Cryo-EM unveils kinesin KIF1A's processivity mechanism and the impact of its pathogenic variant P305L.

Mutations in the microtubule-associated motor protein KIF1A lead to severe neurological conditions known as KIF1A-associated neurological disorders (KAND). Despite insights into its molecular mechanism, high-resolution structures of KIF1A-microtubule complexes remain undefined. Here, we present 2.

Nucleotide-free structures of KIF20A illuminate atypical mechanochemistry in this kinesin-6.

KIF20A is a critical kinesin for cell division and a promising anti-cancer drug target. The mechanisms underlying its cellular roles remain elusive. Interestingly, unusual coupling between the nucleotide- and microtubule-binding sites of this kinesin-6 has been reported, but little is known about how its divergent sequence leads to atypical motility properties.

New insights into the mechanochemical coupling mechanism of kinesin-microtubule complexes from their high-resolution structures.

Kinesin motor proteins couple mechanical movements in their motor domain to the binding and hydrolysis of ATP in their nucleotide-binding pocket. Forces produced through this 'mechanochemical' coupling are typically used to mobilize kinesin-mediated transport of cargos along microtubules or microtubule cytoskeleton remodeling. This review discusses the recent high-resolution structures (<4 Å) of kinesins bound to microtubules or tubulin complexes that have resolved outstanding questions about the basis of mechanochemical coupling, and how family-specific modifications of the motor domain can enable its use for motility and/or microtubule depolymerization.

Cryo-EM Unveils the Processivity Mechanism of Kinesin KIF1A and the Impact of its Pathogenic Variant P305L.

Mutations in the microtubule-associated motor protein KIF1A lead to severe neurological conditions known as KIF1A-associated neurological disorders (KAND). Despite insights into its molecular mechanism, high-resolution structures of KIF1A-microtubule complexes remain undefined. Here, we present 2.

Kinesin-8-specific loop-2 controls the dual activities of the motor domain according to tubulin protofilament shape.

Kinesin-8s are dual-activity motor proteins that can move processively on microtubules and depolymerize microtubule plus-ends, but their mechanism of combining these distinct activities remains unclear. We addressed this by obtaining cryo-EM structures (2.6-3.

Structural basis of mechano-chemical coupling by the mitotic kinesin KIF14.

KIF14 is a mitotic kinesin whose malfunction is associated with cerebral and renal developmental defects and several cancers. Like other kinesins, KIF14 couples ATP hydrolysis and microtubule binding to the generation of mechanical work, but the coupling mechanism between these processes is still not fully clear. Here we report 20 high-resolution (2.

Brain and blood biomarkers of tauopathy and neuronal injury in humans and rats with neurobehavioral syndromes following blast exposure.

Traumatic brain injury (TBI) is a risk factor for the later development of neurodegenerative diseases that may have various underlying pathologies. Chronic traumatic encephalopathy (CTE) in particular is associated with repetitive mild TBI (mTBI) and is characterized pathologically by aggregation of hyperphosphorylated tau into neurofibrillary tangles (NFTs). CTE may be suspected when behavior, cognition, and/or memory deteriorate following repetitive mTBI.

The Human UGT2B7 Nanodisc.

The 20 uridine diphosphate glycosyl-transferases (UGTs) encoded in the human genome form an essential homeostatic network of overlapping catalytic functions that surveil and regulate the activity and clearance of scores of small molecule metabolites. Biochemical and biophysical UGT studies have been hampered by the inability to purify these membrane-bound proteins. Here, using cell-free expression and nanodisc technology, we assemble and purify to homogeneity the first UGT nanodisc-the human UGT2B7•nanodisc.

Kinesin-5 Promotes Microtubule Nucleation and Assembly by Stabilizing a Lattice-Competent Conformation of Tubulin.

Besides sliding apart antiparallel microtubules during spindle elongation, the mitotic kinesin-5, Eg5, promotes microtubule polymerization, emphasizing its importance in mitotic spindle length control. Here, we characterize the Eg5 microtubule polymerase mechanism by assessing motor-induced changes in the longitudinal and lateral tubulin-tubulin bonds that form the microtubule lattice. Isolated Eg5 motor domains promote microtubule nucleation, growth, and stability; thus, crosslinking tubulin by pairs of motor heads is not necessary for polymerase activity.

Author Correction: Cryo-EM reveals the structural basis of microtubule depolymerization by kinesin-13s.

The previously published version of this Article contained an error in Fig. 5. In panels f and g, the α and β symbols were swapped.

Cryo-EM reveals the structural basis of microtubule depolymerization by kinesin-13s.

Kinesin-13s constitute a distinct group within the kinesin superfamily of motor proteins that promote microtubule depolymerization and lack motile activity. The molecular mechanism by which kinesin-13s depolymerize microtubules and are adapted to perform a seemingly very different activity from other kinesins is still unclear. To address this issue, here we report the near atomic resolution cryo-electron microscopy (cryo-EM) structures of Drosophila melanogaster kinesin-13 KLP10A protein constructs bound to curved or straight tubulin in different nucleotide states.

Lack of chronic neuroinflammation in the absence of focal hemorrhage in a rat model of low-energy blast-induced TBI.

Blast-related traumatic brain injury (TBI) has been a common cause of injury in the recent conflicts in Iraq and Afghanistan. Blast waves can damage blood vessels, neurons, and glial cells within the brain. Acutely, depending on the blast energy, blast wave duration, and number of exposures, blast waves disrupt the blood-brain barrier, triggering microglial activation and neuroinflammation.

Use of Single Molecule Fluorescence Polarization Microscopy to Study Protein Conformation and Dynamics of Kinesin-Microtubule Complexes.

Single molecule fluorescence polarization microscopy (smFPM) is a technique that enables to monitor changes in the orientation of a single labeled protein domain. Here we describe a smFPM microscope set-up and protocols to investigate conformational changes associated with the movement of motor proteins along cytoskeletal tracks.

Distinct Interaction Modes of the Kinesin-13 Motor Domain with the Microtubule.

Kinesins-13s are members of the kinesin superfamily of motor proteins that depolymerize microtubules (MTs) and have no motile activity. Instead of generating unidirectional movement over the MT lattice, like most other kinesins, kinesins-13s undergo one-dimensional diffusion (ODD) and induce depolymerization at the MT ends. To understand the mechanism of ODD and the origin of the distinct kinesin-13 functionality, we used ensemble and single-molecule fluorescence polarization microscopy to analyze the behavior and conformation of Drosophila melanogaster kinesin-13 KLP10A protein constructs bound to the MT lattice.

[Clinical Characteristics of Metronidazole-induced Encephalopathy: A Report of Two Cases and a Review of 32 Japanese Cases in the Literature].

Metronidazole is an antibiotic classically used against most anaerobic bacteria and protozoa. Because an intravenous form of metronidazole has recently entered the market, the use of this antibiotic is attracting renewed interest in many clinical settings in Japan. However, neurotoxicity is a major adverse event: in the central nervous system metronidazole-induced encephalopathy is a rare but serious condition.

Ribosome abundance regulates the recovery of skeletal muscle protein mass upon recuperation from postnatal undernutrition in mice.

Nutritionally-induced growth faltering in the perinatal period has been associated with reduced adult skeletal muscle mass; however, the mechanisms responsible for this are unclear. To identify the factors that determine the recuperative capacity of muscle mass, we studied offspring of FVB mouse dams fed a protein-restricted diet during gestation (GLP) or pups suckled from postnatal day 1 (PN1) to PN11 (E-UN), or PN11 to PN22 (L-UN) on protein-restricted or control dams. All pups were refed under control conditions following the episode of undernutrition.

KIF14 binds tightly to microtubules and adopts a rigor-like conformation.

The mitotic kinesin motor protein KIF14 is essential for cytokinesis during cell division and has been implicated in cerebral development and a variety of human cancers. Here we show that the mouse KIF14 motor domain binds tightly to microtubules and does not display typical nucleotide-dependent changes in this affinity. It also has robust ATPase activity but very slow motility.

Dystropathology increases energy expenditure and protein turnover in the mdx mouse model of duchenne muscular dystrophy.

The skeletal muscles in Duchenne muscular dystrophy and the mdx mouse model lack functional dystrophin and undergo repeated bouts of necrosis, regeneration, and growth. These processes have a high metabolic cost. However, the consequences for whole body energy and protein metabolism, and on the dietary requirements for these macronutrients at different stages of the disease, are not well-understood.

Structural model for tubulin recognition and deformation by kinesin-13 microtubule depolymerases.

To elucidate the structural basis of the mechanism of microtubule depolymerization by kinesin-13s, we analyzed complexes of tubulin and the Drosophila melanogaster kinesin-13 KLP10A by electron microscopy (EM) and fluorescence polarization microscopy. We report a nanometer-resolution (1.1 nm) cryo-EM three-dimensional structure of the KLP10A head domain (KLP10AHD) bound to curved tubulin.

Human Fidgetin is a microtubule severing the enzyme and minus-end depolymerase that regulates mitosis.

Fidgetin is a member of the AAA protein superfamily with important roles in mammalian development. Here we show that human Fidgetin is a potent microtubule severing and depolymerizing the enzyme used to regulate mitotic spindle architecture, dynamics and anaphase A. In vitro, recombinant human Fidgetin severs taxol-stabilized microtubules along their length and promotes depolymerization, primarily from their minus-ends.

In utero glucocorticoid exposure reduces fetal skeletal muscle mass in rats independent of effects on maternal nutrition.

Maternal stress and undernutrition can occur together and expose the fetus to high glucocorticoid (GLC) levels during this vulnerable period. To determine the consequences of GLC exposure on fetal skeletal muscle independently of maternal food intake, groups of timed-pregnant Sprague-Dawley rats (n = 7/group) were studied: ad libitum food intake (control, CON); ad libitum food intake with 1 mg dexamethasone/l drinking water from embryonic day (ED)13 to ED21 (DEX); pair-fed (PF) to DEX from ED13 to ED21. On ED22, dams were injected with [(3)H]phenylalanine for measurements of fetal leg muscle and diaphragm fractional protein synthesis rates (FSR).

In vivo measurement of muscle protein synthesis rate using the flooding dose technique.

Skeletal muscle mass is determined by the balance between rates of protein synthesis and degradation. Protein synthesis rates can be measured in vivo by administering an amino acid as a tracer that is labeled with an isotope (radioactive or stable) of C, H, or N. The rate at which the labeled amino acid is incorporated into muscle protein, as a function of the amount of labeled amino acid in the precursor pool at the site of translation, reflects the rate of protein synthesis.

Drosophila katanin is a microtubule depolymerase that regulates cortical-microtubule plus-end interactions and cell migration.

Regulation of microtubule dynamics at the cell cortex is important for cell motility, morphogenesis and division. Here we show that the Drosophila katanin Dm-Kat60 functions to generate a dynamic cortical-microtubule interface in interphase cells. Dm-Kat60 concentrates at the cell cortex of S2 Drosophila cells during interphase, where it suppresses the polymerization of microtubule plus-ends, thereby preventing the formation of aberrantly dense cortical arrays.

Utilization of elderly kidney donors (>70 years) does not affect graft survival in the medium term.

Background: The need for organs for renal transplantation has encouraged the use of grafts from increasingly older donors. Earlier studies performed in Spain have shown the suitability of donors aged 60-65 years. In this single-center study, we evaluated our results using donors >70 years old.