Figure 1

Formation of muNS-Mi microspheres inside the ER. (a) Schematic representation of the IC-Tagging methodology. muNS-Mi forms microspheres in the cytosol (1, white spheres). A protein tagged with the IC-Tag retains its normal location (2, a cytosolic protein seen green). When muNS-Mi and an IC-Tagged protein are expressed in the same cell, the IC-Tag re-localizes the IC-Tagged protein to muNS-Mi MS (3, green spheres). (b) The MS are cytosolic and can be loaded with cytosolic proteins (at the left). Our hypothesis: adding a signal peptide on the sequence of muNS-Mi will create a version of that protein (sec-muNS-Mi) that will form microspheres inside the ER, so they could be loaded with glycoproteins (on the right: the green spots represent sugar modifications). N-nucleus, C-cytosol, E-extracellular medium. (c) Immunofluorescence analysis of DF-1 cells transfected with plasmids expressing muNS-Mi (1) or sec-muNS-Mi (2, 3 and 4). Specific antibodies were used to detect muNS by indirect immunofluorescence (red) and nuclei were counterstained blue with DAPI. (d) Western-blot analysis performed with muNS-specific antibodies of extracts from DF-1 cells transfected with expression plasmids for muNS-Mi (Mi, 2 and 4) or sec-muNS-Mi (sec-Mi, 1 and 3) either before (−) or after treatment with N-glycosidase (+). Full length Western-blot is shown in Figure S7.