title: ERK and RhoA differentially regulate pseudopodia growth and retraction during chemotaxis.
abstract: Nonmotile cells extend and retract pseudopodia-like structures in a random manner, whereas motile cells establish a single dominant pseudopodium in the direction of movement. This is a critical step necessary for cell migration and occurs prior to cell body translocation, yet little is known about how this process is regulated. Here we show that myosin II light chain (MLC) phosphorylation at its regulatory serine 19 is elevated in growing and retracting pseudopodia. MLC phosphorylation in the extending pseudopodium was associated with strong and persistent amplification of extracellular-regulated signal kinase (ERK) and MLC kinase activity, which specifically localized to the leading pseudopodium. Interestingly, inhibition of ERK or MLC kinase activity prevented MLC phosphorylation and pseudopodia extension but not retraction. In contrast, inhibition of RhoA activity specifically decreased pseudopodia retraction but not extension. Importantly, inhibition of RhoA activity specifically blocked MLC phosphorylation associated with retracting pseudopodia. Inhibition of either ERK or RhoA signals prevents chemotaxis, indicating that both pathways contribute to the establishment of cell polarity and migration. Together, these findings demonstrate that ERK and RhoA are distinct pathways that control pseudopodia extension and retraction, respectively, through differential modulation of MLC phosphorylation and contractile processes.
authors.affiliation: Department of Immunology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: Anar A
authors.initials: AA
authors.lastname: Brahmbhatt
authors.forename: Richard L
authors.initials: RL
authors.lastname: Klemke
mesh_terms: D016475:3T3 Cells; D000818:Animals; D019556:COS Cells; D002448:Cell Adhesion / Q000502:physiology*; D002633:Chemotaxis / Q000187:drug effects / Q000502:physiology*; D002522:Chlorocebus aethiops; D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005109:Extracellular Matrix / Q000187:drug effects / Q000502:physiology; D005419:Flavonoids / Q000494:pharmacology; D007700:Kinetics; D008246:Lysophospholipids / Q000494:pharmacology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D011554:Pseudopodia / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D011994:Recombinant Proteins / Q000378:metabolism; D014162:Transfection; D020741:rho GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D016895:Culture Media, Serum-Free; D004791:Enzyme Inhibitors; D005419:Flavonoids; D008246:Lysophospholipids; D011994:Recombinant Proteins; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D020741:rho GTP-Binding Proteins; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one