title: The antagonistic modulation of Arp2/3 activity by N-WASP, WAVE2 and PICK1 defines dynamic changes in astrocyte morphology.
abstract: Astrocytes exhibit a complex, branched morphology, allowing them to functionally interact with numerous blood vessels, neighboring glial processes and neuronal elements, including synapses. They also respond to central nervous system (CNS) injury by a process known as astrogliosis, which involves morphological changes, including cell body hypertrophy and thickening of major processes. Following severe injury, astrocytes exhibit drastically reduced morphological complexity and collectively form a glial scar. The mechanistic details behind these morphological changes are unknown. Here, we investigate the regulation of the actin-nucleating Arp2/3 complex in controlling dynamic changes in astrocyte morphology. In contrast to other cell types, Arp2/3 inhibition drives the rapid expansion of astrocyte cell bodies and major processes. This intervention results in a reduced morphological complexity of astrocytes in both dissociated culture and in brain slices. We show that this expansion requires functional myosin II downstream of ROCK and RhoA. Knockdown of the Arp2/3 subunit Arp3 or the Arp2/3 activator N-WASP by siRNA also results in cell body expansion and reduced morphological complexity, whereas depleting WAVE2 specifically reduces the branching complexity of astrocyte processes. By contrast, knockdown of the Arp2/3 inhibitor PICK1 increases astrocyte branching complexity. Furthermore, astrocyte expansion induced by ischemic conditions is delayed by PICK1 knockdown or N-WASP overexpression. Our findings identify a new morphological outcome for Arp2/3 activation in restricting rather than promoting outwards movement of the plasma membrane in astrocytes. The Arp2/3 regulators PICK1, and N-WASP and WAVE2 function antagonistically to control the complexity of astrocyte branched morphology, and this mechanism underlies the morphological changes seen in astrocytes during their response to pathological insult.
authors.affiliation: School of Biochemistry, Medical Sciences Building, University of Bristol, Bristol BS8 1TD, UK.
authors.forename: Kai
authors.initials: K
authors.lastname: Murk
authors.forename: Elena M
authors.initials: EM
authors.lastname: Blanco Suarez
authors.forename: Louisa M R
authors.initials: LM
authors.lastname: Cockbill
authors.forename: Paul
authors.initials: P
authors.lastname: Banks
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Hanley
mesh_terms: D051376:Actin-Related Protein 2-3 Complex / Q000235:genetics / Q000378:metabolism*; D000577:Amides / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002478:Cells, Cultured; D002490:Central Nervous System / Q000378:metabolism*; D005576:Colforsin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts; D057809:HEK293 Cells; D006576:Heterocyclic Compounds, 4 or More Rings / Q000494:pharmacology; D006801:Humans; D051379:Mice; D024462:Myosin Type II / Q000037:antagonists & inhibitors / Q000378:metabolism; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011725:Pyridines / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D051381:Rats; D013844:Thiazoles / Q000494:pharmacology; D013871:Thiones / Q000494:pharmacology; D014498:Uracil / Q000031:analogs & derivatives / Q000494:pharmacology; D014665:Vasodilator Agents / Q000494:pharmacology; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000235:genetics / Q000378:metabolism*; D020742:rhoA GTP-Binding Protein / Q000037:antagonists & inhibitors / Q000378:metabolism
chemical_list: D051376:Actin-Related Protein 2-3 Complex; D000577:Amides; C543732:CK-0993548; D002352:Carrier Proteins; D004791:Enzyme Inhibitors; D006576:Heterocyclic Compounds, 4 or More Rings; D009687:Nuclear Proteins; C498297:PICk1 protein, human; D011725:Pyridines; D034741:RNA, Small Interfering; C547376:SMIFH2 compound; D013844:Thiazoles; D013871:Thiones; D014665:Vasodilator Agents; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal; C108830:Y 27632; D005576:Colforsin; C472645:blebbistatin; D014498:Uracil; D024462:Myosin Type II; D020742:rhoA GTP-Binding Protein
keywords: Actin dynamics; Arp2/3; Astrocyte; Brain injury; CNS; Central nervous system; Morphology