Differential localization of unconventional myosin I and nonmuscle myosin II during B cell spreading

Exp Cell Res. 2006 Oct 15;312(17):3312-22. doi: 10.1016/j.yexcr.2006.07.002. Epub 2006 Jul 14.


Cross-linking of CD44 in vitro promotes chemokinesis and actin-based dendrite formation in T and B cells. However, the mechanisms by which the adhesion molecule CD44 induces cytoskeleton activation in lymphocytes are still poorly understood. In this study, we have investigated whether myosin isoforms are involved in CD44-dependent dendrite formation in activated B cells. Pharmacological inhibition of myosin with 2,3-butanedione monoxime strongly affected spreading and dendrite formation, suggesting that these cellular motors may participate in these phenomena. Furthermore, immunofluorescence analysis showed differences in subcellular localization of class I and class II myosin during B cell spreading. In response to CD44 cross-linking, myosin-1c was polarized to lamellipodia, where F-actin was high. In contrast, the distribution of cytosplasmic nonmuscle class II myosin was not altered. Expressions of myosin-1c and II were also demonstrated in B cells by Western blot. Although the inhibition of PLCgamma, PI3K and MEK-1 activation affected the spreading and dendrite formation in activated B cells, only PLCgamma and MEK-1 inhibition correlated with absence of myosin-1c polarization. Additionally, myosin-1c polarization was observed upon cross-linking of other surface molecules, suggesting a common mechanism for B cell spreading. This work shows that class I and class II myosin are expressed in B cells, are differentially distributed, and may participate in the morphological changes of these cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / analysis
  • Animals
  • B-Lymphocytes / chemistry
  • B-Lymphocytes / physiology*
  • Cell Movement / drug effects
  • Cell Movement / physiology*
  • Cell Surface Extensions / chemistry*
  • Cell Surface Extensions / drug effects
  • Diacetyl / pharmacology
  • Enzyme Inhibitors / pharmacology
  • Hyaluronan Receptors / metabolism
  • Lymphocyte Activation
  • Mice
  • Mice, Inbred BALB C
  • Myosin Type I / analysis*
  • Myosin Type I / physiology
  • Myosin Type II / analysis*
  • Myosin Type II / physiology
  • Spleen / cytology


  • Actins
  • Enzyme Inhibitors
  • Hyaluronan Receptors
  • Myosin Type I
  • Myosin Type II
  • Diacetyl