title: The effects of collapsing factors on F-actin content and microtubule distribution of Helisoma growth cones.
abstract: Growth cone collapsing factors induce growth cone collapse or repulsive growth cone turning by interacting with membrane receptors that induce alterations in the growth cone cytoskeleton. A common change induced by collapsing factors in the cytoskeleton of the peripheral domain, the thin lamellopodial area of growth cones, is a decline in the number of radially aligned F-actin bundles that form the core of filopodia. The present study examined whether ML-7, a myosin light chain kinase inhibitor, serotonin, a neurotransmitter and TPA, an activator of protein kinase C, which induce growth cone collapse of Helisoma growth cones, depolymerized or debundled F-actin. We report that these collapsing factors had different effects. ML-7 induced F-actin reorganization consistent with debundling whereas serotonin and TPA predominately depolymerized and possibly debundled F-actin. Additionally, these collapsing factors induced the formation of a dense actin-ring around the central domain, the thicker proximal area of growth cones [Zhou and Cohan, 2001: J. Cell Biol. 153:1071-1083]. The formation of the actin-ring occurred subsequent to the loss of actin bundles. The ML-7-induced actin-ring was found to inhibit microtubule extension into the P-domain. Thus, ML-7, serotonin, and TPA induce growth cone collapse associated with a decline in radially aligned F-actin bundles through at least two mechanisms involving debundling of actin filaments and/or actin depolymerization.
authors.affiliation: Division of Anatomy and Cell Biology, University at Buffalo School of Medicine, Buffalo, NY 14214, USA.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Torreano
authors.forename: Clare M
authors.initials: CM
authors.lastname: Waterman-Storer
authors.forename: Christopher S
authors.initials: CS
authors.lastname: Cohan
mesh_terms: D000199:Actins / Q000187:drug effects* / Q000378:metabolism*; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D002478:Cells, Cultured; D003850:Deoxyribonuclease I / Q000378:metabolism; D020439:Growth Cones / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D008870:Microtubules / Q000187:drug effects* / Q000648:ultrastructure; D009281:Naphthalenes / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000648:ultrastructure; D010590:Phalloidine; D040121:Semaphorin-3A / Q000494:pharmacology*; D012701:Serotonin / Q000494:pharmacology; D012908:Snails; D013194:Staining and Labeling; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
chemical_list: D000199:Actins; D001381:Azepines; D009281:Naphthalenes; D040121:Semaphorin-3A; C070571:ML 7; D010590:Phalloidine; D012701:Serotonin; D003850:Deoxyribonuclease I; D013755:Tetradecanoylphorbol Acetate