ZizB, a novel RacGEF regulates development, cell motility and cytokinesis in Dictyostelium.

Abstract

Summary Dock (dedicator of cytokinesis) proteins represent a family of guanine nucleotide exchange factors (GEFs) that include the well-studied Dock180 family and the poorly characterised zizimin family. Our current understanding of Dock180 function is that it regulates Rho small GTPases and thus has a role in a number of cell processes, including cell migration, development and division. Here, we use a tractable model for cell motility research, Dictyostelium discoideum, to help elucidate the role of the related zizimin proteins. We show that gene ablation of zizA causes no change in development, whereas ablation of zizB gives rise to an aberrant developmental morphology and a reduction in cell directionality and velocity, and altered cell shape. Fluorescently labelled ZizA protein associates with the microtubule-organising centre (MTOC), whereas ZizB is enriched in the cortex. Overexpression of ZizB also causes an increase in the number of filopodia and a partial inhibition of cytokinesis. Analysis of ZizB protein binding partners shows that it interacts with Rac1a and a range of actin-associated proteins. In conclusion, our work provides insight into the molecular and cellular functions of zizimin GEF proteins, which are shown to have a role in cell movement, filopodia formation and cytokinesis.

Naringenin inhibits the growth of Dictyostelium and MDCK‐derived cysts in a TRPP2 (polycystin‐2)‐dependent manner

“…Knockout constructs were created using methods described previously (Pakes et al ., 2012). Briefly, 5′ and 3′ fragments flanking the Dictyostelium pkd2 was amplified by PCR (peqSTAR 96 Universal Gradient, Erlangen, Germany) from wild-type genomic DNA.…”

Chemotaxis of a model organism: progress with Dictyostelium

“…SCAR activation probably involves the loss of inhibitory phosphorylations at the C-terminus, as well as activation from Rho-family small GTPases. However, the signalling route from chemoattractant receptor to actin polymerisation remains unclear: for instance systematic knock-out of RhoGEFs with Dbl-domains has not so far yielded a clear candidate [12] whereas some mutants of the Dock/Zizimin family of GEFs do show clear defects in movement or actin polymerisation [13,14].…”

A novel human receptor involved in bitter tastant detection identified using the model organism Dictyostelium discoideum

“…Knockout constructs were created as previously described (Pakes et al, 2012;Terbach et al, 2011). Briefly, 59 and 39 fragments flanking the gene of interest were amplified by PCR (peqSTAR 96 Universal Gradient, Erlangen, Germany) from Ax2 genomic DNA.…”