A phorbol ester-binding protein is required downstream of Rab5 in endosome fusion.
Previous observations indicate that a zinc and phorbol ester binding factor is necessary for endosome fusion. To further characterize the role of this factor in the process, we used an in vitro endosome fusion assay supplemented with recombinant Rab5 proteins. Both zinc depletion and addition of calphostin C, an inhibitor of protein kinase C, inhibited endosome fusion in the presence of active Rab5. Addition of the phorbol ester PMA (phorbol 12-myristate 13-acetate) reversed the inhibition of endosome fusion caused by a Rab5 negative mutant. Moreover, PMA stimulated fusion in the presence of Rab5 immunodepleted cytosol. These results suggest that the phorbol ester binding protein is acting downstream of Rab5 in endosome fusion.
Aballay
A
A
Instituto de Histología y Embriología, Facultad de Ciencias Médicas, Universidad Nacional de Cuy -CONICET, Mendoza, Argentina.
Barbieri
M A
MA
Colombo
M I
MI
Arenas
G N
GN
Stahl
P D
PD
Mayorga
L S
LS
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D011992:Endosomes / Q000378:metabolism*; D019204:GTP-Binding Proteins / Q000378:metabolism*; D008561:Membrane Fusion; D011493:Protein Kinase C / Q000378:metabolism*; D011955:Receptors, Drug / Q000378:metabolism*; D013755:Tetradecanoylphorbol Acetate / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins
D029742:Caenorhabditis elegans Proteins; D002352:Carrier Proteins; D011955:Receptors, Drug; C083141:phorbol ester binding protein; C027776:phorbol ester receptor; D011493:Protein Kinase C; D019204:GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins; D013755:Tetradecanoylphorbol Acetate