KIF4 Motor Regulates Activity-Dependent Neuronal Survival by Suppressing PARP-1 Enzymatic Activity

miR-223-3p Targets KIF4A and Promotes the Oxidative Stress-Mediated Apoptosis of Breast Cancer Cells

Background: The abnormal expression of kinase family member 4A (KIF4A) is linked to breast cancer progression, with numerous miRNAs exhibiting abnormal expression. Thus, there is an urgent need to investigate the mechanisms of action of miRNAs and their target genes for the diagnosis and treatment of breast cancer. Materials and Methods: A bioinformatics analysis was conducted to screen for KIF4A, a key gene involved in oxidative stress in breast cancer cells. Using CCK8, EdU, cell healing, and Transwell assays, the knockdown of KIF4A was found to effectively inhibit the proliferation, migration, and invasion of breast cancer cells. Dual-luciferase assay and Western blotting confirmed that miR-223-3p targets and regulates KIF4A expression. The impact of miR-223-3p and KIF4A on oxidative stress in breast cancer cells was assessed through reactive oxygen species (ROS), superoxide dismutase (SOD), and malondialdehyde (MDA) measurements. Flow cytometry was used to evaluate tumor cell apoptosis. Results: Our results suggest that KIF4A is a downstream target of miR-223-3p. miR-223-3p inhibits the proliferation and invasion of breast cancer cells by directly targeting and downregulating KIF4A. Importantly, we found that miR-223-3p and KIF4A play important roles in regulating oxidative stress and apoptosis in breast cancer cells. Specifically, miR-223-3p promoted apoptosis by inhibiting the expression of KIF4A, increasing the accumulation level of ROS and MDA, and inhibiting the activity of SOD while KIF4A was overexpressed.

PARP1: A comprehensive review of its mechanisms, therapeutic implications and emerging cancer treatments

The Poly (ADP-ribose) polymerase-1 (PARP1) enzyme is involved in several signalling pathways related to homologous repair (HR), base excision repair (BER), and non-homologous end joining (NHEJ). Studies demonstrated that the deregulation of PARP1 function and control mechanisms can lead to cancer emergence. On the other side, PARP1 can be a therapeutic target to maximize cancer treatment. This is done by molecules that can modulate radiation effects, such as DNA repair inhibitors (PARPi). With this approach, tumour cell viability can be undermined by targeting DNA repair mechanisms. Thus, treatment using PARPi represents a new era for cancer therapy, and even new horizons can be attained by coupling these molecules with a nano-delivery system. For this, drug delivery systems such as liposomes encompass all the required features due to its excellent biocompatibility, biodegradability, and low toxicity. This review presents a comprehensive overview of PARP1 biological features and mechanisms, its role in cancer development, therapeutic implications, and emerging cancer treatments by PARPi-mediated therapies. Although there are a vast number of studies regarding PARP1 biological function, some PARP1 mechanisms are not clear yet, and full-length PARP1 structure is missing. Nevertheless, literature reports demonstrate already the high usefulness and vast possibilities offered by combined PARPi cancer therapy.

Oxygen-dependent alternative mRNA splicing and a cone-specific motor protein revealed by single-cell RNA sequencing in hypoxic retinas

Restricted oxygen supply in the aging eye may lead to hypoxic conditions in the outer retina and contribute not only to physiological aging but also to nonhereditary degenerative retinal diseases. To understand the hypoxic response of specific retinal cell types, we performed single-cell RNA sequencing of retinas isolated from mice exposed to hypoxia. Significantly upregulated expression of marker genes in hypoxic clusters confirmed a general transcriptional response to hypoxia. By focusing on the hypoxic response in photoreceptors, we identified and confirmed a kinesin motor protein (Kif4) that was specifically and strongly induced in hypoxic cones. In contrast, RNA-binding proteins Rbm3 and Cirbp were differentially expressed across clusters but demonstrated isoform switching in hypoxia. The resulting short variants of these gene transcripts are connected to epitranscriptomic regulation, a notion supported by the differential expression of writers, readers and erasers of m6A RNA methylations in the hypoxic retina. Our data indicate that retinal cells adapt to hypoxic conditions by adjusting their transcriptome at various levels including gene expression, alternative splicing and the epitranscriptome. Adaptational processes may be cell-type specific as exemplified by the cone-specific upregulation of Kif4 or general like alternative splicing of RNA binding proteins.

X-Linked Bilateral Polymicrogyria With Epilepsy and Intellectual Disability Associated With a Novel KIF4A Variant

We studied three brothers and a maternal half-brother featuring global developmental delay, mild to moderate intellectual disability, epilepsy, microcephaly, and strabismus. All had bilateral perisylvian and perirolandic polymicrogyria, while some also had malformations of the hippocampus (malrotation and dysplasia), cerebellum (heterotopias and asymmetric aplasia), corpus callosum dysgenesis, and brainstem asymmetric dysplasia. Exome sequencing showed that all four patients had a novel variant (c.1597C>T:p.Leu533Phe) on the KIF4A gene on chromosome X. We discuss how this variant is possibly pathogenic and could explain the reported phenotype.

The post-stroke young adult brain has limited capacity to re-express the gene expression patterns seen during early postnatal brain development

The developmental origins of the brain's response to injury can play an important role in recovery after a brain lesion. In this study, we investigated whether the ischemic young adult brain can re-express brain plasticity genes that were active during early postnatal development. Differentially expressed genes in the cortex of juvenile post-natal day 3 and the peri-infarcted cortical areas of young, 3-month-old post-stroke rats were identified using fixed-effects modeling within an empirical Bayes framework through condition-specific comparison. To further analyze potential biological processes, upregulated and downregulated genes were assessed for enrichment using GSEA software. The genes showing the highest expression changes were subsequently verified through RT-PCR. Our findings indicate that the adult brain partially recapitulates the gene expression profile observed in the juvenile brain but fails to upregulate many genes and pathways necessary for brain plasticity. Of the upregulated genes in post-stroke brains, specific roles have not been assigned to Apobec1, Cenpf, Ect2, Folr2, Glipr1, Myo1f, and Pttg1. New genes that failed to upregulate in the adult post-stroke brain include Bex4, Cd24, Klhl1/Mrp2, Trim67, and St8sia2. Among the upregulated pathways, the largest change was observed in the KEGG pathway "One carbon pool of folate," which is necessary for cellular proliferation, followed by the KEGG pathway "Antifolate resistance," whose genes mainly encode the family of ABC transporters responsible for the efflux of drugs that have entered the brain. We also noted three less-described downregulated KEGG pathways in experimental models: glycolipid biosynthesis, oxytocin, and cortisol pathways, which could be relevant as therapeutic targets. The limited brain plasticity of the adult brain is illustrated through molecular and histological analysis of the axonal growth factor, KIF4. Collectively, these results strongly suggest that further research is needed to decipher the complex genetic mechanisms that prevent the re-expression of brain plasticity-associated genes in the adult brain.

Neurons dispose of hyperactive kinesin into glial cells for clearance

Microtubule-based kinesin motor proteins are crucial for intracellular transport, but their hyperactivation can be detrimental for cellular functions. This study investigated the impact of a constitutively active ciliary kinesin mutant, OSM-3CA, on sensory cilia in C. elegans. Surprisingly, we found that OSM-3CA was absent from cilia but underwent disposal through membrane abscission at the tips of aberrant neurites. Neighboring glial cells engulf and eliminate the released OSM-3CA, a process that depends on the engulfment receptor CED-1. Through genetic suppressor screens, we identified intragenic mutations in the OSM-3CA motor domain and mutations inhibiting the ciliary kinase DYF-5, both of which restored normal cilia in OSM-3CA-expressing animals. We showed that conformational changes in OSM-3CA prevent its entry into cilia, and OSM-3CA disposal requires its hyperactivity. Finally, we provide evidence that neurons also dispose of hyperactive kinesin-1 resulting from a clinic variant associated with amyotrophic lateral sclerosis, suggesting a widespread mechanism for regulating hyperactive kinesins.

A novel in-frame deletion in KIF5C gene causes infantile onset epilepsy and psychomotor retardation

Motor proteins, encoded by Kinesin superfamily (KIF) genes, are critical for brain development and plasticity. Increasing studies reported KIF's roles in neurodevelopmental disorders. Here, a 6 years and 3 months-old Chinese boy with markedly symptomatic epilepsy, intellectual disability, brain atrophy, and psychomotor retardation was investigated. His parents and younger sister were phenotypically normal and had no disease-related family history. Whole exome sequencing identified a novel heterozygous in-frame deletion (c.265_267delTCA) in exon 3 of the KIF5C in the proband, resulting in the removal of evolutionarily highly conserved p.Ser90, located in its ATP-binding domain. Sanger sequencing excluded the proband's parents and family members from harboring this variant. The activity of ATP hydrolysis in vitro was significantly reduced as predicted. Immunofluorescence studies showed wild-type KIF5C was widely distributed throughout the cytoplasm, while mutant KIF5C was colocalized with microtubules. The live-cell imaging of the cargo-trafficking assay revealed that mutant KIF5C lost the peroxisome-transporting ability. Drosophila models also confirmed p.Ser90del's essential role in nervous system development. This study emphasized the importance of the KIF5C gene in intracellular cargo-transport as well as germline variants that lead to neurodevelopmental disorders and might enable clinicians for timely and accurate diagnosis and disease management in the future.

KIF4 Gene Variant's Disruption of PARP1 Signaling Increases Anxiety and Seizure Susceptibility

KIF4 Regulates Neuronal Morphology and Seizure Susceptibility via the PARP1 Signaling Pathway Wan Y, Morikawa M, Morikawa M, Iwata S, Naseer MI, Chaudhary AGA, Tanaka Y, Hirokawa N. J Cell Biol . 2023;222(2):e202208108. doi:10.1083/jcb.202208108 Epilepsy is a common neurological disease worldwide, and one of its causes is genetic abnormalities. Here, we identified a point mutation in KIF4A, a member of kinesin superfamily molecular motors, in patients with neurological disorders such as epilepsy, developmental delay, and intellectual disability. KIF4 is involved in the poly (ADP-ribose) polymerase (PARP) signaling pathway, and the mutation (R728Q) strengthened its affinity with PARP1 through elongation of the KIF4 coiled-coil domain. Behavioral tests showed that KIF4-mutant mice exhibited mild developmental delay with lower seizure threshold. Further experiments revealed that the KIF4 mutation caused aberrant morphology in dendrites and spines of hippocampal pyramidal neurons through PARP1-TrkB-KCC2 pathway. Furthermore, supplementing NAD, which activates PARP1, could modulate the TrkB-KCC2 pathway and rescue the seizure susceptibility phenotype of the mutant mice. Therefore, these findings indicate that KIF4 is engaged in a fundamental mechanism regulating seizure susceptibility and could be a potential target for epilepsy treatment.

Kinesins Modify ERR1-Dependent Transcription Using a Conserved Nuclear Receptor Box Motif

Kinesin family motors are microtubule (MT)-stimulated ATPases known best as transporters of cellular cargoes through the cytoplasm, regulators of MT dynamics, organizers of the mitotic spindle, and for insuring equal division of DNA during mitosis. Several kinesins have also been shown to regulate transcription by interacting with transcriptional cofactors and regulators, nuclear receptors, or with specific promotor elements on DNA. We previously showed that an LxxLL nuclear receptor box motif in the kinesin-2 family motor KIF17 mediates binding to the orphan nuclear receptor estrogen related receptor alpha (ERR1) and is responsible for the suppression of ERR1-dependent transcription by KIF17. Analysis of all kinesin family proteins revealed that multiple kinesins contain this LxxLL motif, raising the question as to whether additional kinesin motors contribute to the regulation of ERR1. In this study, we interrogate the effects of multiple kinesins with LxxLL motifs on ERR1-mediated transcription. We demonstrate that the kinesin-3 family motor KIF1B contains two LxxLL motifs, one of which binds to ERR1. In addition, we show that expression of a KIF1B fragment containing this LxxLL motif inhibits ERR1-dependent transcription by regulating nuclear entry of ERR1. We also provide evidence that the effects of expressing the KIF1B-LxxLL fragment on ERR1 activity are mediated by a mechanism distinct from that of KIF17. Since LxxLL domains are found in many kinesins, our data suggest an expanded role for kinesins in nuclear receptor mediated transcriptional regulation.

Loss of non-motor kinesin KIF26A causes congenital brain malformations via dysregulated neuronal migration and axonal growth as well as apoptosis

Kinesins are canonical molecular motors but can also function as modulators of intracellular signaling. KIF26A, an unconventional kinesin that lacks motor activity, inhibits growth-factor-receptor-bound protein 2 (GRB2)- and focal adhesion kinase (FAK)-dependent signal transduction, but its functions in the brain have not been characterized. We report a patient cohort with biallelic loss-of-function variants in KIF26A, exhibiting a spectrum of congenital brain malformations. In the developing brain, KIF26A is preferentially expressed during early- and mid-gestation in excitatory neurons. Combining mice and human iPSC-derived organoid models, we discovered that loss of KIF26A causes excitatory neuron-specific defects in radial migration, localization, dendritic and axonal growth, and apoptosis, offering a convincing explanation of the disease etiology in patients. Single-cell RNA sequencing in KIF26A knockout organoids revealed transcriptional changes in MAPK, MYC, and E2F pathways. Our findings illustrate the pathogenesis of KIF26A loss-of-function variants and identify the surprising versatility of this non-motor kinesin.

KIF5C deficiency causes abnormal cortical neuronal migration, dendritic branching, and spine morphology in mice

BACKGROUND

Malformation of cortical development (MCD) includes a variety of developmental disorders that are common causes of neurodevelopmental delay and epilepsy. Most recently, clinical studies found that patients carrying KIF5C mutations present early-onset MCD; however, the underlying mechanisms remain elusive.

METHODS

KIF5C expression level was examined in mouse primary cortical neurons and human ips-derived forebrain organoids. We studied the cortical neuronal migration, dendritic branching, and dendritic spine growth after knocking down the KIF5C gene by electroporation in vitro and in vivo. Then, we studied the transcriptome differences between the knockdown and control groups through RNA sequencing.

RESULTS

We observed high KIF5C expression in neurons during the early developmental stage in mice and the human brain. Kif5c deficiency results in disturbed cortical neuronal migration, dendritic, and spine growth. Finally, we found that Kif5c knockdown affected several genes associated with cortical neuronal development in vitro.

CONCLUSIONS

These results suggested a critical role for Kif5c in cortical development, providing insights into underlying pathogenic factors of kinesins in MCD.

IMPACT

KIF5C mutation-related MCD might be caused by abnormal early cortical neuronal development. Kif5c deficiency led to abnormal cortical neuronal dendritic and spine growth and neuronal migration. Our findings explain how Kif5c deficiency is involved in the aberrant development of cortical neurons and provide a new perspective for the pathology of MCD.

Molecular Link between DNA Damage Response and Microtubule Dynamics

Microtubules are major components of the cytoskeleton that play important roles in cellular processes such as intracellular transport and cell division. In recent years, it has become evident that microtubule networks play a role in genome maintenance during interphase. In this review, we highlight recent advances in understanding the role of microtubule dynamics in DNA damage response and repair. We first describe how DNA damage checkpoints regulate microtubule organization and stability. We then highlight how microtubule networks are involved in the nuclear remodeling following DNA damage, which leads to changes in chromosome organization. Lastly, we discuss how microtubule dynamics participate in the mobility of damaged DNA and promote consequent DNA repair. Together, the literature indicates the importance of microtubule dynamics in genome organization and stability during interphase.

Therapeutic Potentials of Poly (ADP-Ribose) Polymerase 1 (PARP1) Inhibition in Multiple Sclerosis and Animal Models: Concept Revisiting

Poly (ADP-ribose) polymerase 1 (PARP1) plays a fundamental role in DNA repair and gene expression. Excessive PARP1 hyperactivation, however, has been associated with cell death. PARP1 and/or its activity are dysregulated in the immune and central nervous system of multiple sclerosis (MS) patients and animal models. Pharmacological PARP1 inhibition is shown to be protective against immune activation and disease severity in MS animal models while genetic PARP1 deficiency studies reported discrepant results. The inconsistency suggests that the function of PARP1 and PARP1-mediated PARylation may be complex and context-dependent. The article reviews PARP1 functions, discusses experimental findings and possible interpretations of PARP1 in inflammation, neuronal/axonal degeneration, and oligodendrogliopathy, three major pathological components cooperatively determining MS disease course and neurological progression, and points out future research directions. Cell type specific PARP1 manipulations are necessary for revisiting the role of PARP1 in the three pathological components prior to moving PARP1 inhibition into clinical trials for MS therapy.

Identification of Novel Molecular Therapeutic Targets and Their Potential Prognostic Biomarkers Among Kinesin Superfamily of Proteins in Pancreatic Ductal Adenocarcinoma

Background

Kinesin superfamily of proteins (KIFs) has been broadly reported to play an indispensable role in the biological process. Recently, emerging evidence reveals its oncogenic role in various cancers. However, the prognostic, oncological, and immunological values of KIFs have not been comprehensively explored in pancreatic ductal adenocarcinoma (PDAC) patients. We aimed to illustrate the relationship between KIFs and pancreatic ductal adenocarcinoma by using bioinformatical analysis.

Methods

We use GEPIA, Oncomine datasets, cBioPortal, LOGpc, TIMER, and STRING bioinformatics tools and web servers to investigate the aberrant expression, prognostic values, and oncogenic role of KIFs. The two-gene prognostic model and the correlation between KIFs and KRAS and TP53 mutation were performed using an R-based computational framework.

Results

Our results demonstrated that KIFC1/2C/4A/11/14/15/18A/18B/20B/23 (we name it prognosis-related KIFs) were upregulated and associated with unfavorable clinical outcome in pancreatic cancer patients. KIF21B overexpression is associated with better clinical outcome. The KIFC1/2C/4A/11/14/15/18A/18B/20B/23 profiles were significantly increased compared to grade 1 and grade 2/3. Besides, KIFC1/2C/4A/11/14/15/18A/18B/20B/23 was significantly associated with the mutation status of KRAS and TP53.Notably, most prognosis-related KIFs have strong correlations with tumor growth and myeloid-derived suppressor cells infiltration (MDSCs). A prognostic signature based on KIF20B and KIF21B showed a reliable predictive performance. Receiver operating characteristic (ROC) curve was employed to assess the predictive power of two-gene signature. Consequently, the gene set enrichment analysis (GSEA) showed that KIF20B and KIF21B’s overexpression was associated with the immunological and oncogenic pathway activation in pancreatic cancer. Finally, real-time quantitative PCR (RT-qPCR) was utilized to investigate the expression pattern of KIF20B and KIF21B in pancreatic cancer cell lines and normal pancreatic cell.

Conclusions

Knowledge of the expression level of the KIFs may provide novel therapeutic molecular targets and potential prognostic biomarkers to pancreatic cancer patients.

Expanding the KIF4A-associated phenotype

Kinesin super family (KIF) genes encode motor kinesins, a family of evolutionary conserved proteins, involved in intracellular trafficking of various cargoes. These proteins are critical for various physiological processes including neuron function and survival, ciliary function and ciliogenesis, and cell‐cycle progression. Recent evidence suggests that alterations in motor kinesin genes can lead to a variety of human diseases, including monogenic disorders. Neuropathies, impaired higher brain functions, structural brain abnormalities and multiple congenital anomalies (i.e., renal, urogenital, and limb anomalies) can result from pathogenic variants in many KIF genes. We expand the phenotype associated with KIF4A variants from developmental delay and intellectual disability with or without epilepsy to a congenital anomaly phenotype with hydrocephalus and various brain anomalies at the more severe end of phenotypic manifestations. Additional anomalies of the kidneys and urinary tract, congenital lymphedema, eye, and dental anomalies seem to be variably associated and overlap with clinical signs observed in other kinesinopathies. Caution still applies to missense variants, but hopefully, future work will further establish genotype–phenotype correlations in a larger number of patients and functional studies may give further insights into the complex function of KIF4A.

Towards resolving the enigma of the dichotomy of resveratrol: cis- and trans-resveratrol have opposite effects on TyrRS-regulated PARP1 activation

Unlike widely perceived, resveratrol (RSV) decreased the average lifespan and extended only the replicative lifespan in yeast. Similarly, although not widely discussed, RSV is also known to evoke neurite degeneration, kidney toxicity, atherosclerosis, premature senescence, and genotoxicity through yet unknown mechanisms. Nevertheless, in vivo animal models of diseases and human clinical trials demonstrate inconsistent protective and beneficial effects. Therefore, the mechanism of action of RSV that elicits beneficial effects remains an enigma. In a previously published work, we demonstrated structural similarities between RSV and tyrosine amino acid. RSV acts as a tyrosine antagonist and competes with it to bind to human tyrosyl-tRNA synthetase (TyrRS). Interestingly, although both isomers of RSV bind to TyrRS, only the cis-isomer evokes a unique structural change at the active site to promote its interaction with poly-ADP-ribose polymerase 1 (PARP1), a major determinant of cellular NAD+-dependent stress response. However, retention of trans-RSV in the active site of TyrRS mimics its tyrosine-bound conformation that inhibits the auto-poly-ADP-ribos(PAR)ylation of PARP1. Therefore, we proposed that cis-RSV-induced TyrRS-regulated auto-PARylation of PARP1 would contribute, at least in part, to the reported health benefits of RSV through the induction of protective stress response. This observation suggested that trans-RSV would inhibit TyrRS/PARP1-mediated protective stress response and would instead elicit an opposite effect compared to cis-RSV. Interestingly, most recent studies also confirmed the conversion of trans-RSV and its metabolites to cis-RSV in the physiological context. Therefore, the finding that cis-RSV and trans-RSV induce two distinct conformations of TyrRS with opposite effects on the auto-PARylation of PARP1 provides a potential molecular basis for the observed dichotomic effects of RSV under different experimental paradigms. However, the fact that natural RSV exists as a diastereomeric mixture of its cis and trans isomers and cis-RSV is also a physiologically relevant isoform has not yet gained much scientific attention.

A Two-Step Process of Effector Programming Governs CD4+ T Cell Fate Determination Induced by Antigenic Activation in the Steady State

Various processes induce and maintain immune tolerance, but effector T cells still arise under minimal perturbations of homeostasis through unclear mechanisms. We report that, contrary to the model postulating primarily tolerogenic mechanisms initiated under homeostatic conditions, effector programming is an integral part of T cell fate determination induced by antigenic activation in the steady state. This effector programming depends on a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation. Such molecular circuits advancing specific terminal effector differentiation upon re-stimulation include programmed expression of interferon-γ, whose production then promotes expression of T-bet in the precursors. We further show that effector programming coincides with regulatory conversion among T cells sharing the same antigen specificity. However, conventional type 2 dendritic cells (cDC2) and T cell functions of mammalian target of rapamycin complex 1 (mTORC1) increase effector precursor induction while decreasing the proportion of T cells that can become peripheral Foxp3⁺ regulatory T (pTreg) cells.

The mechanisms in the steady state that govern the formation of effector T cells with potentially autoimmune functions remain unclear. Opejin et al. reveal a two-step process starting with induction of effector precursors that express Hopx and are imprinted with multiple instructions for their subsequent terminal effector differentiation.

Anterograde Axonal Transport in Neuronal Homeostasis and Disease

Neurons are highly polarized cells with an elongated axon that extends far away from the cell body. To maintain their homeostasis, neurons rely extensively on axonal transport of membranous organelles and other molecular complexes. Axonal transport allows for spatio-temporal activation and modulation of numerous molecular cascades, thus playing a central role in the establishment of neuronal polarity, axonal growth and stabilization, and synapses formation. Anterograde and retrograde axonal transport are supported by various molecular motors, such as kinesins and dynein, and a complex microtubule network. In this review article, we will primarily discuss the molecular mechanisms underlying anterograde axonal transport and its role in neuronal development and maturation, including the establishment of functional synaptic connections. We will then provide an overview of the molecular and cellular perturbations that affect axonal transport and are often associated with axonal degeneration. Lastly, we will relate our current understanding of the role of axonal trafficking concerning anterograde trafficking of mRNA and its involvement in the maintenance of the axonal compartment and disease.

Mutations in the KIF21B kinesin gene cause neurodevelopmental disorders through imbalanced canonical motor activity

KIF21B is a kinesin protein that promotes intracellular transport and controls microtubule dynamics. We report three missense variants and one duplication in KIF21B in individuals with neurodevelopmental disorders associated with brain malformations, including corpus callosum agenesis (ACC) and microcephaly. We demonstrate, in vivo, that the expression of KIF21B missense variants specifically recapitulates patients’ neurodevelopmental abnormalities, including microcephaly and reduced intra- and inter-hemispheric connectivity. We establish that missense KIF21B variants impede neuronal migration through attenuation of kinesin autoinhibition leading to aberrant KIF21B motility activity. We also show that the ACC-related KIF21B variant independently perturbs axonal growth and ipsilateral axon branching through two distinct mechanisms, both leading to deregulation of canonical kinesin motor activity. The duplication introduces a premature termination codon leading to nonsense-mediated mRNA decay. Although we demonstrate that Kif21b haploinsufficiency leads to an impaired neuronal positioning, the duplication variant might not be pathogenic. Altogether, our data indicate that impaired KIF21B autoregulation and function play a critical role in the pathogenicity of human neurodevelopmental disorder.

Kinesins regulate intracellular transport and microtubule dynamics. Here, the authors show that KIF21B variants in humans associate with corpus callosum agenesis and microcephaly. Using mice and zebrafish, they showed the cellular mechanisms altered by the missense KIF21B variants.

Role of dynein-dynactin complex, kinesins, motor adaptors, and their phosphorylation in dendritogenesis

One of the characteristic features of different classes of neurons that is vital for their proper functioning within neuronal networks is the shape of their dendritic arbors. To properly develop dendritic trees, neurons need to accurately control the intracellular transport of various cellular cargo (e.g., mRNA, proteins, and organelles). Microtubules and motor proteins (e.g., dynein and kinesins) that move along microtubule tracks play an essential role in cargo sorting and transport to the most distal ends of neurons. Equally important are motor adaptors, which may affect motor activity and specify cargo that is transported by the motor. Such transport undergoes very dynamic fine-tuning in response to changes in the extracellular environment and synaptic transmission. Such regulation is achieved by the phosphorylation of motors, motor adaptors, and cargo, among other mechanisms. This review focuses on the contribution of the dynein-dynactin complex, kinesins, their adaptors, and the phosphorylation of these proteins in the formation of dendritic trees by maturing neurons. We primarily review the effects of the motor activity of these proteins in dendrites on dendritogenesis. We also discuss less anticipated mechanisms that contribute to dendrite growth, such as dynein-driven axonal transport and non-motor functions of kinesins.

The AAA + ATPase Thorase is neuroprotective against ischemic injury

Neuronal preconditioning in vitro or in vivo with a stressful but non-lethal stimulus leads to new protein expression that mediates a profound neuroprotection against glutamate excitotoxicity and experimental stroke. The proteins that mediate neuroprotection are relatively unknown and under discovery. Here we find that the expression of the AAA + ATPase Thorase is induced by preconditioning stimulation both in vitro and in vivo. Thorase provides neuroprotection in an ATP-dependent manner against oxygen-glucose deprivation (OGD) neurotoxicity or glutamate N-Methyl-D-aspartate (NMDA) receptor-mediated excitotoxicity in vitro. Knock-down of Thorase prevents the establishment of preconditioning induced neuroprotection against OGD or NMDA neurotoxicity. Transgenic overexpression of Thorase provides neuroprotection in vivo against middle cerebral artery occlusion (MCAO)-induced stroke in mice, while genetic deletion of Thorase results in increased injury in vivo following stroke. These results define Thorase as a neuroprotective protein and understanding Thorase signaling could offer a new therapeutic strategy for the treatment of neurologic disorders.

PKC, AKT and ERK1/2-Mediated Modulations of PARP1, NF-κB and PEA15 Activities Distinctly Regulate Regional Specific Astroglial Responses Following Status Epilepticus

Status epilepticus (SE, a prolonged seizure activity) leads to reactive astrogliosis and astroglial apoptosis in the regional specific manners, independent of hemodynamics. Poly(ADP-ribose) polymerase-1 (PARP1) activity is relevant to these distinct astroglial responses. Since various regulatory signaling molecules beyond PARP1 activity may be involved in the distinct astroglial response to SE, it is noteworthy to explore the roles of protein kinases in PARP1-mediated reactive astrogliosis and astroglial apoptosis following SE, albeit at a lesser extent. In the present study, inhibitions of protein kinase C (PKC), AKT and extracellular signal-related kinases 1/2 (ERK1/2), but not calcium/calmodulin-dependent protein kinase II (CaMKII), attenuated CA1 reactive astrogliosis accompanied by reducing PARP1 activity following SE, respectively. However, inhibition of AKT and ERK1/2 deteriorated SE-induced dentate astroglial loss concomitant with the diminished PARP1 activity. Following SE, PKC- and AKT inhibitors diminished phosphoprotein enriched in astrocytes of 15 kDa (PEA15)-S104 and -S116 phosphorylations in CA1 astrocytes, but not in dentate astrocytes, respectively. Inhibitors of PKC, AKT and ERK1/2 also abrogated SE-induced nuclear factor-κB (NF-κB)-S311 and -S468 phosphorylations in CA1 astrocytes. In contrast, both AKT and ERK1/2 inhibitors enhanced NF-κB-S468 phosphorylation in dentate astrocytes. Furthermore, PARP1 inhibitor aggravated dentate astroglial loss following SE. AKT inhibition deteriorated dentate astroglial loss and led to CA1 astroglial apoptosis following SE, which were ameliorated by AKT activation. These findings suggest that activities of PARP1, PEA15 and NF-κB may be distinctly regulated by PKC, AKT and ERK1/2, which may be involved in regional specific astroglial responses following SE.

Exome sequencing of fetal anomaly syndromes: novel phenotype-genotype discoveries

The monogenic etiology of most severe fetal anomaly syndromes is poorly understood. Our objective was to use exome sequencing (ES) to increase our knowledge on causal variants and novel candidate genes associated with specific fetal phenotypes. We employed ES in a cohort of 19 families with one or more fetuses presenting with a distinctive anomaly pattern and/or phenotype recurrence at increased risk for lethal outcomes. Candidate variants were identified in 12 families (63%); in 6 of them a definite diagnosis was achieved including known or novel variants in recognized disease genes (MKS1, OTX2, FGFR2, and RYR1) and variants in novel disease genes describing new fetal phenotypes (CENPF, KIF14). We identified variants likely causal after clinical and functional review (SMAD3, KIF4A, and PIGW) and propose novel candidate genes (PTK7, DNHD1, and TTC28) for early human developmental disease supported by functional and cross-species phenotyping evidence. We describe rare and novel fetal anomaly syndromes and highlight the diagnostic utility of ES, but also its contribution to discovery. The diagnostic yield of the future application of prenatal ES will depend on our ability to increase our knowledge on the specific phenotype–genotype correlations during fetal development.

An integrated bioinformatical analysis to evaluate the role of KIF4A as a prognostic biomarker for breast cancer

Purpose

The aim of this study was to investigate the diagnostic and prognostic value of human kinesin family member 4A (KIF4A) as an effective biomarker for breast cancer.

Materials and methods

Cancer Genome Atlas data and 12 independent public breast cancer microarray data sets were downloaded and analyzed using individual and pooled approaches.

Results

The results of our study revealed a strong and positive correlation between KIF4A expression and malignant features of breast cancer. KIF4A had a strong prognostic value in both ER-positive and ER-negative breast cancers comparable to or even better than tumor size, lymph node invasion, and Elston grade. We also found that KIF4A might be the target gene of microRNA-335, which can suppress KIF4A expression by targeting the 3′-untranslated region of its mRNA.

Conclusion

KIF4A might serve as a robust prognostic predictor for breast cancer. Targeting KIF4A activity could be a promising therapeutic option in breast cancer treatment.

Kinesin KIF4A is associated with chemotherapeutic drug resistance by regulating intracellular trafficking of lung resistance-related protein

Multidrug resistance (MDR) is the major impediment to cancer chemotherapy. The expression of lung resistance-related protein (LRP), a non-ATP-binding cassette (ABC) transporter, is high in tumor cells, resulting in their resistance to a variety of cytotoxic drugs. However, the function of LRP in tumor drug resistance is not yet explicit. Our previous studies had shown that Kinesin KIF4A was overexpressed in cisplatin (DDP)-resistant human lung adenocarcinoma cells (A549/DDP cells) compared with A549 cells. The expression of KIF4A in A549 or A549/DDP cells significantly affects cisplatin resistance but the detailed mechanisms remain unclear. Here, we performed co-immunoprecipitation experiments to show that the tail domain of KIF4A interacted with the N-terminal of LRP. Immunofluorescence images showed that both the ability of binding to LRP and the motility of KIF4A were essential for the dispersed cytoplasm distribution of LRP. Altogether, our results shed light on a potential mechanism in that motor protein KIF4A promotes drug resistance of lung adenocarcinoma cells through transporting LRP-based vaults along microtubules towards the cell membrane. Thus KIF4A might be a cisplatin resistance-associated protein and serves as a potential target for chemotherapeutic drug resistance in lung cancer.

Fe-S cluster coordination of the chromokinesin KIF4A alters its sub-cellular localization during mitosis

Fe-S clusters act as co-factors of proteins with diverse functions, e.g. in DNA repair. Down-regulation of the cytosolic iron-sulfur protein assembly (CIA) machinery promotes genomic instability by the inactivation of multiple DNA repair pathways. Furthermore, CIA deficiencies are associated with so far unexplained mitotic defects. Here, we show that CIA2B and MMS19, constituents of the CIA targeting complex involved in facilitating Fe-S cluster insertion into cytosolic and nuclear target proteins, co-localize with components of the mitotic machinery. Down-regulation of CIA2B and MMS19 impairs the mitotic cycle. We identify the chromokinesin KIF4A as a mitotic component involved in these effects. KIF4A binds a Fe-S cluster in vitro through its conserved cysteine-rich domain. We demonstrate in vivo that this domain is required for the mitosis-related KIF4A localization and for the mitotic defects associated with KIF4A knockout. KIF4A is the first identified mitotic component carrying such a post-translational modification. These findings suggest that the lack of Fe-S clusters in KIF4A upon down-regulation of the CIA targeting complex contributes to the mitotic defects.

Eg5 Overexpression Is Predictive of Poor Prognosis in Hepatocellular Carcinoma Patients

Eg5 (kinesin spindle protein) plays an essential role in mitosis. Inhibition of Eg5 function results in cell cycle arrest at mitosis, which leads to cell death. To date, Eg5 expression and its prognostic significance have not been studied in hepatocellular carcinoma (HCC). In this study, 26 freshly frozen HCC tissue samples and matched peritumoral tissue samples were evaluated with a one-step qPCR test and immunohistochemical (IHC) analysis was conducted on 156 HCC samples to investigate the relationships among Eg5 expression, clinicopathological factors, and prognosis. Eg5 mRNA and protein expression levels were significantly higher in HCC tissues relative to matched noncancerous tissues (p < 0.05). High Eg5 protein expression was significantly related to liver cirrhosis (p = 0.038) and TNM stage (p = 0.008). Kaplan-Meier survival and Cox regression analyses revealed that Eg5 overexpression (p = 0.001), liver cirrhosis (p = 0.009), and TNM stage (p = 0.025) were independent prognostic factors for overall survival. These findings indicate that Eg5 expression can be used as a biomarker of poor prognosis and as a novel therapeutic target for HCC.

Kif4 regulates the expression of VEGFR1 through the PI3K/Akt signaling pathway in RAW264.7 monocytes/macrophages

Kinesin superfamily protein 4 (Kif4), a microtubule-based motor protein, has been shown to participate in a number of critical cellular processes, such as cell division, the intracellular transport of membranous vesicles and signal transduction. However, whether KIF4 regulates vascular endothelial growth factor (VEGF) receptor 1 (VEGFR1) expression remains unknown. Thus, in this study, in order to examine the effects of Kif4 on the expression of VEGFR1 in RAW264.7 monocytes/macrophages, Kif4 was silenced using siRNA. RT-qPCR, western blot analysis and ELISA were used to assess the expression of Kif4 and VEGFR1 up- and downstream signaling molecules, including VEGF-A, VEGFR1, soluble form of VEGFR1 (sVEGFR1), phosphorylated (p-)Akt and Akt. The silencing Kif4 inhibited the mRNA expression of VEGF (P<0.01) and p-Akt (P<0.05); however, the level of VEGF-A was increased (P<0.05) compared with the negative control siRNA-transfected group. The silencing of Kif4 decreased the VEGFR1 mRNA (P<0.05), VEGFR1 protein and sVEGFR1 levels in the cell supernatant (P<0.01). Following the application of insulin-like growth factor-1 (100 ng/ml), the specific agonist of PI3K/Akt in the Kif4 siRNA-transfected group, the VEGFR1 mRNA levels (P<0.001), the VEGFR1 protein levels and the sVEGFR1 (P<0.01) levels significantly increased; however, the levels of VEGF in the cell supernatant were decreased (P<0.05). Taken together, these findings suggest that Kif4 regulates the expression of VEGFR1 in RAW264.7 cells and that the PI3K/Akt pathway is involved in this process.

CAMK2γ antagonizes mTORC1 activation during hepatocarcinogenesis

Hepatocellular carcinoma (HCC) is one of the most deadly cancers that still lacks effective treatments. Dysregulation of kinase signaling has frequently been reported to contribute to HCC. In this study, we used bioinformatic approaches to identify kinases that regulate gene expression changes in human HCCs and two murine HCC models. We identified a role for calcium/calmodulin-dependent protein kinases II gamma isoform (CAMK2γ) in hepatocarcinogenesis. CAMK2γ^-/- mice displayed severely enhanced chemical-induced hepatocarcinogenesis compared with wild-type controls. Mechanistically, CAMK2γ deletion potentiates hepatic activation of mechanistic target of rapamycin complex 1 (mTORC1), which results in hyperproliferation of hepatocytes. Inhibition of mTORC1 by rapamycin effectively attenuates the compensatory proliferation of hepatocytes in CAMK2γ^-/- livers. We further demonstrated that CAMK2γ suppressed growth factor- or insulin-induced mTORC1 activation by inhibiting IRS1/AKT signaling. Taken together, our results reveal a novel mechanism by which CAMK2γ antagonizes mTORC1 activation during hepatocarcinogenesis.

Analyzing structure-function relationships of artificial and cancer-associated PARP1 variants by reconstituting TALEN-generated HeLa PARP1 knock-out cells

Genotoxic stress activates PARP1, resulting in the post-translational modification of proteins with poly(ADP-ribose) (PAR). We genetically deleted PARP1 in one of the most widely used human cell systems, i.e. HeLa cells, via TALEN-mediated gene targeting. After comprehensive characterization of these cells during genotoxic stress, we analyzed structure–function relationships of PARP1 by reconstituting PARP1 KO cells with a series of PARP1 variants. Firstly, we verified that the PARP1\E988K mutant exhibits mono-ADP-ribosylation activity and we demonstrate that the PARP1\L713F mutant is constitutively active in cells. Secondly, both mutants exhibit distinct recruitment kinetics to sites of laser-induced DNA damage, which can potentially be attributed to non-covalent PARP1–PAR interaction via several PAR binding motifs. Thirdly, both mutants had distinct functional consequences in cellular patho-physiology, i.e. PARP1\L713F expression triggered apoptosis, whereas PARP1\E988K reconstitution caused a DNA-damage-induced G2 arrest. Importantly, both effects could be rescued by PARP inhibitor treatment, indicating distinct cellular consequences of constitutive PARylation and mono(ADP-ribosyl)ation. Finally, we demonstrate that the cancer-associated PARP1 SNP variant (V762A) as well as a newly identified inherited PARP1 mutation (F304L\V762A) present in a patient with pediatric colorectal carcinoma exhibit altered biochemical and cellular properties, thereby potentially supporting human carcinogenesis. Together, we establish a novel cellular model for PARylation research, by revealing strong structure–function relationships of natural and artificial PARP1 variants.

The PARP family: insights into functional aspects of poly (ADP-ribose) polymerase-1 in cell growth and survival

PARP family members can be found spread across all domains and continue to be essential molecules from lower to higher eukaryotes. Poly (ADP-ribose) polymerase 1 (PARP-1), newly termed ADP-ribosyltransferase D-type 1 (ARTD1), is a ubiquitously expressed ADP-ribosyltransferase (ART) enzyme involved in key cellular processes such as DNA repair and cell death. This review assesses current developments in PARP-1 biology and activation signals for PARP-1, other than conventional DNA damage activation. Moreover, many essential functions of PARP-1 still remain elusive. PARP-1 is found to be involved in a myriad of cellular events via conservation of genomic integrity, chromatin dynamics and transcriptional regulation. This article briefly focuses on its other equally important overlooked functions during growth, metabolic regulation, spermatogenesis, embryogenesis, epigenetics and differentiation. Understanding the role of PARP-1, its multidimensional regulatory mechanisms in the cell and its dysregulation resulting in diseased states, will help in harnessing its true therapeutic potential.

The transcorneal electrical stimulation as a novel therapeutic strategy against retinal and optic neuropathy: a review of experimental and clinical trials

Transcorneal electrical stimulation (TES) is a novel therapeutic approach to activate the retina and related downstream structures. TES has multiple advantages over traditional treatments, such as being minimally invasive and readily applicable in a routine manner. Series of animal experiments have shown that TES protects the retinal neuron from traumatic or genetic induced degeneration. These laboratory evidences support its utilization in ophthalmological therapies against various retinal and optical diseases including retinitis pigmentosa (RP), traumatic optic neuropathy, anterior ischemic optic neuropathy (AION), and retinal artery occlusions (RAOs). Several pioneering explorations sought to clarify the functional mechanism underlying the neuroprotective effects of TES. It seems that the neuroprotective effects should not be attributed to a solitary pathway, on the contrary, multiple mechanisms might contribute collectively to maintain cellular homeostasis and promote cell survival in the retina. More precise evaluations via functional and morphological techniques would determine the exact mechanism underlying the remarkable neuroprotective effect of TES. Further studies to determine the optimal parameters and the long-term stability of TES are crucial to justify the clinical significance and to establish TES as a popularized therapeutic modality against retinal and optic neuropathy.

PKCα and HMGB1 antagonistically control hydrogen peroxide-induced poly-ADP-ribose formation

Harmful oxidation of proteins, lipids and nucleic acids is observed when reactive oxygen species (ROS) are produced excessively and/or the antioxidant capacity is reduced, causing ‘oxidative stress’. Nuclear poly-ADP-ribose (PAR) formation is thought to be induced in response to oxidative DNA damage and to promote cell death under sustained oxidative stress conditions. However, what exactly triggers PAR induction in response to oxidative stress is incompletely understood. Using reverse phase protein array (RPPA) and in-depth analysis of key stress signaling components, we observed that PAR formation induced by H₂O₂ was mediated by the PLC/IP3R/Ca²⁺/PKCα signaling axis. Mechanistically, H₂O₂-induced PAR formation correlated with Ca²⁺-dependent DNA damage, which, however, was PKCα-independent. In contrast, PAR formation was completely lost upon knockdown of PKCα, suggesting that DNA damage alone was not sufficient for inducing PAR formation, but required a PKCα-dependent process. Intriguingly, the loss of PAR formation observed upon PKCα depletion was overcome when the chromatin structure-modifying protein HMGB1 was co-depleted with PKCα, suggesting that activation and nuclear translocation of PKCα releases the inhibitory effect of HMGB1 on PAR formation. Together, these results identify PKCα and HMGB1 as important co-regulators involved in H₂O₂-induced PAR formation, a finding that may have important relevance for oxidative stress-associated pathophysiological conditions.

RecQ helicases and PARP1 team up in maintaining genome integrity

Genome instability represents a primary hallmark of aging and cancer. RecQL helicases (i.e., RECQL1, WRN, BLM, RECQL4, RECQL5) as well as poly(ADP-ribose) polymerases (PARPs, in particular PARP1) represent two central quality control systems to preserve genome integrity in mammalian cells. Consistently, both enzymatic families have been linked to mechanisms of aging and carcinogenesis in mice and humans. This is in accordance with clinical and epidemiological findings demonstrating that defects in three RecQL helicases, i.e., WRN, BLM, RECQL4, are related to human progeroid and cancer predisposition syndromes, i.e., Werner, Bloom, and Rothmund Thomson syndrome, respectively. Moreover, PARP1 hypomorphy is associated with a higher risk for certain types of cancer. On a molecular level, RecQL helicases and PARP1 are involved in the control of DNA repair, telomere maintenance, and replicative stress. Notably, over the last decade, it became apparent that all five RecQL helicases physically or functionally interact with PARP1 and/or its enzymatic product poly(ADP-ribose) (PAR). Furthermore, a profound body of evidence revealed that the cooperative function of RECQLs and PARP1 represents an important factor for maintaining genome integrity. In this review, we summarize the status quo of this molecular cooperation and discuss open questions that provide a basis for future studies to dissect the cooperative functions of RecQL helicases and PARP1 in aging and carcinogenesis.

Shaping of interphase chromosomes by the microtubule network

It is well established that microtubule dynamics play a major role in chromosome condensation and localization during mitosis. During interphase, however, it is assumed that the metazoan nuclear envelope presents a physical barrier, which inhibits interaction between the microtubules located in the cytoplasm and the chromatin fibers located in the nucleus. In recent years, it has become apparent that microtubule dynamics alter chromatin structure and function during interphase as well. Microtubule motor proteins transport several transcription factors and exogenous DNA (such as plasmid DNA) from the cytoplasm to the nucleus. Various soluble microtubule components are able to translocate into the nucleus, where they bind various chromatin elements leading to transcriptional alterations. In addition, microtubules may apply force on the nuclear envelope, which is transmitted into the nucleus, leading to changes in chromatin structure. Thus, microtubule dynamics during interphase may affect chromatin spatial organization, as well as transcription, replication and repair.

Axon diameter and axonal transport: In vivo and in vitro effects of androgens

Testosterone is a sex hormone involved in brain maturation via multiple molecular mechanisms. Previous human studies described age-related changes in the overall volume and structural properties of white matter during male puberty. Based on this work, we have proposed that testosterone may induce a radial growth of the axon and, possibly, modulate axonal transport. In order to determine whether this is the case we have used two different experimental approaches. With electron microscopy, we have evaluated sex differences in the structural properties of axons in the corpus callosum (splenium) of young rats, and tested consequences of castration carried out after weaning. Then we examined in vitro the effect of the non-aromatizable androgen Mibolerone on the structure and bidirectional transport of wheat-germ agglutinin vesicles in the axons of cultured sympathetic neurons. With electron microscopy, we found robust sex differences in axonal diameter (males>females) and g ratio (males>females). Removal of endogenous testosterone by castration was associated with lower axon diameter and lower g ratio in castrated (vs. intact) males. In vitro, Mibolerone influenced the axonal transport in a time- and dose-dependent manner, and increased the axon caliber as compared with vehicle-treated neurons. These findings are consistent with the role of testosterone in shaping the axon by regulating its radial growth, as predicted by the initial human studies.

No evidence of locus heterogeneity in familial microcephaly with or without chorioretinopathy, lymphedema, or mental retardation syndrome

BACKGROUND

Microcephaly with or without chorioretinopathy, lymphedema, or mental retardation syndrome (MCLMR) is a rare autosomal dominant disorder with variable expressivity. It is characterized by mild-to-severe microcephaly, often associated with intellectual disability, ocular defects and lymphedema. It can be sporadic or inherited. Eighty-seven patients have been described to carry a mutation in KIF11, which encodes a homotetrameric motor kinesin, EG5.

METHODS

We tested 23 unreported MCLMR index patients for KIF11. We also reviewed the clinical phenotypes of all our patients as well as of those described in previously published studies.

RESULTS

We identified 14 mutations, 12 of which are novel. We detected mutations in 12 affected individuals, from 6 out of 6 familial cases, and in 8 out of 17 sporadic patients. Phenotypic evaluation of patients (our 26 + 61 earlier published = 87) revealed microcephaly in 91%, eye anomalies in 72%, intellectual disability in 67% and lymphedema in 47% of the patients. Unaffected carriers were rare (4 out of 87: 5%). Family history is not a requisite for diagnosis; 31% (16 out of 52) were de novo cases.

CONCLUSIONS

All inherited cases, and 50% of sporadic cases of MCLMR are due to germline KIF11 mutations. It is possible that mosaic KIF11 mutations cause the remainder of sporadic cases, which the methods employed here were not designed to detect. On the other hand, some of them might have another mimicking disorder and genetic defect, as microcephaly is highly heterogeneous. In aggregate, KIF11 mutations likely cause the majority, if not all, of MCLMR.

Kinesin superfamily proteins (KIFs): Various functions and their relevance for important phenomena in life and diseases

Kinesin superfamily proteins (KIFs) largely serve as molecular motors on the microtubule system and transport various cellular proteins, macromolecules, and organelles. These transports are fundamental to cellular logistics, and at times, they directly modulate signal transduction by altering the semantics of informational molecules. In this review, we will summarize recent approaches to the regulation of the transport destinations and to the physiological relevance of the role of these proteins in neuroscience, ciliary functions, and metabolic diseases. Understanding these burning questions will be essential in establishing a new paradigm of cellular functions and disease pathogenesis.

Impaired angiogenesis and tumor development by inhibition of the mitotic kinesin Eg5

Kinesin motor proteins exert essential cellular functions in all eukaryotes. They control mitosis, migration and intracellular transport through interaction with microtubules. Small molecule inhibitors of the mitotic kinesin KiF11/Eg5 are a promising new class of anti-neoplastic agents currently evaluated in clinical cancer trials for solid tumors and hematological malignancies. Here we report induction of Eg5 and four other mitotic kinesins including KIF20A/Mklp2 upon stimulation of in vivo angiogenesis with vascular endothelial growth factor-A (VEGF-A). Expression analyses indicate up-regulation of several kinesin-encoding genes predominantly in lymphoblasts and endothelial cells. Chemical blockade of Eg5 inhibits endothelial cell proliferation and migration in vitro. Mitosis-independent vascular outgrowth in aortic ring cultures is strongly impaired after Eg5 or Mklp2 protein inhibition. In vivo, interfering with KIF11/Eg5 function causes developmental and vascular defects in zebrafish and chick embryos and potent inhibition of tumor angiogenesis in experimental tumor models. Besides blocking tumor cell proliferation, impairing endothelial function is a novel mechanism of action of kinesin inhibitors.

The role of Kif4A in doxorubicin-induced apoptosis in breast cancer cells

This study was to investigate the mechanism and role of Kif4A in doxorubicin-induced apoptosis in breast cancer. Using two human breast cancer cell lines MCF-7 (with wild-type p53) and MDA-MB-231 (with mutant p53), we quantitated the expression levels of kinesin super-family protein 4A (Kif4A) and poly (ADP-ribose) Polymerase-1 (PARP-1) by Western blot after doxorubicin treatment and examined the apoptosis by flow cytometry after treatment with doxorubicin and PARP-1 inhibitor, 3-Aminobenzamide (3-ABA). Our results showed that doxorubicin treatment could induce the apoptosis of MCF-7 and MDA-MB-231 cells, the down-regulation of Kif4A and upregulation of poly(ADP-ribose) (PAR). The activity of PARP-1 or PARP-1 activation was significantly elevated by doxorubicin treatment in dose- and time-dependent manners (P < 0.05), while doxorubicin treatment only slightly elevated the level of cleaved fragments of PARP-1 (P > 0.05). We further demonstrated that overexpression of Kif4A could reduce the level of PAR and significantly increase apoptosis. The effect of doxorubicin on apoptosis was more profound in MCF-7 cells compared with MDA-MB-231 cells (P < 0.05). Taken together, our results suggest that the novel role of Kif4A in doxorubicin-induced apoptosis in breast cancer cells is achieved by inhibiting the activity of PARP-1.

Kinesin KIF4A transports integrin β1 in developing axons of cortical neurons

CNS axons have poor regenerative ability compared to PNS axons, and mature axons regenerate less well than immature embryonic axons. The loss of regenerative ability with maturity is accompanied by the setting up of a selective transport filter in axons, restricting the types of molecule that are present. We confirm that integrins (represented by subunits β1 and α5) are present in early cortical axons in vitro but are excluded from mature axons. Ribosomal protein and L1 show selective axonal transport through association with kinesin kif4A; we have therefore examined the hypothesis that integrin transport might also be in association with kif4A. Kif4A is present in all processes of immature cortical neurons cultured at E18, then downregulated by 14days in vitro, coinciding with the exclusion of integrin from axons. Kif4a co-localises with β1 integrin in vesicles in neurons and non-neuronal cells, and the two molecules co-immunoprecipitate. Knockdown of KIF4A expression with shRNA reduced the level of integrin β1 in axons of developing neurons and reduced neurite elongation on laminin, an integrin-dependent substrate. Overexpression of kif4A triggered apoptosis in neuronal and non-neuronal cells. In mature neurons expression of kif4A-GFP at a modest level did not kill the cells, and the kif4A was detectable in their axons. However this was not accompanied by an increase in integrin β1 axonal transport, suggesting that kif4A is not the only integrin transporter, and that integrin exclusion from axons is controlled by factors other than the kif4A level.

Minocycline and cisplatin exert synergistic growth suppression on hepatocellular carcinoma by inducing S phase arrest and apoptosis

Minocycline, a semisynthetic tetracycline, is a highly lipophilic molecule capable of infiltrating tissues and blood. Previous studies have revealed the functions and mechanisms of minocycline in anti-inflammation, protection of the nervous system and certain tumors. The role of minocycline has never been investigated in hepatocellular carcinoma (HCC). The functions of minocycline on HCC cells were investigated using immunohistochemical staining and western blotting. Minocycline was applied to L02, HepG2 and Huh7 cells, and the growth characteristics were studied. Cisplatin was administered in combination with minocycline in this study. Cell cycle and apoptosis analyses were employed to investigate the mechanisms underlying the growth regulation associated with minocycline and(or) cisplatin. Minocycline caused S phase cell cycle arrest and an increase in the apoptotic rate associated with upregulation of p27, cleaved-caspase8, cleaved-caspase3 and cleaved-PRAP-1. Low dose of cisplatin promoted cell cycle arrest and apoptosis, whereas minocycline was mainly associated with upregulation of cleaved-PARP-1. The combination of cisplatin and minocycline increased the rate and extent of cell cycle arrest and increased the apoptosis rate caused by minocycline. A novel mechanism was revealed. Minocycline functions as an antitumor drug in HCC by regulating p27, caspase-3 and PARP-1. Cisplatin enhanced minocycline's effect on PARP-1.

(-)-Phenserine attenuates soman-induced neuropathology

Organophosphorus (OP) nerve agents are deadly chemical weapons that pose an alarming threat to military and civilian populations. The irreversible inhibition of the critical cholinergic degradative enzyme acetylcholinesterase (AChE) by OP nerve agents leads to cholinergic crisis. Resulting excessive synaptic acetylcholine levels leads to status epilepticus that, in turn, results in brain damage. Current countermeasures are only modestly effective in protecting against OP-induced brain damage, supporting interest for evaluation of new ones. (-)-Phenserine is a reversible AChE inhibitor possessing neuroprotective and amyloid precursor protein lowering actions that reached Phase III clinical trials for Alzheimer's Disease where it exhibited a wide safety margin. This compound preferentially enters the CNS and has potential to impede soman binding to the active site of AChE to, thereby, serve in a protective capacity. Herein, we demonstrate that (-)-phenserine protects neurons against soman-induced neuronal cell death in rats when administered either as a pretreatment or post-treatment paradigm, improves motoric movement in soman-exposed animals and reduces mortality when given as a pretreatment. Gene expression analysis, undertaken to elucidate mechanism, showed that (-)-phenserine pretreatment increased select neuroprotective genes and reversed a Homer1 expression elevation induced by soman exposure. These studies suggest that (-)-phenserine warrants further evaluation as an OP nerve agent protective strategy.

Involvement of the kinesin family members KIF4A and KIF5C in intellectual disability and synaptic function

INTRODUCTION

Kinesin superfamily (KIF) genes encode motor proteins that have fundamental roles in brain functioning, development, survival and plasticity by regulating the transport of cargo along microtubules within axons, dendrites and synapses. Mouse knockout studies support these important functions in the nervous system. The role of KIF genes in intellectual disability (ID) has so far received limited attention, although previous studies have suggested that many ID genes impinge on synaptic function.

METHODS

By applying next-generation sequencing (NGS) in ID patients, we identified likely pathogenic mutations in KIF4A and KIF5C. To further confirm the pathogenicity of these mutations, we performed functional studies at the level of synaptic function in primary rat hippocampal neurons.

RESULTS AND CONCLUSIONS

Four males from a single family with a disruptive mutation in the X-linked KIF4A (c.1489-8_1490delins10; p.?- exon skipping) showed mild to moderate ID and epilepsy. A female patient with a de novo missense mutation in KIF5C (c.11465A>C; p.(Glu237Lys)) presented with severe ID, epilepsy, microcephaly and cortical malformation. Knock-down of Kif4a in rat primary hippocampal neurons altered the balance between excitatory and inhibitory synaptic transmission, whereas the mutation in Kif5c affected its protein function at excitatory synapses. Our results suggest that mutations in KIF4A and KIF5C cause ID by tipping the balance between excitatory and inhibitory synaptic excitability.

A genomic toolkit to investigate kinesin and myosin motor function in cells

Coordination of multiple kinesin and myosin motors is required for intracellular transport, cell motility and mitosis. However, comprehensive resources that allow systems analysis of the localization and interplay between motors in living cells do not exist. Here, we generated a library of 243 amino- and carboxy-terminally tagged mouse and human bacterial artificial chromosome transgenes to establish 227 stably transfected HeLa cell lines, 15 mouse embryonic stem cell lines and 1 transgenic mouse line. The cells were characterized by expression and localization analyses and further investigated by affinity-purification mass spectrometry, identifying 191 candidate protein-protein interactions. We illustrate the power of this resource in two ways. First, by characterizing a network of interactions that targets CEP170 to centrosomes, and second, by showing that kinesin light-chain heterodimers bind conventional kinesin in cells. Our work provides a set of validated resources and candidate molecular pathways to investigate motor protein function across cell lineages.

Human chromokinesins promote chromosome congression and spindle microtubule dynamics during mitosis

Human chromokinesins hKID and KIF4A contribute to proper attachment of chromosomes by controlling the positioning of the chromosome arms and microtubule dynamics, respectively.

Chromokinesins are microtubule plus end–directed motor proteins that bind to chromosome arms. In Xenopus egg cell-free extracts, Xkid and Xklp1 are essential for bipolar spindle formation but the functions of the human homologues, hKID (KIF22) and KIF4A, are poorly understood. By using RNAi-mediated protein knockdown in human cells, we find that only co-depletion delayed progression through mitosis in a Mad2-dependent manner. Depletion of hKID caused abnormal chromosome arm orientation, delayed chromosome congression, and sensitized cells to nocodazole. Knockdown of KIF4A increased the number and length of microtubules, altered kinetochore oscillations, and decreased kinetochore microtubule flux. These changes were associated with failures in establishing a tight metaphase plate and an increase in anaphase lagging chromosomes. Co-depletion of both chromokinesins aggravated chromosome attachment failures, which led to mitotic arrest. Thus, hKID and KIF4A contribute independently to the rapid and correct attachment of chromosomes by controlling the positioning of chromosome arms and the dynamics of microtubules, respectively.

Mitotic chromosomes are compacted laterally by KIF4 and condensin and axially by topoisomerase IIα

During the shaping of mitotic chromosomes, KIF4 and condensin work in parallel to promote lateral chromatid compaction and in opposition to topoisomerase IIα, which shortens the chromatid arms.

Mitotic chromosome formation involves a relatively minor condensation of the chromatin volume coupled with a dramatic reorganization into the characteristic “X” shape. Here we report results of a detailed morphological analysis, which revealed that chromokinesin KIF4 cooperated in a parallel pathway with condensin complexes to promote the lateral compaction of chromatid arms. In this analysis, KIF4 and condensin were mutually dependent for their dynamic localization on the chromatid axes. Depletion of either caused sister chromatids to expand and compromised the “intrinsic structure” of the chromosomes (defined in an in vitro assay), with loss of condensin showing stronger effects. Simultaneous depletion of KIF4 and condensin caused complete loss of chromosome morphology. In these experiments, topoisomerase IIα contributed to shaping mitotic chromosomes by promoting the shortening of the chromatid axes and apparently acting in opposition to the actions of KIF4 and condensins. These three proteins are major determinants in shaping the characteristic mitotic chromosome morphology.

Functional Aspects of PARP1 in DNA Repair and Transcription

Poly (ADP-ribose) polymerase 1 (PARP1) is an ADP-ribosylating enzyme essential for initiating various forms of DNA repair. Inhibiting its enzyme activity with small molecules thus achieves synthetic lethality by preventing unwanted DNA repair in the treatment of cancers. Through enzyme-dependent chromatin remodeling and enzyme-independent motif recognition, PARP1 also plays important roles in regulating gene expression. Besides presenting current findings on how each process is individually controlled by PARP1, we shall discuss how transcription and DNA repair are so intricately linked that disturbance by PARP1 enzymatic inhibition, enzyme hyperactivation in diseases, and viral replication can favor one function while suppressing the other.