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

• Published in: Experimental cell research 2006-10, Vol.312 (17), p.3312-3322
• Main Authors: Sumoza-Toledo, Adriana, Gillespie, Peter G., Romero-Ramirez, Hector, Ferreira-Ishikawa, Hellen C., Larson, Roy E., Santos-Argumedo, Leopoldo
• Format: Article
• Language: English
• Subjects: Actins - analysis; Animals; B cell; B-Lymphocytes - chemistry; B-Lymphocytes - physiology; CD44; Cell adhesion & migration; Cell Movement - drug effects; Cell Movement - physiology; Cell Surface Extensions - chemistry; Cell Surface Extensions - drug effects; Cellular biology; Cytoskeleton; Diacetyl - pharmacology; Enzyme Inhibitors - pharmacology; F-actin; Genetics; Hyaluronan Receptors - metabolism; Lymphocyte Activation; Mice; Mice, Inbred BALB C; Myosin; Myosin Type I - analysis; Myosin Type I - physiology; Myosin Type II - analysis; Myosin Type II - physiology; Pharmacology; Spleen - cytology; Spreading
• ISSN: 0014-4827; 1090-2422
• DOI: 10.1016/j.yexcr.2006.07.002

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 PLCγ, PI3K and MEK-1 activation affected the spreading and dendrite formation in activated B cells, only PLCγ 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.