Differential activities, subcellular distribution and tissue expression patterns of three members of Slingshot family phosphatases that dephosphorylate cofilin

Genes Cells. 2003 Oct;8(10):811-24. doi: 10.1046/j.1365-2443.2003.00678.x.


Background: Cofilin, a key regulator of actin filament dynamics, is inactivated by phosphorylation at Ser-3 by LIM-kinases and is reactivated by dephosphorylation by a family of protein phosphatases, termed Slingshot (SSH).

Results: We have identified two novel isoforms of SSHs, termed SSH-2L and SSH-3L and characterized them in comparison with SSH-1L that was previously reported. SSH-1L and SSH-2L, but not SSH-3L, tightly bound to and co-localized with actin filaments. When expressed in cultured cells, SSH-1L, SSH-2L and SSH-3L decreased the level of Ser-3-phosphorylated cofilin (P-cofilin) in cells and suppressed LIM-kinase-induced actin reorganization, although SSH-3L was less effective than SSH-1L and SSH-2L. In cell-free assays, SSH-1L and SSH-2L efficiently dephosphorylated P-cofilin, whereas SSH-3L did do so only weakly. Using deleted mutants of SSH-1L and SSH-2L, we found that the N-terminal and C-terminal extracatalytic regions are critical for cofilin-phosphatase and F-actin-binding activities, respectively. In situ hybridization analyses revealed characteristic patterns of expression of each of the mouse Ssh genes in both neuronal and non-neuronal tissues; in particular, expression of Ssh-3 in epithelial tissues is evident.

Conclusion: SSH-1L, SSH-2L and SSH-3L have the potential to dephosphorylate P-cofilin, but subcellular distribution, F-actin-binding activity, specific phosphatase activity and expression patterns significantly differ, which suggests that they have related but distinct functions in various cellular and developmental events.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actin Depolymerizing Factors
  • Actins / metabolism
  • Amino Acid Sequence
  • Animals
  • Antibodies, Monoclonal / metabolism
  • Base Sequence
  • Brain / embryology
  • Brain / enzymology*
  • Brain / metabolism
  • COS Cells
  • Cell Line
  • Chlorocebus aethiops
  • Conserved Sequence
  • HeLa Cells
  • Humans
  • Isoenzymes / genetics
  • Isoenzymes / metabolism
  • Lim Kinases
  • Mice
  • Microfilament Proteins / metabolism*
  • Molecular Sequence Data
  • Phosphoric Monoester Hydrolases / chemistry
  • Phosphoric Monoester Hydrolases / genetics
  • Phosphoric Monoester Hydrolases / metabolism*
  • Phosphorylation
  • Protein Kinases / metabolism
  • Protein Structure, Tertiary
  • RNA, Messenger / metabolism
  • Sequence Homology, Amino Acid


  • Actin Depolymerizing Factors
  • Actins
  • Antibodies, Monoclonal
  • Isoenzymes
  • Microfilament Proteins
  • RNA, Messenger
  • Protein Kinases
  • LIMK1 protein, human
  • Lim Kinases
  • Limk1 protein, mouse
  • Phosphoric Monoester Hydrolases