Connexin 43 maintains tissue polarity and regulates mitotic spindle orientation in the breast epithelium.

Abstract

Cell-cell communication is essential for tissue homeostasis, but its contribution to disease prevention remains to be understood. We demonstrate the involvement of connexin 43 (Cx43) and related gap junction in epithelial homeostasis illustrated by polarity-mediated cell cycle entry and mitotic spindle orientation (MSO). Cx43 is restricted to the apicolateral membrane of phenotypically normal breast luminal epithelial cells in 3D culture and in vivo. Chemically-induced blockade of gap junction intercellular communication (GJIC) as well as the absence of Cx43 disrupt the apicolateral distribution of polarity determinant, tight junction marker ZO-1 and lead to random MSO and cell multilayering. Induced expression of Cx43 in cells that normally lack this protein reestablishes polarity and proper MSO in 3D culture. The Cx43-directed MSO implicates PI3K-aPKC signaling, and Cx43 coprecipitates with signaling node proteins β-catenin and ZO-2 in the polarized epithelium. The distribution of Cx43 is altered by pro-inflammatory breast cancer risk factors like leptin and high fat diet, as shown in cell culture and on tissue biopsy sections. The control of polarity-mediated quiescence and MSO may contribute to the tumor suppressive role of Cx43.