The Survival of Motor Neuron (SMN) protein interacts with the mRNA-binding protein HuD and regulates localization of poly(A) mRNA in primary motor neuron axons

Claudia Fallini, Honglai Zhang, Yuehang Su, Vincenzo Silani, Robert H. Singer, Wilfried Rossoll, Gary J. Bassell

Research output: Contribution to journalArticle

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Abstract

Spinal muscular atrophy (SMA) results from reduced levels of the survival of motor neuron (SMN) protein, which has a well characterized function in spliceosomal small nuclear ribonucleoprotein assembly. Currently, it is not understood how deficiency of a housekeeping protein leads to the selective degeneration of spinal cord motor neurons. Numerous studies have shown that SMN is present in neuronal processes and has many interaction partners, including mRNA-binding proteins, suggesting a potential noncanonical role in axonal mRNA metabolism. In this study, we have established a novel technological approach using bimolecular fluorescence complementation (BiFC) and quantitative image analysis to characterize SMN-protein interactions in primary motor neurons. Consistent with biochemical studies on the SMN complex, BiFC analysis revealed that SMN dimerizes and interacts with Gemin2 in nuclear gems and axonal granules. In addition, using pull down assays, immunofluorescence, cell transfection, and BiFC, we characterized a novel interaction between SMN and the neuronal mRNA-binding protein HuD, which was dependent on the Tudor domain of SMN. A missense mutation in the SMN Tudor domain, which is known to cause SMA, impaired the interaction with HuD, but did not affect SMN axonal localization or selfassociation. Furthermore, time-lapse microscopy revealed SMN cotransport with HuD in live motor neurons. Importantly, SMN knockdown in primary motor neurons resulted in a specific reduction of both HuD protein and poly(A) mRNA levels in the axonal compartment. These findings reveal a noncanonical role for SMN whereby its interaction with mRNA-binding proteins may facilitate the localization of associated poly(A) mRNAs into axons.

Original languageEnglish (US)
Pages (from-to)3914-3925
Number of pages12
JournalJournal of Neuroscience
Volume31
Issue number10
DOIs
StatePublished - Mar 9 2011

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Motor Neurons
Axons
Carrier Proteins
Messenger RNA
Proteins
Spinal Muscular Atrophy
Fluorescence
SMN Complex Proteins
Small Nuclear Ribonucleoproteins
Housekeeping
Missense Mutation
Survival Analysis
Fluorescent Antibody Technique
Transfection
Microscopy
Spinal Cord

ASJC Scopus subject areas

  • Neuroscience(all)

Cite this

The Survival of Motor Neuron (SMN) protein interacts with the mRNA-binding protein HuD and regulates localization of poly(A) mRNA in primary motor neuron axons. / Fallini, Claudia; Zhang, Honglai; Su, Yuehang; Silani, Vincenzo; Singer, Robert H.; Rossoll, Wilfried; Bassell, Gary J.

In: Journal of Neuroscience, Vol. 31, No. 10, 09.03.2011, p. 3914-3925.

Research output: Contribution to journalArticle

Fallini, Claudia ; Zhang, Honglai ; Su, Yuehang ; Silani, Vincenzo ; Singer, Robert H. ; Rossoll, Wilfried ; Bassell, Gary J. / The Survival of Motor Neuron (SMN) protein interacts with the mRNA-binding protein HuD and regulates localization of poly(A) mRNA in primary motor neuron axons. In: Journal of Neuroscience. 2011 ; Vol. 31, No. 10. pp. 3914-3925.
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