dictyNews Electronic Edition Volume 38, number 2 January 13, 2012 Please submit abstracts of your papers as soon as they have been accepted for publication by sending them to dicty@northwestern.edu or by using the form at http://dictybase.org/db/cgi-bin/dictyBase/abstract_submit. Back issues of dictyNews, the Dicty Reference database and other useful information is available at dictyBase - http://dictybase.org. Follow dictyBase on twitter: http://twitter.com/dictybase ========= Abstracts ========= Perturbations of the actin cytoskeleton activate a Dictyostelium STAT signalling pathway Tsuyoshi Araki and Jeffrey G. Williams European Journal of Cell Biology (short communication) The Dictyostelium transcription factor STATc is tyrosine phosphorylated and accumulates in the nucleus when cells are exposed either to hyper-osmotic stress or to the prestalk- inducing polyketide DIF-1. In the case of stress STAT activation is mediated by regulated dephosphorylation; whereby two serine residues on PTP3, the tyrosine phosphatase that de-activates STATc, become phosphorylated after exposure to stress so inhibiting enzymatic activity. We now show that the more highly regulated of the two PTP3 serine residues, S747, is also phosphorylated in response to DIF-1, suggesting a common activation mechanism. Hyper-osmotic stress causes a re-distribution of F-actin to the cortex, cell rounding and shrinkage and we show that DIF-1 induces a similar but transient F-actin re-distribution and rounding response. We also find that two mechanistically distinct inhibitors of actin polymerization, latrunculin A and cytochalasin A, induce phosphorylation at S747 of PTP3 and activate STATc. We suggest that PTP3 phosphorylation, and consequent STATc activation, are regulated by changes in F-actin polymerization status during stress and DIF-induced cytoskeletal remodelling. Submitted by jeff williams [j.g.williamd@dundee.ac.uk] -------------------------------------------------------------------------------------- Ectopic expression of Cyclase associated protein CAP restores the streaming and aggregation defects of Adenylyl Cyclase A deficient Dictyostelium discoideum cells. Sultana, H., Neelakanta, G., Rivero, F., Blau-Wasser, R., Schleicher, M., Noegel, A A. BMC Dev. Biol. Background: Cell adhesion, an integral part of D. discoideum development, is important for morphogenesis and regulated gene expression in the multicellular context and is required to trigger cell-differentiation. G-protein linked adenylyl cyclase pathways are crucially involved and a mutant lacking the aggregation specific adenylyl cyclase ACA does not undergo multicellular development. Results: Here, we have investigated the role of cyclase-associated protein (CAP), an important regulator of cell polarity and F-actin/G-actin ratio in the aca mutant. We show that ectopic expression of GFP-CAP improves cell polarization, streaming and aggregation in aca- cells, but it fails to completely restore development. Our studies indicate a requirement of CAP in the ACA dependent signal transduction for progression of the development of unicellular amoebae into multicellular structures. The reduced expression of the cell adhesion molecule DdCAD1 together with csA is responsible for the defects in aca- cells to initiate multicellular development. Early development was restored by the expression of GFP-CAP that enhanced the DdCAD1 transcript levels and to a lesser extent the csA mRNA levels. Conclusions: Collectively, our data shows a novel role of CAP in regulating cell adhesion mechanisms during development that might be envisioned to unravel the functions of mammalian CAP during animal embryogenesis. Submitted by Angelika Noegel [noegel@uni-koeln.de] ============================================================== [End dictyNews, volume 38, number 2]