Live cell imaging reveals 3′-UTR dependent mRNA sorting to synapses

Abstract

mRNA transport restricts translation to specific subcellular locations, which is the basis for many cellular functions. However, the precise process of mRNA sorting to synapses in neurons remains elusive. Here we use Rgs4 mRNA to investigate 3′-UTR-dependent transport by MS2 live-cell imaging. The majority of observed RNA granules display 3′-UTR independent bidirectional transport in dendrites. Importantly, the Rgs4 3′-UTR causes an anterograde transport bias, which requires the Staufen2 protein. Moreover, the 3′-UTR mediates dynamic, sustained mRNA recruitment to synapses. Visualization at high temporal resolution enables us to show mRNA patrolling dendrites, allowing transient interaction with multiple synapses, in agreement with the sushi-belt model. Modulation of neuronal activity by either chemical silencing or local glutamate uncaging regulates both the 3′-UTR-dependent transport bias and synaptic recruitment. This dynamic and reversible mRNA recruitment to active synapses would allow translation and synaptic remodeling in a spatially and temporally adaptive manner.

Differential regulation of local mRNA dynamics and translation following long-term potentiation and depression

“…The mechanisms underlying the initial capture and enduring sequestration of mRNAs are not well understood. Recent work with Rgs4 indicated that neuronal activity is essential for the capture of mRNAs at dendritic spines; inhibition of neuronal activity with TTX suppressed mRNA-spine association ( 24 ). An activity dependence for spine capture has also been reported with β-actin during glutamate uncaging ( 22 ).…”

“…mRNAs are believed to be transported in a translationally quiescent state, likely only engaged in translation near synapses ( 22 , 23 ). The dynamic and bidirectional ( 22 , 24 – 26 ) scanning behavior of mRNAs in dendrites allows, in principle, for the capture and translation of mRNAs as needed for proteome maintenance and remodeling ( 22 , 23 ). Our understanding of these processes, however, is largely derived from live imaging experiments for a limited number of individual candidate mRNAs including β-actin ( 22 , 25 ) and Arc ( 27 ); the relationship between the sequestration/capture of RNAs and their translation during plasticity is not well understood.…”

Differential regulation of local mRNA dynamics and translation following long-term potentiation and depression

“…mRNAs are believed to be transported in a translationally quiescent state-likely only engaged in translation near synapses 22,23 . The dynamic and bidirectional 22,24–26 scanning behavior of mRNAs in dendrites allows, in principle, for the capture and translation of mRNAs as needed for proteome maintenance and remodeling 22,23 . Our understanding of these processes, however, is largely derived from live imaging experiments for a limited number of individual candidate mRNAs Beta actin 22,25 and Arc 27 ; the relationship between the sequestration/capture of RNAs and their translation during plasticity is not well understood.…”

Cytoplasmic mRNPs revisited: Singletons and condensates

“…mRNA exhibited a complex migratory behavior with an anterograde bias, mediated by the RNA-binding protein Staufen 2. [48] Moreover,…”

“…By means of the MS2‐MCP system in rat hippocampal neurons, it was shown that a reporter mRNA containing the 3′UTR from Rgs4 mRNA exhibited a complex migratory behavior with an anterograde bias, mediated by the RNA‐binding protein Staufen 2. [ 48 ] Moreover, Rgs4 3′UTR also increased mRNA docking and undocking events closer to synapses. However, the anterograde transport bias was not only dependent on the 3′UTR but also on neuronal activity, since its inhibition abolished the bias.…”