title: Skin stem cells orchestrate directional migration by regulating microtubule-ACF7 connections through GSK3β.
abstract: Homeostasis and wound healing rely on stem cells (SCs) whose activity and directed migration are often governed by Wnt signaling. In dissecting how this pathway integrates with the necessary downstream cytoskeletal dynamics, we discovered that GSK3β, a kinase inhibited by Wnt signaling, directly phosphorylates ACF7, a > 500 kDa microtubule-actin crosslinking protein abundant in hair follicle stem cells (HF-SCs). We map ACF7's GSK3β sites to the microtubule-binding domain and show that phosphorylation uncouples ACF7 from microtubules. Phosphorylation-refractile ACF7 rescues overall microtubule architecture, but phosphorylation-constitutive mutants do not. Neither mutant rescues polarized movement, revealing that phospho-regulation must be dynamic. This circuitry is physiologically relevant and depends upon polarized GSK3β inhibition at the migrating front of SCs/progeny streaming from HFs during wound repair. Moreover, only ACF7 and not GSKβ-refractile-ACF7 restore polarized microtubule-growth and SC-migration to ACF7 null skin. Our findings provide insights into how this conserved spectraplakin integrates signaling, cytoskeletal dynamics, and polarized locomotion of somatic SCs.
authors.affiliation: The Howard Hughes Medical Institute, Laboratory of Mammalian Cell Biology and Development, Rockefeller University, New York, NY 10065, USA.
authors.forename: Xiaoyang
authors.initials: X
authors.lastname: Wu
authors.forename: Qing-Tao
authors.initials: QT
authors.lastname: Shen
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Oristian
authors.forename: Catherine P
authors.initials: CP
authors.lastname: Lu
authors.forename: Qinsi
authors.initials: Q
authors.lastname: Zheng
authors.forename: Hong-Wei
authors.initials: HW
authors.lastname: Wang
authors.forename: Elaine
authors.initials: E
authors.lastname: Fuchs
mesh_terms: D000818:Animals; D002465:Cell Movement; D002478:Cells, Cultured; D038362:Glycogen Synthase Kinase 3 / Q000378:metabolism*; D000071679:Glycogen Synthase Kinase 3 beta; D051379:Mice; D008822:Mice, Transgenic; D008840:Microfilament Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D012867:Skin / Q000166:cytology / Q000378:metabolism*; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D014945:Wound Healing
chemical_list: C490632:Macf1 protein, mouse; D008840:Microfilament Proteins; D000071679:Glycogen Synthase Kinase 3 beta; C000605507:Gsk3b protein, mouse; D038362:Glycogen Synthase Kinase 3