[Show abstract][Hide abstract] ABSTRACT: Cellular stress leads to a change in distribution of RNA-binding proteins. HuR, a member of the ELAV/Hu family of RNA-binding proteins, is nuclear in distribution and following heat shock is found in large cytoplasmic stress granules where translation is inhibited. HuD, another ELAV/Hu RNA-binding protein, stabilizes the GAP-43 mRNA in response to nerve growth factor (NGF) stimulation in PC12 cells. We were interested in determining the nuclear distribution of HuD and if neurotrophic stimulation induced changes in the distribution of HuD. In PC12 cells, we found, as expected, that HuR translocates from the nucleus to the cytoplasm in response to heat shock. In response to heat shock, HuD forms large cytoplasmic stress granules, consistent with a role for HuD in the cessation of translation. In unstimulated cells, HuD is distributed in small granules in the cytoplasm and is consistently present at low levels in the nucleus. Stimulation of PC12 cells with NGF induces neuronal differentiation including outgrowth of neurites and increased levels of GAP-43 protein, whereas HuD remains localized in small cytoplasm granules and is still present in the nucleus. These results suggest that, following neurotrophic stimulation, the lack of changes in HuD distribution are due to continued steady state of HuD nuclear shuttling in PC12 cells, or that HuD is not normally shuttled from the nucleus in response to NGF.
Preview · Article · Nov 2006 · Journal of Histochemistry and Cytochemistry
[Show abstract][Hide abstract] ABSTRACT: The neuron-specific ELAV/Hu family member, HuD, interacts with and stabilizes GAP-43 mRNA in developing neurons, and leads to increased levels of GAP-43 protein. As GAP-43 protein is enriched in growth cones, it is of interest to determine if HuD and GAP-43 mRNA are associated in developing growth cones. HuD granules in growth cones are found in the central domain that is rich in microtubules and ribosomes, in the peripheral domain with its actin network, and in filopodia. This distribution of HuD granules in growth cones is dependent on actin filaments but not on microtubules. GAP-43 mRNA is localized in granules found in both the central and peripheral domains, but not in filopodia. Ribosomes were extensively colocalized with HuD and GAP-43 mRNA granules in the central domain, consistent with a role in the control of GAP-43 mRNA stability in the growth cone. Together, these results demonstrate that many of the components necessary for GAP-43 mRNA translation/stabilization are present within growth cones.
Full-text · Article · Nov 2004 · Journal of Neurobiology