PMID:16368433

Citation	Carothers, AM, Javid, SH, Moran, AE, Hunt, DH, Redston, M and Bertagnolli, MM (2006) Deficient E-cadherin adhesion in C57BL/6J-Min/+ mice is associated with increased tyrosine kinase activity and RhoA-dependent actomyosin contractility. Exp. Cell Res. 312:387-400
Abstract	The Min/+ mouse is a model for APC-dependent colorectal cancer (CRC). We showed that tumorigenesis in this animal was associated with decreased E-cadherin adhesion and increased epidermal growth factor receptor (Egfr) activity in the non-tumor intestinal mucosa. Here, we tested whether these abnormalities correlated with changes in the actin cytoskeleton due to increased Rho-ROCK signaling. We treated Apc+/+ (WT) littermate small intestine with EGTA, an inhibitor of E-cadherin, and with LPA, an RhoA activator; both induced effects on adhesion and kinase activity that mimicked the Min/+ phenotype. GTP-bound Rho was increased in Min/+ enterocytes relative to WT. Since RhoA activity is associated with actomyosin contractility, markers of this signaling cascade were assessed including phosphorylated myosin light chain (MLC), cofilin, Pyk2, Src, and MAPK kinases. The increased actomyosin contractility characterizing Min/+ intestinal tissue was suppressed by the ROCK inhibitor, Y27632, but was inducible in the WT by EGTA or LPA. Finally, ultrastructural imaging revealed changes consistent with actomyosin contractility in Min/+ enterocytes. Thus, the positive regulation of E-cadherin adhesion provided by Apc+ in vivo allows proper negative regulation of Egfr, Src, Pyk2, and MAPK, as well as RhoA activities.
Links	PubMed Online version:10.1016/j.yexcr.2005.11.019
Keywords	Actin Depolymerizing Factors/metabolism; Actomyosin/metabolism; Adenomatous Polyposis Coli Protein/genetics; Adenomatous Polyposis Coli Protein/physiology; Amides/pharmacology; Animals; Anti-Inflammatory Agents, Non-Steroidal/pharmacology; Cadherins/genetics; Cadherins/metabolism; Calcium/deficiency; Cardiac Myosins/metabolism; Cell Adhesion/drug effects; Egtazic Acid/pharmacology; Enterocytes/drug effects; Enterocytes/metabolism; Enterocytes/ultrastructure; Focal Adhesion Kinase 2/metabolism; GTP-Binding Protein alpha Subunits, G12-G13/metabolism; Intestinal Mucosa/cytology; Intestinal Mucosa/drug effects; Intestinal Mucosa/metabolism; Intestine, Small/drug effects; Intestine, Small/physiology; Lysophospholipids/pharmacology; Mice; Mice, Inbred C57BL; Mice, Mutant Strains; Microscopy, Electron, Transmission; Mitogen-Activated Protein Kinase 1/metabolism; Muscle Contraction/drug effects; Muscle Relaxants, Central/pharmacology; Myosin Light Chains/metabolism; Phosphorylation/drug effects; Protein Binding/drug effects; Protein-Tyrosine Kinases/metabolism; Pyrazoles/pharmacology; Pyridines/pharmacology; Receptor, Epidermal Growth Factor/agonists; Receptor, Epidermal Growth Factor/antagonists & inhibitors; Receptor, Epidermal Growth Factor/metabolism; Sulfonamides/pharmacology; Tyrphostins/pharmacology; Up-Regulation; beta Catenin/metabolism; rho GTP-Binding Proteins/metabolism; rhoA GTP-Binding Protein/agonists; rhoA GTP-Binding Protein/metabolism
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