Hepatocyte surface polarity

This chapter considers the mechanisms responsible for hepatocellular polarity. Canalicular network formation and hepatocyte polarity require coordinated expression of several key elements, including extracellular matrix, adherens and tight junctions, intracellular protein trafficking machinery, cytoskeleton, and energy production. The liver presents a remarkable example of how cell shape serves function. The two liver epithelial cell types - hepatocytes and bile duct cells - adopt radically different polarity phenotypes that serve their distinct physiological roles. The two liver epithelial cells originate from common precursors, called hepatoblasts. Hepatoblasts delaminate from a monolayered epithelial tube, the foregut, proliferate and invade the surrounding mesenchyme. Cell surface polarity is established when signals generated by local cues or by stochastic fluctuation become amplified through feedback mechanisms to yield a robust segregation of distinct membrane domains. Proper endosomal trafficking and recycling of proteins to all plasma membrane domains requires an intact actin and microtubular cytoskeletal system.