A role for myosin VII in dynamic cell adhesion

Background: The initial stages of phagocytosis and cell motility resemble e ach other. The extension of a pseudopod at the leading edge of a migratory cell and the formation of a phagocytic cup are actin dependent, and each re ly on the plasma membrane adhering to a surface during dynamic extension. Results: A myosin VII null mutant exhibited a drastic loss of adhesion to p articles, consistent with the extent of an observed decrease in particle up take. Additionally, cell-cell adhesion and the adhesion of the leading edge to the substratum during cell migration were defective in the myosin VII n ull cells. GFP-myosin VII rescued the phagocytosis defect of the null mutant and was d istributed in the cytosol and recruited to the cortical cytoskeleton, where it appeared to be enriched at the tips of filopods. It was also localized to phagocytic cups, but only during the initial stages of particle engulfme nt. During migration, GFP-myosin VII is found at the leading edge of the ce ll. Conclusions: Myosin VII plays an important role in mediating the initial bi nding of cells to substrata, a novel role for an unconventional myosin. (C) 2001 Elsevier Science Ltd. All rights reserved.