The regulation of MMP targeting to invadopodia during cancer metastasis

The dissemination of cancer cells from the primary tumor to a distant site, known as metastasis, is the main cause of mortality in cancer patients. Metastasis is a very complex cellular process that involves many steps, including the breaching of the basement membrane to allow the movement of cells through tissues. The basement membrane breach occurs via highly regulated and localized remodeling of the extracellular matrix (ECM), which is mediated by formation of structures, known as invadopodia, and targeted secretion of matrix metalloproteinases (MMPs). Recently, invadopodia have emerged as key cellular structures that regulate the metastasis of many cancers. Furthermore, targeting of various cytoskeletal modulators and MMPs has been shown to play a major role in regulating invadopodia function. Here, we highlight recent findings regarding the regulation of protein targeting during invadopodia formation and function

Making the Final Cut — Mechanisms Mediating the Abscission Step of Cytokinesis

Cytokinesis is the final stage of mitotic cell division that results in a physical separation of two daughter cells. Cytokinesis begins in the early stages of anaphase after the positioning of the cleavage plane and after the chromosomes segregate. This involves the recruitment and assembly of an actomyosin contractile ring, which constricts the plasma membrane and compacts midzone microtubules to form an electron-dense region, termed the midbody, located within an intracellular bridge. The resolution of this intracellular bridge, known as abscission, is the last step in cytokinesis that separates the two daughter cells. While much research has been done to delineate the mechanisms mediating actomyosin ring formation and contraction, the machinery that is responsible for abscission remains largely unclear. Recent work from several laboratories has demonstrated that dramatic changes occur in cytoskeleton and endosome dynamics, and are a prerequisite for abscission. However, the mechanistic details that regulate the final plasma membrane fusion during abscission are only beginning to emerge and are the subject of considerable controversy. Here we review recent studies within this field and discuss the proposed models of cell abscission

FIP 5 phosphorylation during mitosis regulates apical trafficking and lumenogenesis

Apical lumen formation is a key step during epithelial morphogenesis. The establishment of the apical lumen is a complex process that involves coordinated changes in plasma membrane composition, endocytic transport, and cytoskeleton organization. These changes are accomplished, at least in part, by the targeting and fusion of Rab11/ FIP 5‐containing apical endosomes with the apical membrane initiation site ( AMIS ). Although AMIS formation and polarized transport of Rab11/ FIP 5‐containing endosomes are crucial for the formation of a single apical lumen, the spatiotemporal regulation of this process remains poorly understood. Here, we demonstrate that the formation of the midbody during cytokinesis is a symmetry‐breaking event that establishes the location of the AMIS . The interaction of FIP 5 with SNX 18, which is required for the formation of apical endocytic carriers, is inhibited by GSK ‐3 phosphorylation at FIP 5‐T276. Importantly, we show that FIP 5‐T276 phosphorylation occurs specifically during metaphase and anaphase, to ensure the fidelity and timing of FIP 5‐endosome targeting to the AMIS during apical lumen formation. Synopsis This study shows that epithelial lumen formation is regulated by FIP 5 phosphorylation, which inhibits its interaction with SNX 18 during metaphase and anaphase, ensuring that the transport of apical endocytic carriers happens only after the formation of the AMIS . FIP 5‐endosomes travel along the central spindle to the apical membrane initiation site ( AMIS ). FIP 5‐T276 phosphorylation by GSK ‐3 regulates the timing of apical lumen formation. The midbody formation during cytokinesis is a symmetry‐breaking event leading to the establishment of a single apical lumen site. This study shows that epithelial lumen formation is regulated by FIP5 phosphorylation, which inhibits its interaction with SNX18 during metaphase and anaphase, ensuring that the transport of apical endocytic carriers happens only after the formation of the AMIS.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/1/embr201338128-sup-0001-FigS1.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/2/embr201338128-SourceData-Fig4G.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/3/embr201338128-sup-0003-FigS3.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/4/embr201338128.reviewer_comments.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/5/embr201338128.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/6/embr201338128-sup-0004-FigS4.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/7/embr201338128-SourceData-Fig2B-C-D.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/8/embr201338128-sup-0005-FigS5.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/9/embr201338128-sup-0002-FigS2.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/106968/10/embr201338128-sup-0006-Methods.pd

A Rab-bit hole: Rab40 GTPases as new regulators of the actin cytoskeleton and cell migration

The regulation of machinery involved in cell migration is vital to the maintenance of proper organism function. When migration is dysregulated, a variety of phenotypes ranging from developmental disorders to cancer metastasis can occur. One of the primary structures involved in cell migration is the actin cytoskeleton. Actin assembly and disassembly form a variety of dynamic structures which provide the pushing and contractile forces necessary for cells to properly migrate. As such, actin dynamics are tightly regulated. Classically, the Rho family of GTPases are considered the major regulators of the actin cytoskeleton during cell migration. Together, this family establishes polarity in the migrating cell by stimulating the formation of various actin structures in specific cellular locations. However, while the Rho GTPases are acknowledged as the core machinery regulating actin dynamics and cell migration, a variety of other proteins have become established as modulators of actin structures and cell migration. One such group of proteins is the Rab40 family of GTPases, an evolutionarily and functionally unique family of Rabs. Rab40 originated as a single protein in the bilaterians and, through multiple duplication events, expanded to a four-protein family in higher primates. Furthermore, unlike other members of the Rab family, Rab40 proteins contain a C-terminally located suppressor of cytokine signaling (SOCS) box domain. Through the SOCS box, Rab40 proteins interact with Cullin5 to form an E3 ubiquitin ligase complex. As a member of this complex, Rab40 ubiquitinates its effectors, controlling their degradation, localization, and activation. Because substrates of the Rab40/Cullin5 complex can play a role in regulating actin structures and cell migration, the Rab40 family of proteins has recently emerged as unique modulators of cell migration machinery

Interaction between FIP5 and SNX18 regulates epithelial lumen formation

The Rab11 GTPase-binding protein FIP5 collaborates with the sorting nexin 18 to transport proteins to the apical surface and to tubulate membranes during epithelial apical lumen formatio

Peri-Golgi vesicles contain retrograde but not anterograde proteins consistent with the cisternal progression model of intra-Golgi transport

A cisternal progression mode of intra-Golgi transport requires that Golgi resident proteins recycle by peri-Golgi vesicles, whereas the alternative model of vesicular transport predicts anterograde cargo proteins to be present in such vesicles. We have used quantitative immuno-EM on NRK cells to distinguish peri-Golgi vesicles from other vesicles in the Golgi region. We found significant levels of the Golgi resident enzyme mannosidase II and the transport machinery proteins giantin, KDEL-receptor, and rBet1 in coatomer protein I–coated cisternal rims and peri-Golgi vesicles. By contrast, when cells expressed vesicular stomatitis virus protein G this anterograde marker was largely absent from the peri-Golgi vesicles. These data suggest a role of peri-Golgi vesicles in recycling of Golgi residents, rather than an important role in anterograde transport