Local protein synthesis allows neurons to respond rapidly to stimuli and is one mechanism that underlies long-lasting synaptic changes. Krichevsky and Kosik investigated how RNA granules in neurons were affected by depolarization. The RNA granules became more accessible to antibody labeling and were ultrastructurally more dispersed, less compact structures after depolarization. RNA granules did not incorporate radioactive amino acids, nor could various translation factors be detected in them, indicating that they are not translationally competent. Analysis of the distribution of mRNAs in response to depolarization showed that certain somatodendritic RNAs, such as those for calcium-calmodulin-dependent kinase II and the neurotrophin receptor TrkB, redistributed from the granules to the polysome pool for translation. The authors suggest that the RNA granules are a storage site to hold inactive mRNAs, from which they can be rapidly released for translation in response to stimulation.
A. M. Krichevsky, K. S. Kosik, Neuronal RNA granules: A link between RNA localization and stimulation-dependent translation. Neuron 32, 683-696 (2001). [Online Journal]