18 research outputs found
Rgnef (p190RhoGEF) Knockout Inhibits RhoA Activity, Focal Adhesion Establishment, and Cell Motility Downstream of Integrins
Cell migration is a highly regulated process that involves the formation and turnover of cell-matrix contact sites termed focal adhesions. Rho-family GTPases are molecular switches that regulate actin and focal adhesion dynamics in cells. Guanine nucleotide exchange factors (GEFs) activate Rho-family GTPases. Rgnef (p190RhoGEF) is a ubiquitous 190 kDa GEF implicated in the control of colon carcinoma and fibroblast cell motility.Rgnef exon 24 floxed mice (Rgnef(flox)) were created and crossed with cytomegalovirus (CMV)-driven Cre recombinase transgenic mice to inactivate Rgnef expression in all tissues during early development. Heterozygous Rgnef(WT/flox) (Cre+) crosses yielded normal Mendelian ratios at embryonic day 13.5, but Rgnef(flox/flox) (Cre+) mice numbers at 3 weeks of age were significantly less than expected. Rgnef(flox/flox) (Cre+) (Rgnef-/-) embryos and primary mouse embryo fibroblasts (MEFs) were isolated and verified to lack Rgnef protein expression. When compared to wildtype (WT) littermate MEFs, loss of Rgnef significantly inhibited haptotaxis migration, wound closure motility, focal adhesion number, and RhoA GTPase activation after fibronectin-integrin stimulation. In WT MEFs, Rgnef activation occurs within 60 minutes upon fibronectin plating of cells associated with RhoA activation. Rgnef-/- MEF phenotypes were rescued by epitope-tagged Rgnef re-expression.Rgnef-/- MEF phenotypes were due to Rgnef loss and support an essential role for Rgnef in RhoA regulation downstream of integrins in control of cell migration
Nucleotide exchange factor GEF-H1 mediates cross-talk between microtubules and the actin cytoskeleton
Endocytic protein intersectin-l regulates actin assembly via Cdc42 and N-WASP
Intersectin-s is a modular scaffolding protein regulating the formation of clathrin-coated vesicles. In addition to the Eps15 homology (EH) and Src homology 3 (SH3) domains of intersectin-s, the neuronal variant (intersectin-l) also has Dbl homology (DH), pleckstrin homology (PH) and C2 domains. We now show that intersectin-l functions through its DH domain as a guanine nucleotide exchange factor (GEF) for Cdc42. In cultured cells, expression of DH-domain-containing constructs cause actin rearrangements specific for Cdc42 activation. Moreover, in vivo studies reveal that stimulation of Cdc42 by intersectin-l accelerates actin assembly via N-WASP and the Arp2/3 complex. N-WASP binds directly to intersectin-l and upregulates its GEF activity, thereby generating GTP-bound Cdc42, a critical activator of N-WASP. These studies reveal a role for intersectin-l in a novel mechanism of N-WASP activation and in regulation of the actin cytoskeleton
Rho-mediated activation of PI(4)P5K and lipid second messengers is necessary for promotion of angiogenesis by Semaphorin 4D
Phosphatidylinositol 4-phosphate 5-kinase α negatively regulates nerve growth factor-induced neurite outgrowth in PC12 cells
MTORC2 controls actin polymerization required for consolidation of long-term memory
A major goal of biomedical research is the identification of molecular and cellular mechanisms that underlie memory storage. Here we report a previously unknown signaling pathway that is necessary for the conversion from short-to long-term memory. The mammalian target of rapamycin (mTOR) complex 2 (mTORC2), which contains the regulatory protein Rictor (rapamycin-insensitive companion of mTOR), was discovered only recently and little is known about its function. We found that conditional deletion of Rictor in the postnatal murine forebrain greatly reduced mTORC2 activity and selectively impaired both long-term memory (LTM) and the late phase of hippocampal long-term potentiation (L-LTP). We also found a comparable impairment of LTM in dTORC2-deficient flies, highlighting the evolutionary conservation of this pathway. Actin polymerization was reduced in the hippocampus of mTORC2-deficient mice and its restoration rescued both L-LTP and LTM. Moreover, a compound that promoted mTORC2 activity converted early LTP into late LTP and enhanced LTM. Thus, mTORC2 could be a therapeutic target for the treatment of cognitive dysfunction.Fil: Huang, Wei. Baylor College of Medicine. Department of Neuroscience; Estados UnidosFil: Zhu, Ping Jun. Baylor College of Medicine. Department of Neuroscience; Estados UnidosFil: Zhang, Shixing. University Of Houston; Estados UnidosFil: Zhou, Hongyi. Baylor College of Medicine. Department of Neuroscience; Estados UnidosFil: Stoica, Loredana. Baylor College of Medicine. Department of Neuroscience; Estados UnidosFil: Galiano, Mauricio Raul. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - CĂłrdoba. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba. Universidad Nacional de CĂłrdoba. Facultad de Ciencias QuĂmicas. Centro de Investigaciones en QuĂmica BiolĂłgica de CĂłrdoba; Argentina. Baylor College of Medicine. Department of Neuroscience; Estados UnidosFil: Krnjević, Krešimir. McGill Universit; CanadáFil: Roman, Gregg. University Of Houston; Estados UnidosFil: Costa-Mattioli, Mauro. Baylor College of Medicine. Department of Neuroscience; Estados Unido