution), HA.11 Epitope Tag (BioLegend; catalog no.: 901501 or catalog no.: 902301; 1:1000 dilution), and actin (Sigma–Aldrich; catalog no.: A1978; 1:2000 dilution).
Techniques: Knockdown, Western Blot, Plasmid Preparation, Mutagenesis, Co-Immunoprecipitation Assay, Transfection, Ubiquitin Proteomics, Membrane