Rho/Rho-associated kinase-II signaling mediates disassembly of epithelial apical junctions

• Published in: Molecular biology of the cell 2007-09, Vol.18 (9), p.3429-3439
• Main Authors: Samarin, Stanislav N, Ivanov, Andrei I, Flatau, Gilles, Parkos, Charles A, Nusrat, Asma
• Format: Article
• Language: English
• Subjects: Calcium - deficiency; Cell Line; Enzyme Activation - drug effects; Epithelial Cells - cytology; Epithelial Cells - drug effects; Epithelial Cells - enzymology; Guanine Nucleotide Exchange Factors - metabolism; Humans; Intercellular Junctions - drug effects; Intercellular Junctions - enzymology; Intracellular Signaling Peptides and Proteins - antagonists & inhibitors; Intracellular Signaling Peptides and Proteins - metabolism; Models, Biological; Myosin-Light-Chain Kinase - metabolism; Myosin-Light-Chain Phosphatase - metabolism; Protein Kinase Inhibitors - pharmacology; Protein Transport - drug effects; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - metabolism; rho GTP-Binding Proteins - metabolism; Rho Guanine Nucleotide Exchange Factors; rho-Associated Kinases; RNA, Small Interfering - metabolism; Signal Transduction - drug effects
• ISSN: 1059-1524; 1939-4586
• DOI: 10.1091/mbc.E07-04-0315

Apical junctional complex (AJC) plays a vital role in regulation of epithelial barrier function. Disassembly of the AJC is observed in diverse physiological and pathological states; however, mechanisms governing this process are not well understood. We previously reported that the AJC disassembly is driven by the formation of apical contractile acto-myosin rings. In the present study, we analyzed the signaling pathways regulating acto-myosin-dependent disruption of AJC by using a model of extracellular calcium depletion. Pharmacological inhibition analysis revealed a critical role of Rho-associated kinase (ROCK) in AJC disassembly in calcium-depleted epithelial cells. Furthermore, small interfering RNA (siRNA)-mediated knockdown of ROCK-II, but not ROCK-I, attenuated the disruption of the AJC. Interestingly, AJC disassembly was not dependent on myosin light chain kinase and myosin phosphatase. Calcium depletion resulted in activation of Rho GTPase and transient colocalization of Rho with internalized AJC proteins. Pharmacological inhibition of Rho prevented AJC disassembly. Additionally, Rho guanine nucleotide exchange factor (GEF)-H1 translocated to contractile F-actin rings after calcium depletion, and siRNA-mediated depletion of GEF-H1 inhibited AJC disassembly. Thus, our findings demonstrate a central role of the GEF-H1/Rho/ROCK-II signaling pathway in the disassembly of AJC in epithelial cells.