TY - JOUR
T1 - A factor with a zinc- and phorbol ester-binding domain is necessary for endosome fusion
AU - Aballay, Alejandro
AU - Arenas, Nora G.
AU - Quest, Andrew F.G.
AU - Mayorga, Luis S.
N1 - Funding Information:
We thank Cheryl Adles and Alejandra Challa for excellent technical assistance. This work was partly supported by an International Research Scholar of the Howard Hughes Medical Institute and by grants of the National Science Foundation±CONICET International Program, CONICET, CIUNC, and FundacioÂn Antorchas. A.A. is supported by a CONICET fellowship. L.S.M. is a fellow of the Rockefeller Foundation Biotechnology Career. A.F.G.Q. is supported by the Swiss National Science Foundation (SNF 3100-040477) and The Swiss Cancer League (FOR 645).
PY - 1997/8/25
Y1 - 1997/8/25
N2 - An inhibitory effect of several zinc chelators on endosome fusion reconstituted in an in vitro system has been recently reported (A. Aballay et al., 1995, Biochem. J. 312, 919-923). The factor that requires zinc for its activity is still unknown. Since the regulatory domain of protein kinase C (PKC) contains cysteine-rich motifs which coordinate zinc, we suspected that PKC or a PKC-like protein might be that factor. To test this hypothesis, we studied the effect of calphostin C, a specific inhibitor of PKC that interacts with the cysteine-rich motif, and PMA (phorbol 12-myristate 13- acetate), an activator of several PKC isoforms that bind to the same region, on endosome fusion. Calphostin C inhibited endosome fusion in a zinc- regulated manner, whereas PMA enhanced endosome fusion. Moreover, fusion was strongly stimulated when both PMA and zinc were added together to zinc- depleted fusion reactions. Inhibitors of the catalytic domain of PKC had no effect on the assay suggesting that the kinase activity is not required. In contrast, a glutathione S-transferase fusion protein containing a cysteine- rich region of the regulatory domain of PKCγ inhibited endosome fusion in a PMA-dependent manner. Western blot analysis demonstrated the presence of proteins containing PKC-like cysteine-rich regions that are released from endosomal fractions by zinc chelators. These results indicate that the previously proposed zinc-dependent factor required for endosome fusion could be either a PKC isoform or a protein containing the phorbol ester-binding domain of PKC.
AB - An inhibitory effect of several zinc chelators on endosome fusion reconstituted in an in vitro system has been recently reported (A. Aballay et al., 1995, Biochem. J. 312, 919-923). The factor that requires zinc for its activity is still unknown. Since the regulatory domain of protein kinase C (PKC) contains cysteine-rich motifs which coordinate zinc, we suspected that PKC or a PKC-like protein might be that factor. To test this hypothesis, we studied the effect of calphostin C, a specific inhibitor of PKC that interacts with the cysteine-rich motif, and PMA (phorbol 12-myristate 13- acetate), an activator of several PKC isoforms that bind to the same region, on endosome fusion. Calphostin C inhibited endosome fusion in a zinc- regulated manner, whereas PMA enhanced endosome fusion. Moreover, fusion was strongly stimulated when both PMA and zinc were added together to zinc- depleted fusion reactions. Inhibitors of the catalytic domain of PKC had no effect on the assay suggesting that the kinase activity is not required. In contrast, a glutathione S-transferase fusion protein containing a cysteine- rich region of the regulatory domain of PKCγ inhibited endosome fusion in a PMA-dependent manner. Western blot analysis demonstrated the presence of proteins containing PKC-like cysteine-rich regions that are released from endosomal fractions by zinc chelators. These results indicate that the previously proposed zinc-dependent factor required for endosome fusion could be either a PKC isoform or a protein containing the phorbol ester-binding domain of PKC.
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U2 - 10.1006/excr.1997.3643
DO - 10.1006/excr.1997.3643
M3 - Article
C2 - 9281349
AN - SCOPUS:0031586348
SN - 0014-4827
VL - 235
SP - 28
EP - 34
JO - Experimental Cell Research
JF - Experimental Cell Research
IS - 1
ER -