title: Co-localization of rab4 with endocytosis-related proteins in the rat parotid glands.
abstract: Small GTP-binding proteins have been implicated in the regulation of vesicular traffic. We investigated the localization of Rab4 in the rat parotid glands by Western blotting and light-microscopic immunohistochemistry. Rab4 was localized mainly on the intracellular membranes in the subapical-actin terminal web, but was not present in the basolateral region both in acinar and ductal cells. Actin, alpha-adaptin, Rab5A and aquaporin5 were detected in the Rab4-containing intracellular membrane fraction prepared using anti-Rab4 antibody covalently coupled to magnetic beads. Detection of actin indicated that the Rab4-containing intracellular membranes were attached to the actin filaments. Although alpha-adaptin was immunohistochemically distributed along the plasma membrane, this protein coexisted with Rab4 only at the apical region. Rab5A immunoreactivity was distributed all around the cytoplasm. These findings suggested that Rab4 participates in endocytosis at the apical membrane of parotid glands.
authors.affiliation: Department of Biochemistry, The Nippon Dental University School of Dentistry at Niigata, Japan. nashida@ngt.ndu.ac.jp
authors.forename: Tomoko
authors.initials: T
authors.lastname: Nashida
authors.forename: Sumio
authors.initials: S
authors.lastname: Yoshie
authors.forename: Akane
authors.initials: A
authors.lastname: Imai
authors.forename: Hiromi
authors.initials: H
authors.lastname: Shimomura
mesh_terms: D000199:Actins / Q000032:analysis / Q000276:immunology; D033965:Adaptor Protein Complex alpha Subunits / Q000032:analysis / Q000276:immunology; D000818:Animals; D000911:Antibodies, Monoclonal; D051402:Aquaporin 5; D020346:Aquaporins / Q000032:analysis / Q000276:immunology; D015153:Blotting, Western; D004705:Endocytosis / Q000502:physiology*; D007150:Immunohistochemistry; D008297:Male; D008565:Membrane Proteins; D010306:Parotid Gland / Q000737:chemistry*; D051381:Rats; D017208:Rats, Wistar; D020695:rab4 GTP-Binding Proteins / Q000032:analysis* / Q000276:immunology; D020696:rab5 GTP-Binding Proteins / Q000032:analysis / Q000276:immunology
chemical_list: D000199:Actins; D033965:Adaptor Protein Complex alpha Subunits; D000911:Antibodies, Monoclonal; C496040:Aqp5 protein, rat; D051402:Aquaporin 5; D020346:Aquaporins; D008565:Membrane Proteins; D020695:rab4 GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins