E cadherin appears to be an essential on/off switch for initiating bile canaliculi formation

The mechanisms underlying cell polarization are fundamental to biology but remain incompletely understood. This is especially true for hepatocytes, which display a particularly complex polarization that enables the formation of the bile canaliculi (BC) network crucial for liver excretory functions. To identify key proteins involved in hepatocyte polarization, BC formation, structure or function, we employed a proteomic approach comparing the human hepatocyte cell line HepG2 to its sub clone HepG2/C3A known for its markedly greater efficiency in forming mature BCs. Through this analysis, we localized LimA1 and Espin to the BC for the first time, suggesting their important role in this compartment, and confirmed the presence of NHE-RF1. Using a targeted protein repression strategy, we identified E cadherin as essential for the initiation of BC formation, unlike other adherens junction components such as N cadherin or α-catenin. Our findings demonstrate, for the first time, that in the absence of E cadherin, hepatocytes lose the capacity to form BCs. SIGNIFICANCE: This study aims to deepen our understanding of the highly specialized polarization of hepatocytes in relation to bile canaliculus formation. The major finding is the key role of E cadherin in this process, where it appears to be essential for bile canaliculus formation in both 2D and 3D culture models. Additionally, the study led to the identification of several proteins potentially localized to the bile canaliculi, whose functions remain to be elucidated.