Biology subjects

McHugh, T.

Publications and source records attributed to McHugh, T..

3 recordsLinked to original sources

bioRxiv2018

Microtubule end tethering of a processive Kinesin-8 motor Kif18b is required for spindle positioning

Mitotic spindle positioning specifies the plane of cell division during anaphase. Spindle orientation and positioning is therefore critical to ensure symmetric division in mitosis and asymmetric division during development. The control of astral microtubule length plays an essential role in positioning the spindle. Here we show using gene knockout that the Kinesin-8 Kif18b controls microtubule length to center the mitotic spindle at metaphase. Using an integrated approach, we reveal that Kif18b is a highly processive plus end-directed motor that uses a C-terminal non-motor microtubule-binding region to accumulate at growing microtubule plus ends. This region is regulated by phosphorylation to spatially control Kif18b accumulation at plus ends and is essential for Kif18b-dependent spindle positioning and regulation of microtubule length. Finally, we demonstrate that Kif18b shortens microtubules by increasing the catastrophe rate of dynamic microtubules. Overall, our work reveals that Kif18b utilizes its motile properties to reach microtubule ends where it regulates astral microtubule length to ensure spindle centering.

cell biology↗

bioRxiv2017

Single molecule mechanics reveal Kif15 as an active molecular ratchet with acute strain sensitivity

Human Kif15 is a tetrameric kinesin-12 that contributes critically to bipolar spindle assembly in eukaryotes. Here we examine its single molecule mechanics. Under hindering loads, Kif15 steps predominantly towards microtubule plus ends, with its forestep:backstep ratio decreasing exponentially with load and stall occurring at ~6pN. Between steps, Kif15 binds stably, usually via a single head domain. By complete contrast, under assisting loads, Kif15 detaches rapidly, even in AMPPNP. Furthermore, Kif15 can autoinhibit, via an interaction requiring its C-terminus. Autoinhibited Kif15 binds microtubules nucleotide-independently, resists both hindering and assisting loads, and is further stabilized by Tpx2, which interacts with the Kif15 C-terminus. Our data reveal the mechanics of Kif15 to be extraordinarily sensitive to loading direction. When unloaded, it walks rapidly; when pulled forwards it slips and when pulled backwards it grips. We discuss the implications of this unique mechanical behaviour for the roles of Kif15 in spindle function.

cell biology↗

bioRxiv2017

Polymersomes Targeting Mononuclear Phagocytes

Mononuclear phagocytes such as monocytes, tissue-specific macrophages and dendritic cells are primary actors in both innate and adaptive immunity, as well as tissue homoeostasis. They have key roles in a range of physiological and pathological processes, so any strategy targeting these cells will have wide-ranging impact. These phagocytes can be parasitized by intracellular bacteria, turning them from housekeepers to hiding places and favouring chronic and/or disseminated infection. One of the most infamous is the bacteria that cause tuberculosis, which is the most pandemic and one of the deadliest disease with one third of the worlds population infected, and 1.8 million deaths worldwide in 2015. Here we demonstrate the effective targeting and intracellular delivery of antibiotics to both circulating monocytes and resident macrophages, using pH sensitive nanoscopic polymersomes made of poly(2-(methacryloyloxy)ethyl phosphorylcholine)-co-poly(2-(di-isopropylamino)ethyl methacrylate) (PMPC-PDPA). Polymersome selectivity to mononuclear phagocytes is demonstrated and ascribed to the polymerised phosphorylcholine motifs affinity toward scavenger receptors. Finally, we demonstrate the successful exploitation of this targeting for the effective eradication of intracellular bacteria that cause tuberculosis Mycobacterium tuberculosis as well as other intracellular parasites including the Mycobacterium bovis, Mycobacterium marinum and the most common bacteria associated with antibiotic resistance, the Staphylococcus aureus.

immunology↗