Biology subjects

Ohi, R.

Publications and source records attributed to Ohi, R..

4 recordsLinked to original sources

bioRxiv2018

Regulation of KIF1A motility via polyglutamylation of tubulin C-terminal tails

Axonal transport is a highly regulated cellular process responsible for site-specific neuronal cargo delivery. This process is mediated in part by KIF1A, a member of the kinesin-3 family of molecular motors. It is imperative that KIF1As highly efficient, superprocessive motility along microtubules is tightly regulated as misregulation of KIF1A cargo delivery is observed in many neurodegenerative diseases. However, the regulatory mechanisms responsible for KIF1As motility, and subsequent proper spatiotemporal cargo delivery, are largely unknown. One potential regulatory mechanism of KIF1A motility is through the posttranslational modifications (PTMs) of axonal microtubules. These PTMs, often occurring on the C-terminal tails of the microtubule tracks, act as molecular \"traffic signals\" helping to direct kinesin motor cargo delivery. Occurring on neuronal microtubules, C-terminal tail polygutamylation is known to be important for KIF1A cargo transport. KIF1As initial interaction with microtubule C-terminal tails is facilitated by the K-loop, a positively charged surface loop of the KIF1A motor domain. However, the K-loops role in KIF1A motility and response to perturbations in C-terminal tail polyglutamylation is underexplored. Using single-molecule imaging, we present evidence of KIF1As previously unreported pausing behavior on multiple microtubule structures. Further analysis revealed that these pauses link multiple processive segments together, contributing to KIF1As characteristic superprocessive run length. We further demonstrate that KIF1A pausing is mediated by a K-loop/polyglutamylated C-terminal tail interaction and is a regulatory mechanism of KIF1A motility. In summary, we introduce a new mechanism of KIF1A motility regulation, providing further insight into KIF1As role in axonal transport.

biophysics↗

bioRxiv2018

Mitotic chromosome alignment is required for proper nuclear envelope reassembly

Chromosome alignment at the equator of the mitotic spindle is a highly conserved step during cell division, however, its importance to genomic stability and cellular fitness are not understood. Normal mammalian somatic cells lacking Kif18A function complete cell division without aligning chromosomes. These alignment-deficient cells display normal chromosome copy numbers in vitro and in vivo, suggesting that chromosome alignment is largely dispensable for maintenance of euploidy. However, we find that loss of chromosome alignment leads to interchromosomal compaction defects during anaphase, abnormal organization of chromosomes into a single nucleus at mitotic exit, and the formation of micronuclei in vitro and in vivo. These defects slow cell proliferation and reduce postnatal growth and survival with variable penetrance in mice. Our studies support a model in which the alignment of mitotic chromosomes promotes proper nuclear envelope reassembly and continued proliferation by ensuring that chromosomes segregate as a compact mass during anaphase.

cell biology↗

bioRxiv2018

Kinesin Binding Protein (KBP) buffers the activity of Kif18A and Kif15 in mitosis to ensure accurate chromosome segregation

Mitotic kinesins must be regulated to ensure a precise balance of spindle forces and accurate segregation of chromosomes into daughter cells. Here we demonstrate that Kinesin-Binding Protein (KBP) reduces the activity of KIF18A and KIF15 during metaphase. Overexpression of KBP disrupts the movement and alignment of mitotic chromosomes and decreases spindle length, a combination of phenotypes observed in cells deficient for KIF18A and KIF15, respectively. We show through gliding filament and microtubule co-pelleting assays that KBP directly inhibits KIF18A and KIF15 motor activity by preventing microtubule-binding. Consistent with these effects, the mitotic localizations of KIF18A and KIF15 are altered by overexpression of KBP. Cells depleted of KBP exhibit lagging chromosomes in anaphase, an effect that is recapitulated by KIF15 and KIF18A overexpression. Based on these data, we propose a model in which KBP acts as a protein buffer in mitosis, protecting cells from excessive KIF18A and KIF15 activity to promote accurate chromosome segregation.\n\nSUMMARYKinesin-Binding Protein (KBP) is identified as a regulator of the kinesins KIF18A and KIF15 during mitosis. KBP buffers the activity of these motors to control chromosome alignment and spindle integrity in metaphase and prevent lagging chromosomes in anaphase.

cell biology↗

bioRxiv2018

Microtubule minus-end aster organization is driven by processive HSET-tubulin clusters

Higher-order structures of the microtubule (MT) cytoskeleton are comprised of two architectures: bundles and asters. Although both architectures are critical for cellular function, the molecular pathways that drive aster formation are poorly understood. Here, we study aster formation by human minus-end directed kinesin-14 (HSET/KIFC1). We show that HSET is incapable of forming asters from pre-formed, non-growing MTs, but rapidly forms MT asters in the presence of soluble tubulin. HSET binds soluble (non-polymer) tubulin via its N-terminal tail domain to form heterogeneous HSET-tubulin \"clusters\" containing multiple motors. Cluster formation induces motor processivity and rescues the formation of asters from non-growing MTs. We then show that excess soluble tubulin stimulates aster formation in HeLa cells overexpressing HSET during mitosis. We propose a model where HSET can toggle between MT bundle and aster formation in a manner governed by the availability of soluble tubulin.

biophysics↗