MICAL2 enhances branched actin network disassembly by oxidizing Arp3B-containing Arp2/3 complexes

Abstract

The mechanisms regulating the disassembly of branched actin networks formed by the Arp2/3 complex still remain to be fully elucidated. In addition, the impact of Arp3 isoforms on the properties of Arp2/3 are also unexplored. We now demonstrate that Arp3 and Arp3B isocomplexes promote actin assembly equally efficiently but generate branched actin networks with different disassembly rates. Arp3B dissociates significantly faster than Arp3 from the network, and its depletion increases actin stability. This difference is due to the oxidation of Arp3B, but not Arp3, by the methionine monooxygenase MICAL2, which is recruited to the actin network by coronin 1C. Substitution of Arp3B Met293 by threonine, the corresponding residue in Arp3, increases actin network stability. Conversely, replacing Arp3 Thr293 with glutamine to mimic Met oxidation promotes disassembly. The ability of MICAL2 to enhance network disassembly also depends on cortactin. Our observations demonstrate that coronin 1C, cortactin, and MICAL2 act together to promote disassembly of branched actin networks by oxidizing Arp3B-containing Arp2/3 complexes.

ARPC1B binds WASP to control actin polymerization and curtail tonic signaling in B cells

“…This raises the possibility that different NPFs recognize ARP2/3 complexes made up of different isoform combinations. Once assembled, the stability of ARP2/3-branched F-actin networks has also recently been shown to depend on the isoforms of ARP2/3 components ARPC1, ARPC5, and ARP3 ( 10 , 43 ). ARP2/3 isocomplexes composed of ARPC1B and ARPC5L are more stable than those containing ARPC1A and ARPC5, owed to their interaction with cortactin, which opposes debraching by coronin ( 10 ).…”

“…ARP2/3 isocomplexes composed of ARPC1B and ARPC5L are more stable than those containing ARPC1A and ARPC5, owed to their interaction with cortactin, which opposes debraching by coronin ( 10 ). ARP3B-containing complexes, on the other hand, form branch points of a lower stability than those with ARP3, as the former is oxidized by MICAL2, which is recruited by coronin 1C ( 43 ). Taken together, ARP2/3 branching has recently evolved to include a family of complexes that have different properties, including their stabilization by cortactin and their stimulation by NPF partners.…”

The relative binding position of Nck and Grb2 adaptors impacts actin-based motility of Vaccinia virus

“…The expression vectors pE/L-LifeAct-iRFP670 ( Galloni et al, 2021 ), pLVX-GFP-N-WASP ( Donnelly et al, 2013 ), pE/L-GFP-Nck (SH2) ( Frischknecht et al, 1999 ) and pBS SKII RFP-A3L targeting vector ( Weisswange et al, 2009 ) were previously made in the Way lab. The lentiviral expression construct pLVX-GFP-Nck was generated by sub-cloning the Nck1 coding sequence ( Donnelly et al, 2013 ) into NotI/EcoRI sites of a pLVX-N-term-GFP parent vector ( Abella et al, 2016 ).…”

“…Live-cell imaging experiments were performed at 8 hr (HeLa) or 16 hr (MEFs) post-infection in complete MEM (10% FBS) in a temperature-controlled chamber at 37 °C. Cells were imaged on a Zeiss Axio Observer spinning-disk microscope equipped with a Plan Achromat 63 x/1.4 Ph3 M27 oil lens, an Evolve 512 camera, and a Yokagawa CSUX spinning disk ( Galloni et al, 2021 ; Pfanzelter et al, 2018 ). The microscope was controlled by the SlideBook software (3i Intelligent Imaging Innovations).…”

MICAL2 fine-tunes Arp2/3 for actin branching

“…In this issue, Galloni, Carra, et al evaluated the ability of ARP2/3 complexes, containing either ARP3 or the ARP3B isoform (i.e., isocomplexes), to promote actin assembly, and determined isoform-specific differences in their activity and molecular regulation ( 7 ). As a model system, the authors used HeLa cells infected with vaccinia virus to study actin branching, given that this virus induces actin tail nucleation in the host cells.…”