Search

Summary Microtubules regulate signaling, trafficking, and cell mechanics, but the respective contribution of these functions to cell morphogenesis and migration in 3D matrices is unclear. Here, we report that the microtubule plus-end tracking protein (+TIP) SLAIN2, which suppresses catastrophes, is not required for 2D cell migration but is essential for mesenchymal cell invasion in 3D culture and in a mouse cancer model. We show that SLAIN2 inactivation does not affect Rho GTPase activity, trafficking, and focal adhesion formation. However, SLAIN2-dependent catastrophe inhibition determines microtubule resistance to compression and pseudopod elongation. Another +TIP, CLASP1, is also needed to form invasive pseudopods because it prevents catastrophes specifically at their tips. When microtubule growth persistence is reduced, inhibition of depolymerization is sufficient for pseudopod maintenance but not remodeling. We propose that catastrophe inhibition by SLAIN2 and CLASP1 supports mesenchymal cell shape in soft 3D matrices by enabling microtubules to perform a load-bearing function. [ABSTRACT FROM AUTHOR]

The cross-talk between dynamic microtubules and integrin-based adhesions to the extracellular matrix plays a crucial role in cell polarity and migration. Microtubules regulate the turnover of adhesion sites, and, in turn, focal adhesions promote the cortical microtubule capture and stabilization in their vicinity, but the underlying mechanism is unknown. Here, we show that cortical microtubule stabilization sites containing CLASPs, KIF21A, LL5β and liprins are recruited to focal adhesions by the adaptor protein KANK1, which directly interacts with the major adhesion component, talin. Structural studies showed that the conserved KN domain in KANK1 binds to the talin rod domain R7. Perturbation of this interaction, including a single point mutation in talin, which disrupts KANK1 binding but not the talin function in adhesion, abrogates the association of microtubule-stabilizing complexes with focal adhesions. We propose that the talin-KANK1 interaction links the two macromolecular assemblies that control cortical attachment of actin fibers and microtubules. [ABSTRACT FROM AUTHOR]

Development, polarization, structural integrity, and plasticity of neuronal cells critically depend on the microtubule network and its dynamic properties. SLAIN1 and SLAIN2 are microtubule plus-end tracking proteins that have been recently identified as regulators of microtubule dynamics. SLAINs are targeted to microtubule tips through an interaction with the core components of microtubule plus-end tracking protein network, End Binding family members. SLAINs promote persistent microtubule growth by recruiting the microtubule polymerase ch-TOG to microtubule plus-ends. Here, we show that SLAIN1/2 and ch-TOG-proteins are highly enriched in brain and are expressed throughout mouse brain development. Disruption of the SLAIN-ch-TOG complex in cultured primary rat hippocampal neurons by RNA interference-mediated knockdown and a dominant-negative approach perturbs microtubule growth by increasing catastrophe frequency and inhibits axon extension during neuronal development. Our study shows that proper control of microtubule dynamics is important for axon elongation in developing neurons. [ABSTRACT FROM AUTHOR]

Summary: Mechanisms controlling microtubule dynamics at the cell cortex play a crucial role in cell morphogenesis and neuronal development. Here, we identified kinesin-4 KIF21A as an inhibitor of microtubule growth at the cell cortex. In vitro, KIF21A suppresses microtubule growth and inhibits catastrophes. In cells, KIF21A restricts microtubule growth and participates in organizing microtubule arrays at the cell edge. KIF21A is recruited to the cortex by KANK1, which coclusters with liprin-α1/β1 and the components of the LL5β-containing cortical microtubule attachment complexes. Mutations in KIF21A have been linked to congenital fibrosis of the extraocular muscles type 1 (CFEOM1), a dominant disorder associated with neurodevelopmental defects. CFEOM1-associated mutations relieve autoinhibition of the KIF21A motor, and this results in enhanced KIF21A accumulation in axonal growth cones, aberrant axon morphology, and reduced responsiveness to inhibitory cues. Our study provides mechanistic insight into cortical microtubule regulation and suggests that altered microtubule dynamics contribute to CFEOM1 pathogenesis. [ABSTRACT FROM AUTHOR]

Cultured meat is an emerging biotechnology that aims to produce meat from animal cell culture, rather than from the raising and slaughtering of livestock, on environmental and animal welfare grounds. The detailed understanding and accurate manipulation of cell biology are critical to the design of cultured meat bioprocesses. Recent years have seen significant interest in this field, with numerous scientific and commercial breakthroughs. Nevertheless, these technologies remain at a nascent stage, and myriad challenges remain, spanning the entire bioprocess. From a cell biological perspective, these include the identification of suitable starting cell types, tuning of proliferation and differentiation conditions, and optimization of cell-biomaterial interactions to create nutritious, enticing foods. Here, we discuss the key advances and outstanding challenges in cultured meat, with a particular focus on cell biology, and argue that solving the remaining bottlenecks in a cost-effective, scalable fashion will require coordinated, concerted scientific efforts. Success will also require solutions to nonscientific challenges, including regulatory approval, consumer acceptance, and market feasibility. However, if these can be overcome, cultured meat technologies can revolutionize our approach to food.

Three-dimensional (3D) cell motility underlies essential processes, such as embryonic development, tissue repair and immune surveillance, and is involved in cancer progression. Although the cytoskeleton is a well-studied regulator of cell migration, most of what we know about its functions originates from studies conducted in two-dimensional (2D) cultures. This research established that the microtubule network mediates polarized trafficking and signaling that are crucial for cell shape and movement in 2D. In parallel, developments in light microscopy and 3D cell culture systems progressively allowed to investigate cytoskeletal functions in more physiologically relevant settings. Interestingly, several studies have demonstrated that microtubule involvement in cell morphogenesis and motility can differ in 2D and 3D environments. In this Commentary, we discuss these differences and their relevance for the understanding the role of microtubules in cell migration in vivo We also provide an overview of microtubule functions that were shown to control cell shape and motility in 3D matrices and discuss how they can be investigated further by using physiologically relevant models., (© 2017. Published by The Company of Biologists Ltd.)

Development, polarization, structural integrity, and plasticity of neuronal cells critically depend on the microtubule network and its dynamic properties. SLAIN1 and SLAIN2 are microtubule plus-end tracking proteins that have been recently identified as regulators of microtubule dynamics. SLAINs are targeted to microtubule tips through an interaction with the core components of microtubule plus-end tracking protein network, End Binding family members. SLAINs promote persistent microtubule growth by recruiting the microtubule polymerase ch-TOG to microtubule plus-ends. Here, we show that SLAIN1/2 and ch-TOG-proteins are highly enriched in brain and are expressed throughout mouse brain development. Disruption of the SLAIN-ch-TOG complex in cultured primary rat hippocampal neurons by RNA interference-mediated knockdown and a dominant-negative approach perturbs microtubule growth by increasing catastrophe frequency and inhibits axon extension during neuronal development. Our study shows that proper control of microtubule dynamics is important for axon elongation in developing neurons.

We investigated the potential in vivo aneugenic effects associated with paclitaxel treatment. For this purpose, we treated female nude mice with paclitaxel using doses equivalent to those used in weekly schedules at the clinical level (three cycles of 30 mg/kg/week for three consecutive weeks followed by one resting week). We then evaluated the frequencies of micronucleated erythrocytes (MNE) in peripheral blood using the acridine orange micronucleus assay. The frequency of MNE was evaluated after 24 h and 168 h of administration of the last dose of each paclitaxel cycle (STA mice group) as well as after one year of the first dose of treatment (LTA mice group). We also analyzed the cytology of peripheral blood and bone marrows obtained from these mice at each time period. In the STA mice group, three cycles of paclitaxel induced a 2.4-fold increase in MNE frequencies compared to the control group (p < 0.01). This effect was observed after 24 h of the last dose of each chemotherapy cycle and persisted at least for 168 h. In the LTA mice group, paclitaxel-treated mice presented a 1.8-fold increase in the MNE frequency (p = 0.01) indicating that paclitaxel-induced MNE increase lasted for at least one year. Although the appearance of micronuclei in erythrocytes and granulocytes in peripheral blood and bone marrow cytological smears, there was no evidence of myeloproliferative disease. The present data therefore indicate an aneugenic potential of paclitaxel for humans, which should be considered in the risk-benefit analysis of its increasing clinical use.