Fig. 4. Suppression of aPKC activity induces hyper-shrinkage of the circumferential actin cables during LPA-induced junction development in serum-starved MTD1-A cells. Confluent monolayers of MTD1-A cells infected with adenovirus vectors encoding β-galactosidase (– and +LPA) or aPKC kn were incubated in LC medium for 20 hours, with serum depletion from the medium during the last 1 hour, and then subjected to a Ca²⁺ switch by adding CaCl₂ with or without 10 µM LPA. The cells were stained with an anti-ZO-1 antibody (magenta in merged images) and phalloidin (green in merged images) at 2 hours after the Ca²⁺ switch. The images shown are projected views of xy confocal sections. The results did not change even when cells were stained at 6 hours after the Ca²⁺ switch (M.K. and A.S., unpublished). Note that serum starvation results in blockade of the development of dot-like AJs into belt-like AJs and this blockade is released by the addition of LPA. Overexpression of aPKC kn suppresses this LPA-induced junction development and induces hyper-shrinkage of F-actin. Scale bar: 10 µm.