Regulated expression of myosin II heavy chain and RacB using an inducible tRNA suppressor gene

Regulation of the Actin Cytoskeleton via Rho GTPase Signalling in Dictyostelium and Mammalian Cells: A Parallel Slalom

Both Dictyostelium amoebae and mammalian cells are endowed with an elaborate actin cytoskeleton that enables them to perform a multitude of tasks essential for survival. Although these organisms diverged more than a billion years ago, their cells share the capability of chemotactic migration, large-scale endocytosis, binary division effected by actomyosin contraction, and various types of adhesions to other cells and to the extracellular environment. The composition and dynamics of the transient actin-based structures that are engaged in these processes are also astonishingly similar in these evolutionary distant organisms. The question arises whether this remarkable resemblance in the cellular motility hardware is accompanied by a similar correspondence in matching software, the signalling networks that govern the assembly of the actin cytoskeleton. Small GTPases from the Rho family play pivotal roles in the control of the actin cytoskeleton dynamics. Indicatively, Dictyostelium matches mammals in the number of these proteins. We give an overview of the Rho signalling pathways that regulate the actin dynamics in Dictyostelium and compare them with similar signalling networks in mammals. We also provide a phylogeny of Rho GTPases in Amoebozoa, which shows a variability of the Rho inventories across different clades found also in Metazoa.

Overexpression and purification of human myosins from transiently and stably transfected suspension adapted HEK293SF-3F6 cells

The myosin family of motor proteins is an attractive target of therapeutic small-molecule protein inhibitors and modulators. Milligrams of protein quantities are required to conduct proper biophysical and biochemical studies to understand myosin functions. Myosin protein expression and purification represent a critical starting point towards this goal. Established utilization of Dictyostelium discoideum, Drosophila melanogaster, insect and mouse cells for myosin expression and purification is limited, cost, labor and time inefficient particularly for (full-length) human myosins. Here we are presenting detailed protocols for production of several difficult-to-purify recombinant human myosins in efficient quantities up to 1 mg of protein per liter of cell culture. This is the first time that myosins have been purified in large scales from suspension adapted transiently and stably expressing human cells. The method is also useful for expressing other human proteins in quantities sufficient to perform extensive biochemical and biophysical characterization.