title: Small Gtpase rab3A is associated with melanosomes in melanoma cells.
abstract: Rab3A is a small guanosine triphosphate (GTP)-binding protein that has been recently implicated in intracellular vesicle transport and the secretion of neurotransmitters in neuronal cells. We demonstrate here that Rab3A is associated with melanosomes in pigment cells. Rab3A as well as Rabphilin3A, a putative target protein of Rab3A, were detected in the melanosome fraction, purified from B16 murine melanoma cells by sucrose density gradient ultracentrifugation. In contrast, Rab GDP dissociation inhibitor (GDI), a GDP/GTP exchange protein for Rab3A, was found in the cytosol fraction. Further studies using confocal laser scanning microscopy and immunoelectron microscopy revealed that immunoreactive Rab3A is localized in conjunction with the melanosomal membrane. These results suggest the possibility of involvement of Rab3A-Rabphilin3A complex, regulated by Rab GDI, in the intracellular transport of melanosomes in pigment cells.
authors.affiliation: Department of Dermatology, Kobe University School of Medicine, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Araki
authors.forename: T
authors.initials: T
authors.lastname: Horikawa
authors.forename: A K
authors.initials: AK
authors.lastname: Chakraborty
authors.forename: K
authors.initials: K
authors.lastname: Nakagawa
authors.forename: H
authors.initials: H
authors.lastname: Itoh
authors.forename: M
authors.initials: M
authors.lastname: Oka
authors.forename: Y
authors.initials: Y
authors.lastname: Funasaka
authors.forename: J
authors.initials: J
authors.lastname: Pawelek
authors.forename: M
authors.initials: M
authors.lastname: Ichihashi
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D020730:Guanine Nucleotide Dissociation Inhibitors / Q000378:metabolism; D008546:Melanoma, Experimental; D020460:Melanosomes / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018613:Microscopy, Confocal / Q000379:methods; D016253:Microscopy, Immunoelectron / Q000379:methods; D009419:Nerve Tissue Proteins / Q000378:metabolism; D013347:Subcellular Fractions; D014407:Tumor Cells, Cultured; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins / Q000378:metabolism; D020826:rab3A GTP-Binding Protein / Q000378:metabolism*; D000097624:Rabphilin-3A
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D020730:Guanine Nucleotide Dissociation Inhibitors; D009419:Nerve Tissue Proteins; D033921:Vesicular Transport Proteins; D020691:rab GTP-Binding Proteins; D020826:rab3A GTP-Binding Protein; D000097624:Rabphilin-3A; C086796:GDP dissociation inhibitor 1