title: Differential localization of unconventional myosin I and nonmuscle myosin II during B cell spreading.
abstract: 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.
authors.affiliation: Department of Molecular Biomedicine, Centro de Investigación y Estudios Avanzados, Av. IPN #2508. Col. Zacatenco. CP 07360, México, D.F., México.
authors.forename: Adriana
authors.initials: A
authors.lastname: Sumoza-Toledo
authors.forename: Peter G
authors.initials: PG
authors.lastname: Gillespie
authors.forename: Hector
authors.initials: H
authors.lastname: Romero-Ramirez
authors.forename: Hellen C
authors.initials: HC
authors.lastname: Ferreira-Ishikawa
authors.forename: Roy E
authors.initials: RE
authors.lastname: Larson
authors.forename: Leopoldo
authors.initials: L
authors.lastname: Santos-Argumedo
mesh_terms: D000199:Actins / Q000032:analysis; D000818:Animals; D001402:B-Lymphocytes / Q000737:chemistry / Q000502:physiology*; D002465:Cell Movement / Q000187:drug effects / Q000502:physiology*; D022081:Cell Surface Extensions / Q000737:chemistry* / Q000187:drug effects; D003931:Diacetyl / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018960:Hyaluronan Receptors / Q000378:metabolism; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D024461:Myosin Type I / Q000032:analysis* / Q000502:physiology; D024462:Myosin Type II / Q000032:analysis* / Q000502:physiology; D013154:Spleen / Q000166:cytology
chemical_list: D000199:Actins; D004791:Enzyme Inhibitors; D018960:Hyaluronan Receptors; D024461:Myosin Type I; D024462:Myosin Type II; D003931:Diacetyl