title: Stimulation of microtubule-based transport by nucleation of microtubules on pigment granules.
abstract: Microtubule (MT)-based transport can be regulated through changes in organization of MT transport tracks, but the mechanisms that regulate these changes are poorly understood. InXenopusmelanophores, aggregation of pigment granules in the cell center involves their capture by the tips of MTs growing toward the cell periphery, and granule aggregation signals facilitate capture by increasing the number of growing MT tips. This increase could be explained by stimulation of MT nucleation either on the centrosome or on the aggregate of pigment granules that gradually forms in the cell center. We blocked movement of pigment granules to the cell center and compared the MT-nucleation activity of the centrosome in the same cells in two signaling states. We found that granule aggregation signals did not stimulate MT nucleation on the centrosome but did increase MT nucleation activity of pigment granules. Elevation of MT-nucleation activity correlated with the recruitment to pigment granules of a major component of MT-nucleation templates, γ-tubulin, and was suppressed by γ-tubulin inhibitors. We conclude that generation of new MT transport tracks by concentration of the leading pigment granules provides a positive feedback loop that enhances delivery of trailing granules to the cell center.
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling and Department of Cell Biology, UConn Health, Farmington, CT 06030.
authors.forename: Irina
authors.initials: I
authors.lastname: Semenova
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling and Department of Cell Biology, UConn Health, Farmington, CT 06030.
authors.forename: Dipika
authors.initials: D
authors.lastname: Gupta
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Ibaraki 305-8572, Japan.
authors.forename: Takeo
authors.initials: T
authors.lastname: Usui
authors.affiliation: Division of Applied Chemistry, Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan.
authors.forename: Ichiro
authors.initials: I
authors.lastname: Hayakawa
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling and Department of Cell Biology, UConn Health, Farmington, CT 06030.
authors.forename: Ann
authors.initials: A
authors.lastname: Cowan
authors.affiliation: R. D. Berlin Center for Cell Analysis and Modeling and Department of Cell Biology, UConn Health, Farmington, CT 06030 rodionov@uchc.edu.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Rodionov
mesh_terms: D000818:Animals; D001692:Biological Transport; D018929:Cell Culture Techniques; D018385:Centrosome / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000378:metabolism; D022162:Cytoplasmic Vesicles / Q000378:metabolism; D004398:Dyneins / Q000378:metabolism; D008547:Melanophores / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008954:Models, Biological; D009068:Movement / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology; D014404:Tubulin / Q000378:metabolism; D014981:Xenopus / Q000378:metabolism; D014982:Xenopus laevis / Q000378:metabolism
chemical_list: D014404:Tubulin; D004398:Dyneins