Supervillin binds the Rac/Rho-GEF Trio and increases Trio-mediated Rac1 activation.

摘要: We investigated cross-talk between the membrane-associated, myosin II-regulatory protein supervillin and actin-regulatory small GTPases Rac1, RhoA, Cdc42. Supervillin knockdown reduced Rac1-GTP loading, but not GTP loading of RhoA or Cdc42, in HeLa cells with normal levels Rac1-activating Trio. No reduction was observed when were Trio-depleted cells. Conversely, overexpression isoform 1 (SV1) or, especially, 4 (SV4) increased Rac1 activation. Inhibition Trio-mediated guanine nucleotide exchange (GEF) activity ITX3 partially blocked SV4-mediated increase Rac1-GTP. Both SV4 SV1 co-localized Trio at near plasma membrane ruffles cell surface projections. Two sequences within bound directly to spectrin repeats 4–7: SV1-171, which contains N-terminal residues found both SV4-specific differentially spliced coding exons 3, 4, 5 (SV4-E345; amino acids 276 – 669). In addition, SV4-E345 interacted homologous sequence rat kalirin (repeats 4–7, 531 1101). Overexpressed SV1-174 affected only endogenous 771 1057, contain supervillin-interaction sites, exerted a dominant-negative effect on spreading. knockdowns, separately together, inhibited spreading, suggesting that regulates Trio, potentially also kalirin, during spreading lamellipodia extension.