Subcellular localization analysis
We transfected the plasmid encoding HA-tagged full-length mr-s into HEK293T cells, seeded cells on coverslips coated with collagen 48 hr after transfection, fixed with 4% paraformaldehyde in phosphate-buffered saline (PBS) at room temperature for 20 min, and washed with PBS. Then we permeabilized cells in PBS containing 0.1% Triton X-100 for 15 min, washed again with PBS, and incubated in PBS containing 0.1% bovine serum albumin (BSA) for 30 min at room temperature. We incubated cells with anti-HA antibody overnight at 4°C (1:200 in PBS containing 0.2% BSA). The following day, we washed cells three times with PBS and incubated with a Cy3-conjugated goat IgG against rabbit IgG (1:400 in PBS, Jackson ImmunoReseach Laboratories) for 30 min. We rinsed cells three times with PBS, followed by observation using a confocal microscope FV300 (Olympus) equipped with a 60× objective lens.