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J. Cell Biol.,
Volume 141, Number 6, June 15, 1998 1433-1448
-Catenin and Plakoglobin
Department of Molecular Cell Biology, Weizmann Institute of Science, Rehovot 76100, Israel
-Catenin and plakoglobin are homologous proteins that function in cell adhesion by linking cadherins to
the cytoskeleton and in signaling by transactivation together
with lymphoid-enhancing binding/T cell (LEF/TCF) transcription factors. Here we compared the nuclear translocation and transactivation abilities of
-catenin and plakoglobin in mammalian cells. Overexpression of each of the two
proteins in MDCK cells resulted in nuclear translocation and formation of nuclear aggregates. The
-catenin-containing nuclear structures also contained LEF-1 and vinculin,
while plakoglobin was inefficient in recruiting these molecules, suggesting that its interaction with LEF-1 and vinculin is significantly weaker. Moreover, transfection of LEF-1
translocated endogenous
-catenin, but not plakoglobin to
the nucleus. Chimeras consisting of Gal4 DNA-binding domain and the transactivation domains of either plakoglobin or
-catenin were equally potent in transactivating a Gal4-responsive reporter, whereas activation of LEF-1-
responsive transcription was significantly higher with
-catenin. Overexpression of wild-type plakoglobin or mutant
-catenin lacking the transactivation domain induced
accumulation of the endogenous
-catenin in the nucleus and LEF-1-responsive transactivation. It is further shown
that the constitutive
-catenin-dependent transactivation in
SW480 colon carcinoma cells and its nuclear localization
can be inhibited by overexpressing N-cadherin or
-catenin.
The results indicate that (a) plakoglobin and
-catenin differ in their nuclear translocation and complexing with LEF-1
and vinculin; (b) LEF-1-dependent transactivation is preferentially driven by
-catenin; and (c) the cytoplasmic partners of
-catenin, cadherin and
-catenin, can sequester it to the cytoplasm and inhibit its transcriptional activity.
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