title: F-actin bundles direct the initiation and orientation of lamellipodia through adhesion-based signaling.
abstract: Mesenchymal cells such as fibroblasts are weakly polarized and reorient directionality by a lamellipodial branching mechanism that is stabilized by phosphoinositide 3-kinase (PI3K) signaling. However, the mechanisms by which new lamellipodia are initiated and directed are unknown. Using total internal reflection fluorescence microscopy to monitor cytoskeletal and signaling dynamics in migrating cells, we show that peripheral F-actin bundles/filopodia containing fascin-1 serve as templates for formation and orientation of lamellipodia. Accordingly, modulation of fascin-1 expression tunes cell shape, quantified as the number of morphological extensions. Ratiometric imaging reveals that F-actin bundles/filopodia play both structural and signaling roles, as they prime the activation of PI3K signaling mediated by integrins and focal adhesion kinase. Depletion of fascin-1 ablated fibroblast haptotaxis on fibronectin but not platelet-derived growth factor chemotaxis. Based on these findings, we conceptualize haptotactic sensing as an exploration, with F-actin bundles directing and lamellipodia propagating the process and with signaling mediated by adhesions playing the role of integrator.
authors: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695.
authors: Heath E
authors: HE
authors: Johnson
authors: UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599.
authors: Samantha J
authors: SJ
authors: King
authors: UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599.
authors: Sreeja B
authors: SB
authors: Asokan
authors: UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599.
authors: Jeremy D
authors: JD
authors: Rotty
authors: UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599 UNC Lineberger Cancer Center, the Department of Cell Biology and Physiology, and Howard Hughes Medical Institute, The University of North Carolina-Chapel Hill, Chapel Hill, NC 27599.
authors: James E
authors: JE
authors: Bear
authors: Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695 jason_haugh@ncsu.edu.
authors: Jason M
authors: JM
authors: Haugh
mesh_terms: D016475:3T3 Cells; D008841:Actin Cytoskeleton; D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000378:metabolism; D000199:Actins / Q000502:physiology*; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D048430:Cell Shape; D002633:Chemotaxis / Q000235:genetics* / Q000502:physiology; D005347:Fibroblasts / Q000166:cytology; D005353:Fibronectins / Q000378:metabolism; D051416:Focal Adhesion Protein-Tyrosine Kinases / Q000378:metabolism; D051379:Mice; D008840:Microfilament Proteins / Q000096:biosynthesis / Q000235:genetics*; D008856:Microscopy, Fluorescence; D008969:Molecular Sequence Data; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010982:Platelet-Derived Growth Factor / Q000378:metabolism; D011554:Pseudopodia / Q000502:physiology*; D034622:RNA Interference; D034741:RNA, Small Interfering; D018035:Receptors, Odorant / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000199:Actins; D005353:Fibronectins; D051416:Focal Adhesion Protein-Tyrosine Kinases; D008840:Microfilament Proteins; D019869:Phosphatidylinositol 3-Kinases; D010982:Platelet-Derived Growth Factor; D034741:RNA, Small Interfering; D018035:Receptors, Odorant; C544141:Olfr73 protein, mouse