-Catenin is a multifunctional protein that is known to participate in two well defined cellular processes, cell-cell adhesion and Wnt-stimulated transcriptional activation. Here we report that -catenin participates in a third cellular process, the establishment of a bipolar mitotic spindle. During mitosis, -catenin relocalizes to mitotic spindle poles and to the midbody. Furthermore, biochemical fractionation demonstrates the presence of -catenin in purified centrosome preparations. Reduction of cellular -catenin by RNA interference leads to the failure of centrosomes to fully separate, resulting in a marked increase in the frequency of monoastral mitotic spindles. Our results define a new and important function for -catenin in mitosis and demonstrate that -catenin is involved in vital biological processes beyond cell adhesion and Wnt signaling.
The G12 subfamily of heterotrimeric G proteins has been the subject of intense scientific interest for more than 15 years. During this period, studies have revealed more than 20 potential G12-interacting proteins and numerous signaling axes emanating from the G12 proteins, Galpha12 and Galpha13. In addition, more recent studies have begun to illuminate the various and sundry functions that the G12 subfamily plays in biology. In this review, we summarize the diverse range of proteins that have been identified as Galpha12 and/or Galpha13 interactors and describe ongoing studies designed to dissect the biological roles of specific Galpha-effector protein interactions. Further, we describe and discuss the expanding role of G12 proteins in the biology of cells, focusing on the distinct properties of this subfamily in regulating cell proliferation, cell migration, and metastatic invasion.
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