The binding to poly(L-proline) is used for the affinity purification of profilins, but little is known about the structural and thermodynamic aspects of the interaction. We used changes in the intrinsic fluorescence of profilin, CD spectroscopy, and isothermal titration calorimetry to assess how the size and composition of synthetic proline-rich peptides influence binding to Acanthamoeba and hu...

WASP-family proteins are known to promote assembly of branched actin networks by stimulating the filament-nucleating activity of the Arp2/3 complex. Here, we show that WASP-family proteins also function as polymerases that accelerate elongation of uncapped actin filaments. When clustered on a surface, WASP-family proteins can drive branched actin networks to grow much faster than they could by ...

In order to reach their final adult morphology, Gamma neurons in Drosophila brain undergo a process of pruning followed by regrowth of their main axons and branches called remodelling. The mRNA binding protein Imp was identified to play a fundamental role in this process. One of Imp targets, profilin mRNA, encodes for an actin regulator that has been shown to be involved in axon remodelling. In...

Human profilin-1 is a novel protein associated with a recently discovered form of familial amyotrophic lateral sclerosis. This urges the characterization of possible conformational states, different from the fully folded state, potentially able to initiate self-assembly. Under native conditions, profilin-1 is monomeric and possesses a well-defined secondary and tertiary structure. When incubate...

Formins promote processive elongation of actin filaments for cytokinetic contractile rings and other cellular structures. In vivo, these structures are exposed to tension, but the effect of tension on these processes was unknown. Here we used single-molecule imaging to investigate the effects of tension on actin polymerization mediated by yeast formin Bni1p. Small forces on the filaments dramat...

Rho small GTPase regulates cell morphology, adhesion and cytokinesis through the actin cytoskeleton. We have identified a protein, p140mDia, as a downstream effector of Rho. It is a mammalian homolog of Drosophila diaphanous, a protein required for cytokinesis, and belongs to a family of formin-related proteins containing repetitive polyproline stretches. p140mDia binds selectively to the GTP-b...

INTRODUCTION Breast cancer is the most common form of cancer among women. In fact, 1 in 8 women are to be diagnosed with invasive breast cancer, the fatal form of breast cancer. Already in 2016, there have been approximately 250,000 cases of metastatic breast cancer with a death total of around 41,000 women [1]. Clearly, there is a need for better treatment options or detection methods for this...

Formin proteins nucleate actin filaments, remaining processively associated with the fast-growing barbed ends. Although formins possess common features, the diversity of functions and biochemical activities raised the possibility that formins differ in fundamental ways. Further, a recent study suggested that profilin and ATP hydrolysis are both required for processive elongation mediated by the...

Motile and morphogenetic cellular processes are driven by site-directed assembly of actin filaments. Formins, proteins characterized by formin homology domains FH1 and FH2, are initiators of actin assembly. How formins simply bind to filament barbed ends in rapid equilibrium or find free energy to become a processive motor of filament assembly remains enigmatic. Here we demonstrate that the FH1...

We have investigated the role of the actin cytoskeleton during mid-oogenesis and have found that disrupting the actin cytoskeleton with cytochalasin D induces microtubule bundling and microtubule-based cytoplasmic streaming within the oocyte, similar to that which occurs prematurely in cappuccino and spire mutant oocytes. After examining a number of mutants that affect the actin cytoskeleton, w...