Dynamin at actin tails

Abstract

Dynamin, the product of the shibire gene of Drosophila, is a GTPase critically required for endocytosis. Some studies have suggested a functional link between dynamin and the actin cytoskeleton. This link is of special interest, because there is evidence implicating actin dynamics in endocytosis. Here we show that endogenous dynamin 2, as well as green fluorescence protein fusion proteins of both dynamin 1 and 2, is present in actin comets generated by Listeria or by type I PIP kinase (PIPK) overexpression. In PIPKinduced tails, dynamin is further enriched at the interface between the tails and the moving organelles. Dynamin mutants harboring mutations in the GTPase domain inhibited nucleation of actin tails induced by PIPK and moderately reduced their speed. Although dynamin localization to the tails required its proline-rich domain, expression of a dynamin mutant lacking this domain also diminished tail formation. In addition, this mutant disrupted a membrane-associated actin scaffold (podosome rosette) previously shown to include dynamin. These findings suggest that dynamin is part of a protein network that controls nucleation of actin from membranes. At endocytic sites, dynamin may couple the fission reaction to the polymerization of an actin pool that functions in the separation of the endocytic vesicles from the plasma membrane.

RNAi-mediated Hip1R Silencing Results in Stable Association between the Endocytic Machinery and the Actin Assembly Machinery

“…Actin tails or plumes resembling actin comet tails that propel some intracellular pathogens through the cytoplasm have been observed to associate with a variety of endocytic structures (CCSs, endosomes, lysosomes, caveolae, and macropinosomes), and other trafficking vesicles (Heuser and Morisaki, 1992;Frischknecht et al, 1999;Merrifield et al, 1999;Kaksonen et al, 2000;Rozelle et al, 2000;Schafer et al, 2000;Taunton et al, 2000;Kanzaki et al, 2001;Lee and De Camilli, 2002;Merrifield et al, 2002;Orth et al, 2002;Pelkmans et al, 2002). During clathrin-mediated endocysosis, it is now known that actin appears transiently at CCPs just as they begin to move into the cytoplasm (Merrifield et al, 2002).…”

Dynamin 2 regulates biphasic insulin secretion and plasma glucose homeostasis

“…Dynamin may regulate actin function through both direct and indirect mechanisms in β cells. First, dynamin interacts with actin cytoskeleton through direct binding to F-actin (88) and microtubules (89) or through indirect interactions with actin-binding/regulatory molecules (90)(91)(92). For example, dynamin can directly bind actin filaments through a conserved actin-binding domain between amino acid 399 and 444, and the point mutation of this domain specifically decreases the dynamin-binding affinity to actin without affecting endocytosis (88).…”

Dynamin Participates in Focal Extracellular Matrix Degradation by Invasive Cells

“…Other actin-driven cellular structures/events shown to be regulated by Dyn2 are phagocytosis (Gold et al, 1999), membrane remodeling (McNiven et al, 2000b), actin comet movement (Lee and De Camilli, 2002;Orth et al, 2002), and the formation of the above-mentioned podosomes (Ochoa et al, 2000), dynamic plasma membrane protrusions characterized in nontumoral phagocytic cells or virus-transformed cells, and thought to be involved in mediating transient attachment during locomotion. The similarity in molecular composition between podosomes and invadopodia is remarkable and, in this regard, it is interesting to note that invadopodia have been initially characterized in Src-transformed cells cultured on a degradable ECM substrate and termed "invading podosomes" (Chen, 1989).…”

“…Of note, the binding of phosphoinositides to the well-characterized PH domain of dynamin affect both GTPase activity and self-assembly (Lee et al, 1999;Vallis et al, 1999;Muhlberg and Schmid, 2000) and the interactions between the dynamin PH domain and phosphoinositides are important for dynamin function in vivo; indeed, deletion of the PH domain impairs at least some of dynamin's functions (Achiriloaie et al, 1999;Vallis et al, 1999). Recent work points to the ubiquitous dynamin 2 form (Dyn2) as being capable of interacting with the actin cytoskeleton in regulating actin filament reorganization and subsequently cell shape via cortactin (McNiven et al, 2000b), actin comet formation (Lee and De Camilli, 2002;Orth et al, 2002), internalization of particles during phagocytosis (Gold et al, 1999), and the formation of podosomes (Ochoa et al, 2000), an actin-containing plasma membrane structure proposed to mediate cell adhesion and motility of phagocytic cells (Zambonin-Zallone et al, 1988;Nitsch et al, 1989). Because these findings propose Dyn2 as a key regulatory molecule in at least some types of actin-driven cytoskeletal machineries, and in linking the cytoskeleton to both membrane trafficking/remodeling and signaling events (Hinshaw, 2000), we examined whether Dyn2 plays a role in ECM invasion mediated by invadopodia.…”