High impact information on Rab4a

• Both Rab4 peptide and anti-Rab4 antibody enhanced calcium-stimulated amylase release from streptolysin O-permeabilized acini, suggesting the inhibitory role of Rab4 in exocytosis [1].
• RESULTS: Rab4 was localized on zymogen granule membranes [1].
• The participation of protein kinase C in the Rab4 regulation by CCK was confirmed by calphostin C pretreatment of acini [1].
• The Rab4 function in regulated exocytosis was examined by introducing Rab4 hypervariable carboxy-terminal domain peptide (Rab4 peptide) and anti-Rab4 antibody into streptolysin O-permeabilized acini [1].
• Potential role of Rab4 in the regulation of subcellular localization of Glut4 in adipocytes [2].

Biological context of Rab4a

• These findings suggested that Rab4 participates in endocytosis at the apical membrane of parotid glands [3].
• Involvement of Rab4 in regulated exocytosis of rat pancreatic acini [1].
• This hypothesis was strengthened by the fact that Rab4 deltaCT, a Rab4 mutant lacking the geranylgeranylation sites, inhibited insulin-induced recruitement of Glut4-myc to the cell surface, even when moderately overexpressed [2].
• The purpose of this study was to determine if Rab4, a small GTP binding protein that has been implicated in the insulin-stimulated translocation of GLUT4 in adipose cells, is involved in the regulation of transporter translocation in skeletal muscle [4].

Anatomical context of Rab4a

• Although alpha-adaptin was immunohistochemically distributed along the plasma membrane, this protein coexisted with Rab4 only at the apical region [3].
• Membrane marker enzyme, 5' nucleotidase activity, and the early and recycling endosome markers Rab4 and Rab11 were used to verify the enrichment of these fractions [5].
• 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 [3].
• Detection of actin indicated that the Rab4-containing intracellular membranes were attached to the actin filaments [3].
• Rab4 was redistributed to the cytosol and its movement was reversed by insulin withdrawal [6].

Associations of Rab4a with chemical compounds

• A role for Rab4 in the translocation of the glucose transporter Glut4 induced by insulin has been recently proposed [2].
• In the present study, we investigated the insulin effects on the guanine nucleotide exchange on Rab4 [7].
• Guanine nucleotides exchanged into the Rab4 present on the vesicles as shown by solubilization of Rab4 by Rab-GDI; solubilization was inhibited by incubation with GTP-gamma-S and promoted by GDP [8].

Other interactions of Rab4a

• Resensitization was minimally affected by inhibition of vacuolar H(+)-ATPase and phosphatases but was markedly suppressed by disruption of Rab4a and Rab11a [9].
• The induction of such a GDI isoform at the beginning of the recovery stage correlates with the expression pattern of Rab1 and Rab5, but not Rab2 and Rab4 [10].
• These vesicles also containend Rab4 and Akt-2, the latter being only associated after insulin stimulation [11].
• Western blot analysis demonstrated that the 27 kDa, 26 kDa, and 20 kDa proteins were Rab5p, Rab4p and ADP-ribosylation factor (ARF), respectively [12].

Analytical, diagnostic and therapeutic context of Rab4a

• We investigated the localization of Rab4 in the rat parotid glands by Western blotting and light-microscopic immunohistochemistry [3].
• METHODS: Subcellular localization of Rab4 was determined by Western blotting and immunohistochemistry [1].
• Screening for proteins by immunofluorescence microscopy revealed that the small G protein, Rab4, was associated with 80% of hepatocyte-derived early endocytic vesicles that contain the ligand asialoorosomucoid (ASOR) [8].
• Rab4 was associated with GLUT4-containing vesicles isolated by immunoprecipitation [4].
• Plasma membrane and intracellular microsomal membrane fractions were prepared, and the distribution of GLUT4 and Rab4 was determined by immunoblotting [4].

References