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Guanylyl Cyclase Protein and cGMP Product Independently Control Front and Back of Chemotaxing Dictyostelium Cells
Douwe M. Veltman, and
Peter J.M. Van Haastert
Department of Biology, University of Groningen, 9751 NN Haren, The Netherlands
Received for publication May 3, 2006.
Revision received June 2, 2006.
Accepted for publication June 8, 2006.
Monitoring Editor: Yu-li Wang
Chemotaxis of amoeboid cells is driven by actin filaments inleading pseudopodia and actinmyosin filaments in theback and at the side of the cell to suppress pseudopodia. InDictyostelium, cGMP plays an important role during chemotaxisand is produced predominantly by a soluble guanylyl cyclase(sGC). The sGC protein is enriched in extending pseudopodiaat the leading edge of the cell during chemotaxis. We show herethat the sGC protein and the cGMP product have different functionsduring chemotaxis, using two mutants that lose either catalyticactivity (sGCcat) or localization to the leading edge (sGCN).Cells expressing sGCN exhibit excellent cGMP formation and myosinlocalization in the back of the cell, but they exhibit poororientation at the leading edge. Cells expressing the catalyticallydead sGCcat mutant show poor myosin localization at the back,but excellent localization of the sGC protein at the leadingedge, where it enhances the probability that a new pseudopodis made in proximity to previous pseudopodia, resulting in adecrease of the degree of turning. Thus cGMP suppresses pseudopodformation in the back of the cell, whereas the sGC protein refinespseudopod formation at the leading edge.