Deficient E-cadherin adhesion in C57BL/6J-Min/+ mice is associated with increased tyrosine kinase activity and RhoA-dependent actomyosin contractility |
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Authors: | Carothers Adelaide M Javid Sara H Moran Amy E Hunt Daniel H Redston Mark Bertagnolli Monica M |
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Affiliation: | Department of Surgery, Carrie Hall, Room 116, Brigham and Women's Hospital, 75 Francis Street, Boston, MA 02115, USA. acarothers@partners.org |
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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. |
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Keywords: | APC/Apc, Adenomatous polyposis coli Min/+, C57BL/6J-Min/+ WT, C57BL/6J EGFR/Egfr, epidermal growth factor receptor RTK, receptor tyrosine kinase NSAID, nonsteroidal anti-inflammatory drug LPA, lysophosphatidic acid MAPK, mitogen-activated protein kinase GPCRs, G protein-coupled receptors MLC, myosin light chain ROCK, Rho kinase Pyk2, proline-rich tyrosine kinase 2 TEM, transmission electron microscopy GEF, guanine nucleotide exchange factor |
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