Lumens laid out by PAR-1

Epithelial cells form the lumens that define the shape and function of several organs. In the intestine, kidney, or pancreas, lumens are created by column-like cells with lumenal proteins at their apex. Liver epithelia, however, form lateral bile-secreting lumens between adjacent cells. Microtubules in these different cell types are sensibly organized to transport lumenal proteins to the right destination; the microtubule minus ends are found at the top of columnar cells but at the sides of liver epithelia. On page 717, Cohen et al. show that different strengths of the PAR-1 kinase build columnar or liver-like lumens by organizing these microtubule patterns.

Unpolarized epithelia need PAR-1 activity to form lumens. Using RNAi or dominant-negative PAR-1, the authors could prevent lumen generation in both kidney and liver cells and keep...