Arabidopsis BRICK1/HSPC300 is an essential WAVE-complex subunit that selectively stabilizes the Arp2/3 activator SCAR2.
The actin cytoskeleton dynamically reorganizes the cytoplasm during cell morphogenesis. The actin-related protein (Arp)2/3 complex is a potent nucleator of actin filaments that controls a variety of endomembrane functions including the endocytic internalization of plasma membrane , vacuole biogenesis , plasma-membrane protrusion in crawling cells , and membrane trafficking from the Golgi . Therefore, Arp2/3 is an important signaling target during morphogenesis. The evolutionarily conserved Rac-WAVE-Arp2/3 pathway links actin filament nucleation to cell morphogenesis . WAVE translates Rac-GTP signals into Arp2/3 activation by regulating the stability and/or localization of the activator subunit Scar/WAVE . The WAVE complex includes Sra1/PIR121/CYFIP1, Nap1/NAP125, Abi-1/Abi-2, Brick1(Brk1)/HSPC300, and Scar/WAVE : Defining the in vivo function of each subunit is an important step toward understanding this complicated signaling pathway. Brk1/HSPC300 has been the most recalcitrant WAVE-complex protein and has no known function. In this paper, we report that Arabidopsis brick1 (brk1) is a member of the "distorted group" of trichome morphology mutants, a group that defines a WAVE-ARP2/3 morphogenesis pathway . In this paper we provide the first strong genetic and biochemical evidence that BRK1 is a critical WAVE-complex subunit that selectively stabilizes the Arp2/3 activator SCAR2.
Department of Agronomy, Purdue University, Lilly Hall, 915 W. State Street, West Lafayette, Indiana 47907, USA.
Jie
J
Le
Eileen L
EL
Mallery
Chunhua
C
Zhang
Steven
S
Brankle
Daniel B
DB
Szymanski
D051376:Actin-Related Protein 2-3 Complex / Q000378:metabolism*; D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000254:growth & development* / Q000648:ultrastructure; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism* / Q000502:physiology*; D008969:Molecular Sequence Data; D009154:Mutation; D018515:Plant Leaves / Q000648:ultrastructure; D017386:Sequence Homology, Amino Acid; D051300:Wiskott-Aldrich Syndrome Protein Family
D051376:Actin-Related Protein 2-3 Complex; D029681:Arabidopsis Proteins; C493650:BRK1 protein, Arabidopsis; C505420:DIS3 protein, Arabidopsis; D051300:Wiskott-Aldrich Syndrome Protein Family