Arber, S. et al. Regulation of actin dynamics through phosphorylation of cofilin by LIM-kinase. Nature 393, 805-809
ABSTRACT Cell division, cell motility and the formation and maintenance of specialized structures in differentiated cells depend directly on the regulated dynamics of the actin cytoskeleton. To understand the mechanisms of these basic cellular processes, the signalling pathways that link external signals to the regulation of the actin cytoskeleton need to be characterized. Here we identify a pathway for the regulation of cofilin, a ubiquitous actin-binding protein that is essential for effective depolymerization of actin filaments. LIM-kinase 1, also known as KIZ, is a protein kinase with two amino-terminal LIM motifs that induces stabilization of F-actin structures in transfected cells. Dominant-negative LIM-kinasel inhibits the accumulation of the F-actin. Phosphorylation experiments in vivo and in vitro provide evidence that cofilin is a physiological substrate of LIM-kinase 1. Phosphorylation by LIM-kinase 1 inactivates cofilin, leading to accumulation of actin filaments. Constitutively active Rac augmented cofilin phosphorylation and LIM-kinase 1 autophosphorylation whereas phorbol ester inhibited these processes. Our results define a mechanism for the regulation of cofilin and hence of actin dynamics in vivo. By modulating the stability of actin cytoskeletal structures, this pathway should play a central role in regulating cell motility and morphogenesis.
- SourceAvailable from: Xuejun Chai
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- "Chai et al. (2009) have previously shown that Reelin phosphorylates the actindepolymerizing protein cofilin. Phosphorylation of cofilin renders it unable to depolymerize actin, thereby stabilizing the actin cytoskeleton (Arber et al. 1998; Yang et al. 1998). "
ABSTRACT: Newborn neurons migrate along the processes of radial glial cells (RGCs) to reach their final positions in the cortex. Here, we visualized individual migrating neurons and RGCs using in utero electroporation. We show that branching of migrating neurons and RGCs is closely correlated spatiotemporally with the distribution of Reelin. Time-lapse imaging revealed that the leading processes of migrating neurons gave rise to increasingly more branches once their growth cones contacted the Reelin-containing marginal zone. This was accompanied by translocation of the nucleus and gradual shortening of the leading process. Absence of Reelin in reeler mice altered these processes resulting in misorientation, loss of bipolarity, and aberrant migration of cortical neurons. Moreover, in reeler, the branching of the basal processes of RGCs in the marginal zone was severely disrupted. Consistent with previous reports, we show that in dissociated reeler cortical cultures, exposure to recombinant Reelin enhanced dendritic complexity and glial branching. Our results suggest that Reelin induces branching of the leading processes of migrating neurons and that of basal processes of RGCs when they arrive at the Reelin-containing marginal zone. Branching of these processes may be crucial for the termination of nuclear translocation during the migratory process and for correct neuronal positioning.Cerebral Cortex 09/2014; DOI:10.1093/cercor/bhu216 · 8.67 Impact Factor
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- "We have recently reported that the actin-severing activity of CFL-1 is crucial for its localization to the TGN as well as for the facilitation of secretory cargo sorting (von Blume et al., 2009, 2011). Phosphorylation of CFL-1 at Serine 3 (Ser3) by LIM kinase (LIMK) inactivates CFL-1, whereas dephosphorylation reactivates it (Arber et al., 1998). Furthermore, the phosphorylation of CFL-1 at this side impairs its ability to bind to F-actin (Agnew et al., 1995). "
ABSTRACT: The actin filament severing protein cofilin-1 (CFL-1) is required for actin and P-type ATPase secretory pathway calcium ATPase (SPCA)-dependent sorting of secretory proteins at the trans-Golgi network (TGN). How these proteins interact and activate the pump to facilitate cargo sorting, however, is not known. We used purified proteins to assess interaction of the cytoplasmic domains of SPCA1 with actin and CFL-1. A 132–amino acid portion of the SPCA1 phosphorylation domain (P-domain) interacted with actin in a CFL-1–dependent manner. This domain, coupled to nickel nitrilotriacetic acid (Ni-NTA) agarose beads, specifically recruited F-actin in the presence of CFL-1 and, when expressed in HeLa cells, inhibited Ca2+ entry into the TGN and secretory cargo sorting. Mutagenesis of four amino acids in SPCA1 that represent the CFL-1 binding site also affected Ca2+ import into the TGN and secretory cargo sorting. Altogether, our findings reveal the mechanism of CFL-1–dependent recruitment of actin to SPCA1 and the significance of this interaction for Ca2+ influx and secretory cargo sorting.The Journal of Cell Biology 09/2014; 206:635-654. DOI:10.1083/jcb.201311052 · 9.69 Impact Factor
Frontiers in Pharmacology 01/2014; 5. DOI:10.3389/conf.fphar.2014.61.00011 · 3.80 Impact Factor
- "An analysis of the levels of pY421-cortactin at various time points of the TTX treatment, revealed that there were reductions in the amount of pY421-cortactin at all time points analyzed (5, 10, 20 and 30 minutes, and 1, 2 and 24 hours of treatment) compared to the control conditions (data not shown). By contrast, blocking Na V 1.5 had no effect on the phosphorylation of cofilin on S3 (Fig. 4E), which has been shown to be critical for binding to actin (Arber et al., 1998). This suggests that Na V 1.5 might regulate Src kinase and not LIM kinase. "