alpha-Actinin-4/FSGS1 is required for Arp2/3-dependent actin assembly at the adherens junction

作者：Tang Vivian W; Brieher William M^*

来源：The Journal of Cell Biology, 2012, 196(1): 115-130.

DOI：10.1083/jcb.201103116

We have developed an in vitro assay to study actin assembly at cadherin-enriched cell junctions. Using this assay, we demonstrate that cadherin-enriched junctions can polymerize new actin filaments but cannot capture preexisting filaments, suggesting a mechanism involving de novo synthesis. In agreement with this hypothesis, inhibition of Arp2/3-dependent nucleation abolished actin assembly at cell-cell junctions. Reconstitution biochemistry using the in vitro actin assembly assay identified alpha-actinin-4/focal segmental glomerulosclerosis 1 (FSGS1) as an essential factor. alpha-Actinin-4 specifically localized to sites of actin incorporation on purified membranes and at apical junctions in Madin-Darby canine kidney cells. Knockdown of alpha-actinin-4 decreased total junctional actin and inhibited actin assembly at the apical junction. Furthermore, a point mutation of alpha-actinin-4 (K255E) associated with FSGS failed to support actin assembly and acted as a dominant negative to disrupt actin dynamics at junctional complexes. These findings demonstrate that alpha-actinin-4 plays an important role in coupling actin nucleation to assembly at cadherin-based cell-cell adhesive contacts.

• 出版日期2012-1-9