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. Author manuscript; available in PMC: 2015 Nov 23.
Published in final edited form as: Annu Rev Physiol. 2011;73:283–309. doi: 10.1146/annurev-physiol-012110-142150

Figure 5.

Figure 5

Models of tight junction protein behavior. (a) Computer simulations of tight junction FLIP (fluorescence loss in photobleaching) and FRAP (fluorescence recovery after photobleaching) behavior support the presence of different dynamic behaviors for claudin-1 (Cldn1), occludin (Ocln), and zonula occludens-1 (ZO-1). Cldn1 is localized at the tight junction, and fluorescence recovery occurs via diffusion of the mobile pool from adjacent unbleached areas of tight junction. The fixed pool does not exchange. Like Cldn1, Ocln diffuses within the tight junction, but exchange also occurs with a lateral membrane pool. However, unlike Cldn1, there is no fixed Ocln pool. Both fixed and exchangeable ZO-1 pools are present at the tight junction; the latter exchanges with a cytosolic ZO-1 pool. (b) The rate of ZO-1 exchange between the tight junction and cytosol is regulated through interactions with actin. ZO-1 dynamics are best modeled as containing two exchangeable pools at the tight junction. An actin-binding region (ABR)-anchored pool exchanges slowly between the cytosol and the tight junction and is sensitive to myosin light-chain kinase (MLCK) inhibition, whereas a MLCK-independent pool exchanges rapidly between the tight junction and the cytoplasm.