Smn depletion alters profilin II expression and leads to upregulation of the RhoA/ROCK pathway and defects in neuronal integrity

J Mol Neurosci. 2007;32(2):120-31. doi: 10.1007/s12031-007-0024-5.


Spinal muscular atrophy (SMA) is the most common genetic disease resulting in infant mortality due to severe loss of alpha-motor neurons. SMA is caused by mutations or deletions of the ubiquitously expressed survival motor neuron (SMN) gene. However, why alpha-motor neurons of SMA patients are specifically affected is not clear. We demonstrate here that Smn knockdown in PC12 cells alters the expression pattern of profilin II, resulting in an increase in the neuronal-specific profilin IIa isoform. Moreover, the depletion of Smn, a known interacting partner of profilin IIa, further contributes to the increased profilin IIa availability. Altogether, this leads to an increased formation of ROCK/profilin IIa complex and an inappropriate activation of the RhoA/ROCK pathway, resulting in altered cytoskeletal integrity and a subsequent defect in neuritogenesis. This study represents the first description of a mechanism underlying SMA pathogenesis and highlights new targets for therapeutic intervention for this devastating disorder.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adrenal Gland Neoplasms / genetics
  • Adrenal Gland Neoplasms / pathology
  • Animals
  • Cell Differentiation
  • Cyclic AMP Response Element-Binding Protein / deficiency*
  • Cyclic AMP Response Element-Binding Protein / genetics
  • Gene Expression Regulation, Neoplastic*
  • Immunoblotting
  • Nerve Tissue Proteins / deficiency*
  • Nerve Tissue Proteins / genetics
  • Neurons / pathology
  • Neurons / physiology*
  • PC12 Cells
  • Pheochromocytoma / genetics
  • Pheochromocytoma / pathology
  • Profilins / genetics*
  • Protein Isoforms / genetics
  • RNA-Binding Proteins / genetics
  • Rats
  • Reverse Transcriptase Polymerase Chain Reaction
  • SMN Complex Proteins
  • Survival of Motor Neuron 1 Protein
  • rho-Associated Kinases / genetics*
  • rhoA GTP-Binding Protein / genetics*


  • Cyclic AMP Response Element-Binding Protein
  • Nerve Tissue Proteins
  • Profilins
  • Protein Isoforms
  • RNA-Binding Proteins
  • SMN Complex Proteins
  • Smn1 protein, rat
  • Survival of Motor Neuron 1 Protein
  • rho-Associated Kinases
  • rhoA GTP-Binding Protein