FIG. 2.

Association of Caprin-1-containing granules with microtubules and with cellular processes. (A) Caprin-1-containing granules occur on a filamentous network resembling the microtubular network and are enriched in cellular processes. 3T3 cells that stably expressed low amounts of Caprin-1-HA were stained for HA (red). Arrows point to the Caprin-1-positive granules arrayed on a filamentous network and enriched in cellular processes. (B, C) Caprin-1 localizes at sites of adhesion and at the leading and trailing edges of migrating 3T3 fibroblasts and HeLa cells. In panel B, 3T3 cells that stably expressed low amounts of Caprin-1-HA were stained for HA (red). In panel C, HeLa cells were stained for endogenous Caprin-1 (green) and G3BP-1 (red). Nuclei were stained with DAPI (blue). The asterisks indicate concentrations of Caprin-1-HA in panel B and Caprin-1 and G3BP-1 in panel C at the sites of cell adhesion and at the leading and trailing edges of cells. (D) Caprin-1-containing cytoplasmic granules are associated with microtubules. Actively growing HeLa cells were treated with nocodazole (33 μM) for 90 min to disrupt microtubules and stained with rabbit anti-Caprin-1 serum (red) and anti-β-tubulin MAb (green). Note that nocodazole treatment resulted in the loss of the filamentous distribution of Caprin-1 in the cytoplasm and the coredistribution of Caprin-1 and β-tubulin into blebs. (E) Caprin-1-containing cytoplasmic granules are transport RNPs. Actively growing HeLa cells were stained with anti-Caprin-1 serum (green) and the stress granule marker TIA-1 (red). Note the absence of TIA-1 in Caprin-1-positive cytoplasmic granules.