Identification of multiple actin-binding sites in cofilin-phosphatase Slingshot-1L

AbstractSlingshot-1L (SSH1L) is a phosphatase that specifically dephosphorylates and activates cofilin, an actin-severing and -depolymerizing protein. SSH1L binds to and is activated by F-actin in vitro, and co-localizes with F-actin in cultured cells. We examined the F-actin-binding activity, F-actin-mediated phosphatase activation, and subcellular distribution of various mutants of SSH1L. We identified three sites involved in F-actin binding of SSH1L: Trp-458 close to the C-terminus of the phosphatase domain, an LHK motif in the N-terminal region, and an LKR motif in the C-terminal region. These sites play unique roles in the control of subcellular localization and F-actin-mediated activation of SSH1L

A pathway of neuregulin-induced activation of cofilin-phosphatase Slingshot and cofilin in lamellipodia

Cofilin mediates lamellipodium extension and polarized cell migration by stimulating actin filament dynamics at the leading edge of migrating cells. Cofilin is inactivated by phosphorylation at Ser-3 and reactivated by cofilin-phosphatase Slingshot-1L (SSH1L). Little is known of signaling mechanisms of cofilin activation and how this activation is spatially regulated. Here, we show that cofilin-phosphatase activity of SSH1L increases ∼10-fold by association with actin filaments, which indicates that actin assembly at the leading edge per se triggers local activation of SSH1L and thereby stimulates cofilin-mediated actin turnover in lamellipodia. We also provide evidence that 14-3-3 proteins inhibit SSH1L activity, dependent on the phosphorylation of Ser-937 and Ser-978 of SSH1L. Stimulation of cells with neuregulin-1β induced Ser-978 dephosphorylation, translocation of SSH1L onto F-actin–rich lamellipodia, and cofilin dephosphorylation. These findings suggest that SSH1L is locally activated by translocation to and association with F-actin in lamellipodia in response to neuregulin-1β and 14-3-3 proteins negatively regulate SSH1L activity by sequestering it in the cytoplasm

Additional file 1: Figure S1. of Predictive implications of albumin and C-reactive protein for progression to pneumonia and poor prognosis in Stenotrophomonas maltophilia bacteremia following allogeneic hematopoietic stem cell transplantation

The Receiver Operating Characteristics curve analysis for the cut-off value of albumin (a and b) and CRP (c and d). (PPTX 50 kb