Fig. 2.

R3HDM1 and ARPP21 localize to the cytosol and show overlapping staining with the stress granule marker eIF3η in response to stress. a, b FLAG immunostainings of HeLa cells expressing N-terminally FLAG-tagged R3HDM1 or ARPP21 reveal cytosolic localization in small, perinuclear-enriched granules. The right panel in b shows a higher magnification of the dotted box in the left panel. c Diffuse, cytosolic staining of the stress granule marker eIF3η is visible under basal conditions. d Treatment of HeLa cells with arsenite induces stress granules positive for eIF3η. e, f ARPP21 and R3HDM1 colocalize with eIF3η upon arsenite stimulation. g Quantification of eIF3η colocalization with R3HDM1 and the two ARPP21 protein isoforms. Data expressed as mean ± s.d. R3HDM1: n = 94 cells. ARPP21-807aa. n = 89 cells. ARPP21-88aa: n = 141 cells. ***p < 0.001, Student’s t-test. h Schematic depiction of ARPP21 truncation mutants used in i and j. i ARPP21 lacking its C-terminal region (green) shows no colocalization with eIF3η (red) upon cellular stress. j Upon cellular stress localization of the C-terminal ARPP21 construct lacking N-terminal domains (green) overlaps with eIF3η (red). k, l Staining of endogenous ARPP21 (green), eIF3η (magenta), and phalloidin (red) in cultured primary cortical neurons after 4 days in vitro (DIV4). k Under basal conditions ARPP21 localizes to neuronal cell bodies and proximal dendrites. l Upon arsenite treatment ARPP21 colocalizes with the SG marker eIF3η. Scale bar in all images: 10 µm